ANTI-HEPATITIS B VIRUS ANTIBODIES AND USE THEREOF

- XIAMEN UNIVERSITY

Antibodies (especially humanized antibodies) against the hepatitis B surface antigen (HBsAg), a nucleic acid molecule encoding same, a method for preparing same, and a pharmaceutical composition containing same. The anti-HBsAg antibodies have a higher binding affinity to HBsAg at a neutral pH than at an acidic pH, thereby significantly enhancing virus clearance efficiency and prolonging virus inhibition time. The antibodies and pharmaceutical composition may be used to prevent and/or treat HBV infections or diseases related to HBV infection (such as hepatitis B) for use in neutralizing the virulence of HBV in the body of a subject (such as a human) to reduce a serum level of HBV DNA and/or HBsAg in the body of the subject, or to activate a humoral immune response of a subject (such as a person infected with chronic HBV or a patient who has chronic hepatitis B) against HBV.

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Description
TECHNICAL FIELD

The present invention relates to the field of molecular virology and immunology, especially the field of treatment of hepatitis B virus (HBV) infection. Specifically, the present invention relates to an antibody against hepatitis B virus surface antigen (HBsAg) and a nucleic acid encoding the antibody, and a use thereof. The anti-HBsAg antibody of the present invention has a higher binding affinity for HBsAg at neutral pH than at acidic pH. The novel antibody can be used for the prevention and/or treatment of an HBV infection or a disease associated with HBV infection (for example, hepatitis B), for neutralizing a virulence of HBV in a subject (for example, a human), or for reducing a serum level of HBV DNA and/or HBsAg in a subject. Therefore, the present invention further relates to a use of the antibody and variant thereof in the manufacture of a pharmaceutical composition for the prevention and/or treatment of an HBV infection or a disease related to an HBV infection (for example, hepatitis B), for neutralizing a virulence of HBV in a subject (for example, a human), for reducing a serum level of HBV DNA and/or HBsAg in a subject, or for activating a humoral immune response to HBV in a subject (for example, a person with chronic HBV infection or a patient with chronic hepatitis B).

BACKGROUND ART

Hepatitis B virus infection, especially chronic HBV infection, is one of the most important public health problems in the world (Dienstag J L. Hepatitis B virus infection. N Engl J Med 2008 Oct. 2; 359(14):1486-1500). Chronic HBV infection can lead to a series of liver diseases such as chronic hepatitis B (CHB), liver cirrhosis (LC) and primary hepatocellular carcinoma (HCC) (Liaw Y F, Chu C M. Hepatitis B virus infection. Lancet 2009 Feb. 14; 373(9663): 582-592). According to reports, there are currently about 2 billion people in the world who have been infected with HBV, there are now about 350 million persons with chronic hepatitis B virus infections, the risk of these infected persons eventually dying from HBV infection-associated liver diseases can reach 15% to 25%, and more than one million people die from such diseases each year worldwide (Dienstag J L., ibid; and Liaw Y F, et al., ibid).

The current treatment drugs for chronic HBV infection can be divided into interferons (IFNs) and nucleoside or nucleotide analogs (NAs) (Dienstag J L., ibid.; Kwon H, Lok A S. Hepatitis B therapy. Nat Rev Gastroenterol Hepatol 2011 May; 8(5): 275-284; and Liaw Y F et al., ibid.). For HBV-infected patients (such as CHB patients), the above-mentioned drugs alone or in combination can effectively inhibit viral replication in the body and greatly reduce HBV DNA levels; in particular, after 52 weeks or more of such treatments, the response rate where the HBV DNA level in the body is below the lower limit of detection (virological response) can reach 40-80% (Kwon H et al., ibid.). However, the treatment with the above-mentioned drugs alone or in combination cannot completely eliminate the HBV virus in the infected persons, and the response rate of HBsAg negative conversion or HBsAg seroconversion (a sign of complete HBV virus clearance in the infected person) caused thereby is usually less than 5% (Kwon H et al., ibid.).

The development of new drugs for the treatment of chronic HBV infection based on immunological means is one of the important research directions in this field. Immunotherapy for chronic HBV infection is usually carried out in two ways: active immunotherapy (its corresponding drug forms including vaccines, etc.) and passive immunotherapy (its corresponding drug forms including antibodies, etc.). Active immunotherapy refers to administration of a therapeutic vaccine (including protein vaccine, peptide vaccine, nucleic acid vaccine, etc.) in order to stimulate the body of chronic HBV infected person to actively produce a cellular immune response (CTL effect, etc.) or/and humoral immune response against HBV (antibodies, etc.), so as to achieve the purpose of inhibiting or eliminating HBV. Currently, there is no definitely significant and effective active immunotherapy drug/vaccine that can be used to treat chronic HBV infection. Passive immunotherapy (taking antibody as an example) refers to administration of an antibody with therapeutic properties to a HBV infected person, and a therapeutic effect can be achieved by the antibody-mediated virus neutralization to block HBV from infecting newborn hepatocytes, or by the antibody-mediated immune clearance to remove viruses and infected liver cells from the body. At present, the anti-HBs polyclonal antibody purified from the serum/plasma of those who had a response to a prophylactic hepatitis B vaccine or those who have recovered from HBV infection, namely high-potency hepatitis B immunoglobulin (HBIG), has been widely used to block mother-to-child vertical transmission of HBV, prevent HBV reinfection after liver transplantation in patients with chronic HBV infection, and prevent people accidentally exposed to HBV from being infected. However, the direct application of HBIG in the treatment of HBV-infected patients (for example, CHB patients) has no obvious effect, and it has many limitations such as fewer sources for high-potency plasma, high price, unstable nature, and potential safety issues.

Therefore, it is urgent and necessary to develop innovative treatment methods and drugs for HBV infected persons that can more effectively remove HBV virus, especially HBsAg.

Contents of the Present Invention

The present inventors have previously developed an anti-HBsAg humanized antibody with excellent properties, which can neutralize the virulence of HBV in vivo and reduce the serum levels of HBV DNA and/or HBsAg. On the basis of the previous research, the present inventors have paid a lot of creative work to conduct in-depth research and engineering of the humanized antibody, thereby developing an anti-HBsAg antibody with pH-dependent antigen binding ability. The anti-HBsAg antibody of the present invention has a higher binding affinity for HBsAg at neutral pH than at acidic pH, so that the reuse of antibody is realized, the antibody half-life is significantly extended, and the efficiency of HBV clearance is enhanced. Furthermore, the present inventors obtain a scavenger antibody and further extend the antibody half-life by introducing a mutation into the Fc region of the above-mentioned antibody to enhance its affinity to hFcRn or mFcγRII under neutral condition.

The antibody of the present invention is extremely advantageous, since it not only retains the activity of reducing the serum level of HBV DNA and/or HBsAg, but also has a longer time of antigen suppression, thereby greatly reducing the injection dosage and administration frequency of treatment, and having significant clinical value.

Antibody of the Present Invention

Therefore, in one aspect, the present invention provides an antibody or antigen-binding fragment thereof capable of specifically binding to HBsAg, in which the antibody or antigen-binding fragment thereof binds to HBsAg with higher affinity at neutral pH than at acidic pH.

In certain embodiments, the neutral pH is pH 6.7 to pH 7.5, such as pH 7.4.

In certain embodiments, the acidic pH is pH 4.0 to pH 6.5, such as pH 6.0.

In certain embodiments, a ratio of KD of binding to HBsAg at an acidic pH (for example, pH 6.0) to KD of binding to HBsAg at neutral pH (for example, pH 7.4) (i.e., value of KD (acidic pH)/KD (neutral pH)), of the antibody or antigen-binding fragment thereof, is greater than 1, for example not less than 1.5, not less than 2, not less than 3, not less than 4, not less than 5, not less than 6, not less than 7, not less than 8, not less than 9, not less than 10, not less than 15, not less than 20, not less than 30, not less than 40, not less than 50, not less than 60, not less than 70, not less than 80, not less than 90, not less than 100, not less than 300, not less than 500, not less than 800, not less than 1000, not less than 2000, not less than 5000, or not less than 10,000. In some embodiments, the value of KD (acidic pH)/KD (neutral pH) is greater than 1 and not greater than 10000, for example, not greater than 5000, not greater than 2000, not greater than 1000, not Greater than 900, not greater than 800, not greater than 700, not greater than 600, not greater than 500, not greater than 400, not greater than 300, not greater than 200, not greater than 100, not greater than 90, not greater than 80, not greater than 70, not greater than 60, not greater than 50, not greater than 40, not greater than 30, not greater than 20, or not greater than 10. The KD can be measured by a technique known in the art, for example, by SPR technique (for example, Biacore).

In some embodiments, a ratio of KD of binding to HBsAg at pH 6.0 to KD of binding to HBsAg at pH 7.4 of the antibody or antigen-binding fragment thereof, is greater than 1, for example not less than 1.5, not less than 2. In certain embodiments, the KD value of the antibody of the invention at neutral pH may be 10−7M, 10−8M, 10−9M, 10−10M, 10−11M, 10−12M or less. In some embodiments, the KD value of the antibody of the present invention at acidic pH may be 10−9M, 10−8M, 10−7M, 10−6M or more.

In certain embodiments, a ratio of EC50 of binding to HBsAg at an acidic pH (for example, pH 6.0) to EC50 of binding to HBsAg at neutral pH (for example, pH 7.4) (i.e., value of EC50 (acidic pH)/EC50 (neutral pH)), of the antibody or antigen-binding fragment thereof, is greater than 1, for example not less than 1.5, not less than 2, not less than 3, not less than 4, not less than 5, not less than 6, not less than 7, not less than 8, not less than 9, not less than 10, not less than 15, not less than 20, not less than 30, not less than 40, not less than 50, not less than 60, not less than 70, not less than 80, not less than 90, not less than 100, not less than 300, not less than 500, not less than 800, not less than 1000, not less than 2000, not less than 5000, or not less than 10,000. In some embodiments, the value of EC50 (acidic pH)/EC50 (neutral pH) is greater than 1 and not greater than 10000, for example, not greater than 5000, not greater than 2000, not greater than 1000, not greater than 900, and not greater than 800, not greater than 700, not greater than 600, not greater than 500, not greater than 400, not greater than 300, not greater than 200, not greater than 100, not greater than 90, not greater than 80, not greater than 70, not greater than 60, not greater than 50, not greater than 40, not greater than 30, not greater than 20, or not greater than 10. In some embodiments, the EC50 is measured by ELISA method, for example, calculated by the regression analysis of a dose-response curve generated by the ELISA method.

In certain embodiments, a ratio of EC50 of binding to HBsAg at pH 6.0 to EC50 of binding to HBsAg at pH 7.4 of the antibody or antigen-binding fragment thereof, is greater than 1, for example, not less than 1.5, or not less than 2.

In certain embodiments, the antibody or antigen-binding fragment thereof of the present invention is derived from the anti-HBV humanized antibody 162 (which is described in detail in Chinese Patent Application 201610879693.5).

In certain embodiments, the antibody or antigen-binding fragment thereof of the present invention binds to aa121-124 of HBsAg with higher affinity at neutral pH than at acidic pH.

In certain embodiments, the antibody or antigen-binding fragment thereof comprises a heavy chain variable region (VH) comprising HCDR1, HCDR2 and HCDR3, which has one or more of the following characteristics:

(i) HCDR1 has at least one amino acid (for example, 1, 2, 3, 4 or 5 amino acids) replaced with histidine as compared with a sequence shown in SEQ ID NO: 11;

(ii) HCDR2 has at least one amino acid (for example, 1, 2, 3, 4 or 5 amino acids) replaced with histidine as compared with a sequence shown in SEQ ID NO: 12; and/or,

(iii) HCDR3 has at least one amino acid (for example, 1, 2, 3, 4 or 5 amino acids) replaced with histidine as compared with a sequence shown in SEQ ID NO: 13.

In certain embodiments, the antibody or antigen-binding fragment thereof comprises a heavy chain variable region (VL) comprising LCDR1, LCDR2 and LCDR3, which has one or more of the following characteristics:

(i) LCDR1 has at least one amino acid (for example, 1, 2, 3, 4 or 5 amino acids) replaced with histidine as compared with a sequence shown in SEQ ID NO: 14;

(ii) LCDR2 has at least one amino acid (for example, 1, 2, 3, 4 or 5 amino acids) replaced with histidine as compared with a sequence shown in SEQ ID NO: 15; and/or,

(iii) LCDR3 has at least one amino acid (for example, 1, 2, 3, 4 or 5 amino acids) replaced with histidine as compared with a sequence shown in SEQ ID NO: 16.

In certain embodiments, the antibody or antigen-binding fragment thereof comprises:

(a) a heavy chain variable region (VH) comprising the following 3 CDRs:

(i) HCDR1 with a sequence of X1X2YHX3N (SEQ ID NO: 26), wherein X1 is selected from Y or H, X2 is selected from G or R, X3 is selected from W or Y;

(ii) HCDR2 with a sequence of YIX4X5DGSVX6YNPSLEN (SEQ ID NO: 27), wherein X4 is selected from S, N or H, X5 is selected from Y or H, X6 is selected from L, H or Q; and

(iii) HCDR3 with a sequence of GFDH (SEQ ID NO: 13); and/or,

(b) a light chain variable region (VL) comprising the following 3 CDRs:

(iv) LCDR1 with a sequence of RSSQSLVHSYGDX7YLH (SEQ ID NO: 28), wherein X7 is selected from T or N;

(v) LCDR2 with a sequence of KVSNRFS (SEQ ID NO: 15); and

(vi) LCDR3 with a sequence of SQNTHX8PYT (SEQ ID NO: 29), wherein X8 is selected from V, L or H.

In certain embodiments, the antibody or antigen-binding fragment thereof comprises:

(a) a heavy chain variable region (VH) comprising the following 3 CDRs:

(i) HCDR1, which is composed of a sequence selected from the following: SEQ ID NOs: 17, 21, 24;

(ii) HCDR2, which is composed of a sequence selected from: SEQ ID NOs: 18, 20, 22, 12; and

(iii) HCDR3, which is composed of a sequence shown in SEQ ID NO: 13; and/or,

(b) a light chain variable region (VL) comprising the following 3 CDRs:

(iv) LCDR1, which is composed of a sequence selected from the following: SEQ ID NOs: 14, 25;

(v) LCDR2, which is composed of a sequence shown in SEQ ID NO: 15; and

(vi) LCDR3, which is composed of a sequence selected from the following: SEQ ID NOs: 19, 16, 23.

In certain embodiments, X1 is selected from H, X2 is selected from G, X3 is selected from W or Y, X4 is selected from S or H, X5 is selected from Y, X6 is selected from L or H, X7 is selected from T or N, X8 is selected from V, L or H.

In certain embodiments, the antibody or antigen-binding fragment thereof comprises:

(a) a heavy chain variable region (VH) comprising the following 3 CDRs:

(i) HCDR1, which is composed of a sequence selected from the following: SEQ ID NOs: 17, 24;

(ii) HCDR2, which is composed of a sequence selected from: SEQ ID NOs: 18, 12; and

(iii) HCDR3, which is composed of a sequence shown in SEQ ID NO: 13; and/or,

(b) a light chain variable region (VL) comprising the following 3 CDRs:

(iv) LCDR1, which is composed of a sequence selected from the following: SEQ ID NOs: 14, 25;

(v) LCDR2, which is composed of a sequence shown in SEQ ID NO: 15; and

(vi) LCDR3, which is composed of a sequence selected from the following: SEQ ID NOs: 19, 16, 23.

In certain embodiments, the antibody or antigen-binding fragment thereof comprises:

(1) a VH comprising the following 3 CDRs: HCDR1 shown in SEQ ID NO: 21, HCDR2 shown in SEQ ID NO: 22, HCDR3 shown in SEQ ID NO: 13; and, a VL comprising the following 3 CDRs: LCDR1 shown in SEQ ID NO: 14, LCDR2 shown in SEQ ID NO: 15, LCDR3 shown in SEQ ID NO: 23;

(2) a VH comprising the following 3 CDRs: HCDR1 shown in SEQ ID NO: 17, HCDR2 shown in SEQ ID NO: 18, HCDR3 shown in SEQ ID NO: 13; and, a VL comprising the following 3 CDRs: LCDR1 shown in SEQ ID NO: 14, LCDR2 shown in SEQ ID NO: 15, LCDR3 shown in SEQ ID NO: 19;

(3) a VH comprising the following 3 CDRs: HCDR1 shown in SEQ ID NO: 17, HCDR2 shown in SEQ ID NO: 20, HCDR3 shown in SEQ ID NO: 13; and, a VL comprising the following 3 CDRs: LCDR1 shown in SEQ ID NO: 14, LCDR2 shown in SEQ ID NO: 15, LCDR3 shown in SEQ ID NO: 16;

(4) a VH comprising the following 3 CDRs: HCDR1 shown in SEQ ID NO: 24, HCDR2 shown in SEQ ID NO: 12, HCDR3 shown in SEQ ID NO: 13; and, a VL comprising the following 3 CDRs: LCDR1 shown in SEQ ID NO: 25, LCDR2 shown in SEQ ID NO: 15, LCDR3 shown in SEQ ID NO: 16;

(5) a VH comprising the following 3 CDRs: HCDR1 shown in SEQ ID NO: 17, HCDR2 shown in SEQ ID NO: 12, HCDR3 shown in SEQ ID NO: 13; and, a VL comprising the following 3 CDRs: LCDR1 shown in SEQ ID NO: 25, LCDR2 shown in SEQ ID NO: 15, LCDR3 shown in SEQ ID NO: 23; or

(6) a VH comprising the following 3 CDRs: HCDR1 shown in SEQ ID NO: 17, HCDR2 shown in SEQ ID NO: 12, HCDR3 shown in SEQ ID NO: 13; and, a VL comprising the following 3 CDRs: LCDR1 shown in SEQ ID NO: 25, LCDR2 shown in SEQ ID NO: 15, LCDR3 shown in SEQ ID NO: 16.

In certain embodiments, the antibody or antigen-binding fragment thereof further comprises a framework region of a human immunoglobulin (for example, a framework region contained in an amino acid sequence encoded by a human germline antibody gene), and the framework region optionally comprises one or more (for example, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10) back mutations from human residues to murine residues.

In certain embodiments, the antibody or antigen-binding fragment thereof comprises: a heavy chain framework region contained in an amino acid sequence encoded by a human heavy chain germline gene, and/or a light chain framework region contained in an amino acid sequence encoded by a human light chain germline gene.

In certain embodiments, the antibody or antigen-binding fragment thereof comprises: a heavy chain framework region contained in an amino acid sequence encoded by human heavy chain germline gene 4-28-02 (SEQ ID NO: 38), and a light chain framework region contained in an amino acid sequence encoded by human light chain germline gene 2D-28-01 (SEQ ID NO: 39), and the heavy chain framework region and/or the light chain framework region optionally comprises one or more (for example, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10) back mutations from human residues to murine residues.

In certain embodiments, the VH of the antibody or antigen-binding fragment thereof comprises: VH FR1 as shown in SEQ ID NO: 30, VH FR2 as shown in SEQ ID NO: 31, VH FR3 as shown in SEQ ID NO: 32, and VH FR4 shown in SEQ ID NO: 33.

In some embodiments, the VL of the antibody or antigen-binding fragment thereof comprises: VL FR1 as shown in SEQ ID NO: 34, VL FR2 as shown in SEQ ID NO: 35, VL FR3 as shown in SEQ ID NO: 36, and VL FR4 shown in SEQ ID NO: 37.

In certain embodiments, the antibody or antigen-binding fragment thereof comprises:

(a) a heavy chain variable region (VH), which comprises an amino acid sequence selected from the following:

(i) a sequence shown in any one of SEQ ID NOs: 3, 5, 6, 8;

(ii) a sequence with substitution, deletion or addition of one or several amino acids (for example, substitution, deletion or addition of 1, 2, 3, 4 or 5 amino acids) as compared with a sequence shown in any one of SEQ ID NOs: 3, 5, 6, 8; or

(iii) a sequence with a sequence identity of at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% as compared with a sequence shown in any one of SEQ ID NOs: 3, 5, 6, 8;

and

(b) a light chain variable region (VL), which comprises an amino acid sequence selected from the following:

(iv) a sequence shown in any one of SEQ ID NOs: 4, 2, 7, 9, 10;

(v) a sequence with substitution, deletion or addition of one or several amino acids (for example, substitution, deletion or addition of 1, 2, 3, 4 or 5 amino acids) as compared with a sequence shown in any one of SEQ ID NOs: 4, 2, 7, 9, 10; or

(vi) a sequence with a sequence identity of at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% as compared with a sequence shown in any one of SEQ ID NOs: 4, 2, 7, 9, 10.

Preferably, the substitution described in (ii) or (v) is a conservative substitution.

In certain embodiments, the antibody or antigen-binding fragment thereof comprises:

(1) a VH with a sequence shown in SEQ ID NO: 3 and a VL with a sequence shown in SEQ ID NO: 4;

(2) a VH with a sequence shown in SEQ ID NO: 5 and a VL with a sequence shown in SEQ ID NO: 2;

(3) a VH with a sequence shown in SEQ ID NO: 6 and a VL with a sequence shown in SEQ ID NO: 7;

(4) a VH with a sequence shown in SEQ ID NO: 8 and a VL with a sequence shown in SEQ ID NO: 9;

(5) a VH with a sequence shown in SEQ ID NO: 3 and a VL with a sequence shown in SEQ ID NO: 10; or

(6) a VH with a sequence shown in SEQ ID NO: 3 and a VL with a sequence shown in SEQ ID NO: 9.

In certain embodiments, the antibody or antigen-binding fragment thereof further comprises a constant region derived from a human immunoglobulin.

In certain embodiments, the heavy chain of the antibody or antigen-binding fragment thereof comprises a heavy chain constant region derived from a human immunoglobulin (for example, IgG1, IgG2, IgG3, or IgG4), and the light chain of the antibody or antigen-binding fragment thereof comprises a light chain constant region derived from a human immunoglobulin (for example, κ or λ).

In certain embodiments, the antibody or antigen-binding fragment thereof comprises:

(a) a heavy chain constant region (CH) of a human immunoglobulin or a variant thereof, wherein the variant has substitution, deletion or addition of one or more amino acids or any combination thereof (for example, substitution, deletion or addition of at most 20, at most 15, at most 10, or at most 5 amino acids or any combination thereof; for example, substitution, deletion or addition of 1, 2, 3, 4 or 5 amino acids or any combination thereof) as compared with a wild-type sequence from which it is derived; and/or

(b) a light chain constant region (CL) of a human immunoglobulin or a variant thereof, wherein the variant has substitution, deletion or addition of one or more amino acids or any combination thereof (for example, substitution, deletion or addition of at most 20, at most 15, at most 10, or at most 5 amino acids or any combination thereof; for example, substitution, deletion or addition of 1, 2, 3, 4 or 5 amino acids or any combination thereof) as compared with a wild-type sequence from which it is derived.

In certain embodiments, the antibody or antigen-binding fragment thereof comprises a human IgG1 or IgG4 heavy chain constant region. In certain embodiments, the antibody or antigen-binding fragment thereof comprises a heavy chain constant region (CH) as shown in SEQ ID NO: 40.

In certain embodiments, the antibody or antigen-binding fragment thereof of the present invention comprises a variant of a heavy chain constant region (CH) of a human immunoglobulin, in which the variant has an enhanced affinity to hFcRn or mFcγRII at neutral pH (for example, pH 7.4) as compared with a wild-type sequence from which it is derived. In such embodiments, the variant generally has substitution of at least one amino acid as compared with a wild-type sequence from which it is derived.

In certain embodiments, the antibody or antigen-binding fragment thereof comprises a variant of a human IgG1 heavy chain constant region, in which the variant has the following substitutions as compared to a wild-type sequence from which it is derived: (i) M252Y, N286E, N434Y; or, (ii) K326D, L328Y; wherein the above-mentioned amino acid positions are positions according to the Kabat numbering system. In certain embodiments, the antibody or antigen-binding fragment thereof comprises a heavy chain constant region (CH) as shown in SEQ ID NO: 42 or 43.

In certain embodiments, the light chain constant region is a κ light chain constant region. In certain embodiments, the antibody or antigen-binding fragment thereof comprises a light chain constant region (CL) as shown in SEQ ID NO: 41.

In certain embodiments, the antibody or antigen-binding fragment thereof comprises:

(1) a heavy chain comprising a VH shown in SEQ ID NO: 3 and a CH shown in SEQ ID NO: 40, and a light chain comprising a VL shown in SEQ ID NO: 4 and a CL shown in SEQ ID NO: 41;

(2) a heavy chain comprising a VH shown in SEQ ID NO: 3 and a CH shown in SEQ ID NO: 47, and a light chain comprising a VL shown in SEQ ID NO: 4 and a CL shown in SEQ ID NO: 41;

(3) a heavy chain comprising a VH shown in SEQ ID NO: 3 and a CH shown in SEQ ID NO: 48, and a light chain comprising a VL shown in SEQ ID NO: 4 and a CL shown in SEQ ID NO: 41;

(4) a heavy chain comprising a VH shown in SEQ ID NO: 5 and a CH shown in SEQ ID NO: 40, and a light chain comprising a VL shown in SEQ ID NO: 2 and a CL shown in SEQ ID NO: 41;

(5) a heavy chain comprising a VH shown in SEQ ID NO: 5 and a CH shown in SEQ ID NO: 47, and a light chain comprising a VL shown in SEQ ID NO: 2 and a CL shown in SEQ ID NO: 41;

(6) a heavy chain comprising a VH shown in SEQ ID NO: 5 and a CH shown in SEQ ID NO: 48, and a light chain comprising a VL shown in SEQ ID NO: 2 and a CL shown in SEQ ID NO: 41;

(7) a heavy chain comprising a VH shown in SEQ ID NO: 6 and a CH shown in SEQ ID NO: 40, and a light chain comprising a VL shown in SEQ ID NO: 7 and a CL shown in SEQ ID NO: 41;

(8) a heavy chain comprising a VH shown in SEQ ID NO: 6 and a CH shown in SEQ ID NO: 47, and a light chain comprising a VL shown in SEQ ID NO: 7 and a CL shown in SEQ ID NO: 41;

(9) a heavy chain comprising a VH shown in SEQ ID NO: 6 and a CH shown in SEQ ID NO: 48, and a light chain comprising a VL shown in SEQ ID NO: 7 and a CL shown in SEQ ID NO: 41;

(10) a heavy chain comprising a VH shown in SEQ ID NO: 8 and a CH shown in SEQ ID NO: 40, and a light chain comprising a VL shown in SEQ ID NO: 9 and a CL shown in SEQ ID NO: 41;

(11) a heavy chain comprising a VH shown in SEQ ID NO: 8 and a CH shown in SEQ ID NO: 47, and a light chain comprising a VL shown in SEQ ID NO: 9 and a CL shown in SEQ ID NO: 41;

(12) a heavy chain comprising a VH shown in SEQ ID NO: 8 and a CH shown in SEQ ID NO: 48, and a light chain comprising a VL shown in SEQ ID NO: 9 and a CL shown in SEQ ID NO: 41;

(13) a heavy chain comprising a VH shown in SEQ ID NO: 3 and a CH shown in SEQ ID NO: 40, and a light chain comprising a VL shown in SEQ ID NO: 10 and a CL shown in SEQ ID NO: 41;

(14) a heavy chain comprising a VH shown in SEQ ID NO: 3 and a CH shown in SEQ ID NO: 47, and a light chain comprising a VL shown in SEQ ID NO: 10 and a CL shown in SEQ ID NO: 41;

(15) a heavy chain comprising a VH shown in SEQ ID NO: 3 and a CH shown in SEQ ID NO: 48, and a light chain comprising a VL shown in SEQ ID NO: 10 and a CL shown in SEQ ID NO: 41;

(16) a heavy chain comprising a VH shown in SEQ ID NO: 3 and a CH shown in SEQ ID NO: 40, and a light chain comprising a VL shown in SEQ ID NO: 9 and a CL shown in SEQ ID NO: 41;

(17) a heavy chain comprising a VH shown in SEQ ID NO: 3 and a CH shown in SEQ ID NO: 47, and a light chain comprising a VL shown in SEQ ID NO: 9 and a CL shown in SEQ ID NO: 41; or

(18) a heavy chain comprising a VH shown in SEQ ID NO: 3 and a CH shown in SEQ ID NO: 48, and a light chain comprising a VL shown in SEQ ID NO: 9 and a CL shown in SEQ ID NO: 41.

Preparation of Antibody

The antibody of the present invention can be prepared by various methods known in the art, for example, obtained by genetic engineering recombination technology. For example, DNA molecules encoding the heavy chain and light chain genes of the antibody of the present invention are obtained by chemical synthesis or PCR amplification. The resulting DNA molecule is inserted into an expression vector and then transfected into a host cell. Then, the transfected host cell is cultured under specific conditions, and the antibody of the present invention is expressed.

The antigen-binding fragment of the present invention can be obtained by hydrolyzing a complete antibody molecule (see Morimoto et al., J. Biochem. Biophys. Methods 24:107-117 (1992) and Brennan et al., Science 229:81 (1985)). In addition, these antigen-binding fragments can also be directly produced by recombinant host cells (reviewed in Hudson, Curr. Opin. Immunol. 11: 548-557 (1999); Little et al., Immunol. Today, 21: 364-370 (2000))). For example, Fab′ fragments can be obtained directly from host cells; Fab′ fragments can be chemically coupled to form F(ab′)2 fragments (Carter et al., Bio/Technology, 10: 163-167 (1992)). In addition, Fv, Fab or F(ab′)2 fragments can also be directly isolated from a recombinant host cell culture medium. Those of ordinary skill in the art are fully aware of other techniques for preparing these antigen-binding fragments.

Therefore, in another aspect, the present invention provides an isolated nucleic acid molecule comprising a nucleotide sequence encoding the antibody or antigen-binding fragment thereof of the present invention, or heavy chain variable region and/or light chain variable region thereof. In certain preferred embodiments, the isolated nucleic acid molecule encodes the antibody or antigen-binding fragment thereof of the present invention, or heavy chain variable region and/or light chain variable region thereof.

In another aspect, the present invention provides a vector (for example, a cloning vector or an expression vector) comprising the isolated nucleic acid molecule of the present invention. In certain preferred embodiments, the vector of the present invention is, for example, plasmid, cosmid, bacteriophage and the like.

In another aspect, the present invention provides a host cell comprising the isolated nucleic acid molecule of the present invention or the vector of the present invention. Such host cell includes, but is not limited to, prokaryotic cell such as E. coli cell, and eukaryotic cell such as yeast cell, insect cell, plant cell and animal cell (for example, mammalian cell, such as mouse cell, human cell, etc.). In certain preferred embodiments, the host cell of the present invention is a mammalian cell, such as CHO (for example, CHO-K1, CHO-S, CHO DG44).

In another aspect, a method for preparing the antibody or antigen-binding fragment thereof of the present invention is provided, which comprises culturing the host cell of the present invention under conditions that allow expression of the antibody or antigen-binding fragment thereof, and recovering the antibody or antigen-binding fragment thereof from the cultured host cell culture.

Derived Antibody

The antibody or antigen-binding fragment thereof of the present invention can be derivatized, for example linked to another molecule (for example, another polypeptide or protein). Generally, the derivatization (for example, labeling) of the antibody or antigen-binding fragment thereof will not adversely affect its binding to HBsAg. Therefore, the antibody or antigen-binding fragment thereof of the present invention is also intended to include such derivatized forms. For example, the antibody or antigen-binding fragment of the present invention can be functionally linked (by chemical coupling, gene fusion, non-covalent linkage or other means) to one or more other molecular groups, such as another antibody (for example, to form a bispecific antibody), detection reagent, pharmaceutical reagent, and/or protein or polypeptide capable of mediating the antibody or antigen-binding fragment to bind to another molecule (for example, avidin or polyhistidine tag).

Therefore, in certain embodiments, the antibody of the present invention or antigen-binding fragment thereof is labeled. In some embodiments, the antibody or antigen-binding fragment thereof of the present invention bears a detectable label, such as enzyme, radionuclide, fluorescent dye, luminescent substance (for example, chemiluminescent substance), or biotin. The detectable label of the present invention can be any substance that can be detected by fluorescence, spectroscopy, photochemistry, biochemistry, immunology, electrical, optical or chemical means. Such labels are well known in the art, examples of which include, but are not limited to, enzyme (for example, horseradish peroxidase, alkaline phosphatase, (β-galactosidase, urease, glucose oxidase, etc.), radioactive nuclide (for example, 3H, 125I, 35S, 14C or 32P), fluorescent dye (for example, fluorescein isothiocyanate (FITC), fluorescein, tetramethylrhodamine isothiocyanate (TRITC), phycoerythrin (PE), Texas red, rhodamine, quantum dots or cyanine dye derivatives (for example, Cy7, Alexa 750)), luminescent substance (for example, chemiluminescent substance, such as acridine ester compound), magnetic beads (for example, Dynabeads®), calorimetric marker such as colloidal gold or colored glass or plastic (e.g. polystyrene, polypropylene, latex, etc.) beads, and biotin used to ligate avidin (for example, streptavidin) modified by the above-mentioned marker. In certain embodiments, such label can be suitable for immunological detection (for example, enzyme-linked immunoassay, radioimmunoassay, fluorescent immunoassay, chemiluminescence immunoassay, etc.). In certain embodiments, the detectable label as described above can be ligated to the antibody or antigen-binding fragment thereof of the present invention through a linker of different length to reduce potential steric hindrance.

Pharmaceutical Composition and Therapeutic Use

The antibody or antigen-binding fragment thereof of the present invention can be used for the prevention or treatment of an HBV infection in a subject (for example, a human) or a disease associated with HBV infection (for example, hepatitis B), for neutralizing in vitro or in a subject (for example, a human) a virulence of HBV, for reducing a serum level of HBV DNA and/or HBsAg in a subject (for example, a human), and for activating a humoral immune response to HBV in a subject (for example, a patient with chronic HBV infection or chronic hepatitis B).

Therefore, in another aspect, the present invention provides a pharmaceutical composition, which comprises the antibody or antigen-binding fragment thereof of the present invention, and a pharmaceutically acceptable carrier and/or excipient. The pharmaceutical composition of the present invention may also comprises an additional pharmaceutically active agent. In certain embodiments, the additional pharmaceutically active agent is a drug used to prevent or treat an HBV infection or a disease associated with HBV infection (for example, hepatitis B), for example, interferon drug, such as interferon or pegylated interferon.

In another aspect, the present inveiton provides a use of the antibody or antigen-binding fragment thereof of the present invention or the pharmaceutical composition of the present invention in the manufacture of a medicament for the prevention and/or treatment of an HBV infection (for example, a human) or a disease associated with HBV infection (for example, hepatitis B) in a subject, for neutralizing a virulence of HBV in vitro or in a subject (for example, a human), for reducing a serum level of HBV DNA and/or HBsAg in a subject (for example, a human), and/or for activating a humoral immune response to HBV in a subject (for example, a patient with chronic HBV infection or chronic hepatitis B).

In another aspect, the present invention provides a method for preventing or treating an HBV infection or a disease associated with HBV infection (for example, hepatitis B) in a subject (for example, a human), for neutralizing a virulence of HBV in vivo or in a subject (for example, a human), for reducing a serum level of HBV DNA and/or HBsAg in a subject (for example, a human), and/or for activating a humoral immune response to HBV in a subject (for example, a patient with chronic HBV infection or chronic hepatitis B), the method comprises administering an effective amount of the antibody or antigen-binding fragment thereof according to the present invention or the pharmaceutical composition according to the present invention to a subject in need thereof.

The drugs and pharmaceutical compositions provided by the present invention can be used alone or in combination, and can also be used in combination with other pharmaceutically active agents (for example, other antiviral agents, such as interferon drugs, such as interferon or pegylated interferon).

The antibody or antigen-binding fragment thereof of the present invention or the pharmaceutical composition of the present invention can be administered by a traditional route of administration, including but not limited to oral, buccal, sublingual, ocular, topical, parenteral, rectal, intrathecal, intracytoplasmic reticulum, inguinal, intravesical, topical (e.g., powder, ointment or drops), or nasal route. The antibody or antigen-binding fragment thereof of the present invention can be administered by various methods known in the art. However, for many therapeutic applications, the preferred route/mode of administration is parenteral administration (for example, intravenous injection, subcutaneous injection, intraperitoneal injection, intramuscular injection). The skilled person should understand that the route and/or mode of administration will vary according to the intended purpose. In a preferred embodiment, the antibody or antigen-binding fragment thereof of the present invention is administered by intravenous infusion or injection.

The antibody or antigen-binding fragment thereof of the present invention or the pharmaceutical composition of the present invention can be formulated into a variety of dosage forms, such as liquid, semisolid, and solid forms, for example, solution (e.g. injection), dispersion or suspension, tablet, powder, granule, emulsion, pill, syrup, powder, liposome, capsule and suppository. The preferred dosage form depends on the intended mode of administration and therapeutic use.

For example, one preferred dosage form is an injection. Such an injection may be a sterile injectable solution. For example, a sterile injectable solution can be prepared by the following method: a necessary dose of the antibody or an antigen binding fragment thereof according to the invention is incorporated into a suitable solvent, and optionally, other expected ingredients (including, but not limited to, a pH regulator, a surfactant, an adjuvant, an ionic strength enhancer, an isotonic agent, a preservative, a diluent, or any combination thereof) are incorporated simultaneously, and then filtered sterilization is carried out. In addition, the sterile injectable solution can be prepared into a sterile powder (for example, by vacuum drying or freeze drying) for the convenience of storage and use. Such sterile powder can be dispersed in a suitable vehicle before use, such as sterile pyrogen-free water.

Another preferred dosage form is a dispersion. A dispersion can be prepared by the following method: the antibody or an antigen binding fragment thereof according to the invention is incorporated in a sterile vehicle comprising a basic dispersion medium and optionally, other expected ingredients (including, but not limited to, a pH regulator, a surfactant, an adjuvant, an ionic strength enhancer, an isotonic agent, a preservative, a diluent, or any combination thereof). In addition, an absorption delaying agent can also be incorporated in a dispersion, such as monostearate salt and gelatin, in order to obtain an expected pharmacokinetic property.

Another preferred dosage form is an oral solid dosage form, including capsule, tablet, powder, granule, and the like. Such a solid dosage form generally comprises at least one of: (a) inert drug excipient (or vehicle), such as sodium citrate and calcium phosphate; (b) filler, such as starch, lactose, sucrose, mannose and silicic acid; (c) binder, such as carboxymethyl cellulose, alginate, gelatin, polyvinylpyrrolidone, sucrose and arabic gum; (d) wetting agent, such as glycerol; (e) disintegrating agent, such as agar, calcium carbonate, potato or tapioca starch; (f) retarder, such as olefin; (g) absorption enhancer, such as quaternary ammonium compound; (h) humectant, such as cetyl alcohol and glyceryl monostearate; (i) adsorbent, such as kaolin and bentonite; (j) lubricant, such as talc, calcium stearate, magnesium stearate, solid polyethylene glycol, sodium dodecyl sulfate, or any combination thereof. In the case of tablet and capsule dosage forms, a buffer can also be comprised.

In addition, a release rate modifier (i.e. an agent capable of changing drug release rate) may also be added to an oral solid dosage form, in order to obtain a modified release or pulsed release dosage form. Such a release rate modifier includes, but is not limited to carboxypropyl methylcellulose, methylcellulose, carboxymethyl cellulose sodium, ethyl cellulose, cellulose acetate, polyethylene oxide, xanthan gum, isoacrylic amino copolymer, hydrogenated flavoring oil, carnauba wax, paraffin, cellulose acetate phthalate, carboxypropyl methylcellulose phthalate, methacrylic acid copolymer, or any combination thereof. A modified release or pulsed release dosage form may comprise one or a group of release rate modifiers.

Another preferred dosage form is an oral liquid dosage form, including emulsion, solution, suspension, syrup, and the like. In addition to active ingredients, such an oral liquid dosage form may further comprise inert solvents commonly used in the art, for example water or other solvents, such as ethyl alcohol, isopropanol, propylene glycol, 1,3-butylene glycol, oil (such as cotton seed oil, peanut oil, corn oil, olive oil, flavoring oil and sesame oil), glycerol, polyethylene glycol and sorbitan fatty acid ester, and any combination thereof. In addition to these inert solvents, such an oral liquid dosage form may further comprise humectant, emulsifying agent, suspending agent, sweetening agent, flavoring agent, fragrant agent, and the like.

In addition, the antibody or an antigen binding fragment thereof according to the invention may be present in a unit dosage form in a pharmaceutical composition, for the convenience of administration. The pharmaceutical composition according to the invention should be sterile, and stable under the conditions of manufacture and storage conditions.

The medicament and pharmaceutical composition provided in the invention may be used alone or in combination, or may be used in combination with an additional pharmaceutically active agent (for example, other antiviral agents, e.g. interferon-type agents, such as interferon or pegylated interferon). In some preferred embodiments, the antibody or an antigen binding fragment thereof according to the invention is used in combination with other antiviral agent(s), in order to prevent and/or treat a disease associated with HBV infection. The antibody or an antigen binding fragment thereof according to the invention and such antiviral agent(s) can be administered simultaneously, separately or sequentially. Such antiviral agent(s) include, but are not limited to, interferon-type agents, ribavirin, adamantane, hydroxyurea, IL-2, L-12 and pentacarboxy cytosolic acid, etc.

The pharmaceutical composition according to the invention may comprise “a therapeutically effective amount” or “a prophylactically effective amount” of the antibody or an antigen binding fragment thereof according to the invention. “A prophylactically effective amount” refers to an amount that is sufficient to prevent, suppress or delay the development of a disease (such as HBV infection or a disease associated with HBV infection). “A therapeutically effective amount” refers to an amount that is sufficient to cure or at least partially suppress a disease and its complications in a patient with the disease. The therapeutically effective amount of the antibody or an antigen binding fragment thereof according to the invention may vary depending on the following factors: the severity of a disease to be treated, general state of the immune system in a patient, general conditions of a patient such as age, weight and gender, administration modes of drugs, additional therapies used simultaneously, and the like.

A dosage regimen can be adjusted to provide an optimal desired effect (for example, a therapeutic or prophylactic effect). For example, a single dose may be administered, or multiple doses may be administered within a period of time, or the dose can be proportionally reduced or increased as indicated by the exigencies of the therapeutic situation.

For the antibody or antigen binding fragment thereof according to the invention, an exemplary and non-limiting range for a therapeutically or prophylactically effective amount is from 0.025 to 50 mg/kg, more preferably from 0.1 to 50 mg/kg, more preferably 0.1-25 mg/kg, 0.1-10 mg/kg. It should be noticed that a dose can vary depending on the type and severity of a disease to be treated. In addition, a person skilled in the art understands that for any specific patient, specific dosage regimen should be adjusted over time depending on the patient's need and the professional evaluation made by a doctor; the dose range provided here is only provided for the purpose of exemplification, rather than defining the use or scope of the pharmaceutical composition according to the invention.

Kit and Detection Use

The antibody or antigen-binding fragment thereof of the present invention can specifically bind to HBsAg, so that it can be used to detect the presence or level of HBsAg in a sample.

Therefore, in another aspect, the present invention provides a kit comprising the antibody or antigen-binding fragment thereof of the present invention. In some embodiments, the antibody or antigen-binding fragment thereof of the present invention bears a detectable label. In other embodiments, the kit further comprises a second antibody, which specifically recognizes the antibody or antigen-binding fragment thereof of the present invention. Preferably, the second antibody further comprises a detectable label. Such detectable labels are well known to those skilled in the art, and include, but are not limited to, radioisotope, fluorescent substance, luminescent substance, colored substance and enzyme (for example, horseradish peroxidase) and the like.

In another aspect, the present invention provides a method for detecting the presence or level of HBsAg protein in a sample, which comprises: using the antibody or antigen-binding fragment thereof of the present invention. In some embodiments, the antibody or antigen-binding fragment thereof of the present invention further comprises a detectable label. In other embodiments, the method further comprises using a second antibody carrying a detectable label to detect the antibody or antigen-binding fragment thereof of the present invention. The method can be used for diagnostic purposes, or for non-diagnostic purposes (for example, the sample is a cell sample, not a sample from a patient).

In some embodiments, the method comprises: (1) contacting the sample with the antibody or antigen-binding fragment thereof of the present invention; (2) detecting the formation of a complex between the antibody or antigen-binding fragment thereof and HBsAg protein or detecting an amount of the complex. The formation of the complex indicates the presence of HBsAg protein and/or HBV.

In another aspect, the present invention provides a method for diagnosing whether a subject is infected with HBV, which comprises: using the antibody or antigen-binding fragment thereof of the present invention to detect the presence of HBsAg protein in a sample from the subject. In some embodiments, the antibody or antigen-binding fragment thereof of the present invention further comprises a detectable label. In other embodiments, the method further comprises using a second antibody carrying a detectable label to detect the antibody or antigen-binding fragment thereof of the present invention.

In another aspect, there is provided a use of the antibody or antigen-binding fragment thereof of the present invention in the manufacture of a kit for detecting the presence or level of HBsAg protein in a sample, or for diagnosing whether a subject is infected with HBV.

Definition of Terms

In the present invention, unless otherwise specified, the scientific and technical terms used herein have the meanings commonly understood by those skilled in the art. Moreover, the cell culture, biochemistry, nucleic acid chemistry, immunology laboratory and other operating steps used in this article are all routine steps widely used in the corresponding fields. At the same time, in order to better understand the present invention, definitions and explanations of related terms are provided below.

As used herein, the term “antibody” refers to an immunoglobulin molecule typically composed of two pairs of polypeptide chains, each pair having a light chain (LC) and a heavy chain (HC). Antibody light chains can be classified into κ (kappa) and λ (lambda) light chains. Heavy chains can be classified as μ, δ, γ, α, or ε, and the isotypes of antibody are defined as IgM, IgD, IgG, IgA, and IgE, respectively. Within the light and heavy chains, the variable and constant regions are connected by a “J” region of about 12 or more amino acids, and the heavy chain also comprises a “D” region of about 3 or more amino acids. Each heavy chain is composed of a heavy chain variable region (VH) and a heavy chain constant region (CH). The heavy chain constant region is composed of 3 domains (CH1, CH2, and CH3). Each light chain is composed of a light chain variable region (VL) and a light chain constant region (CL). The light chain constant region is composed of a domain CL. The constant domain does not directly participate in the binding of antibody and antigen, but exhibits a variety of effector functions, such as mediating the binding of immunoglobulin to a host tissue or factor, including various cells of immune system (for example, effector cells) and the first component of classical complement system (C1q). The VH and VL regions can also be subdivided into hypervariable regions (called complementarity determining regions (CDRs)), interspersed with relatively conservative regions called framework regions (FRs). Each VH and VL is composed of 3 CDRs and 4 FRs arranged in the following order: FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4 from the amino terminus to the carboxy terminus. The variable regions (VH and VL) of each heavy chain/light chain pair form antigen binding site respectively. The assignment of amino acids in each region or domain can follow the definitions of Kabat, Sequences of Proteins of Immunological Interest (National Institutes of Health, Bethesda, Md. (1987 and 1991)), or Chothia & Lesk (1987) J. Mol. Biol. 196:901-917; Chothia et al. (1989) Nature 342:878-883.

As used herein, the term “complementarity determining region” or “CDR” refers to amino acid residues in a variable region of an antibody that are responsible for antigen binding. Each of the variable regions of the heavy chain and the light chain contains three CDRs, named CDR1, CDR2, and CDR3. The precise boundaries of these CDRs can be defined according to various numbering systems known in the art, for example, according to the Kabat numbering system (Kabat et al., Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, National Institutes of Health, Bethesda, Md., 1991), Chothia numbering system (Chothia & Lesk (1987) J. Mol. Biol. 196:901-917; Chothia et al. (1989) Nature 342:878-883) or IMGT numbering system (Lefranc et al. al., Dev. Comparat. Immunol. 27:55-77, 2003). For a given antibody, those skilled in the art will easily identify the CDRs defined by each numbering system. Moreover, the correspondence between different numbering systems is well known to those skilled in the art (for example, see Lefranc et al., Dev. Comparat. Immunol. 27:55-77, 2003).

In the present invention, the CDRs contained in the antibody or antigen-binding fragment thereof of the present invention can be determined according to various numbering systems known in the art. In certain embodiments, the CDRs contained in the antibody or antigen-binding fragment thereof of the present invention are preferably determined by the Kabat, Chothia or IMGT numbering system. In certain embodiments, the CDRs contained in the antibody or antigen-binding fragment thereof of the present invention are preferably determined by the Kabat numbering system.

As used herein, the term “framework region” or “FR” residues refers to those amino acid residues in a variable region of an antibody other than the CDR residues as defined above.

The term “antibody” is not limited by any specific method for producing the antibody. For example, it comprises recombinant antibody, monoclonal antibody, and polyclonal antibody. The antibody may be an antibody of different isotype, for example, IgG (for example, IgG1, IgG2, IgG3 or IgG4 subtype), IgA1, IgA2, IgD, IgE or IgM antibody.

As used herein, the term “antigen-binding fragment” of antibody refers to a polypeptide comprising a fragment of a full-length antibody that retains the ability to specifically bind to the same antigen to which the full-length antibody binds, and/or competes with the full-length antibody to specifically bind to the antigen, which is also called “antigen binding portion”. See generally, Fundamental Immunology, Ch. 7 (Paul, W., ed., 2nd edition, Raven Press, NY (1989), which is incorporated herein by reference in its entirety for all purposes. Antigen-binding fragment of antibody can be produced by recombinant DNA technology or by the enzymatic or chemical cleavage of the intact antibody. Non-limiting examples of antigen-binding fragment include Fab, Fab′, F(ab′)2, Fd, Fv, complementarity determining region (CDR) fragments, scFv, diabody, single domain antibody, chimeric antibody, linear antibody, nanobody (technology from Domantis), probody and such polypeptides which comprise at least a portion of the antibody that is enough to confer a specific antigen-binding capacity to the polypeptides. Engineered antibody variants are reviewed in Holliger et al., 2005; Nat Biotechnol, 23: 1126-1136.

As used herein, the term “full-length antibody” refers to an antibody composed of two “full-length heavy chains” and two “full-length light chains.” “full-length heavy chain” refers to a polypeptide composed of a heavy chain variable region (VH), a heavy chain constant region CH1 domain, a hinge region (HR), a heavy chain constant region CH2 domain and a heavy chain constant region CH3 domain in the N-terminal to C-terminal direction; and, when the full-length antibody is of the IgE isotype, it optionally also comprises a heavy chain constant region CH4 domain. Preferably, the “full-length heavy chain” is a polypeptide chain composed of VH, CH1, HR, CH2, and CH3 in the N-terminal to C-terminal direction. The “full-length light chain” is a polypeptide chain composed of a light chain variable region (VL) and a light chain constant region (CL) in the N-terminal to C-terminal direction. The two pairs of full-length antibody chains are connected by a disulfide bond between CL and CH1 and a disulfide bond between HRs of the two full-length heavy chains. The full-length antibody of the present invention can be derived from a single species, such as human; it can also be a chimeric antibody or a humanized antibody. The full-length antibody of the present invention comprises two antigen binding sites formed by VH and VL pairs respectively, and the two antigen binding sites specifically recognize/bind the same antigen.

As used herein, the term “Fd” refers to an antibody fragment composed of VH and CH1 domains; the term “dAb fragment” refers to an antibody fragment composed of VH domain (Ward et al., Nature 341:544 546 (1989)); the term “Fab fragment” refers to an antibody fragment composed of VL, VH, CL and CH1 domains; the term “F(ab′)2 fragment” refers to an antibody fragment composed of two Fab fragments connected by a disulfide bridge on the hinge region; the term “Fab′ fragment” refers to a fragment obtained by reducing the disulfide bond connecting the two heavy chain fragments in the F(ab′)2 fragment, and is composed of an intact light chain and a Fd fragment (consisting of VH and CH1 domains) of heavy chain.

As used herein, the term “Fv” refers to an antibody fragment composed of a single-arm VL and VH domains of an antibody. Fv fragment is generally considered to be the smallest antibody fragment that can form a complete antigen-binding site. It is generally believed that six CDRs confer antigen-binding specificity to an antibody. However, even one variable region (e.g., Fd fragment, which contains only three antigen-specific CDRs) can recognize and bind to antigen, although its affinity may be lower than the complete binding site.

As used herein, the term “Fc” refers to an antibody fragment that is formed by linking the second, third constant region of a first heavy chain of an antibody and the second, third constant region of a second heavy chain via disulfide bonding. The Fc fragment of an antibody has many different functions, but does not participate in antigen binding.

As used herein, the term “scFv” refers to a single polypeptide chain comprising VL and VH domains, wherein the VL and VH are connected by a linker (see, for example, Bird et al., Science 242:423 -426 (1988); Huston et al., Proc. Natl. Acad. Sci. USA 85:5879-5883 (1988); and Pluckthun, The Pharmacology of Monoclonal Antibodies, Vol. 113, Roseburg and Moore eds, Springer-Verlag, New York, pp. 269-315 (1994)). Such scFv molecules may have the general structure: NH2-VL-linker-VH-COOH or NH2-VH-linker-VL-COOH. Suitable prior art linkers consist of repeated GGGGS amino acid sequences or variants thereof. For example, a linker having the amino acid sequence (GGGGS)4 can be used, but variants thereof can also be used (Holliger et al. (1993), Proc. Natl. Acad. Sci. USA 90: 6444-6448). Other linkers that can be used in the present invention are described by Alfthan et al. (1995), Protein Eng. 8:725-731, Choi et al. (2001), Eur. J. Immunol. 31: 94-106, Hu et al. (1996), Cancer Res. 56:3055-3061, Kipriyanov et al. (1999), J. Mol. Biol. 293:41-56 and Roovers et al. (2001), Cancer Immunol. In some cases, there may also be disulfide bonds between the VH and VL of the scFv.

As used herein, the term “diabody” refers to that its VH and VL domains are expressed on a single polypeptide chain, but the used linker is too short to allow pairing between the two domains of the same chain, thereby forcing one domain to pair with the complementary domain of another chain and generating two antigen-binding sites (see, for example, Holliger P. et al., Proc. Natl. Acad. Sci. USA 90: 6444-6448 (1993), and Poljak RJ et al., Structure 2:1121-1123 (1994)).

Each of the aforementioned antibody fragments maintains the ability to specifically bind to the same antigen to which the full-length antibody binds, and/or competes with the full-length antibody to specifically bind to the antigen.

Conventional techniques known to those skilled in the art (for example, recombinant DNA technology or enzymatic or chemical fragmentation) can be used to obtain from a given antibody (for example, the antibody provided by the present invention) the antigen-binding fragments of the antibody (for example, the above-mentioned antibody fragments), and can be screened for specificity in the same manner by which intact antibodies are screened.

Herein, unless the context clearly dictates otherwise, when the term “antibody” is referred to, it includes not only intact antibody but also antigen-binding fragments of the antibody.

As used herein, the term “monoclonal antibody”, “McAb” and “mAb” have the same meaning and can be used interchangeably. It refers to an antibody or a fragment of an antibody from a population of highly homologous antibody molecules, i.e. a population of completely identical antibody molecules except for natural mutation that may occur spontaneously. A monoclonal antibody has a high specificity for a single epitope of an antigen. Polyclonal antibody, relative to monoclonal antibody, generally comprises at least two or more different antibodies which generally recognize different epitopes on an antigen. In addition, the modifier “monoclonal” merely indicates the character of the antibody as being obtained from a highly homogeneous population of antibodies, and is not to be construed as requiring production of the antibody by any particular method.

As used herein, the term “chimeric antibody” refers to an antibody that a part of its light chain or/and heavy chain is derived from an antibody (which may be derived from a specific species or belong to a specific antibody class or subclass), and another part of its light chain or/and heavy chain is derived from another antibody (which may be derived from the same or different species or belong to the same or different antibody class or subclass), but in any case, it still retains the binding activity to the target antigen (U.S. Pat. No. 4,816,567 to Cabilly et al.; Morrison et al., Proc. Natl. Acad. Sci. USA, 81:6851 6855 (1984)). For example, the term “chimeric antibody” may include such an antibody (e.g., human-mouse chimeric antibody), in which the heavy and light chain variable regions of the antibody are derived from a first antibody (e.g., mouse antibody), while the heavy chain and light chain constant regions of the antibody are derived from a second antibody (e.g., human antibody). In order to prepare a chimeric antibody, the methods known in the art can be used to link immunoglobulin variable regions of an immunized animal to human immunoglobulin constant regions (see, for example, U.S. Pat. No. 4,816,567 to Cabilly et al.). For example, a DNA encoding VH is operably linked to another DNA molecule encoding the heavy chain constant region to obtain a full-length heavy chain gene. The sequence of the human heavy chain constant region gene is known in the art (see, for example, Kabat, E A et al. (1991), Sequences of Proteins of Immunological Interest, Fifth Edition, US Department of Health and Human Services, NIH Publication No. 91-3242), the DNA fragments comprising these regions can be obtained by standard PCR amplification. The heavy chain constant region may be an IgG1, IgG2, IgG3, IgG4, IgA, IgE, IgM, or IgD constant region, but is generally preferably an IgG1 or IgG4 constant region. For example, the DNA encoding VL is operably linked to another DNA molecule encoding the light chain constant region CL to obtain a full-length light chain gene (and a Fab light chain gene). The sequence of the human light chain constant region gene is known in the art (see, for example, Kabat, EA et al. (1991), Sequences of Proteins of Immunological Interest, Fifth Edition, US Department of Health and Human Services, NTH Publication No. 91-3242), and DNA fragments comprising these regions can be obtained by standard PCR amplification. The light chain constant region can be a ϵ or λ, constant region, but is generally preferably a κ constant region.

As used herein, the term “humanized antibody” refers to a genetically engineered non-human antibody, whose amino acid sequence has been modified to increase homology with the sequence of a human antibody. Generally speaking, all or part of the CDR regions of a humanized antibody are derived from a non-human antibody (donor antibody), and all or part of the non-CDR regions (for example, variable region FR and/or constant region) are derived from a human immunoglobulin (receptor antibody). In some embodiments, the CDR regions of the humanized antibody are derived from a non-human antibody (donor antibodies), and all or part of the non-CDR regions (for example, variable region FR and/or constant regions) are derived from a human immunoglobulin (receptor antibody). The humanized antibody generally retains the expected properties of the donor antibody, including, but not limited to, antigen specificity, affinity, reactivity, etc. The donor antibody may be a mouse, rat, rabbit, or non-human primate (for example, cynomolgus monkey) antibody with desired properties (for example, antigen specificity, affinity, reactivity, etc.). In order to prepare the humanized antibody, the methods known in the art can be used to insert the CDR regions of the immunized animal into the human framework sequences (see U.S. Pat. No. 5,225,539 to Winter; U.S. Pat. No. 5,530,101 to Queen et al.; U.S. PAt. Nos. 5,585,089; 5,693,762 and 6,180,370; and Lo, Benny, K C, editor, in Antibody Engineering: Methods and Protocols, volume 248, Humana Press, New Jersey, 2004).

As used herein, the term “germline antibody gene” or “germline antibody gene segment” refers to a sequence present in the genome of an organism encoding immunoglobulin, which has not undergone a maturation process that can lead to genetic rearrangements and mutations for expression of a particular immunoglobulin. In the present invention, the expression “heavy chain germline gene” refers to an germline antibody gene or gene fragment encoding an immunoglobulin heavy chain, which includes V gene (variable), D gene (diversity), J gene (joining) and C gene (constant); similarly, the expression “light chain germline gene” refers to an germline antibody gene or gene fragment encoding an immunoglobulin light chain, which includes V gene (variable), J gene (joining), and C gene (constant). In the present invention, the amino acid sequence encoded by the germline antibody gene or the germline antibody gene fragment is also referred to as “germline sequence”. The germline antibody gene or germline antibody gene fragment and their corresponding germline sequences are well known to those skilled in the art and can be obtained or queried from professional databases (e.g., IMGT, unswag, NCBI or VBASE2).

As used herein, the term “specific binding” refers to a non-random binding reaction between two molecules, such as the reaction between an antibody and an antigen to which it is directed. The strength or affinity of a specific binding interaction can be expressed by an equilibrium dissociation constant (KD) of the interaction. In the present invention, the term “KD” refers to a dissociation equilibrium constant of a specific antibody-antigen interaction, which is used to describe the binding affinity between the antibody and the antigen. The smaller the equilibrium dissociation constant, the tighter the antibody-antigen binding, and the higher the affinity between the antibody and the antigen. The specific binding properties between two molecules can be measured using methods known in the art, for example, using surface plasmon resonance (SPR) of BIACORE instrument.

As used herein, the expression “binding at a neutral pH with an affinity higher than that at an acidic pH” or the equivalent expression “pH-dependent binding” refers to that the antibody of the present invention has a KD value or EC50 value for binding HBsAg at an acidic pH that is higher than its KD value or EC50 value for binding HBsAg at a neutral pH. The KD can be measured by a technique known in the art, for example, by SPR technique (for example, Biacore). In the present invention, the term “EC50” refers to an antibody-antigen half maximum effect concentration, that is, an antibody concentration required to reach 50% of the maximum binding effect between a specific antibody-antigen, and it is used to describe the binding capacity between the antibody and the antigen. The smaller the EC50, the higher the binding capacity between the antibody and the antigen. The antibody-antigen half maximum effect concentration (EC50) can be determined using methods known in the art, for example, using an enzyme-linked immunosorbent assay (ELISA) in which an antigen is bound to a solid phase carrier, and the antibody specifically binds to the antigen.

As used herein, “neutralizing antibody” refers to an antibody or antigen-binding fragment thereof that can significantly reduce or completely inhibit the virulence (for example, the ability to infect cells) of the target virus. Generally speaking, neutralizing antibodies can recognize and bind the target virus, and prevent the target virus from entering/infecting the subject's cells. The antibody of the present invention is a neutralizing antibody.

However, it should be understood that in the present application, the virus-neutralizing ability of an antibody is not directly equivalent to the virus-clearing ability of an antibody. As used herein, “neutralizing virus” means that the virulence of a target virus is neutralized (i.e. the virulence of a target virus is significantly reduced or completely inhibited) by inhibiting the target virus from entering/infecting the cell of a subject. As used herein, “clearing virus” means that a target virus (no matter it infects a cell or not) is eliminated from an organism, and therefore the organism turns toward the state before infection by the virus (e.g. the serological test result of virus turns negative). Therefore, in general, neutralizing antibodies do not necessarily have virus-clearing ability. However, in the present application, the inventor surprisingly found that the antibodies according to the invention can not only neutralize HBV, but also clear virus (i.e. can clear HBV DNA and/or HBsAg in vivo, clear HBV and HBV-infected cells in vivo), and therefore have important clinical value.

As used herein, the term “isolated” refers to a state obtained from natural state by artificial means. If a certain “isolated” substance or component is present in nature, it is possible because its natural environment changes, or the substance is isolated from natural environment, or both. For example, a certain un-isolated polynucleotide or polypeptide naturally exists in a certain living animal body, and the same polynucleotide or polypeptide with a high purity isolated from such a natural state is called isolated polynucleotide or polypeptide. The term “isolated” excludes neither the mixed artificial or synthesized substance nor other impure substances that do not affect the activity of the isolated substance.

As used herein, the term “vector” refers to a nucleic acid vehicle into which a polynucleotide can be inserted. When a vector enables the expression of a protein encoded by an inserted polynucleotide, the vector is referred to as an expression vector. A vector can be introduced into a host cell by transformation, transduction or transfection, so that the genetic material elements carried by the vector can be expressed in the host cell. Vectors are well known to those skilled in the art and include, but are not limited to: plasmids; phagemids; cosmids; artificial chromosomes, such as yeast artificial chromosomes (YAC), bacterial artificial chromosomes (BAC) or P1-derived artificial chromosomes (PAC); bacteriophages such as λ phage or M13 phage and animal viruses. Animal viruses that can be used as vectors include, but are not limited to, retroviruses (including lentiviruses), adenoviruses, adeno-associated viruses, herpes viruses (e.g., herpes simplex virus), poxviruses, baculoviruses, papillomaviruses, papovavirus (e.g., SV40). A vector may comprise a variety of elements that control expression, including, but not limited to, promoter sequence, transcription initiation sequence, enhancer sequence, selection element, and reporter gene. In addition, the vector may comprise a replication initiation site.

As used herein, the term “host cell” refers to a cell into which a vector can be introduced, which includes, but is not limited to, prokaryotic cell such as Escherichia coli or Bacillus subtilis, fungal cell such as yeast cell or Aspergillus, insect cell such as S2 Drosophila cell or Sf9, or animal cell such as fibroblast, CHO cell, COS cell, NSO cell, HeLa cell, BHK cell, HEK 293 cell or human cell.

As used herein, the term “identity” refers to the match degree between two polypeptides or between two nucleic acids. When two sequences for comparison have the same monomer sub-unit of base or amino acid at a certain site (e.g., each of two DNA molecules has an adenine at a certain site, or each of two polypeptides has a lysine at a certain site), the two molecules are identical at the site. The percent identity between two sequences is a function of the number of identical sites shared by the two sequences over the total number of sites for comparison×100. For example, if 6 of 10 sites of two sequences are matched, these two sequences have an identity of 60%. For example, DNA sequences: CTGACT and CAGGTT share an identity of 50% (3 of 6 sites are matched). Generally, the comparison of two sequences is conducted in a manner to produce maximum identity. Such alignment can be conducted by using a computer program such as Align program (DNAstar, Inc.) which is based on the method of Needleman, et al. (J. Mol. Biol. 48:443-453, 1970). The percent identity between two amino acid sequences can also be determined using the algorithm of E. Meyers and W. Miller (Comput. Appl. Biosci., 4:11-17 (1988)) which has been incorporated into the ALIGN program (version 2.0), using a PAM120 weight residue table, a gap length penalty of 12 and a gap penalty of 4. In addition, the percentage of identity between two amino acid sequences can be determined by the algorithm of Needleman and Wunsch (J. Mol. Biol. 48:444-453 (1970)) which has been incorporated into the GAP program in the GCG software package (available at http://www.gcg.com), using either a Blossum 62 matrix or a PAM250 matrix, and a gap weight of 16, 14, 12, 10, 8, 6, or 4 and a length weight of 1, 2, 3, 4, 5, or 6.

The twenty conventional amino acids involved herein are expressed in routine manners. See, for example, Immunology-A Synthesis (2nd Edition, E. S. Golub and D. R. Gren, Eds., Sinauer Associates, Sunderland, Mass. (1991)), which is incorporated herein by reference. In the present disclosure, the terms “polypeptide” and “protein” have the same meaning and are used interchangeably. Also in the present disclosure, amino acids are generally represented by single letter and three letter abbreviations as known in the art. For example, alanine can be represented by A or Ala. In addition, as used herein, the terms “monoclonal antibody” and “McAb” have the same meaning and can be used interchangeably; the terms “polyclonal antibody” and “PcAb” have the same meaning and can be used interchangeably.

As used herein, the term “a pharmaceutically acceptable carrier and/or excipient” refers to a carrier and/or excipient pharmacologically and/or physiologically compatible with a subject and an active agent, which is well known in the art (see, e.g., Remington's Pharmaceutical Sciences. Edited by Gennaro A R, 19th ed. Pennsylvania: Mack Publishing Company, 1995), and includes, but is not limited to a pH adjuster, a surfactant, an adjuvant, an ionic strength enhancer, a diluent, an osmotic pressure-controlling agent, an absorption delaying agent, and a preservative. For example, the pH adjuster includes, but is not limited to, phosphate buffer. The surfactant includes, but is not limited to, cationic, anionic, or non-ionic surfactant, e.g. Tween-80. The ionic strength enhancer includes, but is not limited to, sodium chloride. The preservative includes, but is not limited to a variety of antibacterial agents and antifungal agents, such as paraben, chlorobutanol, phenol, and sorbic acid. The osmotic pressure-controlling agent includes, but is not limited to sugar, NaCl and analogs thereof. The absorption delaying agent includes, but is not limited to monostearate and gelatin.

As used herein, the term “prevention/preventing” refers to a method that is carried out in order to suppress or delay the occurrence of a disease, a disorder or a symptom (such as HBV infection or a disease associated with HBV infection) in a subject. As used herein, the term “treatment/treating” refers to a method that is carried out in order to obtain a beneficial or desired clinical outcome. For the purpose of the invention, the beneficial or desired clinical outcome includes, but is not limited to, easing symptom, narrowing the scope of disease, stabilizing (i.e. not aggravating) the state of disease, delaying or slowing the progress of disease, and alleviating symptoms (either partially or completely), no matter detectable or not detectable. In addition, “treatment” also refers to a prolonged survival period compared to the expected survival period (if no treatment is accepted). In the present application, the antibody according to the invention has the ability of neutralizing HBV, and therefore can be used to prevent/protect an unaffected subject or a cell thereof from infection by HBV. In addition, the antibody according to the invention has the ability of clearing HBV (i.e. able to clear HBV DNA and/or HBsAg in vivo, clear HBV and cells infected by HBV in vivo), and therefore can be used to treat HBV infection or a disease associated with HBV infection in an infected subject.

As used herein, the term “subject” refers to a mammal, such as a primate mammal, such as a human.

As used herein, the term “an effective amount” refers to an amount that is sufficient to achieve or at least partially achieve the expected effect. For example, an amount effective for preventing a disease (such as HBV infection or diseases associated with HBV infection) refers to an amount effective for preventing, suppressing, or delaying the occurrence of a disease (such as HBV infection or diseases associated with HBV infection). An effective amount for treating a disease refers to an amount effective for curing or at least partially blocking a disease and its complication in a patient having the disease. The determination of such an effective amount is within the ability of a person skilled in the art. For example, an amount effective for a therapeutic use depends on severity of a disease to be treated, general state of the immune system in a patient, general conditions of a patient, such as age, weight and gender, administration means of drugs, additional therapies used simultaneously, and the like.

Beneficial Effects of the Present Invention

The antibody of the present invention not only can specifically recognize/bind HBsAg, can neutralize the virulence of HBV, can reduce the serum level of HBV DNA and/or HBsAg in the subject, and can effectively eliminate HBV and HBV-infected cells in the body, but also has a significantly enhanced antigen clearance effect and antigen suppression time. It is particularly surprising that it is known in the art that patients with chronic hepatitis B tend to produce immune depletion (tolerance) against HBV due to high levels of HBsAg in the body, thereby prolonging the infection, but the antibody of the present invention can activate the subject (for example patients with chronic HBV infection, or patients with chronic hepatitis B) to regenerate a humoral immune response against HBV, thereby increasing the clinical cure rate. Therefore, the antibody of the present invention is particularly suitable for preventing and treating HBV infection and diseases associated with HBV infection (for example, hepatitis B). In addition, the antibody of the present invention has pH-dependent antigen binding properties, and a single molecule of antibody can bind to multiple molecules of antigens, so that it can also reduce the frequency and dosage of administration, and has great clinical value.

The embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings and examples. However, those skilled in the art will understand that the following drawings and examples are only used to illustrate the present invention, but not to limit the scope of the present invention. According to the accompanying drawings and the following detailed description of the preferred embodiments, various objects and advantageous aspects of the present invention will become apparent to those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic diagram of the working principle of an antibody with pH-dependent antigen-binding activity. Human plasma is neutral, with a pH of about 7.4, while the intracellular environment is acidic, with a pH of about 6.0. An antibody with pH-dependent antigen-binding activity can bind to an antigen in the plasma, the antigen-antibody complex is then internalized into the cell. The pH-dependent antibody will dissociate from the antigen in the acidic environment of the endosome. The antibody dissociated from the antigen will be captured by FcRn and circulated to the outside of the cell. In the extracelluar neutral environment, the FcRn releases the antibody, and the antibody returned to the plasma can bind to other antigen again, thereby realizing the cycle use of the antibody.

FIG. 2 shows the results of docking of Fab crystal structure based on the structural analysis of 162 to a short antigen mimic peptide, in which the blue structure is the short antigen peptide, and the red structure is part of the binding region of 162 antibody.

FIG. 3 shows a schematic diagram of the recombinant vector (pCGMT-scFv) encoding the scFv antibody, in which the scFv antibody has a structure of: NH2-VH-linker-VL-COOH.

FIGS. 4A to 4D show the ELISA results of the phage library displaying the pH-dependent scFv antibody derived from 162 and the antigen HBsAg. FIG. 4A: the detection results of binding to HBsAg at pH 7.4 and pH 6.0 for the phage library derived from 162 after the third round of screening, the abscissa represents the phage antibody number, and the ordinate represents the OD value. The results show that these single clones all have strong antigen binding activity and have a significant decrease in binding activity at pH 6.0. FIG. 4B: the detection results of pH-dependent binding to HBsAg for the 13 single clones with high OD(450/630) value at pH 7.4 in the third round and showing the largest difference between OD(450/630) values at pH7.4 and pH 6.0, with 8 gradients and 3-fold dilution, in which the abscissa represents the dilution factor, and the ordinate represents the OD value. The results show that the pH-dependent antigen binding effect is better presented after the gradient dilution, in which the C32, C27, C26 and C19 show the better performance and C27 molecule has the best effect (the remaining 9 molecules are not shown). FIG. 4C: the detection results of binding to HBsAg at pH 7.4 and pH 6.0 for the phage library derived from 162 after the fourth round of screening, the abscissa represents the phage antibody number, and the ordinate represents the OD value. FIG. 4D: the detection results of pH-dependent binding to HB sAg for the 8 single clones with high OD(450/630) value at pH 7.4 in the fourth round and showing the largest difference between OD(450/630) values at pH 7.4 and pH 6.0, with 8 gradients and 3-fold dilution, in which the abscissa represents the dilution factor, and the ordinate represents the OD value. The results show that the pH-dependent antigen binding effect is better presented after the gradient dilution, in which D3, D4 and D5 show the better performance, and D5 molecule has the best effect (the remaining 5 molecules are not shown).

FIG. 5 shows a summary of the mutation sites of C26, C27, C32, D3, D4 and D5.

FIG. 6A shows the detection results of binding to HBsAg at pH 7.4 and pH 6.0 for the quantified cell supernatant obtained from the small scale eukaryotic transfection of C32, C27 and C26 in Example 3. FIG. 6B shows the detection results of binding to HBsAg at pH 7.4 and pH 6.0 for the quantified cell supernatant obtained from the small scale eukaryotic transfection of D3, D4 and D5 in Example 3. The abscissa represents the antibody concentration (Log 10 ng/ml), and the ordinate represents the OD value. The results show that C32, C27, C26, D3, D4 and D5 all can maintain an antigen-binding activity equivalent to that of the parent antibody 162 at neutral pH, and all have a significant decrease in binding activity to antigen at pH 6.0.

FIG. 7 shows the working principle of scavenger antibody. The pH-dependent antigen binding activity plays a role in cells. Thus, if this first limiting factor of cell entry is not broken, the pH-dependent antigen-binding properties will not be applied subsequently, and the benefit of modification will be greatly reduced. A scavenger antibody obtained by further mutation of amino acids in the Fc region can enhance the binding to hFcRn receptor at neutral pH, or enhance the binding to FcγRs receptor. Tthe scavenger antibody is located outside the cell and acts as a “transport helper” for reciprocally transporting antigens into the cell, the antibody half-life can thus be extremely prolonged, and it can bind to antigen again, thereby improving the cell entry efficiency of antigens, and greatly improving the clearance efficiency.

FIGS. 8A to 8B show the protein gel results of pH-dependent antibodies and antibodies with DY modification. FIG. 8A: the picture of protein gel of pH-dependent antibodies, in which 162 is a positive control, and the results show that the expressed C26, D3, D4 and D5 antibodies are single-component. FIG. 8B: the picture of protein gel of antibodies with DY modification, in which 162 is a positive control, and the results show that the expressed antibodies C26 DY, D3 DY, D4 DY and D5 DY are single-component.

FIGS. 9A to 9D show the detection results of pH-dependent antibodies and antibodies with DY modification binding to HBsAg at pH 7.4 and pH 6.0 in Example 4, in which the abscissa represents the antibody concentration (Log 10 ng/ml) and the ordinate represents the OD value. The results show that D26, D3, D4 and D5 can maintain an antigen-binding activity equivalent to that of the parent (162) at the neutral pH, and have a significant decrease in antigen-binding activity under the condition of pH 6.0, and the corresponding antibodies with DY modification also can maintain an antigen-binding activity at the neutral pH and a pH-dependent antigen-binding activity comparable to those of the parent.

FIG. 10A shows the immunofluorescence experiment of mouse primary macrophages for the pH-dependent antibodies and antibodies with DY modification in Example 4, in which the green fluorescence represents hFcRn, the blue fluorescence represents nucleus, and the red fluorescence represents HBsAg. The results show that the DY modification enhances the phagocytosis of murine macrophages to the antigen-antibody complexes. FIG. 10B shows phagocytosis experiment based on human THP-1 phagocytic cells of the pH-dependent antibodies and the antibodies with DY modification in Example 4. The results show that the DY modification enhances the phagocytosis of human THP-1 phagocytic cells to the antigen-antibody complexes.

FIGS. 11A to 11B show the therapeutic effects of the C26 DY scavenger antibody and 162 in HBV transgenic mice after injection with a single dose of 5 mg/kg via tail vein in Example 4. FIG. 11C shows the therapeutic effects of the D3 DY, D3 DY, D4 DY and D5 DY in HBV transgenic mice after injection with a single dose of 5 mg/kg via tail vein in Example 4. FIG. 11A: the abscissa represents the number of days (d) after the injection of antibody, and the ordinate represents the HBsAg level in mouse serum after clearance (log 10 IU/ml). FIG. 11B shows: the changes in the concentration of antibody in mouse serum, in which the abscissa represents the number of days (d) after the injection of antibody, and the ordinate represents the antibody concentration (ng/ml). FIG. 11C: the abscissa represents the number of days (d) after the injection of antibody, and the ordinate represents the HBsAg level in mouse serum after clearance (log 10 IU/ml). The results show that the scavenger antibodies with DY modification C26 DY, D3 DY, D4 DY and D5 DY are stronger in antigen clearance ability by more than one order of magnitude than 162. This indicates that the scavenger antibodies with DY modification C26 DY, D3 DY, D4 DY and D5 DY could play the function of cyclically binding antigens and enhance the effect of antigen clearance at alow injection dose of 5 mg/kg.

 SEQUENCE INFORMATION

Information of partial sequences involved in the present invention is provided in Table 1 below.

TABLE 1 Description of sequences SEQ ID NO Description  Sequence information  1 162 VH EVQLQESGPGLVKPSQTLSLTCAVSGSSITYGYHWNWIRQFPGNKLE WIGYISYDGSVLYNPSLENRVTITRDTSKNQFFLKLSSVTAEDTAKYY CASGFDHWGQGTTLTVSS  2 C27 VK DVVMTQSPLSLPVTLGEPASISCRSSQSLVHSYGDTYLHWYLQKPGQS PKLLIYKVSNRFSGVPDRFSGSGSGTDFTLKISRVETEDLGVYYCSQNT HVPYTFGGGTKLEIK  3 C26 D4 D5 VH EVQLQESGPGLVKPSQTLSLTCAVSGSSITHGYHWNWIRQFPGNKLE WIGYIHYDGSVLYNPSLENRVTITRDTSKNQFFLKLSSVTAEDTAKYY CASGFDHWGQGTTLTVSS  4 C26 VK DVVMTQSPLSLPVTLGEPASISCRSSQSLVHSYGDTYLHVVYLQKPGQS PKLLIYKVSNRFSGVPDRFSGSGSGTDFTLKISRVETEDLGVYYCSQNT HHPYTFGGGTKLEIK  5 C27 VH EVQLQESGPGLVKPSQTLSLTCAVSGSSITHGYHWNWIRQFPGNKLE WIGYINHDGSVLYNPSLENRVTITRDTSKNQFFLKLSSVTAEDTAKYY CASGFDHWGQGTTLTVSS  6 C32 VH EVQLQESGPGLVKPSQTLSLTCAVSGSSITYRYHWNWIRQFPGNKLE WIGYINYDGSVHYNPSLENRVTITRDTSKNQFFLKLSSVTAEDTAKYY CASGFDHWGQGTTLTVSS  7 C32 VK DVVMTQSPLSLPVTLGEPASISCRSSQSLVHSYGDTYLHVVYLQKPGQS PKLLIYKVSNRFSGVPDRFSGSGSGTDFTLKISRVETEDLGVYYCSQNT HLPYTFGGGTKLEIK  8 D3 VH EVQLQESGPGLVKPSQTLSLTCAVSGSSITHGYHYNWIRQFPGNKLEW IGYIHYDGSVLYNPSLENRVTITRDTSKNQFFLKLSSVTAEDTAKYYC ASGFDHWGQGTTLTVSS  9 D3 D5 VK DVVMTQSPLSLPVTLGEPASISCRSSQSLVHSYGDNYLHWYLQKPGQ SPKLLIYKVSNRFSGVPDRFSGSGSGTDFTLKISRVETEDLGVYYCSQN THVPYTFGGGTKLEIK 10 D4 VK DVVMTQSPLSLPVTLGEPASISCRSSQSLVHSYGDNYLHWYLQKPGQ SPKLLIYKVSNRFSGVPDRFSGSGSGTDFTLKISRVETEDLGVYYCSQN THLPYTFGGGTKLEIK 11 162 YGYHWN HCDR1 12 162 D3 D4 D5 YISYDGSVLYNPSLEN HCDR2 13 162 C26 C27 C32 GFDH D3 D4 D5 HCDR3 14 162 C26 C27 C32 RSSQSLVHSYGDTYLH LCDR1 15 162 C26 C27 C32 KVSNRFS D3 D4 D5 LCDR2 16 162 C27 D3 D5 SQNTHVPYT LCDR3 17 C26 C27 D4 D5 HGYHWN HCDR1 18 C26 YIHYDGSVLYNPSLEN HCDR2 19 C26 SQNTHHPYT LCDR3 20 C27 YINHDGSVQYNPSLEN HCDR2 21 C32 YRYHWN HCDR1 22 C32 YINYDGSVHYNPSLEN HCDR2 23 C32 D4 SQNTHLPYT LCDR3 24 D3 HGYHYN HCDR1 25 D3 D4 D5 RSSQSLVHSYGDNYLH LCDR1 26 General formula of X1X1YHX1N HCDR1 27 General formula of YIX4X5DGSVX6YNPSLEN HCDR2 28 General formula of RSSQSLVHSYGDX7YLH LCDR1 29 General formula of SQNTHX8PYT LCDR3 30 C26 C27 C32 D3 D4 EVQLQESGPGLVKPSQTLSLTCAVSGSSIT D5 HFR1 31 C26 C27 C32 D3 D4 WIRQFPGNKLEWIG D5 HFR2 32 C26 C27 C32 D3 D4 RVTITRDTSKNQFFLKLSSVTAEDTAKYYCAS D5 HFR3 33 C26 C27 C32 D3 D4 WGQGTTLTVSS D5 HFR4 34 C26 C27 C32 D3 D4 DVVMTQSPLSLPVTLGEPASISC D5 LFR1 35 C26 C27 C32 D3 D4 WYLQKPGQSPKLLIY D5 LFR2 36 C26 C27 C32 D3 D4 GVPDRFSGSGSGTDFTLKISRVETEDLGVYYC D5 LFR3 37 C26 C27 C32 D3 D4 FGGGTKLEIK D5 LFR4 38 4-28-02 QVQLQESGPGLVKPSQTLSLTCAVSGYSISSSNWWGW1RQPPGKGLE WIGYIYYSGSIYYNPSLKSRVTMSVDTSKNQFSLKLSSVTAVDTAVYY CAR 39 2D-28-01 DIVMTQSPLSLPVTPGEPASISCRSSQSLLHSNGYNYLDWYLQKPGQS PQLLIYLGSNRASGVPDRFSGSGSGTDFTLKISRVEAEDVGVYYC 40 Human IgG1 heavy ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTS chain constant GVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDK region KVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMTSRTPEVTCV VDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTV LHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSR DELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDG SFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK 41 Human κ light chain RTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKVDSAL constant region QSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVTHQGL SSPVTKSFNRGEC 42 Human IgG1 heavy ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTS chain constant GVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDK region with V4 KVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLYISRTPEVTCV mutation VVDVSHEDPEVKFNWYVDGVEVHEAKTKPREEQYNSTYRVVSVLTV LHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSR DELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDG SFFLYSKLTVDKSRWQQGNVFSCSVMHEALHYHYTQKSLSLSPGK 43 Human IgG1 heavy ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTS chain constant GVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDK region with DY KVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCV mutation VVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTV LHQDWLNGKEYKCKVSNDAYPAPIEKTI SKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESN GQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEA LHNHYTQKSLSLSPGK 44 Primer 5′>GTTATTACTCGTGGCCCAGCCGGCCATGGCAGAGGTGCAGCTGC AGGAGTC <3′ 45 Primer 5′>CTCCAGCTTGTTCCCTGGGAACTGCCGGATCCAGTTSYRGTGGT RGYSGTRGGTGATGGAGCTACCAGA <3′ 46 Primer 5′>GTTCCCAGGGAACAAGCTGGAGTGGATTGGGYACMWCMRCYA CSACGGCAGCSWYCWSYACAATCCATCTCTCG <3′ 47 Primer 5′>GACTGTGAGAGTTGTGCCTTGGCCCCAGTGGTSGWRACCACTCG CACAGTA <3′ 48 Primer 5′>CCAGATCCGCCACCTCCACTCCCGCCTCCACCTGAGGAGACTGT GAGAGTTGTGCCTT <3′ 49 Primer 5′>GTGGAGGTGGCGGATCTGGAGGGGGTGGTAGCGATGTTGTGAT GACCCAATC <3′ 50 Primer 5′>CTTTGGAGACTGGCCTGGCTTCTGCAGGTACCAATGSWGGTRGK KGTCTCCATAGYKGTGRWS <3′ 51 Primer 5′>AGCCAGGCCAGTCTCCAAAGCTCCTGATCTACAAAGTTTCCAAC CGATTTTCTG <3′ 52 Primer 5′>TTTCCAGCTTGGTCCCCCCTCCGAAGKKGTRGKGRWSATGGKKG TKSTGAGAGCAGTAATAAAC <3′ 53 Primer 5′>TAGTCGACCAGGCCCCCGAGGCCTTTTATTTCCAGCTTGGTCCC CCCT <3′ 54 Signal peptide MGWSCIILFLVATATGVHS 55 Primer 5′- AGTAGCAACTGCAACCGGTGTACATTCTCAGGTGCAGCTGCAGGA GTC 56 Primer 5′- GATGGGCCCTTGGTCGACGCTGAAGAGACGGTGACGGTGG 57 Primer 5′- AGTAGCAACTGCAACCGGTGTACATTCTGACATACAGATGACGCA GTCTC 58 Primer 5′- ATGGTGCAGCCACCGTACGTTTGATTTCCACCTTGGTCC

EXAMPLES

The present invention will now be described with reference to the following examples which are intended to illustrate the present invention rather than limit the present invention.

Unless otherwise specified, the molecular biology experimental methods and immunoassay methods used in the present invention basically refer to J. Sambrook et al., Molecular Cloning: Laboratory Manual, 2nd Edition, Cold Spring Harbor Laboratory Press, 1989, and F M Ausubel et al., Compiled Molecular Biology Experiment Guide, 3rd edition, John Wiley & Sons, Inc., 1995; the restriction enzymes were used in accordance with the conditions recommended by the product manufacturer. Those skilled in the art know that the examples describe the present invention by way of example, and are not intended to limit the scope of protection sought to be protected by the present invention.

Example 1: Phage Screening of pH-Dependent Anti-HBsAg Antibodies 1.1 Determination of Mutation Sites for pH-Dependent Antibody Modification

The anti-HBV humanized antibody 162 (detailed in Chinese patent application 201610879693.5) developed in the laboratory was used as the parent antibody, and its variable region were modified for pH-dependent antigen binding. As shown in FIG. 1, the modified 162 could maintain the antigen-binding activity under neutral conditions, but its antigen-binding activity under acidic conditions was greatly reduced. The dissociated modified 162 could bind to intracellular FcRn so as to return to the plasma and bind to the antigen again, so that one molecule of the modified 162 with pH-dependent antigen binding ability could repeatedly bind and neutralize a plurality of molecules of antigen. Histidine was protonated under acidic conditions and was a key amino acid to bring the pH-dependent antigen binding properties. The 162 Fab had an analyzed crystal structure, the analyzed crystal structure was docked by simulation with an antigen short peptide, and part of the results was shown in FIG. 2, in which the blue structure represented the antigen short peptide, and the red structure represented part of the binding region of 162 antibody. According to the docking results, a total of 14 key amino acids for antigen and antibody binding were found. Considering that the simulated docking results had greater reference value, the amino acids on the interface and the amino acids on the both sides were selected for mutation, and 26 sites were determined.

1.2 Construction of Phage Library of pH-Dependent scFv Antbodies Derived from 162

Using the variable regions of the light and heavy chains of the 162 antibody as a template, the determined sites in the antibody variable region CDRs were mutated for pH-dependent modification, and the target fragments were amplified according to the primers in Table 2 to obtain the gene fragments coding the pH-dependent scFv antibodies derived from 162. PCR conditions were: 95° C., 5 min; 95° C., 30 s; 57° C., 30 s; 72° C., 30 s; 72° C., 10 min; for 25 amplification cycles; SOE-PCR reaction conditions were: 95° C., 5 min; 95° C., 30 s; 57° C., 30 s; 72° C., 30 s; 72° C., 10 min; for 5 amplification cycles. The amplified products were analyzed by agarose gel electrophoresis, and the amplification products were recovered/purified by using the DNA purification and recovery kit (TianGen, DP214-03), thereby obtaining the gene fragments H-K encoding the humanized scFv antibodies derived from 162. The structure of scFv antibodies was: NH2-VH-linker-VL-COOH, and the linker sequence could be (G4S)3. Each of the gene fragments H-K was digested with SfiI, and then ligated to the vector pCGMT (from Scripps, Making chemistry selectable by linking it to infectivity) at a molar ratio of 10:1 (gene fragment:vector). The ligation products were transformed into competent Escherichia coli ER2738 by electroporation (electroporation conditions: 25 μF, 2.5 KV, 200 Ω). The transformed Escherichia coli was recovered in SOC medium for 45 min, and then 200 μL of bacterial solution was plated on LB plates (comprising 100 g/L ampicillin+tetracycline+2 g/mL glucose), and incubated by standing at 37° C. overnight. All colonies on the plates were the libraries that the mutation sites determined in the variable regions were randomly mutated into histidine, which were used for subsequent screening. Monoclonal colonies were picked out from the plates and sequenced to ensure the correctness of the sequences of recombinant vectors encoding the scFv antibodies. The schematic diagram of the recombinant vector (pCGMT-scFv) encoding the scFv antibody was shown in FIG. 3.

TABLE 2 Mutation primers for pH-dependent scFv antibodies derived from 162 Primer name Primer sequence VH-F SEQ ID NO: 44 HCDR1-R SEQ ID NO: 45 HCDR2-F SEQ ID NO: 46 HCDR3-R SEQ ID NO: 47 VH-R SEQ ID NO: 48 VK-F SEQ ID NO: 49 KCDR1-R SEQ ID NO: 50 KCDR2-F SEQ ID NO: 51 KCDR3-R SEQ ID NO: 52 VK-R SEQ ID NO: 53

1.3 Detection of Humanized scFv Antibodies

The library obtained in the previous step was screened for multiple rounds, and the positive monoclonal colonies obtained in the screening were cultured with 2×YT medium containing ampicillin (100 g/L) and glucose (2 g/mL) to reach an OD value of 0.6, and then added with M13KO7 for auxiliary super-infection. After 2 h, 100 g/L kanamycin was added and the super-infection was performed at 37° C. After 2 h, the culture was centrifuged at 4000 rpm for 10 min, the supernatant was discarded, and the cell pellet was collected. The cell pellet was resuspended in a medium containing ampicillin and kanamycin (100 g/L), and cultured with shaking at 30° C. overnight. Subsequently, the culture was centrifuged at 12000 rpm for 10 min, the cells and supernatant were collected, and stored at 4° C. for testing.

An ELISA plate coated with HBsAg (200 ng/mL) antigen was used, and 100 μL of the supernatant to be tested was added to each well, and incubated at 37° C. for 1 h (two wells for each supernatant). Subsequently, the ELISA plate was washed once with PBST, and then the two wells of each supernatant were added with 120 μL of PBS with pH 7.4 and pH 6.0 respectively and incubated at 37° C. for 30 min. After washing with PBST of corresponding pH for 5 times, 100 μL , of anti M13-HRP diluted at 1:5000 was added, and incubated at 37° C. for 30 min. Subsequently, the ELISA plate was washed 5 times with PBST, and the substrate TMB solution was added. After 15 minutes of color development, the color reaction was terminated with H2SO4, and the reading was measured at OD450/630. The detection results of ELISA of the third round were shown in FIGS. 4A to 4D. The results showed that the phages displaying these scFv antibodies all had reactivity in ELISA detection and weakly bound to antigens at pH 6.0; six strains of pH-dependent phage antibodies with good effects were initially obtained, named C-26, C-27, C-32, D3, D4 and D5, respectively.

Example 2: Preparation of pH-Dependent Anti-HBsAg Antibodies 2.1 Construction of Recombinant Vector for Eukaryotic Expression

In the present invention, a large amount of antibody recombination needed to be carried out, so it was necessary to construct a set of light and heavy chain vectors that can efficiently recombine antibodies. In the present invention, the existing eukaryotic expression vector pTT5 in the laboratory was specially modified to construct a set of light and heavy chain recombinant vectors for double plasmid co-transfection. MGWSCIILFLVATATGVHS (SEQ ID NO: 54) was used as the signal peptide for the light and heavy chains. The sequences encoding the constant regions of the human antibody light and heavy chains were separately ligated to the downstream of signal peptide to construct a set of eukaryotic expression vectors pTT5-CH, pTT5-Cκ and pTT5-Cλ that facilitated antibody recombination.

The six scFv antibodies obtained in 1.3 were used to amplify the light and heavy chain variable region fragments with the primers in Table 3. The specific amplification reaction conditions were: 95° C., 5 min; 95° C., 30 s; 57° C., 30 s; 72° C., 30 s; 72° C., 10 min; for 25 amplification cycles. And the amplification products were recovered from the gel.

The laboratory-made Gibson assembly solution was used to ligate the above constructed eukaryotic expression vector with the recovered PCR product of antibody variable region gene (the primer carried a sequence homologous to the vector) to obtain the recombinant vectors VH+pTT5-CH (comprising the CH shown in SEQ ID NO: 40) and VH+pTT5-Cκ (comprising the CL shown in SEQ ID NO: 41). The recombinant vector was transformed into E. coli DH5α strain, plated on LB plate, and cultivated overnight in a 37° C. incubator. Monoclonal colonies were picked out from the plate and sequenced, and the sequencing results were subjected to sequence comparison using MEGA to confirm the correctness of its genes, and exclude the genes with wrong information.

TABLE 3 Primers for construction of eukaryotic expression vectors Primer name Primer sequence VH-F SEQ ID NO: 55 VH-R SEQ ID NO: 56 VK-F SEQ ID NO: 57 VK-R SEQ ID NO: 58

2.2 Small- and Large-Scale Expression of Antibody Genes

The constructed recombinant vectors VH+pTT5-CH and VH+pTT5-Cκ were co-transfected into HEK293 cells, and double plasmids for small-scale expression were co-transfected into a 24-well plate, 500 μL per well; if the cell supernatant of small-scale expression had antigenic activity, the transfection system was enlarged to 100 mL (determined by the amount of antibody used) of FreeStyle™ 293F suspension cells (the cell density was about 2×106 cells/ml). The transfected cells were cultured in a shake flask in a 32° C., 5% CO2 incubator, and the supernatant was collected after 7 days of expression.

2.3 Antibody Purification

The cell expression supernatant was collected and purified with a Protein A column according to the manufacturer's instructions. The specific steps were as follows: the harvested cell culture supernatant was centrifuged at 8000 rpm for 10 min, the supernatant was retained, the pH value was adjusted to 8.4 with dry powder Na2HPO4, and then filtered with a filter membrane with 0.22 μm pore diameter. 10 mL of Sepharose 4B medium coupled with Protein A was loaded into column, it was connected to AKTA Explorer100 system, the pump A was connected to 0.2 M disodium hydrogen phosphate solution, and the pump B was connected to 0.2 M citric acid solution. Detection wavelength was UV 280 nm, flow rate was 5 mL/min, and the sample injection proportion of pumps A/B was adjusted. The column was first washed with 100% B (pH 2.3) to remove protein impurities, the pH was balanced with 10% B (pH 8.0), the signal at the detection wavelength returned to zero after it was stable, then the sample was loaded. After the flow through peak passed, 10% B was used for balance until the signal at the detection wavelength was reduced to zero and was stable, elution was performed using 70% B (pH 4.0), and the elution peak was collected. The elution peak sample was dialyzed into PBS buffer and subjected to assay of concentration and SDS-PAGE and HPLC analysis to determine the purity of IgG antibody.

Example 3: Property Analysis and Functional Evaluation of pH-Dependent Anti-HB sAg Antibodies

Through the method of Example 1, six strains of pH-dependent phage antibodies that bound to HBsAg were obtained by preliminary screening, named C26, C27, C32, D3, D4 and D5, respectively. Furthermore, the small-scale eukaryotic expression and purification of the 6 strains of phage antibodies were carried out by the method of Example 2. The VH and VL amino acid sequences of the 6 antibodies were shown in Table 4 below. In addition, the CDR sequences of the 6 antibodies were determined, and the CDR amino acid sequences of the heavy chain variable regions and the light chain variable regions thereof were shown in Table 5. The mutation sites that endowed C26, C27, C32, D3, D4 and D5 with pH-dependent antigen binding properties to HBsAg were summarized in FIG. 5.

TABLE 4 Amino acid sequences of C26/C27/C32/D3/D4/D5 light and  heavy chain variable regions Sequence  SEQ  name ID NO Amino acid sequence  C26 VH 3 EVQLQESGPGLVKPSQTLSLTCAVSGSSITHGYHWNWIRQFPGNKL EWIGYIHYDGSVLYNPSLENRVTITRDTSKNQFFLKLSSVTAEDTAK YYCASGFDHWGQGTTLTVSS C26 VK 4 DVVMTQSPLSLPVTLGEPASISCRSSQSLVHSYGDTYLHWYLQKPG QSPKLLIYKVSNRFSGVPDRFSGSGSGTDFTLKISRVETEDLGVYYC SQNTHHYTEGGGTKLEIK C27 VH 5 EVQLQESGPGLVKPSQTLSLTCAVSGSSITHGYHWNWIRQFPGNKL EWIGYINHDGSVLYNPSLENRVTITRDTSKNQFFLKLSSVTAEDTAK YYCASGFDHWGQGTTLTVSS C27 VK 2 DVVMTQSPLSLPVTLGEPASISCRSSQSLVHSYGDTYLHWYLQKPG QSPKLLIYKVSNRFSGVPDRFSGSGSGTDFTLKISRVETEDLGVYYC SQNTHVPYTFGGGTKLEIK C32 VH 6 EVQLQESGPGLVKPSQTLSLTCAVSGSSITYRYHWNWIRQFPGNKL EWIGYINYDGSVHYNPSLENRVTITRDTSKNQFFLKLSSVTAEDTAK YYCASGFDHWGQGTTLTVSS C32 VK 7 DVVMTQSPLSLPVTLGEPASISCRSSQSLVHSYGDTYLHWYLQKPG QSPKLLIYKVSNRFSGVPDRFSGSGSGTDFTLKISRVETEDLGVYYC SQNTHLPYTFGGGTKLEIK D3 VH 8 EVQLQESGPGLVKPSQTLSLTCAVSGSSITHGYHYNWIRQFPGNKLE WIGYIHYDGSVLYNPSLENRVTITRDTSKNQFFLKLSSVTAEDTAKY YCASGFDHWGQGTTLTVSS D3 VK 9 DVVMTQSPLSLPVTLGEPASISCRSSQSLVHSYGDNYLHWYLQKPG QSPKLLIYKVSNRFSGVPDRFSGSGSGTDFTLKISRVETEDLGVYYC SQNTHVPYTFGGGTKLEIK D4 VH 3 EVQLQESGPGLVKPSQTLSLTCAVSGSSITHGYHWNWIRQFPGNKL EWIGYIHYDGSVLYNPSLENRVTITRDTSKNQFFLKLSSVTAEDTAK YYCASGFDHWGQGTTLTVSS D4 VK 10 DVVMTQSPLSLPVTLGEPASISCRSSQSLVHSYGDNYLHWYLQKPG QSPKLLIYKVSNRFSGVPDRFSGSGSGTDFTLKISRVETEDLGVYYC SQNTHLPYTFGGGTKLEIK D5 VH 3 EVQLQESGPGLVKPSQTLSLTCAVSGSSITHGYHWNWIRQFPGNKL EWIGYIHYDGSVLYNPSLENRVTITRDTSKNQFFLKLSSVTAEDTAK YYCASGFDHWGQGTTLTVSS D5 VK 9 DVVMTQSPLSLPVTLGEPASISCRSSQSLVHSYGDNYLHWYLQKPG QSPKLLIYKVSNRESGVPDRFSGSGSGTDFTLKISRVETEDLGVYYC SQNTHVPYTFGGGTKLEIK

TABLE 5 CDR sequences of C26/C27/C32/D3/D4/D5  light and heavy chains C26 VH CDR1 HGYHWN SEQ ID NO: 17 VH CDR2 YIHYDGSVLYNPSLEN SEQ ID NO: 18 VH CDR3 GFDH SEQ ID NO: 13 VL CDR1 RSSQSLVHSYGDTYLH SEQ ID NO: 14 VL CDR2 KVSNRFS SEQ ID NO: 15 VL CDR3 SQNTHHPYT SEQ ID NO: 19 C27 VH CDR1 HGYHWN SEQ ID NO: 17 VH CDR2 YINHDGSVQYNPSLEN SEQ ID NO: 20 VH CDR3 GFDH SEQ ID NO: 13 VL CDR1 RSSQSLVHSYGDTYLH SEQ ID NO: 14 VL CDR2 KVSNRFS SEQ ID NO: 15 VL CDR3 SQNTHVPYT SEQ ID NO: 16 C32 VH CDR1 YRYHWN SEQ ID NO: 21 VH CDR2 YINYDGSVHYNPSLEN SEQ ID NO: 22 VH CDR3 GFDH SEQ ID NO: 13 VL CDR1 RSSQSLVHSYGDTYLH SEQ ID NO: 14 VL CDR2 KVSNRFS SEQ ID NO: 15 VL CDR3 SQNTHLPYT SEQ ID NO: 23 D3 VH CDR1 HGYHYN SEQ ID NO:24 VH CDR2 YISYDGSVLYNPSLEN SEQ ID NO:12 VH CDR3 GFDH SEQ ID NO:13 VL CDR1 RSSQSLVHSYGDNYLH SEQ ID NO:25 VL CDR2 KVSNRFS SEQ ID NO: 15 VL CDR3 SQNTHVPYT SEQ ID NO:16 D4 VH CDR1 HGYHWN SEQ ID NO:17 VH CDR2 YISYDGSVLYNPSLEN SEQ ID NO:12 VH CDR3 GFDH SEQ ID NO:13 VL CDR1 RSSQSLVHSYGDNYLH SEQ ID NO:25 VL CDR2 KVSNRFS SEQ ID NO: 15 VL CDR3 SQNTHLPYT SEQ ID NO:23 D5 VH CDR1 HGYHWN SEQ ID NO:17 VH CDR2 YISYDGSVLYNPSLEN SEQ ID NO:12 VH CDR3 GFDH SEQ ID NO:13 VL CDR1 RSSQSLVHSYGDNYLH SEQ ID NO:25 VL CDR2 KVSNRFS SEQ ID NO:15 VL CDR3 SQNTHVPYT SEQ ID NO:16

The inventors first performed small-scale transfection for the six monoclonal antibodies; after quantifying the supernatant after transfection, the pH-dependent antigen binding ability with HBsAg was detected by ELISA method, and the antibody concentration was uniformly diluted to 1111.11 ng/mL. Subsequently, 20% NBS was used to carry out a 3-fold concentration gradient dilution of the antibody concentration, for a total of 8 concentration gradients. Subsequently, the diluted antibody was added to a commercial HBsAg plate (purchased from Beijing Wantai), and incubated at 37° C. for 1 h (two wells per supernatant). Subsequently, the ELISA plate was washed once with PBST and spin-dried. Then, the two wells of each supernatant were added with 120 μL, of pH 7.4 and pH 6.0 PBS respectively and incubated at 37° C. for 30 min. It was then washed 5 times with PBST of corresponding pH and spin-dried. Subsequently, GAH-HRP-labeled secondary antibody was added, incubated for 30 min, the plate was washed 5 times with PBST, and spin-dried. The substrate TMB solution was added. After 15 minutes of color development, the color reaction was terminated with H2SO4, and the reading was measured at OD450/630.

The results were shown in FIGS. 6A to 6B. It could be seen from the results that the candidate molecules all could maintain an antigen-binding activity comparable to that of the parent antibody 162 at the neutral pH, and the antigen-binding activity was significantly reduced at pH 6.0. The EC50 results were summarized in Table 6.

TABLE 6 EC50 values of pH-dependent activity detection for C26, C27, C32, D3, D4 and D5 EC50 in pH 6.0 EC50 in pH 7.4 EC50(pH 6.0)/ antibody (ng/mL) (ng/mL) EC50(pH 7.4) C26 331.30 37.20 8.90 C27 949.60 491.30 1.93 C32 2255.00 1333 1.69 D3 473.10 35.43 13.35 D4 188.10 37.16 5.06 D5 60.04 21.04 2.85

Example 4: Construction and Functional Evaluation of Scavenger Antibody

The pH-dependent antibody needs to enter the cell to exert its pH-dependent antigen-binding activity. Therefore, if the first limiting factor of cell entry is not broken, the subsequent pH-dependent antigen-binding properties will have no chance to “play”. Therefore, in this example, the scavenger antibody was obtained by further mutation of amino acids in the Fc region, which could enhance the binding to hFcRn receptor at neutral pH, or enhance the binding to FcγRs receptor. As shown in FIG. 7, the scavenger antibody is located outside the cell and played the role of a “transportation helper” that reciprocally transported antigens into the cell, thereby extremely extending the antibody half-life, and it could bind to antigen again, thereby improving the efficiency of cell entry of antigen, and significantly improving the clearance efficiency.

The C26, D3, D4 and D5 were selected as the antibodies for subsequent evaluation, and subjected to Fc DY (K326D, L328Y) mutations to enhance the affinity with mFcγRII under neutral conditions (the modification of C26 Fc was commissioned to the General Biologicals, order number G122413) to obtain scavenger antibodies C26 DY, D3 DY, D4 DY and D5 DY that bound to mFcγRII. The above antibodies were subjected to large-scale eukaryotic expression and purification, and the specific steps were same as Examples 1.2 and 1.3.

FIGS. 8A to 8B showed the protein gel results of the original antibody and the modified antibodies. FIG. 8A: the picture of protein gel of the original antibody, in which the 162 was a positive control. The results showed that the expressed original antibody is single-component. FIG. 8B: the picture of protein gel of antibodies with DY modification, in which the 162 was a positive control. The results showed that the expressed antibodies with DY modification are single-component.

4.1 Evaluation of pH-Dependent Antigen-Binding Activity of Scavenger Antibodies Binding to mFcγRII

For the original antibody and the antibodies with DY modification after expression and purification, the inventors used the ELISA method to detect their pH-dependent antigen binding ability to HBsAg. First, a BCA protein quantification kit was used to determine the concentrations of the purified antibodies, and the antibodies were uniformly diluted to have a concentration of 1111.11 ng/mL. Subsequently, 20% NBS was used to carry out a 3-fold concentration gradient dilution for the antibody concentrations, for a total of 8 concentration gradients. Subsequently, the diluted antibody was added to a commercial HBsAg plate (purchased from Beijing Wantai) and incubated at 37° C. for 1 h (two wells per supernatant). Subsequently, the ELISA plate was washed once with PBST and spin-dried. Then the two wells of each supernatant were added with 120 μL of pH 7.4 PBS and pH 6.0 PBS respectively incubated at 37° C. for 30 min, washed 5 times with PBST of corresponding pH and spin-dried. Subsequently, GAH-HRP-labeled secondary antibody was added, and incubated for 30 min, the plate was washed 5 times with PBST, and spin-dried. And the substrate TMB solution was added. After 15 minutes of color development, the color reaction was terminated with H2SO4, and the reading was measured at OD450/630.

The results were shown in FIGS. 9A to 9D, in which the C26, D3, D4, D5 and their DY modification antibodies all had an antigen-binding activity equivalent to that of antibody 162, but showed a weak binding to antigen at pH 6.0, thereby exhibiting a good pH-dependent antigen-binding activity.

4.2 Verification of Function at Cellular Level for Scavenger Antibodies Binding mFcγRII 4.2.1 Labeling HBsAg with 488 Fluorescence

Take the labeling of 1 mg HBsAg as an example, the whole process was protected from light.

(1) 1 mL of 1 mg/mL HBsAg was dialyzed into borate buffer (PH 8.5, 500 mL), 4° C., 4 h;

(2) the molar ratio of HBsAg to 488 label was 1:5, and 0.1988 mg of 488 fluorescence was required after calculation;

(3) 10 mg/mL of 488 fluorescence solution was prepared with DMF and mixed well;

(4) 19.88 pL of 488 fluorescence was added to 1 mL of the dialyzed HBsAg, mixed well, and incubated at room temperature for 1 h;

(5) the incubation mixture was dialyzed into PBS at 4° C. overnight.

4.2.2 Immunofluorescence Experiment Based on Mouse Primary Macrophages

(1) 4 days before the experiment, 1.5 mL of 3% sodium thioglycolate solution was injected into the abdominal cavity of each mouse, without injecting into the intestine;

(2) two mice were executed and soaked in 75% alcohol for 3 minutes;

(3) the mouse was horizontally fixed on a foam board to expose the abdomen; the abdominal skin was cut with tissue scissors, the peritoneum was disinfected and incised to expose the abdominal cavity, the abdominal incision skin was pulled by two toothed forceps hold in the left hand and fixed, 1640 culture medium was pipetted by Pasteur pipette hold in the right hand for peritoneal lavage with 4 mL/time, for a total of two times. The pipette was used to gently and fully stir the abdominal cavity to make the lavage more fully and thoroughly. After fully stirring for about 2 minutes and standing for about 5 minutes to fully isolate the macrophages, the lavage solution was pipetted and transferred into a centrifuge tube;

(4) 4° C., 1100 g, 5 min;

(5) the supernatant was carefully discard, the cells were washed twice with 1640 medium, 4° C., 1100 g, 5 min, the supernatant was discarded, and the cells were resuspended in RPM1640;

(6) After counting the cells, the cell density was adjusted to 106 cells/mL, the cells were cultured on a 24-well glass-bottom cell imaging culture plate, 250 μL/well, the medium was replaced after 2 h, and washing was carried out once with RPM1640, after the non-adherent cells were discarded, the cells were incubated overnight in a 37° C., CO2 incubator;

(7) the antibody and antigen labeled with the corresponding fluorescence were diluted in serum-free medium to: 800 ng/mL for antigen and 20 μg/mL for antibody;

(8) 125 μL of the antigen and 125 μL of the antibody were mixed uniformly, and then were allowed to stand for 1 hour in a 37° C., CO2 incubator;

(9) the cell supernatant in the cell imaging culture plate was discarded, the antigen-antibody complex was added, shaken evenly, and allowed to stand in a 37° C., CO2 incubator for 2 hours;

(10) the supernatant was discarded, and 1 mL of sterile PBS incubated at 37° C. in advance was used to “wash” the cell surface 3 to 5 times, and then totally removed by a pipette;

(11) the 1:2000 diluted Dio was added in an amount that immersed the cells, and allowed to stand at room temperature for 20 min;

(12) the supernatant was discarded, and 1 mL of sterile PBS incubated at 37° C. in advance was used to “wash” the cell surface 3 to 5 times, and then totally removed by a pipette;

(13) a live cell nuclear dye was added (2 drops were added to 1 mL of volume), allowed to stand at room temperature for 20 min, and placed in a high-content imager for imaging.

The results of the experiment were shown in FIG. 10A. It could be seen from the results that the DY modification enhanced the phagocytosis of mouse macrophages to the antigen-antibody complexes, leading to more antigen degradation.

4.2.3 Validation by Chemiluminescence Method Based on human THP-1 Phagocytic Cells

(1) Adherent THP-1 cells were coated on a plate at 2×105/well, added with 1640 medium containing 10% serum, placed in a carbon dioxide incubator and cultured at 37° C. for 24 h;

(2) HBsAg was diluted with serum-free 1640 medium to 800 ng/mL, and the antibody to be tested with 20 ug/mL as the initial concentration was subjected to 2-fold gradient dilution, for a total of 11 gradients. 300 uL of the diluted HBsAg and 300 uL of the antibody to be tested were mixed at ratio of 1:1, and allowed to stand at 37° C. for 1 h;

(3) the THP-1 cell supernatant was discarded, 250 uL of the HBsAg-antibody mixture was added to the THP-1 cells, placed in a carbon dioxide incubator and cultured at 37° C. for 1 hour;

(4) the THP-1 cell supernatant was discarded, and washed 3 times with sterile PBS;

(5) 120 uL of DDM cell lysis solution was added to each well of THP-1 cells and allowed to stand and react at 4° C. for 1 hour;

(6) the supernatant of the lysate was subjected to detecting the concentration of HBsAg by using hepatitis B surface antigen quantitative detection kit (Beijing Wantai).

The results of the experiment were shown in FIG. 10B. It could be seen from the results that the DY modification enhanced the phagocytosis of human THP-1 phagocytic cells to the antigen-antibody complexes.

4.3 Determination of Therapeutic Effect of Scavenger Antibody Binding to mFcγRI in Animal Models

HBV transgenic mice were selected as animal models. The C26 DY, D3 DY, D4 DY and D5 DY scavenger antibodies and 162 were injected at a single dose of 5 mg/kg via tail vein (4 mice in each group) to the 6-8 weeks old HBV transgenic mice. By detecting the concentrations of HBsAg, antibody and HBV DNA in serum, the antigen clearance rates and antibody half-life of the scavenger antibodies in vivo were analyzed.

Quantitative Detection of HBsAg

(1) Preparation of reaction plate: the mouse monoclonal antibody HBs-45E9 was diluted with 20 mM PB buffer (Na2HPO4/NaH2PO4 buffer, pH 7.4) to 2 μg/mL, and 100 μL of coating solution was added to each well of a chemiluminescence plate, and the coating was carried out at 2-8° C. for 16-24 h, followed by another 2 hours at 37° C., the plate was washed once with PBST washing solution, and spin-dried. After washing, 200 μL of blocking solution was added to each well and the blocking was carried out at 37° C. for 2 h. Subsequently, the blocking solution was discarded, and the plate was placed in a drying room to dry, and stored at 2-8° C. for later use.

(2) Sample dilution: the collected mouse serum was diluted with a PBS solution containing 20% NB S (newborn bovine serum) at two gradients of 1:30 and 1:150 for subsequent quantitative detection.

(3) Sample denaturation treatment: 15 μL of the above-diluted serum sample was mixed well with 7.5 μL of denaturation buffer (15% SDS, dissolved in 20 mM PB7.4), and reacted at 37° C. for 1 h. Then, 90 μL of stop buffer (4% CHAPS, dissolved in 20 mM PB7.4) was added, and mixed well.

(4) Sample reaction: 100 μL of the above-mentioned denatured serum sample was added to a reaction plate, and reacted at 37° C. for 1 hour. Subsequently, the reaction plate was washed 5 times with PBST and spin-dried.

(5) Enzymatic label reaction: the HBs-A6A7-HRP reaction solution was added at 100 μL/well to a chemiluminescence plate, and reacted at 37° C. for 1 h. Then, the plate was washed 5 times with PBST and spin-dried.

(6) Luminescence reaction and measurement: a luminescence solution (100 μL/well) was added to the chemiluminescence plate, and light intensity measurement was performed.

(7) Calculation of HBsAg concentration in mouse serum sample: parallel experiments were performed using standard products, and a standard curve was drawn based on the measurement results of the standard products. Then, the light intensity measurement value of the mouse serum sample was substituted into the standard curve, and the concentration of HBsAg in the serum sample to be tested was calculated.

The results of the detection of HBsAg in the serum were shown in FIG. 11A and FIG. 11C. It could be seen from FIG. 11A that the scavenger antibody with DY modification C26 DY had an antibody clearance ability stronger more than one order of magnitude than that of 162, which was consistent with the detection results of antibody half-life in the serum (FIG. 11B). In the comparison of the concentrations of antibodies in the serum, the half-life of C26 DY was longer than that of 162 by nearly 12 days, which indicated that the scavenger antibody C26 DY had the function of circularly and reciprocally binding antigen, thereby increasing the duration time of antigen clearance. The experimental results in FIG. 11C showed that the antigen clearance ability of D3 DY, D4 DY and D5 DY was equivalent to that of C26 DY, and the duration time was longer than that of C26 DY, indicating that at a low injection dose of 5 mg/kg, the scavenger antibodies with DY modification D3 DY, D4 DY and D5 DY had a better function of circularly and reciprocally binding antigen, thereby performing better antigen clearance.

Example 5: Affinity Determination of 162 and C26

HBsAg was dissolved in sodium acetate (pH 4.5) at 5 μg/mL, and the chip coating program was run on the Biacore 3000 device to coat HBsAg on the CM5 chip. The coating volume of HBsAg was 2400 RU. The analyte was diluted 2-fold from 100 nM to prepare samples of 7 concentrations. The affinity determination program was run on the Biacore 3000 device, the flow rate was set to 50 μl/min, the binding time was set to 90 s, the dissociation time was set to 600 s, the temperature of sample chamber was set to 10° C., the regeneration solution was 50 mM NaOH, the regeneration flow rate was set to 50 μL/min, and the regeneration time was set to 60 s. The results were summarized in Table 7.

TABLE 7 Affinity determination of 162 and C26 KD(M) in KD(M) in KD(pH 6.0)/ Antibody pH 7.4 pH 6.0 KD(pH 7.4) 162 9.34E−10 C26 3.45E−09 9.82E−09 2.85

Although the specific embodiments of the present invention have been described in details, those skilled in the art will understand that various modifications and changes can be made to the details according to all the teachings that have been published, and these changes are within the protection scope of the present invention. All of the present invention is given by the appended claims and any equivalents thereof.

Claims

1. An antibody or antigen-binding fragment thereof capable of specifically binding to HBsAg, wherein the antibody or antigen-binding fragment thereof binds to HBsAg with higher affinity at neutral pH than at acidic pH, and the antibody or antigen-binding fragment thereof comprises:

(a) a heavy chain variable region (VH) comprising the following 3 CDRs:
(i) HCDR1 with a sequence of X1X2YHX3N (SEQ ID NO: 26), wherein X1 is selected from Y or H, X2 is selected from G or R, X3 is selected from W or Y;
(ii) HCDR2 with a sequence of YIX4X5DGSVX6YNPSLEN (SEQ ID NO: 27), wherein X4 is selected from S, N or H, X5 is selected from Y or H, X6 is selected from L, H or Q; and
(iii) HCDR3 with a sequence of GFDH (SEQ ID NO: 13); and/or,
(b) a light chain variable region (VL) comprising the following 3 CDRs:
(iv) LCDR1 with a sequence of RSSQSLVHSYGDX7YLH (SEQ ID NO: 28), wherein X7 is selected from T or N;
(v) LCDR2 with a sequence of KVSNRFS (SEQ ID NO: 15); and
(vi) LCDR3 with a sequence of SQNTHX8PYT (SEQ ID NO: 29), wherein X8 is selected from V, L or H.

2. The antibody or antigen-binding fragment thereof according to claim 1, wherein the antibody or antigen-binding fragment thereof comprises:

(a) a heavy chain variable region (VH) comprising the following 3 CDRs:
(i) HCDR1, consisting of a sequence selected from the following: SEQ ID NOs: 17, 21, 24;
(ii) HCDR2, consisting of a sequence selected from: SEQ ID NOs: 12, 18, 20, 22; and
(iii) HCDR3, consisting of a sequence shown in SEQ ID NO: 13; and/or,
(b) a light chain variable region (VL) comprising the following 3 CDRs:
(iv) LCDR1, consisting of a sequence selected from the following: SEQ ID NOs: 14, 25;
(v) LCDR2, consisting of a sequence shown in SEQ ID NO: 15; and
(vi) LCDR3, consisting of a sequence selected from the following: SEQ ID NOs: 16, 19, 23.

3. The antibody or antigen-binding fragment thereof according to claim 1 or 2, wherein the antibody or antigen-binding fragment thereof comprises:

(1) a VH comprising the following 3 CDRs: HCDR1 shown in SEQ ID NO: 21, HCDR2 shown in SEQ ID NO: 22, HCDR3 shown in SEQ ID NO: 13; and, a VL comprising the following 3 CDRs: LCDR1 shown in SEQ ID NO: 14, LCDR2 shown in SEQ ID NO: 15, LCDR3 shown in SEQ ID NO: 23;
(2) a VH comprising the following 3 CDRs: HCDR1 shown in SEQ ID NO: 17, HCDR2 shown in SEQ ID NO: 18, HCDR3 shown in SEQ ID NO: 13; and, a VL comprising the following 3 CDRs: LCDR1 shown in SEQ ID NO: 14, LCDR2 shown in SEQ ID NO: 15, LCDR3 shown in SEQ ID NO: 19;
(3) a VH comprising the following 3 CDRs: HCDR1 shown in SEQ ID NO: 17, HCDR2 shown in SEQ ID NO: 20, HCDR3 shown in SEQ ID NO: 13; and, a VL comprising the following 3 CDRs: LCDR1 shown in SEQ ID NO: 14, LCDR2 shown in SEQ ID NO: 15, LCDR3 shown in SEQ ID NO: 16;
(4) a VH comprising the following 3 CDRs: HCDR1 shown in SEQ ID NO: 24, HCDR2 shown in SEQ ID NO: 12, HCDR3 shown in SEQ ID NO: 13; and, a VL comprising the following 3 CDRs: LCDR1 shown in SEQ ID NO: 25, LCDR2 shown in SEQ ID NO: 15, LCDR3 shown in SEQ ID NO: 16;
(5) a VH comprising the following 3 CDRs: HCDR1 shown in SEQ ID NO: 17, HCDR2 shown in SEQ ID NO: 12, HCDR3 shown in SEQ ID NO: 13; and, a VL comprising the following 3 CDRs: LCDR1 shown in SEQ ID NO: 25, LCDR2 shown in SEQ ID NO: 15, LCDR3 shown in SEQ ID NO: 23; or
(6) a VH comprising the following 3 CDRs: HCDR1 shown in SEQ ID NO: 17, HCDR2 shown in SEQ ID NO: 12, HCDR3 shown in SEQ ID NO: 13; and, a VL comprising the following 3 CDRs: LCDR1 shown in SEQ ID NO: 25, LCDR2 shown in SEQ ID NO: 15, LCDR3 shown in SEQ ID NO: 16.

4. The antibody or antigen-binding fragment thereof according to any one of claims 1 to 3, wherein the antibody or antigen-binding fragment thereof further comprises a framework region of a human immunoglobulin (for example, a framework region contained in an amino acid sequence encoded by a human germline antibody gene), and the framework region optionally comprises one or more (for example, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10) back mutations from human residues to murine residues;

preferably, the antibody or antigen-binding fragment thereof comprises: a heavy chain framework region contained in an amino acid sequence encoded by a human heavy chain germline gene, and/or a light chain framework region contained in an amino acid sequence encoded by a human light chain germline gene;
preferably, the antibody or antigen-binding fragment thereof comprises: a heavy chain framework region contained in an amino acid sequence encoded by human heavy chain germline gene 4-28-02 (SEQ ID NO: 38), and a light chain framework region contained in an amino acid sequence encoded by human light chain germline gene 2D-28-01 (SEQ ID NO: 39), and the heavy chain framework region and/or the light chain framework region optionally comprises one or more (for example, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10) back mutations from human residues to murine residues;
preferably, the VH of the antibody or antigen-binding fragment thereof comprises: VH FR1 as shown in SEQ ID NO: 30, VH FR2 as shown in SEQ ID NO: 31, VH FR3 as shown in SEQ ID NO: 32, and VH FR4 shown in SEQ ID NO: 33;
preferably, the VL of the antibody or antigen-binding fragment thereof comprises: VL FR1 as shown in SEQ ID NO: 34, VL FR2 as shown in SEQ ID NO: 35, VL FR3 as shown in SEQ ID NO: 36, and VL FR4 shown in SEQ ID NO: 37.

5. The antibody or antigen-binding fragment thereof according to any one of claims 1 to 4, wherein the antibody or antigen-binding fragment thereof comprises:

(a) a heavy chain variable region (VH), which comprises an amino acid sequence selected from the following:
(i) a sequence shown in any one of SEQ ID NOs: 3, 5, 6, 8;
(ii) a sequence with substitution, deletion or addition of one or several amino acids (for example, substitution, deletion or addition of 1, 2, 3, 4 or 5 amino acids) as compared with a sequence shown in any one of SEQ ID NOs: 3, 5, 6, 8; or
(iii) a sequence with a sequence identity of at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% as compared with a sequence shown in any one of SEQ ID NOs: 3, 5, 6, 8;
and
(b) a light chain variable region (VL), which comprises an amino acid sequence selected from the following:
(iv) a sequence shown in any one of SEQ ID NOs: 2, 4, 7, 9, 10;
(v) a sequence with substitution, deletion or addition of one or several amino acids (for example, substitution, deletion or addition of 1, 2, 3, 4 or 5 amino acids) as compared with a sequence shown in any one of SEQ ID NOs: 2, 4, 7, 9, 10; or
(vi) a sequence with a sequence identity of at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% as compared with a sequence shown in any one of SEQ ID NOs: 2, 4, 7, 9, 10;
preferably, the substitution described in (ii) or (v) is a conservative substitution.

6. The antibody or antigen-binding fragment thereof according to any one of claims 1 to 5, wherein the antibody or antigen-binding fragment thereof comprises:

(1) a VH with a sequence shown in SEQ ID NO: 3 and a VL with a sequence shown in SEQ ID NO: 4;
(2) a VH with a sequence shown in SEQ ID NO: 5 and a VL with a sequence shown in SEQ ID NO: 2;
(3) a VH with a sequence shown in SEQ ID NO: 6 and a VL with a sequence shown in SEQ ID NO: 7;
(4) a VH with a sequence shown in SEQ ID NO: 8 and a VL with a sequence shown in SEQ ID NO: 9;
(5) a VH with a sequence shown in SEQ ID NO: 3 and a VL with a sequence shown in SEQ ID NO: 10; or
(6) a VH with a sequence shown in SEQ ID NO: 3 and a VL with a sequence shown in SEQ ID NO: 9.

7. The antibody or antigen-binding fragment thereof according to any one of claims 1 to 6, wherein the antibody or antigen-binding fragment thereof further comprises a constant region derived from a human immunoglobulin;

preferably, the heavy chain of the antibody or antigen-binding fragment thereof comprises a heavy chain constant region derived from a human immunoglobulin (for example, IgG1, IgG2, IgG3 or IgG4), and the light chain of the antibody or antigen-binding fragment thereof comprises a light chain constant region derived from a human immunoglobulin (for example, κ or λ);
preferably, the antibody or antigen-binding fragment thereof comprises a light chain constant region (CL) as shown in SEQ ID NO: 41.

8. The antibody or antigen-binding fragment thereof according to any one of claims 1 to 7, wherein the antibody or antigen-binding fragment thereof comprises a variant of a human IgG1 heavy chain constant region, the variant has the following substitution as compared to a wild-type sequence from which it is derived: (i) M252Y, N286E, N434Y; or, (ii) K326D, L328Y; wherein the above-mentioned amino acid positions are positions according to the Kabat numbering system;

preferably, the antibody or antigen-binding fragment thereof comprises a heavy chain constant region (CH) as shown in SEQ ID NO: 42 or 43.

9. The antibody or antigen-binding fragment thereof according to any one of claims 1 to 7, wherein the antibody or antigen-binding fragment thereof comprises a heavy chain constant region (CH) as shown in SEQ ID NO: 40.

10. The antibody or antigen-binding fragment thereof according to any one of claims 1 to 9, wherein the antibody or antigen-binding fragment thereof comprises:

(1) a heavy chain comprising a VH shown in SEQ ID NO: 3 and a CH shown in SEQ ID NO: 40, and a light chain comprising a VL shown in SEQ ID NO: 4 and a CL shown in SEQ ID NO: 41;
(2) a heavy chain comprising a VH shown in SEQ ID NO: 3 and a CH shown in SEQ ID NO: 47, and a light chain comprising a VL shown in SEQ ID NO: 4 and a CL shown in SEQ ID NO: 41;
(3) a heavy chain comprising a VH shown in SEQ ID NO: 3 and a CH shown in SEQ ID NO: 48, and a light chain comprising a VL shown in SEQ ID NO: 4 and a CL shown in SEQ ID NO: 41;
(4) a heavy chain comprising a VH shown in SEQ ID NO: 5 and a CH shown in SEQ ID NO: 40, and a light chain comprising a VL shown in SEQ ID NO: 2 and a CL shown in SEQ ID NO: 41;
(5) a heavy chain comprising a VH shown in SEQ ID NO: 5 and a CH shown in SEQ ID NO: 47, and a light chain comprising a VL shown in SEQ ID NO: 2 and a CL shown in SEQ ID NO: 41;
(6) a heavy chain comprising a VH shown in SEQ ID NO: 5 and a CH shown in SEQ ID NO: 48, and a light chain comprising a VL shown in SEQ ID NO: 2 and a CL shown in SEQ ID NO: 41;
(7) a heavy chain comprising a VH shown in SEQ ID NO: 6 and a CH shown in SEQ ID NO: 40, and a light chain comprising a VL shown in SEQ ID NO: 7 and a CL shown in SEQ ID NO: 41;
(8) a heavy chain comprising a VH shown in SEQ ID NO: 6 and a CH shown in SEQ ID NO: 47, and a light chain comprising a VL shown in SEQ ID NO: 7 and a CL shown in SEQ ID NO: 41;
(9) a heavy chain comprising a VH shown in SEQ ID NO: 6 and a CH shown in SEQ ID NO: 48, and a light chain comprising a VL shown in SEQ ID NO: 7 and a CL shown in SEQ ID NO: 41;
(10) a heavy chain comprising a VH shown in SEQ ID NO: 8 and a CH shown in SEQ ID NO: 40, and a light chain comprising a VL shown in SEQ ID NO: 9 and a CL shown in SEQ ID NO: 41;
(11) a heavy chain comprising a VH shown in SEQ ID NO: 8 and a CH shown in SEQ ID NO: 47, and a light chain comprising a VL shown in SEQ ID NO: 9 and a CL shown in SEQ ID NO: 41;
(12) a heavy chain comprising a VH shown in SEQ ID NO: 8 and a CH shown in SEQ ID NO: 48, and a light chain comprising a VL shown in SEQ ID NO: 9 and a CL shown in SEQ ID NO: 41;
(13) a heavy chain comprising a VH shown in SEQ ID NO: 3 and a CH shown in SEQ ID NO: 40, and a light chain comprising a VL shown in SEQ ID NO: 10 and a CL shown in SEQ ID NO: 41;
(14) a heavy chain comprising a VH shown in SEQ ID NO: 3 and a CH shown in SEQ ID NO: 47, and a light chain comprising a VL shown in SEQ ID NO: 10 and a CL shown in SEQ ID NO: 41;
(15) a heavy chain comprising a VH shown in SEQ ID NO: 3 and a CH shown in SEQ ID NO: 48, and a light chain comprising a VL shown in SEQ ID NO: 10 and a CL shown in SEQ ID NO: 41;
(16) a heavy chain comprising a VH shown in SEQ ID NO: 3 and a CH shown in SEQ ID NO: 40, and a light chain comprising a VL shown in SEQ ID NO: 9 and a CL shown in SEQ ID NO: 41;
(17) a heavy chain comprising a VH shown in SEQ ID NO: 3 and a CH shown in SEQ ID NO: 47, and a light chain comprising a VL shown in SEQ ID NO: 9 and a CL shown in SEQ ID NO: 41; or
(18) a heavy chain comprising a VH shown in SEQ ID NO: 3 and a CH shown in SEQ ID NO: 48, and a light chain comprising a VL shown in SEQ ID NO: 9 and a CL shown in SEQ ID NO: 41.

11. The antibody or antigen-binding fragment thereof according to any one of claims 1 to 10, wherein the antibody or antigen-binding fragment thereof is selected from the group consisting of scFv, Fab, Fab′, (Fab′)2, Fv fragment, diabody, bispecific antibody, multispecific antibody, probody, chimeric antibody or humanized antibody; preferably, the antibody is a chimeric antibody or a humanized antibody.

12. The antibody or antigen-binding fragment thereof according to any one of claims 1 to 10, wherein the antibody or antigen-binding fragment thereof is able to specifically bind to HBsAg, neutralize a virulence of HBV, and/or reduce a serum level of HBV DNA and/or HBsAg in a subject.

13. An isolated nucleic acid molecule, which encodes the antibody or antigen-binding fragment thereof according to any one of claims 1 to 12, or its heavy chain variable region and/or light chain variable region.

14. A vector, which comprises the nucleic acid molecule according to claim 13; preferably, the vector is a cloning vector or an expression vector.

15. A host cell, which comprises the nucleic acid molecule according to claim 13 or the vector according to claim 14.

16. A method for preparing the antibody or antigen-binding fragment thereof according to any one of claims 1 to 12, which comprises culturing the host cell according to claim 15 under a condition that allows the expression of the antibody or antigen-binding fragment thereof, and recovering the antibody or antigen-binding fragment thereof from the cultured host cell culture.

17. A pharmaceutical composition, which comprises the antibody or antigen-binding fragment thereof according to any one of claims 1 to 12, and a pharmaceutically acceptable carrier and/or excipient.

18. Use of the antibody or antigen-binding fragment thereof according to any one of claims 1 to 12 or the pharmaceutical composition according to claim 17 in the manufacture of a medicament for the prevention and/or treatment of an HBV infection or HBV infection-associated disease (for example, hepatitis B) in a subject (for example, a human), for neutralizing a virulence of HBV in vitro or in a subject (for example, a human), for reducing a serum level of HBV DNA and/or HBsAg in a subject (for example, a human), and/or for activating a humoral immune response against HBV in a subject (for example, a person with chronic HBV infection or a patient with chronic hepatitis B).

19. The antibody or antigen-binding fragment thereof according to any one of claims 1 to 12 or the pharmaceutical composition according to claim 17, for use in the prevention and/or treatment of an HBV infection or HBV infection-associated disease (for example, hepatitis B) in a subject (for example, a human), for use in neutralizing a virulence of HBV in vitro or in a subject (for example, a human), for use in reducing a serum level of HBV DNA and/or HBsAg in a subject (for example, a human), and/or for use in activating a humoral immune response against HBV in a subject (for example, a person with chronic HBV infection or a patient with chronic hepatitis B).

20. A method, which is used for the prevention and/or treatment of an HBV infection or HBV infection-associated disease (for example, hepatitis B) in a subject, for neutralizing a virulence of HBV in a subject (for example, a human), for reducing a serum level of HBV DNA and/or HBsAg in a subject (for example, a human), and/or for activating a humoral immune response against HBV in a subject (for example, a person with chronic HBV infection or a patient with chronic hepatitis B), the method comprises administering an effective amount of the antibody or antigen-binding fragment thereof according to any one of claims 1 to 12, or the pharmaceutical composition according to claim 17 to a subject in need thereof.

Patent History
Publication number: 20220251173
Type: Application
Filed: May 22, 2020
Publication Date: Aug 11, 2022
Applicants: XIAMEN UNIVERSITY (Xiamen), YANG SHENG TANG COMPANY, LTD. (Hangzhou)
Inventors: Wenxin LUO (Xiamen), Yichao JIANG (Xiamen), Chao YU (Xiamen), Xiaoqing CHEN (Xiamen), Jixian TANG (Xiamen), Quan YUAN (Xiamen), Tianying ZHANG (Xiamen), Ningshao XIA (Xiamen)
Application Number: 17/613,392
Classifications
International Classification: C07K 16/08 (20060101); A61P 31/20 (20060101);