polypeptides and polybnucleotides encoding same and their use in vaccinal and diagnostic applications
The present invention relates to the field of Streptococcus. More specifically, the present invention relates to the identification of polypeptides and polynucleotide sequences encoding the same which are involved in the pathogenic mechanism of S. suis. The present invention also relates to the use of such polypeptides in compositions and methods for the prevention, the treatment and diagnosis of S. suis-associated diseases and infections caused by S. suis.
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This is an application for reissue of U.S. Pat. No. 7,927,608, and is a reissue divisional of application Ser. No. 13/866,780, which is also an application for reissue of U.S. Pat. No. 7,927,608, now reissue U.S. Pat. No. Re. 45,467.
FIELD OF THE INVENTIONThe present invention relates to the field of Streptococcus. More specifically, the present invention relates to the identification of polypeptides and polynucleotide sequences encoding the same which are involved in the pathogenic mechanism of S. suis. The present invention also relates to the use of such polypeptides in compositions and methods for the prevention, the treatment and diagnosis of S. suis-associated diseases and infections caused by S. suis.
SEQUENCE LISTINGIn accordance with 37 CFR §1.52(e)(5), the present specification makes reference to a Sequence Listing (submitted electronically as a .txt file named “SeqListing.txt” on Jan. 31, 2011 Feb. 27, 2015). The .txt file was generated on Jan. 20, 2011 and is 40 Jan. 13, 2014 and is 48 kb in size. The entire contents of the Sequence Listing are herein incorporated by reference.
BACKGROUND OF THE INVENTIONStreptococcus suis is an important swine pathogen that causes many pathological conditions such as arthritis, endocarditis, meningitis, pneumonia and septicemia (13, 14). It is also an important zoonotic agent for people in contact with contaminated pigs or their by-products, causing meningitis and endocarditis (1, 36). Thirty-three serotypes (types 1 to 31, 33 and 1/2) based on capsular antigens are currently known (9-11, 15, 17, 31). Type 2 is considered the most virulent and prevalent type in diseased pigs. The mechanisms involved in the pathogenesis and virulence of S. suis are not completely understood (13) and attempts to control the infection are hampered by the lack of effective vaccines.
Several approaches have been made to develop vaccines for S. suis. However, little success was achieved because the protection was either serotype or strain dependent and results, in most instances, were equivocal (16, 30). For example, some protection with killed whole cells and live avirulent vaccines were reported, but this required repeated immunization and the protection against heterologous challenges was not determined (18, 38). Exposure of young pigs with live virulent strains showed a positive effect in reducing clinical signs characteristics of S. suis infection, but not in central nervous sign and mortality (35). Since the S. suis capsule plays an important role in virulence, attempts have been made to develop a vaccine based on capsular material. However, this vaccination was unsatisfactory because the capsular polysaccharide is poorly immunogenic (7). More recently, interest has shifted toward protein antigens of S. suis as vaccine candidates. Subunit vaccines using suilysin (20), or MRP (muramidase-released protein) and EF (extracellular proteins factor) (39) have been shown to protect pigs from homologous and heterologous serotype 2 strains, but their use is hindered by the fact that a substantial number of the virulent strains in some geographical regions do not express these proteins (8, 12, 29). Thus, identification of other antigenic factors, especially surface proteins, could contribute to the development of a subunit vaccine.
There is thus a need for the discovery and use of new targets for the prevention, the treatment and the diagnosis of S. suis-associated diseases and infections caused by S. suis.
SUMMARY OF THE INVENTIONAn object of the invention is to fullfill the above-mentioned need. More specifically, the object is achieved by providing an isolated polypeptide comprising at least 15 contiguous amino acids in the N-terminal region of the amino acid sequence set forth in SEQ ID NO: 1.
Another object of the invention also concerns an polynucleotide encoding a polypeptide as defined above.
The present invention is further concerned with an antibody which specifically binds to a polypeptide of the invention.
A further object of the invention is to provide a vector comprising the polynucleotide as defined above.
Yet another object of the invention is to provide a composition for preventing or treating Streptococcus suis-associated diseases or infection caused by S. suis, comprising an acceptable carrier and at least one of the following elements:
-
- a polypeptide as defined above;
- a polypeptide as defined above;
- an antibody as defined above;
- a vector as defined above.
Another object of the invention concerns a method for treating and/or preventing a Streptococcus suis-associated disease or infection in an animal, the method comprising the step of administering to the animal a composition as defined above.
A further object concerns a method for detecting the presence or absence of a Streptococcus suis strain in a sample, comprising the steps of:
-
- a) contacting the sample with an antibody of the invention for a time and under conditions sufficient to form an immune complex; and
- b) detecting the presence or absence of the immune complex formed in a).
Another object of the invention concerns a method for detecting the presence or absence of antibodies raised against a Streptococcus suis strain in a sample, comprising the steps of:
-
- a) contacting the sample with a polypeptide of the invention for a time and under conditions sufficient to form an immune complex; and
- b) detecting the presence or absence of the immune complex formed in a).
The present invention also provide in another object a diagnostic kit for the detection of the presence or absence of antibodies indicative of Streptococcus suis strain, comprising:
-
- a polypeptide according to the invention;
- a reagent to detect polypeptide-antibody immune complex;
- a biological reference sample lacking antibodies that immunologically bind with said peptide; and
- a comparison sample comprising antibodies which can specifically bind to said peptide;
wherein said polypeptide, reagent, biological reference sample, and comparison sample are present in an amount sufficient to perform said detection.
Yet another object is to provide a diagnostic kit for the detection of the presence or absence of antibodies indicative of Streptococcus suis strain, comprising:
-
- an antibody of the invention;
- a reagent to detect polypeptide-antibody immune complex;
- a biological reference sample polypeptides that immunologically bind with said antibody; and
- a comparison sample comprising polypeptides which can specifically bind to said peptide;
wherein said antibody, reagent, biological reference sample, and comparison sample are present in an amount sufficient to perform said detection.
Further objects are to provide an isolated polypeptide comprising an amino acid sequence substantially identical to the sequence as set forth in SEQ ID NO 11 or functional derivative thereof, and an isolated polynucleotide encoding said polypeptide, and their use in a composition and/or a method for treating and/or preventing a Streptococcus suis-associated disease or infection in an animal.
Unless specifically indicated to the contrary, the terms “SP1” and “Sao” are used interchangeably.
The inventors have surprisingly found two novel S. suis polypeptides and polynucleotides encoding same that are involved during the S. suis pathogenic mechanism. In this connection, the present invention specifically relates to their identification and to the use of said polypeptides or polynucleotides in compositions and methods for the prevention, the treatment and the diagnosis of Streptococcus suis-associated diseases or infection caused by S. suis.
A non-exhaustive list of Streptococcus suis-associated diseases which the methods of the invention may be useful for, includes those, such as arthritis, endocarditis, meningitis, pneumonia and septicemia.
Definitions
The term “isolated” is meant to describe a polynucleotide, a polypeptide or an antibody that is in an environment different from that in which the polynucleotide, the polypeptide, the antibody, or the host cell naturally occurs.
The term “animal” refers to any animal susceptible to be infected by a Streptococcus strain, such as S. suis. Specifically, such an animal may be, but not limited to, mice, pig, sheep, horse and human. More specifically, the animal consists of a pig.
The term “treating” refers to a process by which the symptoms of an infection or a disease associated with a Streptococcus strain are alleviated or completely eliminated. As used herein, the term “preventing” refers to a process by which symptoms of an infection or a disease associated with a Streptococcus strain are obstructed or delayed.
The term “protective response” means prevention of onset of a Streptococcus suis-associated disease or an infection caused by S. suis. or lessening the severity of such a disease existing in an animal. The level of “protective response” may be evaluated, for instance, by the assignment of clinical scores such as those defined in Example 4.
The expression “an acceptable carrier” means a vehicle for containing the compounds obtained by the method of the invention that can be administered to an animal host without adverse effects. Suitable carriers known in the art include, but are not limited to, gold particles, sterile water, saline, glucose, dextrose, or buffered solutions. Carriers may include auxiliary agents including, but not limited to, diluents, stabilizers (i.e., sugars and amino acids), preservatives, wetting agents, emulsifying agents, pH buffering agents, viscosity enhancing additives, colors and the like.
The term “fragment”, as used herein, refers to a polynucleotide sequence (e.g., cDNA) which is an isolated portion of the subject nucleic acid constructed artificially (e.g., by chemical synthesis) or by cleaving a natural product into multiple pieces, using restriction endonucleases or mechanical shearing, or a portion of a nucleic acid synthesized by PCR, DNA polymerase or any other polymerizing technique well known in the art, or expressed in a host cell by recombinant nucleic acid technology well known to one of skill in the art.
1 Polynucleotides and Polypeptides of the Invention
In a first embodiment, the present invention concerns an isolated polypeptide which consists of a surface protein, and more particularly a C-terminal-anchored surface protein of Streptococcus suis, namely called SP1 or Sao (Genbank accession number AY864331). As shown in the Example section, the SP1 polypeptide advantageously elicits a protective response to a Streptococcus suis strain challenge when administered to an animal, such as a pig.
Specifically, the isolated polypeptide of the first embodiment of the invention comprises at least 15 or even preferably at least 25 or even more at least 35 contiguous amino acids in the N-terminal region of the amino acid sequence set forth in SEQ ID NO: 1. As one skilled in the art may appreciate, the term “N-terminal region” in the context of the present invention when referring to the Sao protein, preferably consists of the region spanning from amino acid residue 1 to 293 of the amino acid sequence set forth in SEQ ID NO: 1.
According to a preferred embodiment, the isolated polypeptide of the first embodiment may further comprises at least one repetitive amino acid sequence such as shown in
wherein
Xaa1 is Val, Thr or Ile;
Xaa3 is Lys or Glu;
Xaa4 is Lys or Glu;
Xaa5 is Ala or Gln;
Xaa7 is Thr or Pro;
Xaa8 is Gly, Ser or Val;
Xaa9 is Lys, Val, Ile or Asn;
Xaa10 is Glu or Val;
Xaa11 is Lys or Asn;
Xaa12 is Gly, Glu or Asp;
Xaa13 is Asn or Met;
Xaa14 is Ile, Ala or Val;
Xaa15 is Glu or Val;
Xaa16 is Pro or Thr;
Xaa18 is Glu or Gln;
Xaa19 is Lys or Glu;
Xaa22 is Thr or Ala
Xaa26 is Lys or Asn;
Xaa27 is Asp or Glu;
Xaa28 is Asn or Lys;
Xaa29 is Ile or Val and
Xaa30 is Glu or Val.
It will be understood that the preferred SP1 polypeptide of the invention may comprises only one of said repetitive sequence, whereas in some other cases, the preferred SP1 polypeptide of the invention may comprises at least two repetitive sequences or even more than ten of such repetitive sequences.
In accordance with another preferred embodiment of the invention, the isolated SP1 polypeptide advantageously comprises at least 15 or even preferably 25 or even more preferably 35 contiguous amino acids in the C-terminus region of the amino acid sequence set forth in SEQ ID NO: 1. Preferably, the C-terminus region comprises a membrane anchor motif, such as the one consisting of the amino acid sequence as set forth is SEQ ID NO 10, namely Leu Pro Val Thr Gly.
As one skilled in the art may appreciate, the term “C-terminus region” in the context of the present invention when referring to the SP1 protein, preferably consists of the region spanning from amino acid residue 593 to 670 of the amino acid sequence set forth in SEQ ID NO: 1.
In accordance with an even more preferred embodiment, a SP1 polypeptide of the invention comprises an amino acid sequence substantially identical to a sequence selected from the group consisting of SEQ ID NOS 1 to 3 or functional derivative thereof. Most preferably, a SP1 polypeptide of the invention consists of an amino acid sequence substantially identical to the sequence shown in SEQ ID NO 1, or a functional derivative thereof.
A “functional derivative”, as is generally understood and used herein, refers to a protein/peptide sequence that possesses a functional biological activity that is substantially similar to the biological activity of the whole protein/peptide sequence. In other words, it preferably refers to a polypeptide or fragment(s) thereof that substantially retain(s) the capacity of eliciting an immune response, such as a protective response to a S. suis strain challenge when said functional derivative is administered to an animal. A preferred functional derivative contemplated by the present invention comprises an amino acid sequence substantially identical to the sequence as set forth in SEQ ID NO 4. More specifically, a preferred functional derivative consists of a 315-amino acids fragment (S28-K342) of SEQ ID NO 1. Such a fragment or polypeptide is designed as SP1A and its nucleotide and amino acid sequences are shown in
According to a second embodiment, the present invention relates to another isolated S. suis polypeptide, namely called SP2, which advantageously elicits a protective response in an animal.
Specifically, the isolated polypeptide of the second embodiment of the invention comprises an amino acid sequence substantially identical to a sequence as set forth in SEQ ID NO: 11 or functional derivative thereof.
By “substantially identical” when referring to an amino acid sequence, it will be understood that the polypeptide of the present invention preferably has an amino acid sequence having at least 75% homology, or even preferably 85% homology, or even more preferably 95% homology to part or all of the sequence shown in SEQ ID NOS 1 to 4 and 11.
“Homology” in this context, means identical or similar to the referenced sequence while straightforward replacements/modifications of any of the amino acids provided, are included as well. A homology search in this respect can be performed with the BLAST-P (Basic Local Alignment Search Tool), a program well known to those of skill in the art. For the corresponding nucleic acid sequence, homology is referred to the BLASTX and BLASTN programs known in the art.
The present invention also concerns an isolated polynucleotide encoding a preferred SP1 or a preferred SP2 polypeptide of the invention. Preferably, the isolated polynucleotide of the invention comprises a nucleotide sequence substantially identical to the sequence shown in SEQ ID NOS 5 to 7 when referring to SP1 and SEQ ID NO 12 when referring to SP2 and their respective functional fragments thereof.
By “substantially identical” when referring to a nucleic acid sequence, it will be understood that the polynucleotide of the invention preferably has a nucleic acid sequence which is at least 65% identical, more particularly 80% identical and even more particularly 95% identical to part or all of the sequence shown in SEQ ID NOS 5 to 7 and 12 or functional fragments thereof.
A “functional fragment”, as is generally understood and used herein, refers to a nucleic acid sequence that encodes for a functional biological activity that is substantially similar to the biological activity of the whole nucleic acid sequence. In other words, and within the context of the present invention, it preferably refers to a nucleic acid or fragment(s) thereof that substantially retains the capacity of encoding a polypeptide/protein which elicits an immune response, and more preferably a protective response, to a Streptococcus suis strain challenge when administered to an animal. For instance, such a fragment is the polynucleotide shown in SEQ ID NO 8, which codes for the SP1A polypeptide as defined above.
In another embodiment, the invention is further directed to vector (e.g., cloning or expression vector) comprising a polynucleotide of the invention as defined above.
As used herein, the term “vector” refers to a polynucleotide construct designed for transduction/transfection of one or more cell types. Vectors may be, for example, “cloning vectors” which are designed for isolation, propagation and replication of inserted nucleotides, “expression vectors” which are designed for expression of a nucleotide sequence in a host cell, or a “viral vector” which is designed to result in the production of a recombinant virus or virus-like particle, or “shuttle vectors”, which comprise the attributes of more than one type of vector.
A number of vectors suitable for stable transfection of cells and bacteria are available to the public (e.g., plasmids, adenoviruses, baculoviruses, yeast baculoviruses, plant viruses, adeno-associated viruses, retroviruses, Herpes Simplex Viruses, Alphaviruses, Lentiviruses), as are methods for constructing such cell lines. It will be understood that the present invention encompasses any type of vector comprising any of the polynucleotide molecule of the invention.
2. Antibodies
In another embodiment, the invention features antibodies that specifically bind to the polypeptides of the invention. More specifically, the antibody is a purified polyclonal or monoclonal antibody that specifically binds to the preferred S. suis polypeptides as defined above.
The antibodies of the invention may be prepared by a variety of methods known to one skilled in the art. For example, the polypeptides of the invention may be administered to an animal in order to induce the production of polyclonal antibodies. Alternatively, and as mentioned above, antibodies used as described herein may be monoclonal antibodies, which are prepared using known hybridoma technologies (see, e.g., Hammerling et al., In Monoclonal Antibodies and T-Cell Hybridomas, Elsevier, N.Y., 1981; Charland, N., M. Jacques, S. Iacouture and M. Gottschalk. 1997. Characterization and protective activity of a monoclonal antibody against a capsular epitope shared by Streptococcus suis serotypes 1, 2 and 1/2. Microbiology 143 (Pt 11): 3607-14).
With respect to antibodies of the present invention, the term “specifically binds to” refers to antibodies that bind with a relatively high affinity to one or more epitopes of the SP1 or SP2 polypeptide of the invention, but which do not substantially recognize and bind molecules other than the SP1 or SP2 polypeptides of the invention. As used herein, the term “relatively high affinity” means a binding affinity between the antibody and the SP1 or SP2 polypeptides of at least 106 M−1, and preferably of at least about 107 M−1 and even more preferably 108 M−1 to 1010 M−1. Determination of such affinity is preferably conducted under standard competitive binding immunoassay conditions which are common knowledge to one skilled in the art.
3. Methods of Treatment and Compositions
The SP1 and SP2 polypeptides, polynucleotides encoding same and antibodies of the invention may be used in many ways in the treatment and/or prevention of Streptococcus suis-associated diseases or infection caused by S. suis.
For instance, and according to an aspect of the invention, the SP1 and/or SP2 polypeptides of the invention may be used as immunogens for the production of specific antibodies for the treatment and/or prevention of Streptococcus suis infection. Suitable antibodies may be determined using appropriate screening methods, for example by measuring the ability of a particular antibody to passively protect against Streptococcus suis infection in a test model. Examples of an animal model are the mouse and pig models described in the examples herein.
According to another aspect, the polynucleotides encoding polypeptides of the invention or derivatives thereof may be used in a DNA immunization method. That is, they can be incorporated into a vector which is replicable and expressible upon injection thereby producing the antigenic polypeptide in vivo. For example polynucleotides may be incorporated into a plasmid vector under the control of the CMV promoter which is functional in eukaryotic cells. Preferably the vector is injected intramuscularly.
The use of a polynucleotide of the invention in genetic immunization will preferably employ a suitable delivery method or system such as direct injection of plasmid DNA into muscles [Wolf et al. H M G (1992) 1: 363, Turnes et al., Vaccine (1999), 17: 2089, Le et al., Vaccine (2000) 18: 1893, Alves et al., Vaccine (2001) 19: 788], injection of plasmid DNA with or without adjuvants [Ulmer et al., Vaccine (1999) 18: 18, MacLaughlin et al., J. Control Release (1998) 56: 259, Hartikka et al., Gene Ther. (2000) 7:1171-82, Benvenisty and Reshef, PNAS USA (1986) 83: 9551, Singh et al., PNAS USA (2000) 97: 811], targeting cells by delivery of DNA complexed with specific carriers [Wa et al., J Biol Chem (1989) 264: 16985, Chaplin et al., Infect. Immun. (1999) 67:6434], injection of plasmid complexed or encapsulated in various forms of liposomes [Ishii et al., AIDS Research and Human Retroviruses (1997) 13: 142, Perrie et al., Vaccine (2001) 19:3301], administration of DNA with different methods of bombardment [Tang et al., Nature (1992) 356: 152, Eisenbraun et al., DNA Cell Biol (1993) 12: 791, Chen et al., Vaccine (2001) 19:2908], and administration of DNA with lived vectors [Tubulekas et al., Gene (1997) 190: 191, Pushko et al., Virology (1997) 239: 389, Spreng et al. FEMS (2000) 27: 299, Dietrich et al., Vaccine (2001) 19: 2506].
A further aspect of the invention is the use of the antibodies directed to the polypeptides of the invention for passive immunization. One could use the antibodies described in the present application.
In this connection, another embodiment of the present invention relates to a composition for preventing or treating such diseases or infections. The composition of the present invention advantageously comprises an acceptable carrier and a SP1 and/or SP2 polypeptide(s) of the invention. Alternatively, the composition of the invention can comprise an antibody and/or a polynucleotide and/or an expression vector of the invention.
In a preferred embodiment, the composition of the invention further comprises an adjuvant. As used herein, the term “adjuvant” means a substance added to the composition of the invention to increase the composition's immunogenicity. The mechanism of how an adjuvant operates is not entirely known. Some adjuvants are believed to enhance the immune response (humoral and/or cellular response) by slowly releasing the antigen, while other adjuvants are strongly immunogenic in their own right and are believed to function synergistically. Known adjuvants include, hut are not limited to, oil and water emulsions (for example, complete Freund's adjuvant and incomplete freund's adjuvant), Corytzebactei-ium parvuin, Quil A, cytokines such as IL12, Emulsigen-Plus®, Bacillus Calmette Guerin, aluminum hydroxide, glucan, dextran sulfate, iron oxide, sodium alginate, Bacto Adjuvant, certain synthetic polymers such as poly amino acids and co-polymers of amino acids, saponin, paraffin oil, and muramyl dipeptide. Adjuvants also encompass genetic adjuvants such as immunomodulatory molecules encoded in a co-inoculated DNA, or as CpG oligonucleolides. The coin-oculated DNA can be in the same plasmid construct as the plasmid immunogen or in a separate DNA vector.
Yet, a further embodiment of the present invention is to provide a method for treating and/or preventing a Streptococcus suis-associated disease or infection in an animal. The method of the invention comprises the step of administering to the animal a composition according to the invention.
Further agents can be added to the composition of the invention. For instance, the composition of the invention may also comprise agents such as drugs, immunostimulants (such as α-interferon, β-interferon, γ-interferon, granulocyte macrophage colony stimulator factor (GM-CSF), macrophage colony stimulator factor (M-CSF), and interleukin 2 (IL2)), antioxidants, surfactants, flavoring agents, volatile oils, buffering agents, dispersants, propellants, and preservatives. For preparing such compositions, methods well known in the art may be used.
The amount of the components or the elements of the composition of the invention is preferably a therapeutically effective amount. A therapeutically effective amount of the contemplated component is the amount necessary to allow the same to perform their immunological role without causing overly negative effects in the host to which the composition is administered. The exact amount of the components to be used and the composition to be administered will vary according to factors such as the type of condition being treated, the type and age of the animal to be treated, the mode of administration, as well as the other ingredients in the composition.
The composition of the invention may be given to an animal through various routes of administration. For instance, the composition may be administered in the form of sterile injectable preparations, such as sterile injectable aqueous or oleaginous suspensions. These suspensions may be formulated according to techniques known in the art using suitable dispersing or wetting agents and suspending agents. The sterile injectable preparations may also be sterile injectable solutions or suspensions in non-toxic parenterally-acceptable diluents or solvents. They may be given parenterally, for example intravenously, intramuscularly or sub-cutaneously by injection, by infusion or per os. Suitable dosages will vary, depending upon factors such as the amount of each of the components in the composition, the desired effect (short or long term), the route of administration, the age and the weight of the animal to be treated. Any other methods well known in the art may be used for administering the composition of the invention.
4. Methods of Detection or Diagnosis and Kits
The SP1 and/or SP2 polypeptides, polynucleotides encoding same and antibodies of the invention may also be used in different ways in the detection and diagnosis of Streptococcus suis-associated diseases or infections caused by S. suis.
In this connection and in a further embodiment, the present invention provides a method for detecting the presence or absence of a Streptococcus suis strain in a sample, comprising the steps of:
-
- a) contacting the sample with an antibody of the invention as defined above for a time and under conditions sufficient to form a complex; and
- b) detecting the presence or absence of the complex formed in a).
As used herein, the term “sample” refers to a variety of sample types obtained from an animal and can be used in a diagnostic or detection assay. The definition encompasses blood and other liquid samples of biological origin, solid tissue samples such as a biopsy specimen or tissue culture or cells derived therefrom.
Yet, in another embodiment, the present invention provides a method for detecting the presence or absence of antibodies raised against a Streptococcus suis strain in a sample, comprising the steps of:
-
- a) contacting the sample with a polypeptide of the invention as defined above for a time and under conditions sufficient to form an immune complex; and
- b) detecting the presence or absence of the immune complex formed in a).
One skilled in the art will recognize that this diagnostic test may take several forms, including an immunological test such as an enzyme-linked immunosorbent assay (ELISA) or a radioimmunoassay, essentially to determine whether antibodies specific for the protein (such as SP1 and/or SP2) are present in an organism.
The present invention further provides kits for use within any of the above diagnostic methods. Such kits typically comprise two or more components necessary for performing a diagnostic assay. Components may be compounds, reagents, containers and/or equipment. For example, one container within a kit may contain an antibody or fragment thereof that specifically binds to a SP1 or SP2 polypeptide of the invention. One or more additional containers may enclose elements, such as reagents or buffers, to be used in the assay.
In this connection, the present invention also provides a diagnostic kit for the detection of the presence or absence of antibodies indicative of Streptococcus suis strain, comprising:
-
- a SP1 and/or SP2 polypeptide according to the invention;
- a reagent to detect polypeptide-antibody immune complex;
- a biological reference sample lacking antibodies that immunologically bind with said peptide; and
- a comparison sample comprising antibodies which can specifically bind to said peptide;
wherein said polypeptide, reagent, biological reference sample, and comparison sample are present in an amount sufficient to perform said detection.
Another diagnostic kit preferably contemplated is a kit for the detection of the presence or absence of polypeptides indicative of Streptococcus suis strain, comprising:
-
- an antibody according to the invention;
- a reagent to detect polypeptide-antibody immune complex;
- a biological reference sample polypeptides that immunologically bind with said antibody; and
- a comparison sample comprising polypeptides which can specifically bind to said peptide;
wherein said antibody, reagent, biological reference sample, and comparison sample are present in an amount sufficient to perform said detection.
The present invention will be more readily understood by referring to the following examples. These examples are illustrative of the wide range of applicability of the present invention and are not intended to limit its scope. Modifications and variations can be made therein without departing from the spirit and scope of the invention. Although any methods and materials similar or equivalent to those described herein can be used in the practice for testing of the present invention, preferred methods and materials are described hereinafter.
Example 1 Identification of a Surface Protein of Streptococcus suis and Evaluation of its Immunogenic and Protective Capacity in PigsA new Streptococcus suis surface protein reacting with a convalescent serum from pigs clinically infected by S. suis type 2 was identified. The apparent 110 kDa protein designated SP1 exhibits typical features of membrane-anchored surface proteins of Gram-positive bacteria such as a signal sequence and a LPVTG (SEQ ID NO: 10) membrane anchor motif. Moreover, a conserved avirulence domain that often found in plant pathogens has been detected. Electron microscopy using a SP1-specific antiserum has confirmed the surface location of SP1 protein on S. suis. The SP1-specific antibody reacts with the cell lysates of most S. suis serotypes and type 2 isolates in immunoblots, demonstrating its high conservation in S. suis species. Immunization of piglets with the recombinant SP1 by intramuscular route elicits a significant total immunoglobulin G (IgG) antibody response. However, the antibody response is not reflected in protection of pigs that are intratracheally challenged with a virulent strain in our conventional vaccination model.
Materials and Methods
Bacterial strains, phage, plasmids and media. Reference strain S735 of S. suis serotype 2 was used for the genomic library construction. Reference strains of the thirty-three serotypes (types 1 to 31, 33 and 1/2), 26 field strains of serotype 2 from different origin as well as five other Gram-positive organisms are listed in Table 1. Phage Lambda Zap II and Escherichia coli XL1-Blue MRF strain were obtained from a commercial source (Stratagene, La Jolla, Calif.). S. suis were grown in Todd-Hewitt broth (THB, Difco, Detroit, Mich.) or agar plates (Quelab Laboratories, Montreal, Canada) at 37° C. with 5% of CO2, while other Gram-positive bacteria were grown as recommended by the ATCC catalogue. E. coli was grown in either Luria-Bertani (LB) medium alone or LB medium supplemented with 2 g of maltose/liter at 37° C. Where appropriate, E. coli was grown in the presence of 50 μg of ampicillin/ml and 0.8 mM isopropyl-β-D-thiogalactopyranoside (IPTG). pMal™-p vector (New England BioLabs) was used for generating the MBP-SP1 fusion protein.
Antisera. Convalescent swine sera were collected from pigs clinically infected with S. suis type 2 strain S735. Monospecific anti-SP1 serum was obtained by immunizing New Zealand White rabbits intravenously with 230 μg of purified SP1 emulsified with 0.5 ml of Freud's incomplete adjuvant. The rabbits received two booster injections with the same dose of the SP1 at 2-week intervals and then were bled 10 days after the last booster immunization. Sera were stored at −20° C. until used.
Identification, cloning, and sequencing of the sp1 gene. Chromosomal DNA from S. suis S735 strain was isolated as previously described (33). Purified chromosomal DNA was partially digested with the restriction enzyme EcoRI, and the resulting fragments were electrophoresed in 1% agarose gel. Fragments in the 6- to 10-kb size range were extracted from the gel and ligated to the EcoRI arms of λZAPII vector, and the vector was encapsidated using the Gigapack II packaging extract (Stratagene). The recombinant phages were used to infect E. coli XL1-Blue MRF′. which was then plated onto LB agar. The resulting plaques were lifted onto nitrocellulose membranes (Bio-Rad, Mississauga, Ontario, Canada). The membranes were blocked using Tris-saline buffer (TBS) with 2% skim milk and sequentially incubated with the convalescent swine serum from S. suis serotype 2 infection, peroxidase-conjugated rabbit anti-swine immunoglobulin G (IgG) antisera (Jackson Immuno Research Laboratories, Inc., West Grove, Pa.), and O-phenylenediamine. The positive plaques were purified to homogeneity. The recombinant pBluescript plasmids were excised with ExAssist helper phage (Stratagene) according to the manufacturer's instructions. The sequence of the insert was determined using T3 and T7 promoters as primers in DNA Sequencing Facility, University of Maine (Orono, Me., USA). The nucleotide and amino acid sequences deduced from open reading frames (ORFs) were analyzed using programs available on the internet.
The sequence coding for mature SP1 was amplified from purified chromosomal DNA of strain S735 by PCR primers P1 (5′-ATGGATCCATTGAAGGCCGCTCGGCACAAGAAGTAAAA-3′; SEQ ID NO 13) and P2 (5′-CCAAGTCGACTTATAATTTACGTTTACGTGTA-3′; SEQ ID NO 14), which contained BamHI and Sal I restriction sites, respectively. The PCR was performed with 5 min at 94° C., followed by 30 cycles of 1 min at 94° C., 30 s at 56° C., and 1 min at 72° C. The resulting PCR fragment was cloned into Bam HI and Sal I sites of pMAL-p expression vector. The recombinant plasmid containing the sp1 gene was named pORF3.
Expression and purification of recombinant SP1 protein. The purified plasmid pORF3 was used to transform E. coli XL1-Blue strain by electroporation with Genepulse II apparatus (Bio-Rad) following the manufacturer's recommendations. This recombinant strain was grown in LB medium plus 2 g of glucose/L and 50 μg of ampicillin/ml. For over-expression, the culture was inoculated from an overnight culture with its starting OD600 adjusted to 0.1. The culture was incubated with agitation until OD600 of approximately 0.8, and then IPTG was added in order to induce production of the MBP-SP1 fusion protein. After 2 hours of the induction, the fusion protein was found in the bacterial periplasm as well as in the cytoplasm. It was decided to use extracts of the bacterial lysates for purification of the SP1 protein.
The fusion protein was purified by affinity chromatography using an amylose resin (New England BioLabs) following the manufacturer's instructions. The E. coli cell pellet was suspended in the affinity column binding buffer (20 mM Tris-HCl, 50 mM NaCl, pH 7.4) and cells were lysed using the French Pressure Cell Press (SLM Instruments, Inc.). After filtration with a 0.45 μm membrane, the supernatant was subjected to the amylose resin. The MBP-SP1 fusion protein was eluted with 1% maltose in the binding buffer and protein-containing fractions were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The purified fusion protein was cleaved with protease Factor Xa (New England BioLabs) at a concentration of 20 μg/mg protein, and applied to a mono-Q column (Amersham Pharmacia Biotech, Baie d'Urfee, Canada). The recombinant SP1 devoid of MBP carrier was eluted from the column by using a linear NaCl gradient (0 to 0.4 M NaCl in 20 mM Tris-HCl, pH 7.4). The SP1-containing fractions were combined and dialyzed against PBS buffer. The purity of the recombinant SP1 was evaluated by SDS-PAGE, and the concentration of the protein was determined by the Bradford protein assay (Bio-Rad) according to the manufacturer's instructions.
SDS-PAGE and western immunoblotting. SDS-PAGE was performed as described by Laemmli (21). Total cell extract or purified protein was separated on a 10% acrylamide gel and the gel was then stained with Coomassie brilliant blue R250 (Sigma, St. Louis, Mo.). Prestained low molecular mass markers (Bio-Rad) were used to determine the apparent molecular weights of proteins. Alternatively, Western blotting of proteins transferred to nitrocellulose membranes was performed essentially as described by Burnette (5).
Immunoelectron microscopy. S. suis S735 strain was grown in 5 ml of THB overnight, centrifuged, and resuspended in 500 μl of PBS (pH8.0). 20 μl of the bacterial suspension was placed on nickel-formvar grids (INRS, Institut Armand Frappier, Laval, Canada) and allowed to partially air dry. After blocking for 30 min with 10% normal donkey serum in dilution buffer (PBS-1% bovine albumin-1% Tween 20, pH8.0), the grids were soaked in 50 μl of SP1-specific rabbit serum or control rabbit anti-MBP serum (New England BioLabs) diluted 1/25 in the dilution buffer for 2 h at room temperature. The grids were washed three times in PBS-1% Tween20, and then transferred into 50 μl of 12 nm colloidal gold-affinipure donkey anti-rabbit IgG (Jackson Immuno Research Laboratories) diluted 1/30 in the dilution buffer and incubated for 1 h at room temperature. After three washes with PBS-1% tween20 and one wash with distilled water, bacteria were stained with 1% phosphotungstic acid and examined with an electron microscope (Philips 201) at an accelerating voltage of 60 kV.
Immunization and protection study. Pigs were used to perform the immunization and protection assay at VIDO (Saskatoon, Canada) in accordance with principles outlined in the “guide to the care and use of experimental animals” of the Canadian Council on Animal Care using a protocol that was approved by the University Committee on Animal Care (37). Three week-old piglets with average weight of 8.23 kg from a herd that is free of S. suis serotype 2 were randomly assigned to two groups of eight. The pigs were injected intramuscularly twice at a 3-week interval with 1 ml of either 100 μg purified SP1 mixed with 30% Emulsigen-Plus (MVP Laboratories, Ralston, Nebr.) adjuvant or 30% Emulsigen-Plus in physiological saline as a control. Eleven days after the second injection, the immunized and control animals were challenged by aerosol of 1 ml (4.6×106 CPU) of a log-phase culture of S. suis virulent strain 166, which has been confirmed to be highly virulent (3). Blood samples were collected prior to each injection, challenge and the end of the experiment for determination of antibody responses. Pigs were monitored daily for clinical signs, body temperature and mortality for ten days after challenge. All pigs were examined postmortem for gross pathology and blood was cultured to detect the presence of S. suis bacteremia.
ELISA. Serum SP1-specific total IgG and IgG isotypes (IgG1 and IgG2) of immunized piglets were determined by enzyme-linked immunosorbent assay (ELISA). Polysorb plates (Nunc-Immunoplates, Rochester, N.Y., USA) were coated overnight at 4° C. with 100 μl per well of the purified recombinant SP1 at a concentration of 0.3 μg/ml in carbonate buffer. After three washes with PBS containing 0.05% Tween20 (PBST), the plates were blocked with 5% skim milk in PBST for 1 h at 37° C. for determination of total IgG, swine sera from the control and vaccine groups were diluted 1/5000 in PBST and added to appropriate wells in duplicate at 100 μl per well. After incubation for 1 h at 37° C. and washing three times, bound antibodies were detected by incubation for 1 h at 37° C. with peroxidase-conjugated goat anti-swine IgG(H+L) antisera (Jackson Immuno Research Laboratories). For IgG1 and IgG2 detection, 1/500 diluted swine sera from vaccine group were added at 100 μl per well. Mouse anti-porcine IgG1 or IgG2 (Serotec, Kidlington, Oxford, UK) was used as the primary antibody, and peroxidase-conjugated goat anti-mouse IgG(H+L) (Serotec) was used as the secondary antibody. The plates were developed with TMB substrate (Zymed, S. San Francisco, USA). Absorbance was measured at 450 nm in an ELISA reader (Power Wave 340, Bio-Tek Instruments, Inc.). Results were expressed as the means±S.D. Statistical significance was determined by Student's t test.
Nucleotide sequence accession number. The sequence of the gene encoding SP1 protein of S. suis is shown in
Results
Identification of sp1 gene. The S. suis chromosomal library was constructed from the S. suis S735 strain in λZAPII and screened using convalescent swine sera from S. suis serotype 2 infected animals. One clone, which expressed a protein with an apparent molecular weight (MW) of 110 kDa that was strongly reactive against the convalescent swine serum, was selected for further characterization. The recombinant pBluescript plasmid, designated pSS735, was excised from the bacteriophage arms, and its schematic organization is presented in
SP1 is a novel C-terminal-anchored surface protein of S. suis. The 2010 bp of sp1 gene starts with an ATG codon which is preceded by putative Shine-Dalgarno sequence (GAAAGGA) 10 bp upstream of the start codon and terminates with a TAA codon (
Analysis of the amino acid composition revealed a region of absence of aromatic residues between Glu272 and Thr630, which spans all of the repeat sequences. Furthermore, a conserved domain search using BLAST identified an avirulence domain in Lys319 to Val601 region, which exhibits similarity with AvrXa7 avirulence factor from the plant pathogen Xanthomonas oryzae pv. oryzae (41) with 20% identity (
Production of the recombinant SP1. The sequence coding for mature SP1 protein was amplified by PCR and ligated into the IPTG-inducible pMAL-p vector. The resulting recombinant plasmid was expressed in E. coli XL1-Blue strain. As shown in
The fusion protein was purified by using affinity matrix amylose column and eluting with maltose, and showed a single protein band of approximate 150 kDa on SDS-PAGE (lane 4). The purified fusion protein was proteolytically cleaved with Factor Xa, yielding the apparent 110 kDa of mature SP1 and the expected 45 kDa of MBP tag (lane 5). The mature SP1 devoid of MBP was obtained by subsequent purification with ion-exchange chromatography, with a purity>95% estimated by SDS-PAGE (lane 6). Both the MBP-SP1 fusion protein and the purified recombinant SP1 demonstrated specific reactivity in a western blot to the convalescent swine serum used for the initial screening of the genomic library (
Cell surface expression of SP1 in S. suis. To confirm the location of SP1 on the surface of S. suis cells, immunoelectron microscopy was conducted by using a monospecific polyclonal anti-SP1 antibody, R44. Immunogold particles were found to be evenly distributed on the surface of the S. suis S735 strain. This indicates that SP1 protein is homogeneously expressed on the cellular surface. Rabbit anti-MBP serum was used as control and did not show any labeling (
Distribution of the SP1 among S. suis. To evaluate the conservation of SP1 among reference strains of deferent serotypes of S. suis and serotype 2 field strains, whole cell preparations of the bacteria were applied to western blots and detected by SP-specific antibody R44. As shown in Table 1, except for strains of serotypes 13, 16, 20, 22 and 24, R44 reacted with other 28 S. suis serotypes, while 25 of 26 tested type 2 isolates from different geographic origins reacted with the R44 antibody. Five strains from other species of Streptococci were used to verify the specificity of SP1 and no SP1 protein were detected.
Immunogenicity of SP1 and protection of pigs against challenge with S. suis. Groups of 8 piglets were immunized twice intramuscularly with either 100 μg of purified recombinant SP1 emulsified with the adjuvant or adjuvant only. Immunization of pigs with SP1 triggered an antigen-specific response (
Discussion
First immunization of pigs elicited rapid SP1-specific humoral antibody response that can be significantly boosted by a subsequent injection. However, the antibody to SP1 did not confer immunity against an heterologous challenge using S. suis strain 166. This discrepancy between antibody response and protection have been reported in some other surface antigens of Gram-positive bacteria, such as streptococcal fibronectin binding protein (Sfb1) (26), pneumococcal surface protein A (PspA) (27), group B polysaccharide (25) and M-like protein (SeM) of Streptococcus equi (34). The reason why antibodies against SP1 were not protective against the challenge by S. suis 166 is unclear. In a phagocytic killing study, presence of pooled serum from the SP1-immunized pigs did not promote S. suis killing by porcine neutrophils, suggesting that the antibodies are lacking opsonophagocytic function. Host protection against infection caused by S. suis, a highly encapsulated microorganism, is mediated primarily by phagocytosis (32). Therefore, total IgG levels generated in the Applicant's conventional vaccination model may not adequately reflect the presence of protective antibodies that are capable of triggering leukocyte effector functions. To further illustrate the immune response types trigged by SP1, IgG isotypes in immunized sera were assessed. IgG1 levels were consistently higher then IgG2 levels suggesting the induction of Th2-like responses. Although the concept of “Th1/Th2” balance is not yet well documented in pigs as in some other species, recent evidence showed that porcine IgG2 had greater complement activating ability than did IgG1 (6).
Emulsigen-Plus was used as an adjuvant in this study, because it was believed to be capable of creating an antigen depot at the site of inoculation from which the antigen is slowly released and thus providing prolonged stimulation to the immune system (23, 37). However, recent evidence showed that vaccine formulated with Emulsigen alone triggered predominantly an IgG1 response but very weak Th1-type immune response (19, 28). Evidence from vaccination using surface antigens of other Gram-positive bacteria has demonstrated that efficiency of opsonophagocytosis can be dramatically enhanced by using Th1-directing adjuvants, such as CpG and interleukin-12 (IL-12) (4, 22, 24). These adjuvants promote a Th1-type immune response characterized by enhanced production of opsonizing antibodies, specially IgG2 isotype. Furthermore, the enhanced antibody-mediated opsonization was clearly reflected in protection (2, 40).
In conclusion, SP1 is a novel C-terminal-anchored surface protein of S. suis, as demonstrated by analysis of the molecular features and electron microscopy. Vaccination with the recombinant SP1 elicited significant humoral antibody response in piglets, along with the fact that convalescent swine sera present high titers of antibody against this protein, suggesting that SP1 is an exposed antigen of S. suis. Taken together with its wide distribution in different S. suis serotypes, these findings made the SP1 a candidate for consideration in the development of a subunit vaccine. The potential of SP1 as a vaccine candidate will be demonstrated in the following Examples.
Example 2 Recombinant SP1 Protects Mice Against S. suis Challenge InfectionThis study is to evaluate whether the SP1 recombinant protein is protective as a subunit vaccine candidate in a mouse model with a modified immunization route and adjuvant.
EXPERIMENTAL PROCEDURE: Mice (CD1) were randomly assigned to two groups of ten, and immunized subcutaneously twice at 2-week interval with either 20 μg of purified SP1 mixed with 20 μg of Quil A as a adjuvant or 20 μg of Quil A only as a control (Table 1). Ten days after the second vaccination, the animals were challenged i.p. with 1×108 CFU of a S. suis virulent strain (31533). The mice were monitored twice a day for clinical signs and mortality until day 14 after the infection. Blood samples were collected prior to each vaccination and challenge for determining antibody responses.
RESULTS: Vaccination with SP1 elicited significant humoral IgG responses in mice after primary immunization (mean titre 3×104) and a booster injection significantly increased the antibody titre (1.8×106). In contrast, the SP1-specific IgG in sera of control group was at undetectable level (
Sixteen hours after administering the challenge infection, all mice in control group started to exhibit clinical signs (septicemia), such as the ruffled hair coat (suggesting fever) and slow response to stimuli. Starting from day 4 after the challenge, 8 of 10 mice in this group successively developed severe central nervous system symptoms (meningitis) such as running in circles and opisthotonos. All of the 8 ill mice died, or had to be euthanized due to the severity of the condition. In contrast, except for 6 of 10 mice in SP1-vaccinated group had transient clinical signs such as slight rough hair and reluctant to move during 16-40 hours after the challenge, all mice in this group remained healthy during the observation period (
DISCUSSION AND CONCLUSION: The difference in protection observed in mouse and pig models is explained by well-balanced IgG subclass levels evoked in the mouse vaccination model, especially the extremely high IgG2a titre. Among murine antibody isotypes, IgG2a has been shown to be the most effective at activating opsonophagocytic function of leukocytes (2, 42, 43)). Furthermore, S. suis, an encapsulated bacterial, is most effectively eliminated by opsonophagocytosis. Thus, it is likely that predominant IgG2 production contributed most to the observed protection. Nevertheless, these data indicate that immunization of mice with SP1 by using a Th1 inducing adjuvant, such as Quil A, can induce an efficient antigen-specific response, and protect mice against challenge infection with a lethal dose of a virulent S. suis strain and result in complete protection from S. suis death (
In the Applicant's continued effort to understand the pathogenic mechanism of S. suis and search for its protein(s) that may be useful in the development of a reliable diagnostic reagent or vaccine, a new protein which exhibits IgG-binding activity was identified from a virulent strain of S. suis serotype 2. This apparent 58-kDa protein designed SP2 contains a 23 amino acids cleavable N-terminal signal sequence and a lysine M motif near the N-terminus, and six identical repeats of 13 amino acids each within the C-terminal part. SP2 is highly conserved among different S. suis serotypes as demonstrated by PCR amplification of the SP2 gene. Recombinant SP2 strongly reacted with a convalescent swine serum collected from pigs clinically infected by S. suis type 2. Immunization of mice with the purified recombinant SP2 elicits a significant antibody response that conferred a partial protection against challenge infection with a virulent S. suis strain.
These results show that SP2 is a potential diagnostic agent and vaccine candidate for S. suis infection.
Experimental Procedures and Results
Identification of SP2 Gene
A positive phage which reacted by non immune mechanism with different classes and species of Ig (Pig IgG, Human IgG and IgA) was identified by screening the constructed S. suis serotype 2 genomic library. Sequence of the DNA insert revealed a 6.3 kb insert which contains three ORFs coding for dehydrogenases, SP2 and dextran glycosidases (44), respectively (
Characterization of SP2 Protein
The 1158 bp SP2 gene encodes a 386-aa SP2 protein, with a theoretical pl of 4.40 and molecular mass of 42.5 kDa. This protein was rich in valine (15%), glutamic acid (10%), and alanine (9%). Charge distribution analysis of SP2 revealed one positive charge cluster (K2-K26) at the N-terminus and one negative charge cluster (D168-E242) in middle of the protein (
Distribution of SP2 Gene in Different S. suis Serotypes
To evaluate the conservation level of SP2, PCR were performed using primers covering the full-length SP2 gene. PCR was performed with an initial denaturing at 94° C. for 5 min followed by 30-cycles of 1 min at 94° C., 1 min at 52° C. and 2 min at 72° C., and a final elongation period of 10 min at 72° C.
The forward and reverse primers used for SP2 distribution in different serotypes were respectively:
SP2 gene was amplified from 31 of the 33 serotype reference strains with some size variations (
Production and Purification of Recombinant SP2
The gene coding for mature SP2 was generated by PCR from S. suis S735 chromosome and subcloned to a pET32+ vector (New England BioLabs). The construct was used to transform E. coli DE3 strain by electroporation with Genepulse II apparatus (Bio-Rad) following the manufacturer's recommendations. For over-expression, the culture was inoculated from an overnight culture with its starting OD600 adjusted to 0.1. The culture was incubated with agitation until OD600 of approximately 0.8, and then IPTG (0.5 mM) was added in order to induce production of the Trx-His-SP2 fusion protein. After 2 hours of the induction, bacterial cytoplasm were prepared and used for purification of the SP2 protein.
The Trx-His-SP2 fusion protein was purified from the cytoplasm by affinity chromatography using Ni+ column (Amersham Pharmacia Biotech, Baie d'Urfee, Canada). The cytoplasm was filtered with a 0.45 μm membrane and subjected to the column. The fusion protein was eluted with 500 mM imidazole in binding buffer and protein-containing fractions were determined by SDS-PAGE. The purified fusion protein was cleaved by 0.001% (w/w) of enterokinase (New England BioLabs), yielding an apparent 58 kDa SP2 and the expected 20 kDa Trx-His tag (
SP2 is an Immunogenic Protein of S. suis and Exhibits IgG-Binding Activity
SP2-specific antibody was generated by immunizing New Zealand White rabbits intramuscularly with 100 μg of recombinant SP2 protein emulsified with 0.5 ml of Freud's incomplete adjuvant. The rabbits received two booster injections with the same dose of the SP2 at 2-week intervals and then were bled 10 days after the last booster immunization. The SP2 specific antibody conversely recognized SP2 in S. suis cell preparation in a western blot (
The binding activities of the recombinant SP2 to human and pig IgG were demonstrated in
Recombinant SP2 Partially Protects Mice Against S. Suis Challenge Infection
Mice (CD1) were randomly assigned to two groups of eleven (vaccine group) and ten (control), and immunized subcutaneously twice at 2-week interval with either 50 μg of purified SP2 mixed with 20 μg of Quil A as a Th1 inducing adjuvant or 20 μg of Quil A only as a control. Ten days after the second vaccination, the animals were challenged i.p. with 1×108 CFU of a S. suis virulent strain (31533). The mice were monitored twice a day for clinical signs and mortality until day 14 after the infection. Blood samples were collected prior to each vaccination and challenge for determining antibody responses.
Vaccination with SP2 elicited significant humoral IgG responses in mice. In contrast, the SP2-specific IgG in sera of control group was at undetectable level (
Conclusion
SP2 is a new described S. suis immunogenic protein which shares little identity with oilier known sequences. Convalescent swine sera present antibody against this protein, demonstrating that SP2 is a potent antigen that is expressed during S. suis infection. These findings, along with its wide distribution in different S. suis serotypes, make the SP2 a candidate for consideration in the development of a diagnostic reagent. Since vaccination of mice with recombinant SP2 resulted in protection, it is thus clear that SP2 is a potential vaccine candidate against S. suis infection.
Example 4 Effect of Immunization of Piglets with Experimental Streptococcus Suis VaccineThis study evaluates the protective effect of recombinant Sao protein on S. suis serotype 2 challenge infection in piglets.
Materials and Methods
Animals, Allocation to Treatment and Exclusion Criteria:
A total of 24 crossbred piglets from S. suis disease-free herd (H & M Fast Farms Inc.) without any previous vaccination against S. suis were used. The pigs were kept under commercial conditions at the herd of origin from birth until they were weaned at an average weight of 7.79 kg at 23.5 days of age. Pigs were housed with controlled temperature (27 to 30° C.) and ventilation, on vinyl-covered metal flooring, and were provided with water via nipple waterers and had free access to commercially-prepared, nutritionally balanced, antibiotic-free feed. A veterinarian examined the pigs prior to the beginning of the study. All were healthy. At weaning, the piglets were randomly assigned to two groups, balanced by body weight.
Group 1: 200 μg Sao and 400 μg Quil A in 1 mL Saline
Group 2: 400 μg Quil A in 1 mL Saline (control)
Any animals that receive an unintended treatment or succumb to an unrelated disease will be excluded from analysis.
Vaccination and Challenge:
All pigs were vaccinated IM with 1 ml twice at 2-week interval. Blood samples were collected before each injection and challenge. There were no adverse events as a result of these treatments.
Two weeks after the second vaccination, the pigs were anesthetized with halothane and challenged by aerosol of 1 ml of a suspension of S. suis 166. The bacteria were from a log-phase culture grown in filter sterilized Todd-Hewitt Yeast Broth to an OD620 of 0.8 and diluted 1:100 in saline (0.85% NaCl). The bacterial concentration administered to pigs was later measured to be 6.8×106 CFU/ml.
Clinical Observations:
A veterinarian or trained animal care technician clinically evaluated the pigs once daily and measured body temperatures during assignment of clinical scores each morning for ten days after challenge. A daily clinical score (from 0 to 4) was derived as the sum of attitude and locomotion scores for each animal based upon signs of nervous, musculoskeletal or respiratory disease as follows:
Attitude:
- 0=Normal attitude and response to stimuli
- 1=Inactive and slow to respond; oculo-nasal secretions
- 2=Only responsive to repeated stimuli, apathetic
- 3=Recumbent, nonresponsive, unaware of surroundings
- 4=Dead
Locomotion: - 0=Normal gait and posture
- 1=Slight in coordination, lameness and/or joint swelling but rises without assistance
- 2=Clearly uncoordinated or lame but stands without assistance
- 3=Severe lameness, severe ataxia, does not remain standing
- 4=Dead
Pigs having a clinical score greater than 2 on either scale were euthanized by lethal injection. Pigs with rectal temperatures equal to or greater than 40.6° C. and a clinical score greater than 0, as well as those pigs that were dead, were recorded as sick on that day. Pigs that died or were euthanized prior to the end of the experiment on day 9 were recorded as dead for evaluation of the effect of treatment on mortality rate. All individuals making judgements about animals, evaluating clinical signs of disease, or performing laboratory assays were blind to the identity of the treatment.
Haemotologic Condition:
A heparin-treated blood sample was obtained by venipuncture for detection of S. suis bacteremia (by culture on days 0 and 3 after challenge and postmortem).
Antibody Titre:
Titers of Sao-specific total IgG and IgG subclasses (IgG1 and IgG2) in sera were determined by ELISA. The serum dilution that resulted in an OD450 reading of 0.1 after background subtration was considered the titer of this serum.
Necropsy:
All pigs were examined postmortem and the following tissues were cultured for bacteria: cerebellum swab, tracheobronchial lymph node, a joint swab (an affected joint if lesions are present; otherwise a stifle joint), and blood. The number of S. suis bacteria that were recovered was recorded on an ordinal scale from 0 to 4 (approximating the log10 number of colonies). In addition, the extent (percentage) of pulmonary involvement was estimated by visual examination.
Statistical Analysis
The significance of differences between groups in nominal data (mortality, presence or absence of S. suis in the tissues, days sick or well) was determined using contingency table analysis and Likelihood-Ratio Fisher Exact Test. The significance of differences between groups in ordinal data (clinical score) was transformed by ranking and determined by t-test. The significance of differences between groups in survival curves was determined by survival analysis using the logrank test (equivalent to the Mantel-Haenszel test). The significance of differences among groups in continuous data (length of survival after challenge, body temperature, log2 CFU/ml of blood) was determined using t-test (after appropriate transformation to normality as required).
Results
Excluded Animals:
One pig was humanely killed on day 5 after the challenge because of persistent; worsening prolapsed rectum. This pig will be excluded from analysis.
Clinical Observations:
- 1. Response to immunisation: There were no unusual reactions attributable to vaccination.
- 2. Body temperature: The body temperature data as analysed by t-test, showed no significant difference between the two group (p>0.05). Generally the vaccinated pigs tended to have lower temperatures (
FIG. 20 ) - 3. Clinical disease: The “clinical score” is a measure of the amount of disease and incorporates both mortality and morbidity. The two groups were compared using Mann-Whitney analysis of an effect of vaccine on clinical score, and the clinical disease in vaccinated group was significantly less than that in control (p=0.024) (
FIG. 21 ). - 4. Survival of pigs after S. suis challenge: The survival rate is 82% in vaccination group and 42% in control group, respectively. Comparison of survival curves using the two data sets, shows that the survival time of vaccinated pigs was significantly longer than that of control (p=0.048) (
FIG. 22 ).
Bacteriology - 1. Bacteremia: Bacteria in the blood of piglets were not detected (ND) before challenge. The bacteremia pigs after challenge and postmortem were not significant different between the two groups. However, the vaccinated pigs had less bacteremia (table 3).
- 2. Infection postmortem: Microbiologic culture of samples from the brain, tracheobronchial lymph node, and joint of all of the pigs that were challenged was done to monitor the level of infection. Number of tissues from that bacteria with colonial morphology typical of the challenge strain were recovered was shown in table 4. The Wilcoxon Rank Sum test for the effect of vaccinated group on the median bacteriology score (median of the sum of scores for all tissues of each pig) showed that this difference was significant (p=0.007).
Pathology (Post-Mortem)
Pathologic lesions of arthritis or pneumonia were detected in only 6 pigs (2 in vaccinated group and 4 in control). Other dead or euthanized pigs had no gross pathologic signs. One of characterizations of S. suis infection is that acute infection can be fatal without appreciable gross signs of pathology. The tracheobronchial lymph node was enlarged. There was a trace of fibrin on the mesentery, indicating a mild peritonitis. There was evidence of arthritis in both stifles, in which there was a small amount of purulent material, and in the left shoulder, where there was a trace of purulent exudate.
Antibody Response
Immunization of pigs with Sao in combination with Quil A elicited significant humoral IgG responses after primary immunization and a booster injection significantly enhanced the antibody titre (
Summary and Discussion
The vaccine was shown to be safe since pigs that were vaccinated twice did not have any adverse reaction. Immunization of pigs with Sao in combination with Quil A elicited significant IgG titres with a dominant IgG2 production, suggesting a predominant Th1-type immune response. Aerosol challenge of pigs resulted in disease with an overall mortality rate of approximately 58% in controls. The survival of vaccinated pigs after challenge was significantly better than controls (p<0.05). Some pigs in each group became ill after challenge, and there was significantly less disease (lower clinical score) in the vaccinated pigs. Vaccination had no significant effect on the occurrence of gross pathology post-mortem; however acute streptococcal septicaemia can be fatal without appreciable gross signs of pathology. Less S. suis bacteria were recovered from vaccinated pigs than control pigs post mortem (p<0.01).
Example 5 Immunization of Mice and Piglets with Fragment SP1AImmunization of Mice
Three groups of 10 mice were immunized two times (Day 1 and Day 17) via i.p. with 40 μg of purified SP1A-maltose-binding protein (MBP) fusion protein, 20 μg of MBP or only PBS, using Freund Incomplete as an adjuvant. The sera were obtained before each immunization or 10 days after the second injection, and were 1:5000 diluted for ELISA assay. (See Table 5)
Immunization of Pigs
Three groups of 3 pigs were immunized two times (Day 1 and Day 17) via i.m. with 200 μg of purified SP1A-MBP fusion protein, 100 μg of MBP or only PBS, using Emulsigen as an adjuvant. The sera were obtained before each immunization or 10 days after the second injection, and were 1:5000 diluted for ELISA assay. (See Table 6)
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- 11. Gottschalk, M., R. Higgins, M. Jacques, K. R. Mittal, and J. Henrichsen. 1989. Description of 14 new capsular types of Streptococcus suis. J Clin Microbiol 27:2633-6.
- 12. Gottschalk, M., A. Lebrun, H. Wisselink, J. D. Dubreuil, H. Smith, and U. Vecht. 1998. Production of virulence-related proteins by Canadian strains of Streptococcus suis capsular type 2. Can J Vet Res 62:75-9.
- 13. Gottschalk, M., and M. Segura. 2000. The pathogenesis of the meningitis caused by Streptococcus suis: the unresolved questions. Vet Microbiol 76:259-72.
- 14. Higgins, R., and M. Gottschalk. 1998. Distribution of Streptococcus suis capsular types in 1997. Can Vet J 39:299-300.
- 15. Higgins, R., M. Gottschalk, M. Boudreau, A. Lebrun, and J. Henrichsen. 1995. Description of six new capsular types (29-34) of Streptococcus suis. J Vet Diagn Invest 7:405-6.
- 16. Higgins, R., M. Gottschalk. 2005. Streptococcal diseases (In press). In B. E. Straw, S. D'Allaire, W. L. Mengeling, and D. J. Taylor (9th ed), Diseases of swine. Iowa State University Press, Ames.
- 17. Hill, J. E., M. Gottschalk, R. Brousseau, J. Harel, S. M. Hemmingsen, and S. H. Goh. 2005. Biochemical analysis, cpn60 and 16S rDNA sequence data indicate that Streptococcus suis serotypes 32 and 34, isolated from pigs, are Streptococcus orisratti. Vet Microbiol 107:63-9.
- 18. Holt, M. E., M. R. Enright, and T. J. Alexander. 1988. Immunisation of pigs with live cultures of Streptococcus suis type 2. Res Vet Sci 45:349-52.
- 19. Ioannou, X. P., P. Griebel, R. Hecker, L. A. Babiuk, and S. van Drunen Littel-van den Hurk. 2002. The immunogenicity and protective efficacy of bovine herpesvirus 1 glycoprotein D plus Emulsigen are increased by formulation with CpG oligodeoxynucleotides. J Virol 76:9002-10.
- 20. Jacobs, A. A., A. J. van den Berg, and P. L. Loeffen. 1996. Protection of experimentally infected pigs by suilysin, the thiol-activated haemolysin of Streptococcus suis. Vet Rec 139:225-8.
- 21. Laemmli, U. K. 1970. Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature 227:680-5.
- 22. Lefeber, D. J., B. Benaissa-Trouw, J. F. Vliegenthart, J. P. Kamerling, W. T. Jansen, K. Kraaijeveld, and H. Snippe. 2003. Th1-directing adjuvants increase the immunogenicity of oligosaccharide-protein conjugate vaccines related to Streptococcus pneumoniae type 3. Infect Immun 71:6915-20.
- 23. Lofthouse, S. A., A. E. Andrews, A. D. Nash, and V. M. Bowles. 1995. Humoral and cellular responses induced by intradermally administered cytokine and conventional adjuvants. Vaccine 13:1131-7.
- 24. Lynch, J. M., D. E. Briles, and D. W. Metzger. 2003. Increased protection against pneumococcal disease by mucosal administration of conjugate vaccine plus interleukin-12. Infect Immun 71:4780-8.
- 25. Marques, M. B., D. L. Kasper, A. Shroff, F. Michon, H. J. Jennings, and M. R. Wessels. 1994. Functional activity of antibodies to the group B polysaccharide of group B streptococci elicited by a polysaccharide-protein conjugate vaccine. Infect Immun 62:1593-9.
- 26. McArthur, J., E. Medina, A. Mueller, J. Chin, B. J. Currie, K. S. Sriprakash, S. R. Talay, G. S. Chhatwal, and M. J. Walker. 2004. Intranasal vaccination with streptococcal fibronectin binding protein Sfb1 fails to prevent growth and dissemination of Streptococcus pyogenes in a murine skin infection model. Infect Immun 72:7342-5.
- 27. Miyaji, E. N., D. M. Ferreira, A. P. Lopes, M. C. Brandileone, W. O. Dias, and L. C. Leite. 2002. Analysis of serum cross-reactivity and cross-protection elicited by immunization with DNA vaccines against Streptococcus pneumoniae expressing PspA fragments from different clades. Infect Immun 70:5086-90.
- 28. Nichani, A. K., R. S. Kaushik, A. Mena, Y. Popowych, D. Dent, H. G. Townsend, G. Mutwiri, R. Hecker, L. A. Babiuk, and P. J. Griebel. 2004. CpG oligodeoxynucleotide induction of antiviral effector molecules in sheep. Cell Immunol 227:24-37.
- 29. Okwumabua, O., O. Abdelmagid, and M. M. Chengappa. 1999. Hybridization analysis of the gene encoding a hemolysin (suilysin) of Streptococcus suis type 2: evidence for the absence of the gene in some isolates. FEMS Microbiol Lett 181:113-21.
- 30. Pallares, F. J., C. S. Schmitt, J. A. Roth, R. B. Evans, J. M. Kinyon, and P. G. Halbur. 2004. Evaluation of a ceftiofur-washed whole cell Streptococcus suis bacterin in pigs. Can J Vet Res 68:236-40.
- 31. Perch, B., K. B. Pedersen, and J. Henrichsen. 1983. Serology of capsulated streptococci pathogenic for pigs: six new serotypes of Streptococcus suis. J Clin Microbiol 17:993-6.
- 32. Segura, M., M. Gottschalk, and M. Olivier. 2004. Encapsulated Streptococcus suis inhibits activation of signaling pathways involved in phagocytosis. Infect Immun 72:5322-30.
- 33. Serhir, B., D. Dugourd, M. Jacques, R. Higgins, and J. Harel. 1997. Cloning and characterization of a dextranase gene (dexS) from Streptococcus suis. Gene 190:257-61.
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- 39. Wisselink, H. J., U. Vecht, N. Stockhofe-Zurwieden, and H. E. Smith. 2001. Protection of pigs against challenge with virulent Streptococcus suis serotype 2 strains by a muramidase-released protein and extracellular factor vaccine. Vet Rec 148:473-7.
- 40. Wortham, C., L. Grinberg, D. C. Kaslow, D. E. Briles, L. S. McDaniel, A. Lees, M. Flora, C. M. Snapper, and J. J. Mond. 1998. Enhanced protective antibody responses to PspA after intranasal or subcutaneous injections of PspA genetically fused to granulocyte-macrophage colony-stimulating factor or interleukin-2. Infect Immun 66:1513-20.
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Claims
1. An isolated polypeptide comprising an amino acid sequence having at least 75% identity to the amino acid sequence set forth in SEQ ID NO: 1 or in SEQ ID NO: 4.
2. The isolated polypeptide of claim 1, comprising at least one repetitive amino acid sequence consisting of the amino acid sequence Xaa1 Ser Xaa3 Xaa4 Xaa5 Met Xaa7 Xaa8 Xaa9 Xaa10 Xaa11 Xaa12 Xaa13 Xaa14 Xaa15 Xaa16 Pro Xaa18 Xaa19 Gln Met Xaa22 Asn Lys Glu Xaa26 Xaa27 Xaa28 Xaa29 Xaa30 SEQ ID NO 9) wherein
- Xaa1 is Val, Thr or Ile;
- Xaa3 is Lys or Glu;
- Xaa4 is Lys or Glu;
- Xaa5 is Ala or Gln;
- Xaa7 is Thr or Pro;
- Xaa8 is Gly, Ser or Val;
- Xaa9 is Lys, VaI, Ile or Asn;
- Xaa10 is Glu or Val;
- Xaa11 is Lys or Asn;
- Xaa12 is Gly, Glu or Asp;
- Xaa13 is Asn or Met;
- Xaa14 is Ile, Ala or Val;
- Xaa15 is Glu or Val;
- Xaa16 is Pro or Thr;
- Xaa18 is Glu or Gln;
- Xaa19 is Lys or Glu;
- Xaa22 is Thr or Ala;
- Xaa26 is Lys or Asn;
- Xaa27 is Asp or Glu;
- Xaa28 is Asn or Lys;
- Xaa29 is Ile or Val and
- Xaa30 is Glu or Val.
3. The isolated polypeptide of claim 1, comprising the amino acid sequence as set forth in SEQ ID NO 10.
4. The isolated polypeptide of claim 1, comprising an amino acid having at least 85% identity to the amino acid sequence set forth in SEQ ID NO 1 or in SEQ ID NO 4.
5. The isolated polypeptide of claim 1, comprising an amino acid sequence having at least 95% identity to the amino acid sequence set forth in SEQ ID NO 1.
6. The isolated polypeptide of claim 1, comprising an amino acid sequence having at least 95% identity to the amino acid sequence set forth in SEQ ID NO 4.
7. The isolated polypeptide of claim 1, wherein it elicits a protective response to a Streptococcus suis strain challenge when administered to an animal.
8. The isolated polypeptide of claim 3, comprising at least one repetitive amino acid sequence consisting of the amino acid sequence Xaa1 Ser Xaa3 Xaa4 Xaa5 Met Xaa7 Xaa8 Xaa9 Xaa10 Xaa11 Xaa12 Xaa13 Xaa14 Xaa15 Xaa16 Pro Xaa18 Xaa19 Gln Met Xaa22 Asn Lys Glu Xaa26 Xaa27 Xaa28 Xaa29 Xaa30 SEQ ID NO 9) wherein
- Xaa1 is Val, Thr or Ile;
- Xaa3 is Lys or GIu;
- Xaa4 is Lys or GIu;
- Xaa5 is Ala or Gln;
- Xaa7 is Thr or Pro;
- Xaa8 is Gly, Ser or Val;
- Xaa9 is Lys, VaI, Ile or Asn;
- Xaa10 is Glu or Val;
- Xaa11 is Lys or Asn;
- Xaa12 is Gly, Glu or Asp;
- Xaa13 is Asn or Met;
- Xaa14 is Ile, Ala or Val;
- Xaa15 is Glu or Val;
- Xaa16 is Pro or Thr;
- Xaa18 is Glu or Gln;
- Xaa19 is Lys or Glu;
- Xaa22 is Thr or Ala;
- Xaa26 is Lys or Asn;
- Xaa27 is Asp or Glu;
- Xaa28 is Asn or Lys;
- Xaa29 is Ile or Val and
- Xaa30 is Glu or Val.
9. The isolated polypeptide of claim 4, comprising at least one repetitive amino acid sequence consisting of the amino acid sequence Xaa1 Ser Xaa3 Xaa4 Xaa5 Met Xaa7 Xaa8 Xaa9 Xaa10 Xaa11 Xaa12 Xaa13 Xaa14 Xaa15 Xaa16 Pro Xaa18 Xaa19 Gln Met Xaa22 Asn Lys Glu Xaa26 Xaa27 Xaa28 Xaa29 Xaa30 (SEQ ID NO 9) wherein
- Xaa1 is Val, Thr or Ile;
- Xaa3 is Lys or GIu;
- Xaa4 is Lys or GIu;
- Xaa5 is Ala or Gln;
- Xaa7 is Thr or Pro;
- Xaa8 is Gly, Ser or Val;
- Xaa9 is Lys, VaI, Ile or Asn;
- Xaa10 is GIu or Val;
- Xaa11 is Lys or Asn;
- Xaa12 is Gly, Glu or Asp;
- Xaa13 is Asn or Met;
- Xaa14 is Ile, Ala or Val;
- Xaa15 is Glu or Val;
- Xaa16 is Pro or Thr;
- Xaa18 is Glu or Gln;
- Xaa19 is Lys or Glu;
- Xaa22 is Thr or Ala;
- Xaa26 is Lys or Asn;
- Xaa27 is Asp or Glu;
- Xaa28 is Asn or Lys;
- Xaa29 is Ile or Val and
- Xaa30 is Glu or Val.
10. The isolated polypeptide of claim 5, comprising at least one repetitive amino acid sequence consisting of the amino acid sequence Xaa1 Ser Xaa3 Xaa4 Xaa5 Met Xaa7 Xaa8 Xaa9 Xaa10 Xaa11 Xaa12 Xaa13 Xaa14 Xaa15 Xaa16 Pro Xaa18 Xaa19 Gln Met Xaa22 Asn Lys Glu Xaa26 Xaa27 Xaa28 Xaa29 Xaa30 (SEQ ID NO 9) wherein
- Xaa1 is Val, Thr or Ile;
- Xaa3 is Lys or GIu;
- Xaa4 is Lys or GIu;
- Xaa5 is Ala or Gln;
- Xaa7 is Thr or Pro;
- Xaa8 is Gly, Ser or Val;
- Xaa9 is Lys, VaI, Ile or Asn;
- Xaa10 is Glu or Val;
- Xaa11 is Lys or Asn;
- Xaa12 is Gly, Glu or Asp;
- Xaa13 is Asn or Met;
- Xaa14 is Ile, Ala or Val;
- Xaa15 is Glu or Val;
- Xaa16 is Pro or Thr;
- Xaa18 is Glu or Gln;
- Xaa19 is Lys or Glu;
- Xaa22 is Thr or Ala;
- Xaa26 is Lys or Asn;
- Xaa27 is Asp or Glu;
- Xaa28 is Asn or Lys;
- Xaa29 is Ile or Val and
- Xaa30 is Glu or Val.
11. The isolated polypeptide of claim 6, comprising at least one repetitive amino acid sequence consisting of the amino acid sequence Xaa1 Ser Xaa3 Xaa4 Xaa5 Mel Xaa7 Xaa8 Xaa9 Xaa10 Xaa11 Xaa12 Xaa13 Xaa14 Xaa15 Xaa16 Pro Xaa18 Xaa19 Gln Met Xaa22 Asn Lys Glu Xaa26 Xaa27 Xaa28 Xaa29 Xaa30 (SEQ ID NO 9) wherein
- Xaa1 is Val, Thr or Ile;
- Xaa3 is Lys or GIu;
- Xaa4 is Lys or GIu;
- Xaa5 is Ala or Gln;
- Xaa7 is Thr or Pro;
- Xaa8 is Gly, Ser or Val;
- Xaa9 is Lys, VaI, Ile or Asn;
- Xaa10 is GIu or Val;
- Xaa11 is Lys or Asn;
- Xaa12 is Gly, Glu or Asp;
- Xaa13 is Asn or Met;
- Xaa14 is Ile, Ala or Val;
- Xaa15 is Glu or Val;
- Xaa16 is Pro or Thr;
- Xaa18 is Glu or Gln;
- Xaa19 is Lys or Glu;
- Xaa22 is Thr or Ala;
- Xaa26 is Lys or Asn;
- Xaa27 is Asp or Glu;
- Xaa28 is Asn or Lys;
- Xaa29 is Ile or Val and
- Xaa30 is Glu or Val.
12. The isolated polypeptide of claim 1, comprising an amino acid sequence having 100% identity to the amino acid sequence set forth in SEQ ID NO 1.
13. The isolated polypeptide of claim 1, comprising an amino acid sequence having 100% identity to the amino acid sequence set forth in SEQ ID NO 4.
14. An isolated polypeptide, comprising an amino acid sequence having at least 95% identity to the amino acid sequence set forth in SEQ ID NO 2.
15. The isolated polypeptide of claim 14, comprising an amino acid sequence having 100% identity to the amino acid sequence set forth in SEQ ID NO 2.
16. An isolated polypeptide, comprising an amino acid sequence having at least 95% identity to the amino acid sequence set forth in SEQ ID NO 3.
17. The isolated polypeptide of claim 16, comprising an amino acid sequence having 100% identity to the amino acid sequence set forth in SEQ ID NO 3.
18. A composition comprising an acceptable carrier and at least one of the following elements:
- a polypeptide as defined in any one of claims 1, 2, 3, 4, 5, 6, 7, and 8 to 17.
19. A composition for eliciting an immune response to Streptococcus or treating Streptococcus suis-associated diseases or infection caused by S. suis, comprising an acceptable carrier and at least one of the following elements:
- a polypeptide as defined in any one of claims 1, 2, 3, 4, 5, 6, 7, and 8 to 17.
20. The composition of claim 19, further comprising an adjuvant.
21. A method of screening for a polypeptide having immunogenic potential for preventing a Streptococcus suis-associated disease, comprising:
- (a) administering to an animal, a test polypeptide comprising at least 15 contiguous amino acids of the amino acid sequence of SEQ ID NO: 4; and
- (b) processing a biological sample from said animal to detect the presence or absence in said sample of an antibody having binding specificity to the polypeptide, wherein the presence of said antibody is indicative of the polypeptide having immunogenic potential for preventing the Streptococcus suis-associated disease.
22. The method of claim 21, wherein the test polypeptide comprises at least 25 contiguous amino acids of the amino acid sequence of SEQ ID NO: 4.
23. The method of claim 21, wherein the test polypeptide comprises at least 35 contiguous amino acids of the amino acid sequence of SEQ ID NO: 4.
24. The method of claim 21, wherein the test polypeptide comprises the amino acid sequence of SEQ ID NO: 9.
25. The method of claim 24, wherein the amino acid sequence of SEQ ID NO: 9 is a first repetitive amino acid sequence of a plurality of said repetitive amino acid sequence.
26. The method of claim 21, wherein said polypeptide is a recombinant polypeptide.
27. The method of claim 21, wherein said animal is a pig.
28. A method for preventing a Streptococcus suis-associated disease in an animal, comprising administering to the animal a polypeptide comprising at least 15 contiguous amino acids of the amino acid sequence of SEQ ID NO: 4.
29. The method of claim 28, said animal being a pig.
30. A microbial culture, comprising cells having a recombinant DNA molecule encoding a polypeptide comprising an amino acid sequence having at least 95% identity to the amino acid sequence set forth in SEQ ID NO: 4.
31. A method for producing a polypeptide comprising an amino acid sequence having at least 95% identity to the amino acid sequence of SEQ ID NO: 4, comprising cultivating a microbial culture comprising cells having a recombinant DNA molecule encoding said polypeptide under conditions conducive for production of said polypeptide, and recovering said polypeptide.
32. A method for preventing a Streptococcus suis-associated disease in an animal, comprising administering to the animal a polypeptide comprising an amino acid sequence having at least 95% identity to the amino acid sequence of SEQ ID NO: 4.
33. The method of claim 28, wherein the polypeptide comprises at least 25 contiguous amino acids of the amino acid sequence of SEQ ID NO: 4.
34. The method of claim 28, wherein the polypeptide comprises at least 35 contiguous amino acids of the amino acid sequence of in SEQ ID NO: 4.
| 5610011 | March 11, 1997 | Smith et al. |
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Type: Grant
Filed: Feb 27, 2015
Date of Patent: Jan 24, 2017
Assignee: VALORISATION-RECHERCHE, LIMITED PARTNERSHIP (Montreal)
Inventors: Josée Harel (Quebec), Marcelo Gottschalk (Quebec), Yuanyi Li (Quebec)
Primary Examiner: Bruce Campell
Application Number: 14/634,396
