Method of preventing T cell-mediated responses by the use of the major histocompatibility complex class II analog protein (map protein) from Staphylococcus aureus

Info

Publication number: 20070092533
Type: Application
Filed: Dec 22, 2006
Publication Date: Apr 26, 2007
Inventors: Eric Brown (Houston, TX), Lawrence Lee (Houston, TX), Magnus Hook (Houston, TX)
Application Number: 11/643,714

Abstract

A method of immunomodulating the T cell response in Staphylococcal bacteria is provided wherein an effective amount of the Map protein from Staphylococcus aureus is administered to a host to prevent or suppress the T cell response. The present method may be utilized with either the Map protein or an effective subdomain or fragment thereof such as the Map19 protein. The present invention is advantageous in that suppression or prevention of the T cell response in a host can prevent or ameliorate a wide variety of the pathogenic conditions such as toxic shock syndrome and other diseases associated with the T cell-mediated response caused by staphylococcal infection, and is particularly useful in cases where patients have had chronic or recurrent infections from S. aureus or other staphylococcal bacteria.

Description

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent application Ser. No. 10/041,775, filed Jan. 10, 2002, and claims the benefit of U.S. Provisional application Ser. No. 60/260,523, filed Jan. 10, 2001, said applications incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates in general to the utilization of major histocompatibility complex class II analog protein, or “Map” protein, and its biologically effective fragments and domains thereof, in therapeutic methods to combat bacterial infection and associated immunological disruption, and in particular to the use of the Map protein and effective or active fragments thereof, including the Map19 protein, in methods of suppressing or modulating T cell-mediated responses to infection from staphylococcal bacteria such as Staphylococcus aureus, so as to be useful in the treatment of and protection against S. aureus infections.

BACKGROUND OF THE INVENTION

Staphylococcus aureus (SA) is an opportunistic pathogen that can cause a wide spectrum of infections from superficial local skin infections to life-threatening systemic infections that can affect internal organs and tissues. In addition, bacterial arthritis, as well as acute and chronic osteomyelitis caused by haematogenous spread or by direct inoculation in open trauma or surgical intervention such as internal fixation or joint replacement, affect hundreds of thousands of patients each year (1-6). SA is also a major cause of infections associated with indwelling medical devices, such as catheters and prosthesis (6). The cost to society in patient care, which often involves extended hospital stays and repeated surgery, can be estimated at several billion dollars per year. With the documented emergence of multidrug resistance SA strains, the threat of this widely distributed pathogen is now appreciated and novel therapies for treatment and prevention are needed.

The successful colonization of the host is a process required for most microorganisms, including S. aureus, to cause infections in animals and humans. Microbial adhesion is the first crucial step in a series of events that can eventually lead to disease. Pathogenic microorganisms colonize the host by attaching to host tissues or serum conditioned implanted biomaterials, such as catheters, artificial joints, and vascular grafts, through specific adhesins present on the surface of the bacteria. MSCRAMM™s (Microbial Surface Components Recognizing Adhesive Matrix Molecules) are a family of cell surface adhesins that recognize and specifically bind to distinct components in the host's extracellular matrix. Once the bacteria have successfully adhered and colonized host tissues, their physiology is dramatically altered and damaging components such as toxins and proteolytic enzymes are secreted. Moreover, adherent bacteria often produce a biofilm and quickly become more resistant to the killing effect of most antibiotics.

S. aureus is thus known to express a repertoire of different MSCRAMM™s that can act individually or in concert to facilitate microbial adhesion to specific host tissue components. A search for such MCSRAMM's which recognized host components uncovered a 72-kDa protein identified as the major histocompatibility complex class II analog protein, or “Map” protein, a surface localized protein expressed by virtually every S. aureus strain (7). Cloning and sequencing of the gene encoding the Map protein revealed a protein consisting of roughly 110-amino acid-long domains repeated six times with each domain containing a 31 amino acid-long subdomain with homology to MHC Class II. If conservative amino acid substitutions were included, the respective subdomains were 61, 65, 52, 59, 52 and 45% similar to the amino-terminal end of the b chain of many MHC class II proteins from different mammalian species (8).

However, previous studies varied with regard to how the Map protein affected immune function, and thus it would be highly desirable to utilize the Map protein so as to affect host immune responses, such as on T cells, so as to reduce or prevent infection from bacteria such as S. aureus.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a method of utilizing the S. aureus Map protein, or effective fragments and domains thereof, to immunomodulate S. aureus so as to protect against and treat staphylococcal infections.

It is also an object of the present invention to provide and utilize binding subdomains of the S. aureus MAP protein, including the Map19 protein, in methods of protecting against staphylococcal infections or reducing their persistence and virulence.

It is also an object of the present invention to provide isolated Map proteins and active fragments and regions therefrom to prevent T cell-mediated responses in Staphylococcal bacteria and thus reduce or prevent occurrence and spread of bacterial diseases.

These and other objects are provided by virtue of the present invention which provides methods of utilizing the Map protein and/or its binding subdomains or other effective fragments thereof, in immunomodulating Staphylococcal bacteria so as to be able to treat or prevent Staphylococcus infection. Use and administration of an effective amount of the Map protein or its effective subdomains or fragments thereof can thus be utilized in a host to reduce T cell proliferation and achieve a significant reduction in T cell-mediated processes such as delayed-type hypersensitivity (DTH). Suitable compositions and vaccines based on the isolated MAP protein and its effective regions and subdomains, such as the Map10 and Map19 proteins, as well as methods for their use, are also contemplated by the present invention.

These embodiments and other alternatives and modifications within the spirit and scope of the disclosed invention will become readily apparent to those skilled in the art from reading the present specification and/or the references cited herein, all of which are incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIGS. 1a-1c are graphic representations showing the Map-induced inhibition of DTH in accordance with the present invention. DpbA-immunized mice were treated with either native Map (A) or recombinant Map19 (B-C) on the day of immunization (day 0) and on days 2, 4, and 6 post immunization. On day 7, BALB/c (A-B) and C3H/Hen (C) mice were challenged with DbpA and footpads were measured 0 and 24 h after challenge. Mice treated with supernatant from Map⁺SA (A) or recombinant Map19 (B-C) had a significantly reduced DTH response compared to immunized and challenged mice (p<0.0001*; Student's t test). Data are expressed as the mean±SE of 5 mice.

FIG. 2 shows the Map19 dose-response for inhibition of DTH in accordance with the present invention. DbpA-immunized mice were treated with various doses of Map19 (25-200 μg) or ACE19 (200 μg) as described previously. On day 7, mice were challenged with DbpA and footpads were measured 0 and 24 h after challenge. Significant values are indicated by an * (Students t test). Data are expressed as the mean±SE of 5 mice.

FIG. 3 is a graphic representation of tests showing that adoptively transferred T cells from Map-treated mice do not elicit a DTH response in naive mice. DbpA-immunized mice were treated with either Map19 or SdrF as described above. On day 7, mice were sacrificed and spleens were harvested and enriched for T cells by nylon wool purification. 5×10⁷cells were injected i.p. into syngeneic recipients. 24 h later, recipient mice were challenged with DbpA and the DTH response was assessed as described above. DbpA-immunized and DbpA-immunized, SdrF-treated mice developed a significant DTH response compared to unimmunized but challenged mice (p<0.04*; Student's t test). DbpA-immunized, Map19-treated mice had a significantly reduced DTH response compared to the other treatment groups (p<0.001**; Student's t test). Data are expressed as the mean±SE of 5 mice.

FIG. 4 is a graphic representation of the Map-induced inhibition of T cell proliferation using the method of the present invention. In this test, BAT2.2 T cell proliferation was measured after 40 h in culture in the presence of APCs and antigen in the presence of various proteins. 100 μg of each protein was added per well. Data are expressed as the mean absorbance±SE of triplicate wells.

FIG. 5 shows Map-induced apoptosis of BAT2.2 T cells in accordance with the present invention. BAT2.2 cells (5 U I-2/ml) were incubated in media alone (lane 1), or in the presence of either 100 μg Map19 (lane 2) or ACE40 (lane 3). DNA from U937 cells were used as a positive control (lane 5).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the present invention, there are provided methods and immunogenic compositions for suppressing, preventing or immunomodulating T cell-mediated responses caused by staphylococcal bacteria by the use of an immunogenic, immunologically effective amount of an isolated natural or recombinant Map protein or an immunologically active fragment or domain therefrom such as the Map19 protein. The MAP protein is a surface localized protein expressed by virtually every S. aureus strain. McGavin et al (7) originally identified the 72 kDa surface protein, from S. aureus strain FDA 574, that binds a variety of host proteins including BSP, fibrinogen, fibronectin, vitronectin, and thrombospondin. The gene, designated map, was cloned and sequenced (U.S. Pat. No. 5,648,240, incorporated herein by reference). The gene encoding the MAP protein is shown in SEQ ID NO:5 along with the region coding for the MAP protein (SEQ ID NO: 6).

Reinfection of humans with SA is one of the hallmarks of diseases caused by this pathogen and the roles of acquired and innate immunity in protection against infection vary with the many manifestations of disease resulting from SA infections (25-28). While SA infections affecting the skin appear to be exacerbated by strong cellular responses, it is clear that cellular immunity is critical in orchestrating the clearance of systemic SA infections and in preventing reinfection with the same or similar pathogens (29-33). One possible reason for recurring SA infections is the reduction in chemotactic, phagocytic and bactericidal functions of polymorphonuclear leukocytes from patients with chronic or recurrent SA infections (27, 30, 33). Whether this is a function of the bacterial infection or a preexisting condition in these individuals is not known (27, 30, 33).

Regardless, the presence of SA-immunoregulatory molecules suggests that these bacteria have the potential to counteract or evade host defense mechanisms. Both superantigens and protein A produced by SA during an infection serve immune-evasion functions. Superantigens can activate between about 5-20% of T cells by directly binding to both the major histocompatibility complex (MHC) class II molecules on antigen-presenting cells and to the T cell receptor (TCR) on T cells. This interaction can initiate apoptosis in T cells and thymocytes in vivo and in vitro. The in vivo effects of such massive T cell stimulation often results in disease (e.g., toxic shock syndrome and food poisoning in humans) (34). Protein A, while less harmful to the host compared to superantigens, may also serve as a means of immune evasion by binding to the Fc fragment of immunoglobulins (i.e. IgG) resulting in loss of antibody function.

As shown herein, the Map protein and its effective regions or subdomains such as Map19 appear to function as an immune modulator with the capacity to affect host immune responses during SA infections. In addition to its role as a bacterial adhesin, Map has the capacity to interfere with T cell activation and/or proliferation facilitating SA survival in mammals (8, 11, 24, 35, 36) and can serve to potentiate survival in mammals of varied genetic backgrounds.

Studies in accordance with the present invention have shown that Map serves as an immunomodulatory protein as evidenced in double infection studies in which a primary infection with Map⁻SA conferred significant protection against reinfection with Map⁺SA. This contrasts significantly with SA-induced pathology from mice receiving primary and secondary infections with Map⁺SA. Accordingly, T cell-mediated responses in Map⁺SA-infected mice appear to be abrogated by the presence of Map compared to Map⁻SA-infected mice which develop cell-mediated immunity over the course of infection. Map⁻SA infection, which is cleared over time, results in a memory response capable of controlling a secondary Map⁺SA infection. That a primary Map⁻SA infection conferred significant but not complete protection against Map⁺SA challenge suggested that the delicate balance between an anamnestic response and Map-mediated immunomodulation could be affected by the challenge dose. Inhibition of DTH responses directly or as a result of adoptively transferred T cells from Map-treated mice combined with the in vitro effects of Map on T cell proliferation, have evidenced a direct involvement of Map with T cells resulting in apoptosis. Flow cytometric analysis of fluorescein isothiocyanate (FITC)-labeled Map19 revealed binding to 100% of BAT2.2 T cells.

Additional tests of nylon wool-purified naive T cells cultured in the presence of Map19 were not induced to either proliferate or undergo apoptosis. Furthermore, proliferation of naive T cells as a result of incubation with concanavalin A or by antibody-cross-linking of the TCR was not inhibited by Map. This result evidenced that activated T cells but not naive T cells are susceptible to Map and that T cell proliferation via ‘non classical’ pathways bypasses the Map-mediated inhibition of T cell proliferation. The present data provides evidence that Map functions as an immunoregulatory protein during SA infections and it appears that this protein is yet another weapon used by SA to escape immune recognition and clearance.

Accordingly, in accordance with the present invention, methods of utilizing an immunologically effective amount of the Map protein or its effective regions or subdomains such as Map19 are provided which can be used to treat or prevent T cell-mediated responses to staphylococcal bacteria, such as DTH.

In addition, the administration of immunologically effective amounts of an isolated and/or purified S. aureus Map protein or one of its effective regions such as Map19 can be utilized in methods of treating or preventing pathological conditions associated with overstimulation of T cells such as toxic shock syndrome and food poisoning. In accordance with the present invention, a method is provided which comprises administering to a human or animal patient in need of such treatment an immunologically effective amount of an isolated natural or recombinant Map protein. By Map protein is meant the whole natural or recombinant Map protein, or any effective or otherwise immunologically active fragment, fraction, domain, subdomain or region thereof which also has effective immunogenic properties so as to prevent or suppress a T cell-mediated response in the patient. In accordance with the invention, one such region is the Map19 protein, the nucleic acid sequence of which is provided herein as SEQ ID NO:1, and the amino acid sequence is provided as SEQ ID NO:2. Accordingly, the present invention also relates to methods of administering immunologically effective amounts of an isolated and/or purified S. aureus Map19 protein so as to be utilized in methods of treating or preventing pathological conditions associated with T cell proliferation or other T cell-mediated responses such as those caused by infection from S. aureus.

As would be recognized by one of ordinary skill in the art, immunogenic compositions containing an immunogenically effective amount of the Map protein or the Map19 protein can be prepared and administered to a human or animal patient in need of such treatment, particularly those patients requiring treatment or prevention of pathological conditions and other diseases associated with the T cell-mediated response, such as patients with chronic or recurrent SA infections. By effective amount, it would be recognized that the preferred dose for administration of a composition containing the Map or Map19 protein in accordance with the present invention is that amount will be effective in preventing or modulating the T cell response caused by a staphylococcal infection, and one would readily recognize that this amount will vary greatly depending on the nature of the infection and the condition of a patient. Accordingly, an “effective amount” of a pharmaceutical or immunological agent to be used in accordance with the invention is intended to mean a nontoxic but sufficient amount of the agent, such that the desired prophylactic, immunological or therapeutic effect is produced.

As one of skill in the art would recognize, the exact amount of an effective composition that is required will thus vary from subject to subject, depending on the species, age, and general condition of the subject, the severity of the condition being treated, the particular carrier or adjuvant being used and its mode of administration, and the like. Accordingly, the “effective amount” of any particular composition will vary based on the particular circumstances, and an appropriate effective amount may be determined in each case of application by one of ordinary skill in the art using only routine experimentation. The dose should be adjusted to suit the individual to whom the composition is administered and will vary with age, weight and metabolism of the individual. The compositions may additionally contain stabilizers or pharmaceutically acceptable preservatives, such as thimerosal (ethyl(2-mercaptobenzoate-S) mercury sodium salt) (Sigma Chemical Company, St. Louis, Mo.).

The compositions of the invention may also be used as vaccines which will be useful in generating antibodies in a host patient to treat or prevent a staphylococcal infection. As would be recognized by one skilled in this art, a vaccine may be prepared for administration in a number of suitable ways, such as by parenteral (i.e., intramuscular, intradermal or subcutaneous) administration or nasopharyngeal (i.e., intranasal) administration, and the general composition comprises the effective isolated Map or Map19 protein along with a pharmaceutically acceptable vehicle, carrier or excipient. In one such mode, the vaccine is injected intramuscularly, e.g., into the deltoid muscle, however, the particular mode of administration will depend on the nature of the bacterial infection and the condition of the patient. The vaccine is thus preferably combined any of a variety of pharmaceutically acceptable vehicles, carriers or excipients, such as water or a buffered saline, that would be well known to those of ordinary skill in the art. In addition, the vaccine may be lyophilized for resuspension at the time of administration or in solution.

In carrying out the method of the present invention, the isolation and/or purification of the Map protein or of the Map19 protein, or other active fragments or domains of the Map protein, can be accomplished in a number of suitable ways as would be recognized by one skilled in the art. For example, both the Map protein (SEQ ID NO: 6) and the Map19 protein (SEQ ID NO: 2) may be produced recombinantly using conventional techniques well known in the industry. With regard to the Map protein, the production of this protein is disclosed for example in U.S. Pat. No. 5,648,240, incorporated herein by reference. With regard to the Map19 protein, one such suitable method would be through expression in E. coli (e.g., JM101 from Qiagen, Chatsworth, Calif.) harboring the appropriate plasmid (11-16). In this method, E. coli was grown at 37° C. in LB containing the appropriate antibiotics until they reached an A₆₀₀of 0.6 (17). Isopropyl-β-D-thiogalactopyranoside (IPTG) (Life Technologies) was added to a final concentration of 0.2 mM, and the cells were incubated at 37° C. for an additional 4 hours. Cells from a 1 L culture were harvested by centrifugation and resuspended in 10 ml “binding buffer” (BB) (20 mM Tris HCl, 0.5 M NaCl, 15 mM imidazole, pH 8.0) and lysed in a French pressure cell at 11,000 pounds/inch²(13). The lysate was centrifuged at 40,000×g for 15 min and the supernatant filtered through a 0.45 μm filter. A 1 ml iminodiacetic acid Sepharose column (Sigma, St. Louis, Mo.) was charged with 75 mM NiCl₂.6H₂O and equilibrated with BB. The filtered supernatant was applied to the column and washed with 10 volumes of BB, then 10 volumes of BB containing 60 mM imidazole. The bound proteins were eluted with BB containing 200 mM imidazole, dialyzed against PBS containing 10 mM EDTA, then dialyzed against PBS (13). Protein concentrations were determined by the Bicinchoninic Acid (BCA) Protein Assay (Pierce) and proteins were stored at −20° C. until use.

In addition to obtaining isolates of the Map protein through recombinant means, natural isolates of the Map protein may be obtained for use in the present invention by a number of suitable means as well. For example, the natural Map protein can be extracted using standard methods. In one such suitable method, Map⁺SA and Map⁻SA were grown overnight as described above. Bacteria were pelleted by centrifugation and resuspended in 1 M LiCl (one tenth of the original media volume). The suspension was incubated at 42° C. with shaking for two hours. The bacteria were pelleted and the supernatant was removed and quantified for protein by UV spectrophotometry using 1 M LiCl as a blank. Extracted proteins were diluted to 0.2-mg/ml in PBS and passed through a 0.45-micron filter for sterilization prior to i.p. injection (7).

As indicated above, and in the examples below, the method of the present invention is carried by administering effective amounts to human or animal patients so as to achieve the desired prophylactic, immunological or therapeutic effect immunization against staphylococcal infections, e.g. the reduction or modulation of the T cell response thereto, and such effective amounts would be determined through routine means as indicated above for a particular patient based on factors such as type and size of patient, type of infection, level of virulence, etc.

In short, the present invention can thus be utilized advantageously as a means of treating or preventing otherwise persistent, chronic or recurrent infections from staphylococcal bacteria such as S. aureus and will be useful in suppressing or modulating the T cell-mediated responses in a human or animal patient so as to treat, prevent or ameliorate a wide variety of conditions caused by the T cell-mediated responses to staphylococcal infection.

EXAMPLES

The following examples are provided which exemplify aspects of the preferred embodiments of the present invention. It should be appreciated by those of skill in the art that the techniques disclosed in the examples which follow represent techniques discovered by the inventors to function well in the practice of the invention, and thus can be considered to constitute preferred modes for its practice. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of the invention.

Example 1

Overview

Staphylococcus aureus (SA) expresses a 72-kDa protein with the capacity to bind to a variety of extracellular matrix components (ECM), suggesting that at least one role for this protein involves adherence and colonization of host tissues. Analysis of Map, however, also revealed homologies to a segment of the peptide-binding groove of the b chain of the major histocompatability class (MHC) II mammalian proteins. Map-deficient SA (Map⁻ SA) were generated to examine Map's role in the infection process. Map⁻SA-infected mice presented with significantly reduced levels of arthritis, osteomylitis, and abscess formation compared to Map⁺SA-infected control animals. Furthermore, Map⁻SA-infected mice challenged with Map⁺SA were significantly protected against SA-induced pathology compared to mice infected and challenged with Map⁺SA. Native and recombinant forms of Map were tested for their ability to interfere with T cell response in vivo and in vitro. T cells or mice treated with recombinant Map had reduced levels of T cell proliferation and significant reduction of the delayed-type hypersensitivity (DTH) response to challenge antigen, respectively. The data presented here evidence a role for Map as an immunomodulatory protein which may play a role in persistent SA infections and thus may function to potentiate SA survival in mammals by affecting the host's cellular immune responses.

Background

Staphylococcus aureus (SA) is an opportunistic pathogen that can cause a wide spectrum of infections from superficial local skin infections to life-threatening systemic infections that can affect internal organs and tissues. In addition, bacterial arthritis, as well as acute and chronic osteomyelitis caused by haematogenous spread or by direct inoculation in open trauma or surgical intervention such as internal fixation or joint replacement, affect hundreds of thousands of patients each year (1-6). SA is also a major cause of infections associated with indwelling medical devices, such as catheters and prosthesis (6). The cost to society in patient care, which often involves extended hospital stays and repeated surgery, can be estimated at several billion dollars per year. With the documented emergence of multidrug resistance SA strains, the threat of this widely distributed pathogen is now appreciated and novel therapies for treatment and prevention are needed.

A search for SA adhesins recognizing host components uncovered a 72-kDa protein capable of binding a variety of host proteins (7). Cloning and sequencing of this gene revealed a protein consisting of 110-amino acid-long domains repeated six times with each domain containing a 31 amino acid-long subdomain with homology to MHC class II. If conservative amino acid substitutions were included, the respective subdomains were 61, 65, 52, 59, 52, and 45% similar to the amino-terminal end of the □ chain of many MHC class II proteins from different mammalian species (8).

The present work supports a role for Map as an immunomodulatory protein. Mice infected with SA genetically manipulated to be deficient in Map (Map⁻SA) have significantly reduced levels of arthritis and abscess formation (heart and kidneys) following reinfection with wild-type SA (Map⁺SA) compared to mice infected and reinfected with Map⁺SA or mice receiving a single inoculum of Map⁺SA. Evidence linking interactions between Map and T cells came from experiments in which nude mice were infected with Map⁻SA. The severity of osteomyelitis and arthritis was greater in nude mice compared to genotype controls infected with SA⁻Map, suggesting not only a role for T cells in protection against SA infections but also a role for Map in circumventing T cell-mediated immunity. Testing the hypothesis that Map acts to interfere with cellular immunity, various T cell-mediated responses were measured in vivo and in vitro in the presence of Map. DTH, which is a CD4⁺-mediated response, was significantly reduced in Map-treated mice and T cell proliferation in vitro was significantly reduced in the presence of Map, likely as a function of Map-induced apoptosis. These data evidence that Map is a virulence factor whose abilities to potentially alter T cell function in vivo may affect SA persistence and survival and may function in facilitating recurring SA infections.

Materials and Methods

Mice

Specific pathogen-free (MTV⁻) BALB/c and C3H/Hen mice were purchased from Harlan Sprague Dawley, Indianapolis, Ind. The animals were maintained in facilities approved by the American Association for Accreditation of Laboratory Animal Care in accordance with current regulations and standards of the United States Department of Agriculture, Department of Health and Human Services, and National Institutes of Health. All animal procedures were approved by the Institutional Animal Care and Use Committee. Female mice were 8-10 weeks old at the start of each experiment.

Expression and Purification of Recombinant Proteins

Recombinant Map19, DbpA SdrF, M55, CNA, ACE19 and ACE40 were expressed in E. coli (JM101) (Qiagen, Chatsworth, Calif.) harboring the appropriate plasmid (11-16). E. coli was grown at 37° C. in LB containing the appropriate antibiotics until they reached an A₆₀₀of 0.6 (17). Isopropyl-β-D-thiogalactopyranoside (IPTG) (Life Technologies) was added to a final concentration of 0.2 mM, and the cells were incubated at 37° C. for an additional 4 hours. Cells from a 1 L culture were harvested by centrifugation and resuspended in 10 ml “binding buffer” (BB) (20 mM Tris HCl, 0.5 M NaCl, 15 mM imidazole, pH 8.0) and lysed in a French pressure cell at 11,000 pounds/inch²(13). The lysate was centrifuged at 40,000×g for 15 min and the supernatant filtered through a 0.45 μm filter. A 1 ml iminodiacetic acid Sepharose column (Sigma, St. Louis, Mo.) was charged with 75 mM NiCl₂.6H₂O and equilibrated with BB. The filtered supernatant was applied to the column and washed with 10 volumes of BB, then 10 volumes of BB containing 60 mM imidazole. The bound proteins were eluted with BB containing 200 mM imidazole, dialyzed against PBS containing 10 mM EDTA, then dialyzed against PBS (13). Protein concentrations were determined by the Bicinchoninic Acid (BCA) Protein Assay (Pierce) and proteins were stored at −20° C. until use.

Quantitation of S. aureus and Intravenous Injections

Map⁺SA and Map⁻SA (strain Newman 8325) were grown overnight in Lennox broth (LB) (Difco, Detroit, Mich.) media at 37° C. with shaking and used in all infection experiments. 50 μl of this culture was used to inoculate 10 ml of fresh LB in a 250 ml Erlenmeyer flask. The new cultures were grown as above until the optical density reached 0.5 at 600 nm with a 1-cm quartz cuvette. Aliquots of each culture were quantified for colony forming units (CFU). The remainder of each culture was washed three times in sterile PBS. The cultures, based on prior growth-curve determinations, were diluted to approximate 2×10⁷CFU/ml. Mice were in injected i.v. with 1×10⁷S. aureus in 0.5 ml PBS and monitored for up to eight weeks. At the conclusion of the experiment, mice were sacrificed and the joints were examined histologically for arthritis development as described previously (18, 19).

Extraction of Map from Staphylococcus aureus

Map⁺SA and Map⁻SA were grown overnight as described above. Bacteria were pelleted by centrifugation and resuspended in 1 M LiCl (one tenth of the original media volume). The suspension was incubated at 42° C. with shaking for two hours. The bacteria were pelleted and the supernatant was removed and quantified for protein by UV spectrophotometry using 1 M LiCl as a blank. Extracted proteins were diluted to 0.2-mg/ml in PBS and passed through a 0.45-micron filter for sterilization prior to i.p. injection (7).

In Vitro Proliferation of BAT2.2 T Cells

The Borrelia burgdorferi-specific T cell line BAT2.2 was stimulated with whole, inactive Borrelia and antigen presenting cells (APC) as described previously (18, 20). Briefly, 1×10⁵BAT2.2 T cells were cultured in 96-well flat-bottom plates (Costar, Cambridge Mass.) along with 3×10⁵mitomycin-treated APC in complete medium (CTL) (RPMI 1640 containing 2 mM L-glutamine, 100 units/ml penicillin, 100 μg/ml streptomycin, 50 μg/ml gentamicin, 0.2 mM nonessential amino acids, 11 μg/ml sodium pyruvate, 0.02 M N-2-hydroxyethylpiperaxine-N′-2ethanesulfonic acid, and 5×10⁻⁵N 2-mercaptoethanol+10% heat-inactivated fetal bovine serum), and Borrelia (2 μg) in the presence of various proteins. Each treatment group was done in triplicate in a final volume of 200 μl complete medium. 10, 50, and 100 μg of each protein was added to each well and the T cells were allowed to proliferate for 24-48 hours at 37° C. 4 h before the end of the proliferation period, 20 μl/well of 3-{4,5-Dimethylthizol-2-y}-2,5diphenyl-tetraxolium bromide (MTT) (5 mg/ml) was added to each well. After 4 h incubation at 37° C., 100 μl of solubilization buffer (0.04 N HCl in isopropanol) was added to each well and absorbance measured at 590 nm. Data are expressed as mean±SE of the mean of triplicate wells.

Delayed Type Hypersensitivity (DTH) Assay

Mice were immunized with 20 μg of decorin binding protein A (DbpA) in complete Freund's adjuvant (day 0) (19). 7 days post immunization, mice were challenged with 2.5 μg DbpA (13). DbpA was administered in 50 μl of PBS. At the time of immunization, days 2, 4, and 6 post immunization, mice were injected i.p. with 100 μg of native Map (N-Map) extracted from Map⁺SA, supernatant from Map⁻SA, or with 100 μg of the recombinant proteins Map19, SdrF, M55 or ACE40 in 500 μl of PBS (11-15, 21). The footpads were measured before challenge and 24 h later, using a spring-loaded micrometer (Mitutoyo, Tokyo, Japan). Mice were anesthetized with Metofane™ during footpad measurements (22).

Adoptive T Cell Transfer

BALB/c mice (5 mice/group) were immunized with DbpA and were treated with recombinant Map19 or recombinant ACE19 as described above. The day after the last Map19 or ACE40 treatment mice were sacrificed and the spleens from each treatment group were enriched for T cells by passage over nylon wool columns as described previously (20). 24 h after i.p. injection of T cells (5×10⁷nylon wool-enriched T cells/mouse in 500 μl complete media), mice were challenged in the hind footpads with DbpA and the DTH response was assessed as described above.

Map-Induced Apoptosis of BAT2.2 Cells

2×10⁶BAT2.2 T cells/well (5 U I-2/ml) were incubated in the presence of Map19 or ACE19 in a final volume of 200 μl complete media and examined for apoptosis using an Apoptotic DNA Ladder Kit (Roche Molecular Biochemicals, Indianapolis, Ind.) according to manufacturers instructions. 100 μg of each protein was used and apoptosis measured after a 24 h incubation at 37° C. DNA was treated with 2 μg/ml RNase (DNase free) for 20 min. at room temperature before examination by agarose gel electrophoresis.

Flow Cytometry

Nylon wool enriched T cells (1×10⁶/tube) were washed in PBS containing 3% FBS and stained with the following monoclonal antibodies: fluorescein isothiocyanate (FITC)-conjugated anti-mouse CD8a (Ly2) and phycoerythrin (PE)-conjugated anti-mouse CD4 (L3T4) (PharMingen, San Diego, Calif.). The cells were incubated with the directly conjugated antibodies for 1 h at 4° C. and then washed and analyzed on a Coulter EpicProfile (Coulter Corp., Miami, Fla.).

Results

Experimental S. aureus Infection

Infection parameters that resulted in high degrees of arthritis incidence were used to examine what role Map played in SA infection (23). BALB/c mice were injected in the tail i.v. with 1×10⁷SA and sacrificed 4 weeks later for histological examination of hind tibiotarsal joints. These preliminary experiments revealed that Map⁻SA-infected mice had both a reduced frequency and severity of arthritis compared to Map⁺SA-infected controls. The hypothesis that Map acted as an immunomodulator resulting in impaired immunity to SA with a concomitant inability to respond to a challenge infection was tested by infecting mice with Map⁻SA and Map⁺SA respectively, and challenging both groups with Map⁺SA 4 weeks later. Significant differences were observed in abscess formation in hearts and kidneys between the Map⁻/Map⁺-infected group and the Map⁺/Map⁺- and −/Map⁺-infected groups (Table I). Less than 50% of hearts and 25% of kidneys from Map⁻/Map⁺ infected mice presented with abscesses compared to >75% abscess formation in both hearts and kidneys from Map⁺/Map⁺ and −/Map⁺ infected mice (Table I). Significant differences were also observed in arthritis and osteomyelitis scores and frequencies (Table II). Arthritis was prevalent in 54% of mice infected with Map⁻/Map⁺ compared to >80% incidence in Map⁺/Map⁺ and −/Map⁺ infected mice (Table II). The mean arthritis and osteomyelitis scores recorded were also more than 2 times less in Map⁻/Map⁺ infected mice compared to scores from Map⁺/Map⁺- and −/Map⁺-infected mice (Table II).

Map-Mediated Inhibition of Delayed-Type-Hypersensitivity (DTH)

The similarity between Map and the peptide-binding region of class II MHC combined with the high levels of Map recoverable from the surface of SA prompted experiments designed to address the question regarding the potential role of Map on cellular immunity (7, 8). DTH responses are initiated and mediated by CD4⁺ T cells in response to recall antigens and result in specific, measurable inflammation at the site of challenge. Mice immunized with recombinant decorin-binding protein A (DbpA) emulsified in complete Freund's adjuvant (CFA) developed a significant DTH response to DbpA as measured by footpad swelling 7 days post immunization (FIG. 1) (19). However, mice treated with native Map (⁺Map Supernatant) or recombinant Map19 on the day of immunization (day 0) and days 2, 4 and 6 post immunization had a significantly reduced DTH response to DbpA compared to control mice (FIG. 1). Neither supernatants from Map⁻SA (FIG. 1a) or recombinant control protein ACE19 had any measurable effects on the DTH response to DbpA (FIG. 1b-c). Map19's inhibitory effects were not affected by genetic differences since the DTH response was diminished in both BALB/c and C3H/Hen mice following immunization and challenge (FIGS. 1b and c, respectively).

Map Time Course and Dose Response for DTH Inhibition

Both the induction and elicitation of the DTH response were affected by Map treatment since Map19 injected either before or after immunization resulted in a significant reduction in the DTH response (Table III). Although all Map19-treated mice had a significantly reduced response to DbpA challenge following immunization, mice receiving Map19 on both the day of immunization and challenge (in addition to d2 and d4, Experiment I Table III) had the greatest reduction in footpad swelling compared to control mice (13.7±1.46 vs. 34.75±3.47 mm×10⁻², respectively) (Experiment I, Table III). The hypothesis that Map19 could act to prevent DTH by interfering with either the induction or elicitation of DTH was tested by comparing challenge responses in untreated mice to groups either treated with Map19 every other day (starting on the day of immunization) or to mice treated with Map19 only on the day of immunization and challenge (Experiment 2, Table III). Map19-treated mice had a significantly reduced DTH response compared to untreated or ACE40-treated controls (Experiment II, Table III). Since mice treated only on the days of immunization and challenge had a significantly reduced DTH response indistinguishable from the response observed in mice treated with Map19 every other day, it evidenced that Map19's inhibitory activity correlated with T cell activation and that it's capacity to interfere with T cell function was maximal during the T cell activation stages of DTH. Doses of Map in the excess of 100 μg did not further reduce the DTH response, however, 25 μg, the lowest dosed tested in this experiment, still significantly reduced the DTH response (FIG. 2).

Adoptively Transferred T Cells from Map-Treated Mice

Mice immunized with DbpA were either left untreated or injected i.p. with either Map19 or the recombinant control protein SdrF on the day of immunization (day 0) and on days 2, 4, and 6 post immunization. On day 7, mice were sacrificed and single cell suspensions from whole spleens were prepared and enriched for T cells by passage over nylon wool columns (20). Adoptive transfer of nylon wool-purified T cells from Map19-treated mice did not elicit a DTH response to DbpA in naive recipients compared to mice adoptively transferred with enriched T cells from control groups (FIG. 3). Flow cytometric analysis of cells nylon wool-collected cells revealed a profile that was 46.83±0.92% CD4⁺, 31.63±0.96% CD8⁺, 1.2±0.26% CD4⁺ CD8⁺, and 20.4±1.33% CD4⁻ CD8⁻. These data are expressed as the mean percentage of positive cells±SE for the 3 groups examined.

INHIBITION of T Cell Proliferation and Apoptosis Induction In Vitro.

Recombinant Map10 (SEQ ID NOS. 3 and 4) and Map19 (SEQ ID NOS. 1 and 2) were tested for their ability to inhibit the proliferation of the Borrelia-specific T cell line BAT 2.2 (8, 20). T cell proliferation was measured at 40 h after plating in the presence of mitomycin C-treated syngeneic antigen presenting cells (APC) and inactive Borrelia (iBb) (20). Proliferation was measured as a function of tetrazolium blue production following a 4 h incubation in the presence of MTT. BAT 2.2 cells in the presence of either Map10 or 19 but not in the presence of recombinant control proteins CNA or M55 were inhibited from proliferating (FIG. 4) (24). BAT 2.2 incubated in the presence of Borrelia only were plotted as baseline as the control group with the highest background proliferation (FIG. 4). In a similar experiment, BAT2.2 cells in the presence of IL-2 were cultured in the presence of Map19 for 24 h. DNA extracted from BAT2.2 T cells incubated in the presence of Map19 was examined for fragmentation by gel electrophoresis (FIG. 5). DNA fragmentation comparable to apoptotic-positive control DNA (lane 5) was only observed in DNA extracted from Map19-treated T cells (lane 3) but not untreated (lane 2) or ACE40-treated (lane 4) T cells (FIG. 5).

Summary

Reinfection of humans with SA is one of the hallmarks of diseases caused by this pathogen and the roles of acquired and innate immunity in protection against infection vary with the many manifestation of disease resulting from SA infections (25-28). While SA infections affecting the skin appear to be exacerbated by strong, cellular responses, it is clear that cellular immunity is critical in orchestrating the clearance of systemic SA infections and in preventing reinfection with the same or similar pathogens (29-33). One possible reason for recurring SA infections is the reduction in chemotactic, phagocytic and bactericidal functions of polymorphonuclear leukocytes from patients with chronic or recurrent SA infections (27, 30, 33). Whether this is a function of the bacterial infection or a preexisting condition in these individuals is not known (27, 30, 33). Regardless, the presence of SA-immunoregulatory molecules suggests that these bacteria have the potential to counteract or evade host defense mechanisms. Both superantigens and protein A produced by SA during an infection serve immune-evasion functions. Superantigens can activate between 5-20% of T cells by directly binding to both the major histocompatibility complex (MHC) class II molecules on antigen-presenting cells and to the T cell receptor (TCR) on T cells. This interaction can initiate apoptosis in T cells and thymocytes in vivo and in vitro. The in vivo effects of such massive T cell stimulation often results in disease (i.e. toxic shock syndrome and food poising in humans) (34). Protein A, while less harmful to the host compared to superantigens, may also serve as a means of immune evasion by binding to the Fc fragment of immunoglobulins (i.e. IgG) resulting in loss of antibody function.

The present series of tests supported the idea that Map may function as an immune modulator with the capacity to affect host immune responses during SA infections. In addition to its potential role as a bacterial adhesin; our tests showed that Map apparently has the capacity to interfere with T cell activation and/or proliferation facilitating SA survival in mammals (8, 11, 24, 35, 36). Sequence analysis of the SA genome revealed 5 open-reading frames encoding Map-like proteins (14). While only one of these Map proteins (SA1751) had a >80% homology to Newman stain Map (8, 14), the presence of other Map-like proteins suggested a critical role for Map in SA survival; perhaps the potential to encode a variety of MHC II-like proteins can serve to potentiate survival in mammals of varied genetic backgrounds.

Additional evidence suggesting Map serves as an immunomodulatory protein stemmed from double infection studies in which a primary infection with Map⁻SA conferred significant protection against reinfection with Map⁺SA. This contrasts significantly with SA-induced pathology from mice receiving primary and secondary infections with Map⁺SA. Accordingly, it appears that T cell-mediated responses in Map⁺SA-infected mice are abrogated by the presence of Map compared to Map⁻SA-infected mice which develop cell-mediated immunity over the course of infection. Map⁻SA infection, which is cleared over time, results in a memory response capable of controlling a secondary Map⁺SA infection. That a primary Map⁻SA infection conferred significant but not complete protection against Map⁺SA challenge suggested that the delicate balance between an anamnestic response and Map-mediated immunomodulation could be affected by the challenge dose. Our tests showed inhibition of DTH responses directly or as a result of adoptively transferred T cells from Map-treated mice, and this combined with the in vitro effects of Map on T cell proliferation evidenced a direct involvement of Map with T cells resulting in apoptosis. Flow cytometric analysis of fluorescein isothiocyanate (FITC)-labeled Map19 revealed binding to 100% of BAT2.2 T cells (data not shown).

In additional tests evidencing the effect on the Map protein on T cell-mediated responses, nylon wool-purified naive T cells cultured in the presence of Map19 were not induced to either proliferate or undergo apoptosis. Furthermore, proliferation of naive T cells as a result of incubation with concanavalin A or by antibody-cross-linking of the TCR was not inhibited by Map. This evidence that activated T cells but not naive T cells are susceptible to Map and that T cell proliferation via ‘non classical’ pathways bypasses the Map-mediated inhibition of T cell proliferation. Based on Map's effects on cellular immune responses in vivo and in vitro, it appears that this protein is yet another weapon used by SA to escape immune recognition and clearance. Accordingly, in accordance with the present invention, the administration of effective amounts of the Map protein or its active regions or fragments such as Map19 appears to be useful in achieving the suppression or modulation of T cell-mediated responses to a host cell against S. aureus and thus may be useful in methods to prevent or reduce the persistence or virulence of infection by staphylococcal bacteria.

TABLE I Abscess formation in heart and kidneys harvested from Map⁻ and Map⁺SA-infected mice^A Tissue Examined^B Infecting Strains Heart Kidneys Map−/Map⁺ 12/26 (46%)^C,D 13/52 (25%)^E Map⁺/Map⁺ 17/19 (89%) 33/38 (86%) —/Map⁺ 29/31 (94%) 48/62 (77%)
^ABALB/c mice were infected i.v. with either 1 × 10⁷Map⁺ or Map⁻SA strain Newman or left untreated. 4 weeks post primary infection, mice from all groups received 1 × 10⁷Map⁺SA i.v. 4 weeks latter hearts and kidneys were examined grossly and histologically for abscess formation.

^BThe data are pooled observations from three separate experiments.

^Cp < .005 versus Map⁺/Map⁺ group; Fisher's exact test.

^Dp < .0001 versus —/Map⁺; Fisher's exact test.

^Ep < .0001 versus Map⁺/Map⁺ and −Map⁺ groups; Fisher's exact test.

TABLE II Histological examination of joints harvested from Map⁻ and Map⁺SA-infected mice^A Infecting Strains Mean Arthritis Rating Arthritis Frequency (%) Mean Ostomylitis Score Osteomyelitis Frequency (%) Map−/Map+ 0.84^B 14/26 (54%)^C 0.57^B 6/26^D (23%) Map+/Map+ 1.65 18/21 (86%) 1.95 14/21 (66%) −/Map+ 2.06 28/32 (88%) 1.48 14/32 (44%)
^ABALB/c mice were infected i.v. with either 1 × 10⁷Map⁻ or Map⁺SA strain Newman or left untreated. 4 weeks post primary infection, mice from all groups received 1 × 10 Map⁺SA i.v. 4 weeks latter, the right hind limb joint was harvested and examined histologically for arthritis and osteomylitis.

^Bp < 0.05 versus control groups; Student's t test.

^Cp < 0.05 versus control groups; Fisher's exact test.

^Dp < 0.005 versus +Map/+Map group; Fisher's exact test.

TABLE III Histological examination of joints harvested from SA⁻Map or SA⁺Map-infected nude mice^A Infecting Strains Mean Arthritis Rating Arthritis Frequency (%) Mean Ostomylitis Score Osteomyelitis Frequency (%) nu/+/Map⁺SA 2.86 7/7 (100%) 2.29 5/7 (71%) nu/+/Map⁻SA 1.33 8/9 (89%)^C 0.44^B 3/9 (33%) nu/nu/Map⁺SA 2.43 8/8 (100%) 2.62 8/8 (100%) nu/nu/Map⁻SA 2.10 7/10 (70%) 1.20 6/10 (60%)
^AHsd nu/nu and nu/+ mice were infected i.v. with either 1 × 10⁷Map⁻or Map⁺SA strain Newman or left untreated. 4 weeks post primary infection, mice from all groups received 1 × 10⁷Map⁺SA i.v. 4 weeks latter, the right hind limb joint was harvested and examined histologically for arthritis and osteomylitis.

^Bp < 0.05 versus nu/+/Map⁺SA; Student's t test.

TABLE IV The Effect of Map19 Treatment at Various Times Before and After Immunization on the Elicitation of DTH^A Time Course Treatment^B d -6 d -4 d -2 d 0^E d 2 d 4 d 7^F Mean Footpad Swelling^C SF^D Exp. I Map19 + + + +IM CH 18.75^G ±3.26 Map19 + + +IM CH 22.75^G ±2.66 Map19 + +IM CH 20.25^G ±1.93 Map19 +IM CH 23.00^G ±1.36 Map19 +IM + CH 17.75^H ±2.06 Map19 +IM + + CH 23.62^G ±3.48 Map19 +IM + + +CH 13.75^I ±1.46 — CH 5.50^I ±1.24 — IM CH 34.75 ±3.47 Exp. II Map19 +IM + + +CH 13.30^I ±1.50 Map19 +IM +CH 10.10^I ±0.82 ACE40 +IM + + +CH 26.60^J ±2.83 ACE40 +IM +CH 26.75^J ±1.73 — CH 3.10^I ±0.67 — IM CH 33.56 ±3.04
^ABALB/c mice were immunized with DbpA on day zero.

^B+ Indicates treatment with 100 μg of recombinant Map19 at various time points prior to and after immunization. Control mice in Exp I were treated with ACE40 in a parallel experiment and had DTH responses similar to control mice (data not shown).

^CFootpads were measured at 0 and 24 h after challenge. The data are expressed as the mean footpad swelling of five mice/group.

^DStandard Error

^EMice were immunized with 5 μg of DbpA emulsified in CFA i.p.

^F7 days after immunization the mice were challenged in both hind footpads with 2 μg of DpbA in 50 μl of PBS.

^Gp < 0.05; Students t test compared to IM and CH control.

^Hp < 0.005; Students t test compared to IM and CH control.

^Ip < p < 0.0001; Students t test compared to IM and CH control.

^JNot significant compared to IM and CH control.

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Claims

1. A method of preventing or modulating a T cell-mediated response in a host comprising administering to the host an isolated S. aureus Map protein having an amino acid sequence as set forth in SEQ ID NO:6 in an amount effective to prevent or modulate said T cell-mediated response in the host.

2. The method according to claim 1 wherein the T cell-mediated response is delayed-type hypersensitivity (DTH).

3. The method according to claim 1 wherein the Map protein is encoded by a nucleotide sequence according to SEQ ID NO:5.

4. A method of treating or preventing a pathological condition associated with overstimulation of T cells in a human or animal patient comprising administering to the patient an isolated S. aureus Map protein having an amino acid sequence according to SEQ ID NO:6 in an amount effective to treat or prevent said condition associated with overstimulation of T cells.

5. The method according to claim 4 wherein the condition associated with overstimulation of T cells is toxic shock syndrome.

6. The method according to claim 4 wherein the Map protein is encoded by a nucleotide sequence according to SEQ ID NO:5 or degenerates thereof.

7. A method of treating or preventing a T cell lymphoproliferative disease in a human or animal patient comprising administering to the patient an isolated S. aureus Map protein having the amino acid sequence according to SEQ ID NO:6, in an amount effective to treat or prevent a T cell lymphoproliferative disease.

8. The method according to claim 7 wherein the Map protein is encoded by a nucleotide sequence according to SEQ ID NO:5 or degenerates thereof.

9. A pharmaceutical composition for preventing or modulating a T cell-mediated response to a staphylococcal infection comprising an isolated S. aureus Map protein having the amino acid sequence according to SEQ ID NO:6 in an amount effective to prevent or modulate a T cell-mediated response and a pharmaceutically acceptable vehicle, carrier or excipient.

10. The pharmaceutical composition of claim 6 wherein the Map protein is encoded by a nucleotide sequence according to SEQ ID NO: 5 or degenerates thereof.

11. A method of reducing or eliminating T cell-mediated proliferation in a patient in need of such treatment comprising administering to the patent an isolated S. aureus Map protein according to SEQ ID NO: 6 in an amount effective to reduce or eliminate T cell proliferation in the patient following a staphylococcal infection.

12. The method according to claim 11 wherein the Map protein is encoded by a nucleotide sequence according to SEQ ID NO:5 or degenerates thereof.