Immunological relationship between the class I epitope of streptococcal M protein and myosin

Recent Advances in the Development of Peptide Vaccines and Their Delivery Systems Against Group A Streptococcus

Group A Streptococcus (GAS) infection can cause a variety of diseases in humans, ranging from common sore throats and skin infections, to more invasive diseases and life-threatening post-infectious diseases, such as rheumatic fever and rheumatic heart disease. Although research has been ongoing since 1923, vaccines against GAS are still not available to the public. Traditional approaches taken to develop vaccines for GAS failed due to poor efficacy and safety. Fortunately, headway has been made and modern subunit vaccines that administer minimal bacterial components provide an opportunity to finally overcome previous hurdles in GAS vaccine development. This review details the major antigens and strategies used for GAS vaccine development. The combination of antigen selection, peptide epitope modification and delivery systems have resulted in the discovery of promising peptide vaccines against GAS; these are currently in preclinical and clinical studies.

Molecular Mimicry, Autoimmunity, and Infection: The Cross-Reactive Antigens of Group A Streptococci and their Sequelae

The group A streptococci are associated with a group of diseases affecting the heart, brain, and joints that are collectively referred to as acute rheumatic fever. The streptococcal immune-mediated sequelae, including acute rheumatic fever, are due to antibody and cellular immune responses that target antigens in the heart and brain as well as the group A streptococcal cross-reactive antigens as reviewed in this article. The pathogenesis of acute rheumatic fever, rheumatic heart disease, Sydenham chorea, and other autoimmune sequelae is related to autoantibodies that are characteristic of autoimmune diseases and result from the immune responses against group A streptococcal infection by the host. The sharing of host and streptococcal epitopes leads to molecular mimicry between the streptococcal and host antigens that are recognized by the autoantibodies during the host response. This article elaborates on the discoveries that led to a better understanding of the pathogenesis of disease and provides an overview of the history and the most current thought about the immune responses against the host and streptococcal cross-reactive antigens in group A streptococcal sequelae.

Anti-microbial Antibodies, Host Immunity, and Autoimmune Disease

Autoimmune diseases are a spectrum of clinical inflammatory syndromes with circulating autoantibodies. Autoimmune diseases affect millions of patients worldwide with enormous costs to patients and society. The diagnosis of autoimmune diseases relies on the presence of autoantibodies and the treatment strategy is to suppress the immune system using specific or non-specific immunosuppressive agents. The discovery of anti-microbial antibodies in the blood of patients with Crohn's disease and Sjogren's syndrome and cross-reactivity of anti-microbial antibodies to human tissue suggests a new molecular mechanism of pathogenesis, raising the possibility of designing a new therapeutic strategy for these patients. The presence of anti-microbial antibodies indicates the failure of the innate immunity system to clear the microbial agents from the blood and activation of adaptive immunity through B-lymphocytes/plasma cells. More importantly, the specific antibodies against the microbial proteins are directed toward the commensal microbes commonly present on the surface of the human host, and these commensal microbes are important in shaping the development of the immune system and in maintaining the interaction between the human host and the environment. Persistence of these anti-microbial antibodies in patients but not in normal healthy individuals suggests abnormal interaction between the human host and the commensal microbes in the body. Elimination of the organism/organisms that elicits the antibody response would be a new avenue of therapy to investigate in patients with autoimmune diseases.

Repeat exposure to group A streptococcal M protein exacerbates cardiac damage in a rat model of rheumatic heart disease

Rheumatic fever and rheumatic heart disease (RF/RHD) develop following repeated infection with group A streptococci (GAS). We used the Rat Autoimmune Valvulitis (RAV) model of RF/RHD to demonstrate that repetitive booster immunization with GAS-derived recombinant M protein (rM5) resulted in an enhanced anti-cardiac myosin antibody response that may contribute to the breaking of immune tolerance leading to RF/RHD and increased infiltration of heart valves by mononuclear cells. With each boost, more inflammatory cells were observed infiltrating heart tissue which could lead to severe cardiac damage. We also found evidence that both complement and anti-M protein antibodies in serum from rM5-immunized rats have the potential to contribute to inflammation in heart valves by activating cardiac endothelium. More importantly, we have demonstrated by electrocardiography for the first time in the RAV model that elongation of P-R interval follows repetitive boost with rM5. Our observations provide experimental evidence for cardiac alterations following repeated exposure to GAS M protein with immunological and electrophysiological features resembling that seen in humans following recurrent GAS infection.

Molecular Mimicry and Autoimmunity

The term Molecular mimicry describes the sequence similarity between foreign (microorganism's peptides) and self peptides (the host's antigen). This phenomenon has been recently discovered as a one of the major mechanism in which there is a break-down of self-tolerance of the immune system following autoimmunity. After a short preface, the chapter contains examples of common infectious agents and their role in autoimmune diseases. Later on, it describes the autoimmune diseases in which there was found a relation to infectious agents via molecular mimicry mechanism. The data is summarized in two tables.

Rheumatic heart disease in Uganda: the association between MHC class II HLA DR alleles and disease: a case control study

BACKGROUND

Rheumatic heart disease (RHD), the only long term consequence of acute rheumatic fever, remains a leading cause of morbidity and mortality among young adults in Uganda. An inherited susceptibility to acute rheumatic fever centers around the major histocompatibility class II human leucocyte antigens. However, there is paucity of data from sub-Saharan Africa. This study compares the frequency of HLA class II DR alleles between RHD cases and normal controls in Uganda.

METHODS

One hundred ninety-nine participants including 96 established RHD cases aged 5-60 years and 103 age and sex matched normal controls were recruited for participation. DNA was manually extracted from buffy coat samples and HLA analysis was performed. HLA-DR allelic frequency comparison between cases and controls were estimated using conditional logistic regression with 95% confidence intervals. P -values were corrected for multiple hypothesis testing.

RESULTS

199 participants (103 female, 51.8%) completed the study. The mean (SD) age in years for cases and controls were 29.6 (10.2) and 29(18), respectively. After conditional logistic regression and multiple hypothesis testing, HLA-DR1was associated with a decreased risk of RHD (OR = 0.42, CI 0.21-085, P = 0.01, Corrected P value (PC) = 0.09,) while HLA-DR11 was associated with increased risk of RHD (OR = 3.31, CI 1.57-6.97, P = <0.001, Pc < 0.001). No other significant associations were found.

CONCLUSION

In this first study of HLA genetic susceptibility to RHD in Uganda, HLA- DR1 was more common in normal controls while HLA- DR11 was more common among RHD cases suggesting a disease susceptibility association. In future studies, high resolution HLA analysis and genome wide studies should be carried out to confirm this pattern.

StreptInCor: a candidate vaccine epitope against S. pyogenes infections induces protection in outbred mice

Infection with Streptococcus pyogenes (S. pyogenes) can result in several diseases, particularly in children. S. pyogenes M protein is the major virulence factor, and certain regions of its N-terminus can trigger autoimmune sequelae such as rheumatic fever in susceptible individuals with untreated group A streptococcal pharyngitis. In a previous study, we utilized a large panel of human peripheral blood cells to define the C-terminal protective epitope StreptInCor (medical identity), which does not induce autoimmune reactions. We recently confirmed the results in HLA-transgenic mice. In the present study, we extended the experimental assays to outbred animals (Swiss mice). Herein, we demonstrate high titers of StreptInCor-specific antibodies, as well as appropriate T-cell immune responses. No cross-reaction to cardiac myosin was detected. Additionally, immunized Swiss mice exhibited 87% survival one month after challenge with S. pyogenes. In conclusion, the data presented herein reinforce previous results in humans and animals and further emphasize that StreptInCor could be an effective and safe vaccine for the prevention of S. pyogenes infections.

Streptococcus and rheumatic fever

PURPOSE OF REVIEW

To give an overview of the current hypotheses of the pathogenesis of rheumatic fever and group A streptococcal autoimmune sequelae of the heart valve and brain.

RECENT FINDINGS

Human monoclonal antibodies (mAbs) derived from rheumatic heart disease have provided evidence for crossreactive autoantibodies that target the dominant group A streptococcal epitope of the group A carbohydrate, N-acetyl-beta-D-glucosamine (GlcNAc), and heart valve endothelium, laminin and laminar basement membrane. T cells in peripheral blood and in rheumatic heart valves revealed the presence of T cells crossreactive with streptococcal M protein and cardiac myosin. For initiation of disease, evidence suggests a two-hit hypothesis for antibody attack on the valve endothelium with subsequent extravasation of T cells through activated endothelium into the valve to form granulomatous lesions and Aschoff bodies. Autoantibodies against the group A streptococcal carbohydrate epitope GlcNAc and cardiac myosin and its peptides appear during progression of rheumatic heart disease. However, autoantibodies against collagen that are not crossreactive may form because of the release of collagen from damaged valve or to responses to collagen bound in vitro by certain serotypes of streptococci. In Sydenham chorea, human mAbs derived from disease target the group A carbohydrate epitope GlcNAc and gangliosides and dopamine receptors found on the surface of neuronal cells in the brain. Human mAbs and autoantibodies in Sydenham chorea were found to signal neuronal cells and activate calcium calmodulin-dependent protein kinase II (CaMKII) in neuronal cells and recognize the intracellular protein biomarker tubulin.

SUMMARY

To summarize, pathogenic mechanisms of crossreactive autoantibodies which target the valve in rheumatic heart disease and the neuronal cell in Sydenham chorea share a common streptococcal epitope GlcNAc and target intracellular biomarkers of disease including cardiac myosin in the myocardium and tubulin, a protein abundant in the brain. However, intracellular antigens are not believed to be the basis for disease. The theme of molecular mimicry in streptococcal autoimmune sequelae is the recognition of targeted intracellular biomarker antigens such as cardiac myosin and brain tubulin, while targeting extracellular membrane antigens such as laminin on the valve surface endothelium or lysoganglioside and dopamine receptors in the brain. Antibody binding to these cell surface antigens may lead to valve damage in rheumatic heart disease or neuropsychiatric behaviors and involuntary movements in Sydenham chorea.

Molecular mimicry in the autoimmune pathogenesis of rheumatic heart disease

Molecular mimicry is a hallmark of the pathogenesis of rheumatic fever where the streptococcal group A carbohydrate epitope, N-acetyl glucosamine, and the a-helical coiled-coil streptococcal M protein structurally mimic cardiac myosin in the human disease, rheumatic carditis, and in animal models immunized with streptococcal M protein and cardiac myosin. Recent studies have unraveled the potential pathogenic mechanisms by which the immune response against the group A streptococcus attacks the rheumatic valve leading to chronic rheumatic heart disease. Both B- and T-cell responses are involved in the process, and evidence for the hypotheses of molecular mimicry and epitope spreading are reviewed.

Comprehensive analysis of antibody responses to streptococcal and tissue antigens in patients with acute rheumatic fever

Acute rheumatic fever (ARF) is an autoimmune disease occurring in individuals following untreated group A streptococcal infection believed to be triggered by antibodies to bacterial components that cross-react with human tissues. We developed a multiplexed immunoassay for the simultaneous quantitation of antibodies to nine streptococcal-related antigens including streptolysin O (SLO), DNase B, collagen I and IV, fibronectin, myosin, group A carbohydrate, M6 protein and streptococcal C5a peptidase. Utilizing this method, we examined serum from 49 ARF, 58 pharyngitis patients and age- and sex-matched controls in samples collected at initial disease onset, and at 4 weeks, 6 months and 1 year after diagnosis. Antibody responses were significantly higher for SLO, DNase B, M6 protein, group A carbohydrate and the cross-reactive antigens collagen I and myosin in ARF compared with pharyngitis patients (P <or= 0.05). Moreover, we found significantly elevated antibody responses in the ARF patients with rheumatic heart disease to fibronectin and collagen I compared with ARF patients without heart disease. The major differences between the ARF patients with and without carditis appear to be in the immune response to the putative heart valve components, collagen I and fibronectin.

Development of a multiplexed fluorescent immunoassay for the quantitation of antibody responses to group A streptococci

The host immunologic response to group A streptococcal infections gives rise to numerous antibodies directed against cellular and extracellular bacterial antigens. For determining individual immune status, or studying the pathogenesis of group A streptococcal associated diseases, such as acute rheumatic fever (ARF), an assay capable of determining antibodies responses to multiple antigens would be of great advantage. We have developed a microsphere based, multiplexed immunoassay for the simultaneous quantitation of antibodies to nine different extracellular, ARF related tissue and group A streptococci specific antigens using only 5 microl of sample. Through the selection of microspheres and serum diluent, non-specific antibody binding was reduced by 17%. Different formulations of the coupling buffer were found to greatly influence the efficiency of coupling antigens to the carboxylated microspheres. Monoclonal antibodies against the different antigens demonstrated assay specificity as well as sensitivities of less than 1 ng/ml of antibody. This multiplexed assay should be a powerful research and clinical tool in determining antibody responses to group A streptococcal infections and in potentially determining the role of a variety of cross-reactive antigens in rheumatic fever and rheumatic heart disease.

Myocardial tissue damage in rabbits injected with group A streptococci, types M1 and M22. Role of bacterial immunoglobulin G-binding surface proteins

Acute rheumatic fever (ARF) and acute poststreptococcal glomerulonephritis (APSGN), two important sequelae of streptococcal throat or skin infections, according to current concepts may be elicited by autoimmune mechanisms due to molecular mimicry between group A streptococci (GAS) and human tissue. In the case of APSGN, however, our experimental data have indicated that GAS immunoglobulin-binding surface proteins (IgG BPs) might be of pathogenic significance by triggering anti-IgG production and immune complex formation leading to renal damage. Thus, rabbits injected with IgG-binding, as opposed to non-binding, GAS strains were found to develop renal deposition of IgG and complement factor C3 and inflammatory and degenerative glomerular changes resembling the picture seen in APSGN. In the present study, cardiac tissue material from rabbits injected with GAS was investigated. After 8 or more weeks of intravenous (i.v.) injections, minimal changes were seen in those animals receiving an IgG non-binding GAS strain, type T27, whereas those animals receiving either of two IgG-binding GAS strains, types M1 or M22, developed strong inflammatory and degenerative myocardial changes accompanied by deposition of IgG and C3. Furthermore, on injecting rabbits with defined mutants of a type M22 strain, the development of myocardial tissue damage proved to be dependent on the presence of streptococcal IgG-binding activity. Our results demonstrate that myocardial tissue changes may be induced in the rabbit by i.v. injection of whole heat-killed GAS of at least two M serotypes. Conceivably, induction of immune complexes by bacterial IgG BPs may lead to myocardial deposition of IgG, in turn triggering a series of events, involving the complement system and proinflammatory cytokines, with resulting tissue damage. Though many virulence factors may be involved in the development of ARF and APSGN, and a given GAS strain will never cause both, our results may suggest a new pathogenetic mechanism common to these two major non-suppurative complications.

Prospective longitudinal study of children with tic disorders and/or obsessive-compulsive disorder: relationship of symptom exacerbations to newly acquired streptococcal infections

BACKGROUND

It has been proposed that infection by group A beta-hemolytic streptococci (GABHS) can trigger acute symptom exacerbations among patients with Tourette's syndrome (TS) or obsessive-compulsive disorder (OCD), via autoimmune mechanisms.

OBJECTIVE

To examine the temporal relationship between newly acquired GABHS infections (and other immunologic indices) and acute exacerbations of tics and obsessive-compulsive symptoms.

METHODS

Pediatric patients (7-17 years of age) with TS and/or OCD (N = 47) and healthy control subjects (N = 19) were prospectively monitored for newly acquired GABHS infections, nonspecific markers of acute inflammatory responses, and D8/17-reactive cells (a marker of rheumatic fever). Objective monthly ratings of tic and obsessive-compulsive symptom severity were used to determine the timing of symptom exacerbations.

RESULTS

The overall rate of acute exacerbations of neuropsychiatric symptoms was 0.56 exacerbations per patient per year. The average rate of new GABHS infections, using a stringent definition, was 0.42 infections per subject per year among patients, compared with 0.28 infections per subject per year for control subjects. The association between symptom exacerbations and new GABHS infections among patients was no greater than that expected on the basis of chance. At baseline, patients demonstrated significantly higher levels of D8/17-reactive cells and neopterin, compared with control subjects, but there was no consistent pattern of change when exacerbation time points were compared with baseline or follow-up time points.

CONCLUSIONS

The results suggest no clear relationship between new GABHS infections and symptom exacerbations in an unselected group of patients with TS and/or OCD.

Evaluation of synthetic, M type-specific peptides as antigens in a multivalent group A streptococcal vaccine

The recent development of emm gene sequence-based typing methodology has allowed group A streptococci (GAS) M serotype prevalence data to be determined. This information has been used to identify the components of a multivalent M protein peptide vaccine that could theoretically prevent most of the GAS-mediated diseases in the USA. In this study, we have evaluated in mice the immunogenicity and protective ability of multiple synthetic, M type-specific peptides, derived from the N-termini of three prevalent GAS serotypes (three peptides per serotype, total of nine peptides). At least one peptide, representing each of the three M types tested, was immunogenic. Five of the nine synthetic peptides tested, elicited an immune response in mice, and sera raised against four of the peptides, all possessed functional activity as demonstrated in a bactericidal assay. In vivo nasopharyngeal challenge experiments were carried out with peptides from the M1 (peptide M1-3) and M3 (peptide M3-2) proteins induced in vivo immune protection by reducing intranasal carriage. Reduction in colonization for M1-3 and M3-2 was 90% (P=0.02) and 66% (P<0.17), respectively. A reduction in colonization of 67% (P=0.03) was observed for M3-2 immunized mice when M43, a heterologous serotype, was used as the challenge strain. These results show the utility of synthetic, M type-specific peptides as antigens in a multivalent GAS vaccine.

Self epitopes shared between human skeletal myosin and Streptococcus pyogenes M5 protein are targets of immune responses in active juvenile dermatomyositis

OBJECTIVE

To identify self T cell epitopes associated with proinflammatory immune responses and clinically active juvenile dermatomyositis (juvenile DM). The target of our search for relevant epitopes was represented by amino acid sequences shared between human skeletal myosin and Streptococcus pyogenes M5 protein. The long-term objective of the project is to identify suitable targets for immunotherapy of the disease.

METHODS

We used computerized algorithms to identify putative agretopes on both the human myosin and Streptococcus M5 proteins. Direct binding assays for homolog peptides were used to confirm such predictions. Antigenicity and functional cross-reactivity were evaluated by cytotoxicity assays and by measurement of cytokine levels. Specific T cells were isolated by T cell capture, and T cell receptor (TCR) V(beta) gene usage was identified by reverse transcriptase-polymerase chain reaction.

RESULTS

We identified peptides that are targets of disease-specific cytotoxic T cell responses. T cell reactivity against the self peptides correlates with clinical signs of early, active myositis. Such reactivity is accompanied by production of proinflammatory cytokines, which may contribute to the damage. T cell cross-recognition of bacterial and human homologs was shown functionally as well as by sorting peptide-specific T cells and identifying oligoclonal and largely overlapping TCR V(beta) gene usage.

CONCLUSION

These findings represent the first identification of a self epitope in juvenile DM, providing a potential candidate for antigen-specific immune therapy.

Fluoride exposure attenuates expression of Streptococcus pyogenes virulence factors

Fluoridation causes an obvious reduction of dental caries by interference with cariogenic streptococci. However, the effect of fluoride on group A streptococci that causes rheumatic fever and acute poststreptococcal glomerulonephritis is not known. We have used proteomic analysis to create a reference proteome map for Streptococcus pyogenes and to determine fluoride-induced protein changes in the streptococci. Cellular and extracellular proteins were resolved by two-dimensional polyacrylamide gel electrophoresis and identified by matrix-assisted laser desorption ionization mass spectrometry. 183 protein spots were visualized, and 74 spots representing 60 unique proteins were identified. A 16-h exposure to sodium fluoride caused decreased expression of proteins required to respond to cellular stress, including anti-oxidants, glycolytic enzymes, transcriptional and translational regulators, and protein folding. Fluoride caused decreased cellular expression of two well-characterized S. pyogenes virulence factors. Fluoride decreased expression of glyceraldehyde-3-phosphate dehydrogenase, which acts to bind fibronectin and promote bacterial adherence. We also performed proteomic analysis of protein released by S. pyogenes into the culture supernatant and observed decreased expression of M proteins following fluoride exposure. These data provide evidence that fluoride causes decreased expression by S. pyogenes proteins used to respond to stress, virulence factors, and implicated in non-suppurative complications of S. pyogenes, including glomerulonephritis and rheumatic fever.

Molecular analysis of group A Streptococcus type emm18 isolates temporally associated with acute rheumatic fever outbreaks in Salt Lake City, Utah

Acute rheumatic fever (ARF) and subsequent rheumatic heart disease are rare but serious sequelae of group A Streptococcus (GAS) infections in most western countries. Salt Lake City (SLC), Utah, and the surrounding intermountain region experienced a resurgence of ARF in 1985 which has persisted. The largest numbers of cases were encountered in 1985-1986 and in 1997-1998. Organisms with a mucoid colony phenotype when grown on blood agar plates were temporally associated with the higher incidence of ARF. To develop an understanding of the molecular population genetic structure of GAS strains associated with ARF in the SLC region, 964 mucoid and nonmucoid pharyngeal isolates recovered in SLC from 1984 to 1999 were studied by sequencing the emm gene. Isolates with an emm18 allele were further characterized by sequencing the spa, covR, and covS genes. Peak periods of ARF were associated with GAS isolates possessing an emm18 allele encoding the protein found in serotype M18 isolates. Among the serotype M18 isolates, the difference in the number of C repeats produced three size variants. Variation was limited in spa, a gene that encodes a streptococcal protective antigen, and covR and covS, genes that encode a two-component regulatory system that, when inactivated, results in a mucoid phenotype and enhanced virulence in mouse infection models. Pulsed-field gel electrophoresis showed a single restriction profile for serotype M18 organisms isolated during both peak periods of ARF. In SLC, the incidence of ARF coresurged with the occurrence of GAS serotype M18 isolates that have very restricted genetic variation.

Reactivity of rheumatic fever and scarlet fever patients' sera with group A streptococcal M protein, cardiac myosin, and cardiac tropomyosin: a retrospective study

Archived sera (collected in 1946) from acute rheumatic fever (ARF) and untreated scarlet fever and/or pharyngitis patients were reacted with streptococcal M protein, cardiac myosin, and cardiac tropomyosin. Except for very low levels to tropomyosin, antibodies to other antigens were not elevated in the sera of ARF patients relative to those of non-ARF patients, even though there was roughly equivalent exposure to group A streptococci. This suggests that antibodies to these molecules may not play a central role in the induction of ARF.

Cytotoxic mAb from rheumatic carditis recognizes heart valves and laminin

Anti-streptococcal antibodies cross-reactive with N-acetyl-betaD-glucosamine (GlcNAc) and myosin are present in the sera of patients with rheumatic fever (RF). However, their role in tissue injury is not clear. In this study, we show that anti-GlcNAc/anti-myosin mAb 3.B6 from a rheumatic carditis patient was cytotoxic for human endothelial cell lines and reacted with human valvular endothelium and underlying basement membrane. Reactivity of mAb 3.B6 with the valve was inhibited by human cardiac myosin > laminin > GlcNAc. The mAb 3.B6 epitopes were localized in fragments of human cardiac myosin, including heavy meromyosin (HMM), the S1 subfragment, and two light meromyosin (LMM) peptides containing amino acid sequences KEALISSLTRGKLTYTQQ (LMM 1) and SERVQLLHSQNTSLINQK (LMM 33). A novel feature of mAb 3.B6 was its reactivity with the extracellular matrix protein laminin, which may explain its reactivity with the valve surface. A laminin A-chain peptide (HTQNT) that includes homology to LMM33 inhibited the reactivity of mAb 3.B6 with human valve. These data support the hypothesis that cross-reactive antibodies in rheumatic carditis cause injury at the endothelium and underlying matrix of the valve.

Pathogenesis of group A streptococcal infections

Group A streptococci are model extracellular gram-positive pathogens responsible for pharyngitis, impetigo, rheumatic fever, and acute glomerulonephritis. A resurgence of invasive streptococcal diseases and rheumatic fever has appeared in outbreaks over the past 10 years, with a predominant M1 serotype as well as others identified with the outbreaks. emm (M protein) gene sequencing has changed serotyping, and new virulence genes and new virulence regulatory networks have been defined. The emm gene superfamily has expanded to include antiphagocytic molecules and immunoglobulin-binding proteins with common structural features. At least nine superantigens have been characterized, all of which may contribute to toxic streptococcal syndrome. An emerging theme is the dichotomy between skin and throat strains in their epidemiology and genetic makeup. Eleven adhesins have been reported, and surface plasmin-binding proteins have been defined. The strong resistance of the group A streptococcus to phagocytosis is related to factor H and fibrinogen binding by M protein and to disarming complement component C5a by the C5a peptidase. Molecular mimicry appears to play a role in autoimmune mechanisms involved in rheumatic fever, while nephritis strain-associated proteins may lead to immune-mediated acute glomerulonephritis. Vaccine strategies have focused on recombinant M protein and C5a peptidase vaccines, and mucosal vaccine delivery systems are under investigation.

Molecular cloning, purification and immunological responses of recombinants GroEL and DnaK from Streptococcus pyogenes

To better understand the roles of heat shock proteins in streptococcal diseases, the groEL and dnaK genes from Streptococcus pyogenes were cloned and their products (GroEL and DnaK) and derivatives (F2GroEL, F3GroEL and C1DnaK) purified as His-tagged fusion proteins. Western blot analysis of the purified proteins with sera from individuals with streptococcal diseases demonstrated that 29 out of 36 sera tested were reactive with GroEL and eight recognized DnaK. Rabbit antiserum against myosin recognized both GroEL and DnaK. Antibodies raised against purified F2GroEL and DnaK reacted with myosin in the ELISA but not in a Western immunoblot. These data indicate that the S. pyogenes GroEL and DnaK may be important immunogens during streptococcal infections. Furthermore, we provide evidence of an immunogenic relatedness of the GroEL and DnaK proteins with myosin that could play a role in the pathogenesis of streptococcal non-suppurative sequelae.

M protein of a Streptococcus dysgalactiae human wound isolate shows multiple binding to different plasma proteins and shares epitopes with keratin and human cartilage

Besides group A (GAS), Lancefield group C beta-haemolytic streptococci (GCS) have been implicated as a causative agent in outbreaks of purulent pharyngitis. In this study we have investigated a class CI M protein of a Streptococcus dysgalactiae1:256, revealed that 26% of these sera showed serological cross-reactivity between a 68-kDa cartilage protein and the N-terminal part of MC. Only 8% of the sera of healthy patients showed this property. In additional, MC also cross-reacted with antibodies recognising epidermal keratins. The cross-reacting 68-kDa protein from cartilage was different from human serum albumin, but was recognised with anti-vimentin immune serum. The MC was cloned and the gene sequenced. By using PCR, recombinant gene fragments encoding characteristic peptide fragments of MC were expressed in Escherichia coli. The peptides were used to map the binding sites for plasma proteins and to locate the cross-reacting epitopes on the MC molecule. In consequence, sequence alignments revealed that MC shared homologous regions with vimentin and different keratins. Our data, obtained with MC, suggest that not only infections with GAS but also infections with GCS and possibly GGS (the latter species can also produce class CI M-like proteins) may be responsible for the formation of streptococcal-associated sequel diseases.