Rheumatic fever. The relationships between host, microbe, and genetics

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-endothelial cell antibodies in rheumatic heart disease

To evaluate the anti-endothelial cell antibodies (AECA), anti-cardiolipin antibodies (aCL) and serum mannose-binding lectin (MBL) profiles of a large cohort of Yemeni patients with rheumatic heart disease (RHD) and to correlate these findings with clinical features of the disease. Patients (n = 140) were recruited from Al-Thawra Hospital in Sana'a, Yemen. All had RHD diagnosed according to modified Jones' criteria. We also studied 140 sex- and age-matched healthy blood donors from the same area. Echocardiography was performed according to the recommendations of the American Society of Echocardiography. Solid phase enzyme-linked immunosorbent assays (ELISAs) were used to measure AECA and aCL titres and serum MBL levels. Forty per cent of the patients were AECA-positive, but only 7·8% were positive for aCL antibodies. Serum MBL levels were significantly lower in the RHD group (median 4221 ng/ml versus 5166 ng/ml in healthy controls). AECA titres were correlated positively with patient age, duration of RHD and the severity of aortic stenosis, as determined by echocardiographic findings. In several autoimmune rheumatic diseases, such as systemic lupus erythematosus, vasculitis and scleroderma, AECA have been shown to play pathogenic roles by producing proinflammatory and procoagulant effects (increased expression of adhesion molecules and tissue factors, increased cytokine release) in endothelial cells. In RHD, these autoantibodies might represent a pathological link between activation of the valvular endothelium and valvular damage.

The role of viral agents in aetiopathogenesis of acute rheumatic fever

The reason why abnormal immune response exists in acute rheumatic fever is not exactly explained. The influence of co-pathogens like certain viruses were mentioned regarding the initiation of the immunological reaction in acute rheumatic fever patients by several authors since 1970. This study was designed to find the role or effect of some viral infections in the development of rheumatic fever. In this study, 47 cases with acute rheumatic fever (acute rheumatic arthritis, acute rheumatic carditis, and chorea), 20 cases with chronic rheumatic fever, 20 cases with streptococcal pharyngitis, and 20 healthy age- and gender-matched control cases were involved. Serological and molecular tests were made including hepatitis B virus, hepatitis C virus, rubella virus, herpes simplex virus (HSV group 1), and Epstein-Barr virus (EBV). HBsAg, rubella IgM and EBV IgM positivity were not seen in any of patients with rheumatic fever. Although antiHBs seropositivity was higher in the control group, it was not statistically significant (p > 0.05). There was no difference in rubella IgG, HSV IgM seropositivity, either (p > 0.05). EBV DNA was searched by the polymerase chain reaction technique; due to the latent nature of the virus, no significant difference was found between the control group and the other groups (p > 0.05). In this study, no positive correlation could be found to support the synergism theories regarding the streptoccocus infection and viral infections in the development of acute rheumatic fever. Only EBV DNA positivity was found in all acute rheumatic fever cases but not in the control group may lead to further studies with larger series of patients.

Ficolin 2 (FCN2) functional polymorphisms and the risk of rheumatic fever and rheumatic heart disease

Ficolins are pattern-recognition proteins involved in innate immunity, which upon binding to their specific pathogen-associated molecular patterns on the microbial surfaces trigger the immune response either by binding to collectin cellular receptors or by initiating the complement lectin pathway. In humans, three ficolin genes have been identified, which encode ficolin-1 (M-ficolin), ficolin-2 (L-ficolin) and ficolin-3 (H-ficolin or Hakata antigen). Ficolin-2 was shown to bind to lipoteichoic acid, a cell wall constituent in all Gram-positive bacteria such as Streptococcus pyogenes, which is the aetiological agent of rheumatic fever (RF) and its most severe sequelae, chronic rheumatic heart disease (CRHD). Here we investigated polymorphisms in the promoter region of the FCN2 gene (at positions -986/-602 and +4) in 122 patients with RF and CRHD and in 210 healthy subjects from the same geographic region and socioeconomic background. The haplotype -986/-602/-4 G/G/A, which is related to low levels of L-ficolin, was observed more frequently in the CRHD group when compared to the healthy subjects [99/162, 61.1% versus 211/420, 50.2%, odds ratio (OR) 1.6, confidence interval (CI) 95% 1.1-2.3, P = 0.021]. The haplotype -986/-602/-4 A/G/A was observed more frequently in the healthy group when compared to the affected (RF plus CRHD) subjects (31/420, 7.4% versus 6/244, 2.5%, OR 3.2, CI 95% 0.13-0.77, P = 0.008). Based on those findings, one can conclude that polymorphisms associated with low levels of L-ficolin level may predispose an individual to recurrent and/or more severe streptococcal infection.

[Acute rheumatic fever: 27 year experience from the Montreal's pediatric tertiary care centers]

OBJECTIVES

To examine the epidemiology, clinical characteristics and outcomes in a cohort of children with acute rheumatic fever (RF) over the past 27 years in Montreal.

METHODS

The medical records of patients younger than 18 years of age hospitalized and diagnosed with RF in Montreal between January 1979 and December 2005 were reviewed.

RESULTS

Among the initial 134 charts selected, 36 children were already followed-up for chronic RF and the remaining 98 patients (51 % females) who fulfilled the Jones criteria for acute RF were included in the analysis. The mean age at diagnosis was 10.1 +/- 3.0 years (range: 3-17). Over the 27-year study period, there was a mean incidence of 3.6 patients/year without peaks, but onset occurred in the last 15 years in almost two-thirds of the patients. Forty-nine percent of the patients were Canadian-born non-aboriginal (CbnA) and the remaining patients were Canadian-born aboriginal (CbA) or foreign-born (Fb). Carditis was diagnosed in 73 % of the patients and Sydenham's chorea in 49 %. Of the CbnA children, 39 % had carditis compared with 61 % of children from other ethnic groups (P = 0.003). However, the form of presentation was chorea in 69 % of CbnA children vs. 31 % of children from other ethnic groups (P < 0.001). No deaths were attributable to acute RF although 2 % of the patients relapsed during the study period. Severe cardiac sequelae requiring valve replacements occurred in 6.1 %.

CONCLUSION

The incidence of acute RF in Montreal was low but consistent over the 27-year study period. Clinical presentation varied depending on ethnicity.

The association between mannose-binding lectin gene polymorphism and rheumatic heart disease

Mannan-binding lectin (MBL) is an innate pattern recognition molecule known to play a key role in pathogen clearance. As MBL2 gene polymorphism is associated to an increased susceptibility to infection, we aimed to determine genetic variations in the MBL2 gene in rheumatic heart disease (RHD). Genetic variations in the promoter and exon 1 region of the MBL2 gene were analyzed in 107 patients with RHD and 105 controls by real-time polymerase chain reaction. The frequency of MBL2* A/A genotype was significantly higher in RHD patients (71/107, 66.36% vs 52/105, 49.52%, p<or=0.02, OR=1.99, 95% CI, 1.15-3.50). A/A genotypes were associated with higher levels of MBL in RHD compared with controls with the same genotype (p<or=0.004). The frequency of HYPA/HYPA, HYPA/LYQA, and LYQA/LYQA haplotypes was also increased in RHD (p<or=0.03, OR=1.98, 95% CI, 1.05-3.73). However, the frequency of MBL2 variant alleles (termed "O") was lower among patients (39/214, 18.2% vs 63/210, 30.0%, p<or=0.006, OR=0.52, 95% CI, 0.33-0.82), which was also seen for O/O genotypes (3/107, 2.8% vs 10/105, 9.5%, p<or=0.05, OR=0.27, 95% CI, 0.07-1.03). This data suggests a role for MBL genotypes in the susceptibility to RHD. However, it still remains unclear whether A/A homozygosity is a risk factor for RHD or rheumatic fever itself.

Overlapping humoral autoimmunity links rheumatic fever and the antiphospholipid syndrome

OBJECTIVE

Rheumatic fever (RF) and the antiphospholipid syndrome (APS) are autoimmune diseases that share similar cardiac and neurological pathologies. We assessed the presence of shared epitopes between M protein, N-acetyl-beta-D-glucosamine (GlcNAc) and beta2 glycoprotein-I (beta2GPI), the pathogenic molecules engaged in these autoimmune conditions.

METHODS

Sera from the APS patients were affinity-purified on beta2GPI and beta2GPI-related peptide columns. Sera from RF patients were affinity-purified on protein G column. The beta2GPI and M protein-related peptides were prepared by conventional solid-phase peptide synthesis. The enzyme-linked immunosorbent assay direct binding and inhibition studies were performed on the RF and APS sera for the presence, and cross-reactivity, of antibodies against beta2GPI, beta2GPI-related peptides, streptococcal M protein, M-derived peptides and GlcNAc.

RESULTS

Antibodies (Abs) to beta2GPI were found in 24.4% of 90 RF patients. Antibodies against various beta2GPI-related peptides were found in 1.1-36.7% of the patients. The immunoglobulin G sera from RF patients possessed significant anti-beta2GPI activity, while sera from APS patients contained a considerable anti-streptococcal M protein as well as anti-GlcNAc activity. Furthermore, affinity-purified anti-beta2GPI and anti-beta2GPI-related peptide Abs from APS patients cross-reacted with streptococcal M protein and M5 peptide, while beta2GPI and beta2GPI-related peptides inhibited anti-streptococcal M protein activity from RF patients. The results were confirmed by immunoblot analyses. The beta2GPI also inhibited anti-GlcNAc activity from APS patients with chorea.

CONCLUSIONS

The results of our study, showing a considerable overlap of humoral immunity in RF and APS, support a hypothesis that common pathogenic mechanisms underlie the development of cardiac valve lesions and Central Nervous System abnormalities in both diseases.

Paediatric rheumatology—A global perspective

This chapter aims to give a global perspective to paediatric rheumatology. The main points covered are the incidence, recognition of paediatric autoimmune diseases, and ethnic/geographic distribution. The most prevalent disease is juvenile idiopathic arthritis; robust data are still required for childhood-onset systemic lupus erythematosus, dermatomyositis, and scleroderma. Mimicking or overlapping infections are a major challenge in developing countries, and immunization policies in our patients in these areas need specific attention. The delivery of paediatric rheumatology care is also overviewed. Discrepancies in health-care resources and priorities are found in developing countries. Although most anti-rheumatic treatments are available worldwide, they are prohibitively expensive in many countries. For more traditional anti-rheumatic drugs there is still an ongoing need for good core outcome data across the world to ensure valid comparisons. Parent/patient education has been implemented worldwide in paediatric rheumatology through the power of the Internet. Physician and undergraduate training goals must be met to facilitate competent musculoskeletal assessment, a proper understanding of age-dependent variations, diagnosis, referral to specialists, and improved standards of care.

Significantly increased levels of mannose-binding lectin (MBL) in rheumatic heart disease: a beneficial role for MBL deficiency

Although mannose-binding lectin (MBL) is known to be involved in the primary defense against microorganisms, there are emerging lines of evidence for an active proinflammatory role for MBL in different chronic diseases. In this study we determined the circulating levels of MBL in patients with rheumatic heart disease (RHD). A total of 100 patients (77 women, 23 men; mean age 45.8 +/- 11 years, range 19-76 years) with chronic RHD, and a previous diagnosis of rheumatic fever, were studied. Transthoracic echocardiography was performed in all patients to evaluate valvular heart disease. Ninety-nine healthy individuals matched for age, sex and ethnic origin were included as controls. MBL concentration was measured by enzyme-linked immunosorbent assay and C3 and C4 levels by turbidimetry. MBL levels were significantly higher in patients with RHD than in healthy subjects (mean +/- SEM: 3036.2 +/- 298.9 ng/ml versus 1942.6 +/- 185.5 ng/ml, P <0.003). In addition, MBL deficiency was more prevalent in controls (17.1%) than in patients (9% P <0.09). Concentrations of C4 were within the normal range (22.7 +/- 0.8 mg/dl, normal: 10.0-40.0 mg/dl), while C3 concentrations were found to be elevated (109.2 +/- 3.6 mg/dl, normal: 50.0-90.0 mg/dl). No correlation was observed between serum MBL levels and valve area or the type of surgical procedure. The significantly elevated circulating MBL levels in patients with RHD together with the greater prevalence of MBL deficiency in controls suggest that MBL may cause undesirable complement activation contributing to the pathogenesis of RHD.

Serum intercellular adhesion molecule-1 levels in acute rheumatic fever

In order to determine the role of soluble intercellular adhesion molecule-1 (sICAM-1) in the pathogenesis and course of acute rheumatic fever (ARF), serum levels of ICAM-1 were measured in 30 patients at onset of ARF, in remission and during inactive periods of the disease (group 1), in 20 patients who had had ARF at least a year beforehand and had no evidence of exacerbation of the disease (group 2) and in 20 healthy children. Serum levels of sICAM-1 were increased in group 1, peaking in the active phase of the disease and declining during remission to the inactive phase of the disease when they were still significantly higher than in the controls, despite their ESR and fibrinogen levels having fallen to normal limits. The levels in group 2 were similar to those in the healthy controls. We consider that ICAM-1 plays a role in the pathogenesis of ARF and that improvement of ARF might best be determined by serum sICAM-1 levels, even when clinical and other laboratory test results have returned to normal, but additional studies are needed to clarify this hypothesis.

Restriction in the usage of variable beta regions in T-cells infiltrating valvular tissue from rheumatic heart disease patients

Rheumatic Heart Disease (RHD) is a delayed consequence of a pharyngeal infection with group A streptococcus (GAS), usually ascribed to a cross-reactive immune response to the host's cardiac tissues. Several GAS proteins have been reported to be superantigens, also raising the possibility that T cells in RHD could be driven by superantigens. We therefore analysed the variable beta (V beta) repertoire of T cells infiltrating heart valves from chronic RHD patients undergoing elective valvular surgery. We analysed 15 valve specimens from patients with longstanding quiescent RHD and control valves from four non-rheumatic individuals. Total RNA was extracted from fresh valve tissue and employed to amplify 22 V beta genes by RT-PCR. In valvular tissue, a restricted number of only 2 to 9 V beta regions were detected as opposed to the findings in control valves. In 8 RHD valves, the expression of V beta1, 2, 3, 5.1, 7, 8, 9 or 14 was marked. These V beta regions have been related to GAS superantigens. Our results evidence the presence of a restricted set of T lymphocytes in valvular tissue from a majority of patients with chronic RHD and suggest that valvular sequelae in these patients might be related to a local antigen or superantigen driven inflammatory process that persists even many years after the initial triggering event.

Streptococcal Scl1 and Scl2 proteins form collagen-like triple helices

The collagens are a family of animal proteins containing segments of repeated Gly-Xaa-Yaa (GXY) motifs that form a characteristic triple-helical structure. Genes encoding proteins with repeated GXY motifs have also been reported in bacteria and phages; however, it is unclear whether these prokaryotic proteins can form a collagen-like triple-helical structure. Here we used two recently identified streptococcal proteins, Scl1 and Scl2, containing extended GXY sequence repeats as model proteins. First we observed that prior to heat denaturation recombinant Scl proteins migrated as homotrimers in gel electrophoresis with and without SDS. We next showed that the collagen-like domain of Scl is resistant to proteolysis by trypsin. We further showed that circular dichroism spectra of the Scl proteins contained features characteristic of collagen triple helices, including a positive maximum of ellipticity at 220 nm. Furthermore the triple helices of Scl1 and Scl2 showed a temperature-dependent unfolding with melting temperatures of 36.4 and 37.6 degrees C, respectively, which resembles those seen for collagens. We finally demonstrated by electron microscopy that the Scl proteins are organized into "lollipop-like" structures, similar to those seen in human proteins with collagenous domains. This implies that the repeated GXY tripeptide motif is a structural indicator of collagen-like triple helices in proteins from such phylogenetically distant sources as bacteria and humans.

Will genetic testing alter the management of disease caused by infectious agents? A cost-effectiveness analysis of gene-testing strategies for prevention of rheumatic Fever

Cost-effectiveness analysis was done to evaluate the potential health and economic effects of a genetic screening program to identify individuals at risk for rheumatic fever (RF). The current RF prevention strategy was compared with a new, primary prevention strategy involving early genetic testing and intensive prophylaxis to prevent a first attack among individuals at high risk for RF. When analysis of a hypothetical 2000 birth cohort was done from a societal perspective, the prevention strategy involving genetic screening and prophylaxis for high-risk persons reduced the number of RF cases and increased life span at an estimated discounted cost of $7900 per quality-adjusted life-year gained. Genetic screening became the preferred (least expensive) strategy if the test specificity was >/=98%, the annual cost of prophylaxis was <$550, or the annual cost of caring for an individual with severe rheumatic heart disease increased to >$32,000. When used with available antibiotic prophylaxis, genetic testing has the potential to provide a cost-effective strategy for the primary prevention of RF and its sequelae.

Therapy of systemic lupus erythematosus: a look into the future

The prognosis for patients with systemic lupus erythematosus has greatly improved over the past two decades. However, therapies that are more effective and that have fewer sequelae are needed to rescue patients from organ failure and further reduce mortality. Research under way, including that into induction of tolerance to self-antigens, prevention of the consequences of pathogenic autoantibody production, interference with the cytokine network and signal transduction, the identification and treatment of any infectious triggers, and stem cell therapy, offers hope of improved remedies or even of cure. Given the fact that a number of biological therapies for rheumatologic disease are already in use or are in the development stage, such progress may come soon.

Rheumatic fever

Rheumatic fever is a multisystem inflammatory disease that occurs as a delayed sequel to group A streptococcal pharyngitis. It is less common than it was 50 years ago but is still a major cause of heart disease in developing areas of the world. The relationship between the site of infection, the type of causative organism, and susceptibility of the host is essential in the development of the disease. Its major clinical manifestations include carditis, migratory polyarthritis, chorea, erythema marginatum, and subcutaneous nodules. It can manifest as an acute febrile illness consisting of migratory polyarthritis involving the large joints, as carditis and valvulitis, or as Sydenham's chorea with involvement of the central nervous system. The disorder in its milder form resolves itself without sequelae. Carditis is the condition most associated with increased mortality and morbidity and may be fatal in its severe forms. Penicillin is the most appropriate primary and secondary prophylaxis. Anti- inflammatory agents provide symptomatic relief but do not prevent rheumatic heart disease.

The varicella-autoantibody syndrome

This cross-sectional study was conducted to determine the incidence of autoantibodies to phospholipids and coagulation proteins in children with acute varicella zoster virus (VZV) infection. Study groups included children with VZV alone or complicated by purpura fulminans and/or thromboembolism. VZV naïve children and children who had VZV >1 y before sample collection formed a control group. Blood was assayed for the following: free protein S (PS), protein C, antithrombin, and prothrombin; antibody binding to these proteins; lupus anticoagulant; anticardiolipin antibody; antiphospholipid antibodies; and prothrombin fragment 1+2. Data regarding coinfections was collected. Forty-three VZV-infected children showed an increased frequency of lupus anticoagulant, anticardiolipin antibody, antiphospholipid antibodies, and autoantibodies to PS, protein C, prothrombin, and antithrombin in comparison to 52 children without acute VZV (p < 0.0001). Seventeen children with VZV and purpura fulminans and/or thromboembolism showed a statistically significant decrease in free PS, significantly increased PS IgG antibody, and significantly increased prothrombin fragment 1+2 (p < 0.0001) compared with the group without acute VZV and the group with uncomplicated VZV. Twenty-six children with uncomplicated VZV showed increased PS IgG antibody (p < 0.001) compared with the children without acute VZV. For all groups combined, elevated PS IgG antibody showed negative correlation with free PS (p < 0.0001) and positive correlation with prothrombin fragment 1+2 (p = 0.0002). Autoantibodies were transient. Transient antiphospholipid and coagulation protein autoantibodies were common with VZV infection, but were not predictive of thrombotic complications.

Induction of autoimmune valvular heart disease by recombinant streptococcal m protein

Rheumatic heart disease is an autoimmune sequela of group A streptococcal infection. Previous studies have established that streptococcal M protein is structurally and immunologically similar to cardiac myosin, a well-known mediator of inflammatory heart disease. In this study, we investigated the hypothesis that streptococcal M protein could produce inflammatory valvular heart lesions similar to those seen in rheumatic fever (RF). Fifty percent (3 of 6) of Lewis rats immunized with recombinant type 6 streptococcal M protein (rM6) developed valvulitis as well as focal lesions of myocarditis. Valvular lesions initiated at the valve surface endothelium spread into the valve. Anitschkow cells and verruca-like lesions were present. T cells from rM6-immunized rats proliferated in the presence of purified cardiac myosin, but not skeletal myosin. A T-cell line produced from rM6-treated rats proliferated in the presence of cardiac myosin and rM6 protein. The study demonstrates that the Lewis rat is a model of valvular heart disease and that streptococcal M protein can induce an autoimmune cell-mediated immune attack on the heart valve in an animal model. The data support the hypothesis that a bacterial antigen can break immune tolerance in vivo, an important concept in autoimmunity.

Identification and characterization of the scl gene encoding a group A Streptococcus extracellular protein virulence factor with similarity to human collagen

Group A Streptococcus (GAS) expresses cell surface proteins that mediate important biological functions such as resistance to phagocytosis, adherence to plasma and extracellular matrix proteins, and degradation of host proteins. An open reading frame encoding a protein of 348 amino acid residues was identified by analysis of the genome sequence available for a serotype M1 strain. The protein has an LPATGE sequence located near the carboxy terminus that matches the consensus sequence (LPXTGX) present in many gram-positive cell wall-anchored molecules. Importantly, the central region of this protein contains 50 contiguous Gly-X-X triplet amino acid motifs characteristic of the structure of human collagen. The structural gene (designated scl for streptococcal collagen-like) was present in all 50 GAS isolates tested, which together express 21 different M protein types and represent the breadth of genomic diversity in the species. DNA sequence analysis of the gene in these 50 isolates found that the number of contiguous Gly-X-X motifs ranged from 14 in serotype M6 isolates to 62 in a serotype M41 organism. M1 and M18 organisms had the identical allele, which indicates very recent horizontal gene transfer. The gene was transcribed abundantly in the logarithmic but not stationary phase of growth, a result consistent with the occurrence of a DNA sequence with substantial homology with a consensus Mga binding site immediately upstream of the scl open reading frame. Two isogenic mutant M1 strains created by nonpolar mutagenesis of the scl structural gene were not attenuated for mouse virulence as assessed by intraperitoneal inoculation. In contrast, the isogenic mutant derivative made from the M1 strain representative of the subclone most frequently causing human infections was significantly less virulent when inoculated subcutaneously into mice. In addition, both isogenic mutant strains had significantly reduced adherence to human A549 epithelial cells grown in culture. These studies identify a new extracellular GAS virulence factor that is widely distributed in the species and participates in adherence to host cells and soft tissue pathology.

Rheumatic disorders associated with streptococcal infections

The proteins in the cell wall of Streptococcus have many functions, with some proteins being regarded as a marker of their rheumatological potential. High levels of antibodies directed against some proteins are seen in patients with acute rheumatic fever. The theory of molecular mimicry forms the basis of the relationship between the bacteria and the disease acute rheumatic fever. A distinct entity which does not fulfil Jones' criteria, and which is known as post-streptococcal reactive arthritis following infection with beta-haemolytic streptococci, is being encountered more frequently. A pyogenic form of arthritis due to Streptococcus is one of the most common and serious joint infections and requires prompt recognition and treatment.

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.