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Group A streptococcal (GAS) infection is associated with a spectrum of autoimmune diseases including acute rheumatic fever/rheumatic heart disease (ARF/RHD) and neurobehavioral abnormalities. Antibodies against GAS M proteins cross‐react with host tissue proteins in the heart and brain leading to the symptomatology observed in ARF/RHD. As throat carriage of Streptococcus dysgalactiae subspecies equisimilis (SDSE) has been reported to be relatively high in some ARF/RHD endemic regions compared with GAS, and both SDSE and GAS express coiled‐coil surface protein called M protein, we hypothesized that streptococci other than GAS can also associated with ARF/RHD and neurobehavioral abnormalities. Neurobehavioral assessments and electrocardiography were performed on Lewis rats before and after exposure to recombinant GAS and SDSE M proteins. Histological assessments were performed to confirm inflammatory changes in cardiac and neuronal tissues. ELISA and Western blot analysis were performed to determine the cross‐reactivity of antibodies with host connective, cardiac and neuronal tissue proteins. Lewis rats injected with M proteins either from GAS or SDSE developed significant cardiac functional and neurobehavioral abnormalities in comparison to control rats injected with phosphate‐buffered saline. Antibodies against GAS and SDSE M proteins cross‐reacted with cardiac, connective and neuronal proteins. Serum from rats injected with streptococcal antigens showed higher immunoglobulin G binding to the striatum and cortex of the brain. Cardiac and neurobehavioral abnormalities observed in our experimental model were comparable to the cardinal symptoms observed in patients with ARF/RHD. Here for the first time, we demonstrate in an experimental model that M proteins from different streptococcal species could initiate and drive the autoimmune‐mediated cardiac tissue damage and neurobehavioral abnormalities. [ABSTRACT FROM AUTHOR]

The C-terminal region of the M-protein of Streptococcus pyogenes is a major target for vaccine development. The major feature is the C-repeat region, consisting of 35–42 amino acid repeat units that display high but not perfect identity. SV1 is a S. pyogenes vaccine candidate that incorporates five 14mer amino acid sequences (called J14i variants) from differing C-repeat units in a single recombinant construct. Here we show that the J14i variants chosen for inclusion in SV1 are the most common variants in a dataset of 176 unique M-proteins. Murine antibodies raised against SV1 were shown to bind to each of the J14i variants present in SV1, as well as variants not present in the vaccine. Antibodies raised to the individual J14i variants were also shown to bind to multiple but different combinations of J14i variants, supporting the underlying rationale for the design of SV1. A Lewis Rat Model of valvulitis was then used to assess the capacity of SV1 to induce deleterious immune response associated with rheumatic heart disease. In this model, both SV1 and the M5 positive control protein were immunogenic. Neither of these antibodies were cross-reactive with cardiac myosin or collagen. Splenic T cells from SV1/CFA and SV1/alum immunized rats did not proliferate in response to cardiac myosin or collagen. Subsequent histological examination of heart tissue showed that 4 of 5 mice from the M5/CFA group had valvulitis and inflammatory cell infiltration into valvular tissue, whereas mice immunised with SV1/CFA, SV1/alum showed no sign of valvulitis. These results suggest that SV1 is a safe vaccine candidate that will elicit antibodies that recognise the vast majority of circulating GAS M-types. [ABSTRACT FROM AUTHOR]

Background. Concern about the emergence of antibiotic-resistant strains and about morbidity and/or mortality related to rheumatic fever and rheumatic heart disease has been a continuous impetus for the development of a safe, effective vaccine against group A Streptococcus (GAS). To date, >120 GAS M types are known, as identified by serological typing. in general, serum immunoglobulin G directed to the hypervariable NH2 terminal portion of M protein leads to complement fixation and opsonophagocytosis of the homologous streptococcal serotype by polymorphonuclear leukocytes, and the protection is type specific. The sequence variation at the N terminus ultimately affects the binding of opsonic antibodies. Because of hypervariability in these opsonic sequences from different M types, it was relevant to use epitopes derived from these multiple sequences in a "multivalent vaccine" design for evaluation of protection against these M types of GAS. Thus, any attempts to design vaccines for a given community will require information on N terminal-sequence typing and variation. Methods. in the present study, we performed molecular characterization of isolates recovered from patients in northern india-to our knowledge, for the first time-in an attempt to study the circulating M types and their N terminal sequence variability. Results. We report tremendous diversity in GAS strains recovered from symptomatic patients, with implications on the design of appropriate vaccines. Fifty-nine isolates represented 33 different sequence types. Very few novel types and no predominant clones were found. Conclusions. The high diversity of emm types encountered in a single year suggests that any M protein-based multivalent vaccine would have to be specifically tailored for this region. [ABSTRACT FROM AUTHOR]

Group A Streptococcus (GAS) is a human-specific pathogen responsible for a wide variety of human diseases. Numerous GAS surface antigens interact with the human immune system and only some of these proteins have been studied in depth. A few of these may elicit protective response against GAS infection. In this study, we have used an in silico approach to identify antigenic peptides from GAS surface proteins. Putative GAS surface proteins from the M1 GAS genome were identified by the presence on LPxTG cell-wall anchoring motif and an export signal sequence. This technique identified 17 proteins of known or putative function, and another 11 which do not have known homologues. Peptides derived from predicted antigenic sequences near the amino terminus of six of these proteins, and another seven peptides derived from the two known surface proteins, GRAB and MtsA, were conjugated to keyhole lymphocyanin (KLH), and investigated for their capacity to induce opsonic antibody responses in outbred Quackenbush mice. All peptide-KLH antisera demonstrated opsonic capacity against both 88/30 and M1 GAS. However, KLH sera alone was also able to induce opsonic antibodies, suggesting that anti-KLH antibodies contributed to the opsonisation seen in the peptide-KLH antisera. KLH is therefore a promising carrier molecule for potential GAS peptide vaccines. [Copyright &y& Elsevier]

Extracellular localisation of manganese-dependent superoxide dismutase (SodA) by group A streptococcus (GAS) may have a role in protection of this pathogenic bacterium from exogenously produced reactive oxygen species. In this study we show that SodA is found both in surface protein extracts and in culture supernatants of GAS. To investigate whether SodA is a possible vaccine candidate outbred Quackenbush mice were subcutaneously vaccinated with recombinant SodA. Strong antibody responses which were moderately opsonic were elicited. These antibodies were unable to protect mice from intraperitoneal challenge with M1 GAS. We also show that SodA and p145 (a conserved peptide from the M-protein) antibodies are present at significantly higher levels amongst patients with rheumatic heart disease than in control subjects from the same endemic region. The higher SodA antibody levels in patients may be indicative of a role for this protein in pathogenesis of rheumatic heart disease but are more likely to be a marker of recent or recurrent streptococcal infection. [Copyright &y& Elsevier]

Abstract: The development of a group A streptococcal (GAS) vaccine has focused on the M protein, a major virulence factor. Antibodies against the amino terminal domain of the M protein are generally protective but only provide type-specific immunity. J14, a 29-mer peptide sequence which contains a conserved epitope from the C-repeat region of the M protein, offers the possibility of a vaccine which will elicit protective opsonic antibodies against multiple GAS strains. In this study we have shown that antibodies raised against J14 are capable of opsonising 37 GAS isolates representing different emm types derived from a region in which GAS infection is endemic. We also demonstrate that J14 antisera is capable of opsonising GAS isolates containing J14 homologues but not J14-specific sequences, further increasing the strain coverage of this vaccine candidate. Isolates with three C-repeats were opsonised more efficiently than isolates with two repeats. Opsonisation of a strain with only a single C-repeat was dramatically lower than other strains tested. The number of C-repeats present in the M protein of individual isolates therefore appears to be the critical factor in determining bactericidal capacity of J14 antisera. The reduced opsonic capacity of sera against this strain was shown to correlate with a reduced capacity to bind J14 antisera, as demonstrated by immunofluorescence microscopy and FACS analysis. In vivo challenge experiments also confirmed the protective efficacy of immunisation with J14 peptide. [Copyright &y& Elsevier]