title: Synthetic peptide fragments of streptococcal M proteins.
abstract: The surface M proteins of group A streptococci prevent phagocytosis by the non-immune host but antibodies subsequently developed against these M proteins opsonize the organism to allow phagocytosis and killing. In some cases, antibodies developed against M proteins are cross-reactive with host tissue and have been implicated in rheumatic fever. Peptide fragments of several serotypes, namely type 24, 5 and 6 M proteins were chemically synthesized and tested for their ability to induce protective and tissue cross-reactive antibodies in rabbits. Two synthetic 35 residue peptides of type 24 M protein, S-CB3 and S-CB7 had previously been shown to evoke high ELISA titers as well as opsonic antibody titers in each of three rabbits. Neither contained host tissue cross-reactive antibodies when examined with human heart tissue. Subpeptides of CB7 were synthesized to identify the smallest protective epitope. Three synthetic subpeptides (S-CB7-(13-35), - (18-35) and - (23-35) C were covalently linked to tetanus toxoid and evoked opsonic antibodies in rabbits and thus protective immunity with no tissue cross-reactive epitopes. Synthetic peptides of the NH2-terminal region of peptide M 5, which is known to contain cardiac tissue cross-reactive epitopes, were also tested. When covalently linked to tetanus toxoid, the synthetic peptide S-M 5 (1-20), but not S-M5 (20-40), evoked antibodies which were protective against type 5 streptococci; no heart cross-reactive antibodies were evoked even when large excesses of the synthetic peptides were injected.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000096:biosynthesis / Q000276:immunology; D000942:Antigens, Bacterial / Q000276:immunology*; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000276:immunology*; D002352:Carrier Proteins; D003429:Cross Reactions; D000939:Epitopes / Q000276:immunology; D006801:Humans; D009206:Myocardium / Q000276:immunology; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000276:immunology*; D011817:Rabbits
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D000939:Epitopes; D010446:Peptide Fragments; C014689:streptococcal M protein