title: Epitopes of streptococcal M proteins that evoke antibodies that cross-react with human brain.
abstract: There is evidence suggesting that Sydenham's chorea, which is a major manifestation of acute rheumatic fever, may be mediated by streptococcal antibodies that cross-react with the brain. Our studies were undertaken to determine whether streptococcal M protein, the major virulence factor of group A streptococci, evoked antibodies that cross-react with human brain. Rabbits were immunized with pepsin-extracted M protein from rheumatogenic type 6 streptococci. Immune sera were screened for the presence of antibodies that cross-reacted with human brain by indirect immunofluorescence tests and immunoblot analyses. Type 6 M protein evoked antibodies that cross-reacted with several brain proteins and antibody binding to these proteins was completely inhibited by type 6 M protein and partially inhibited by types 5 and 19 M proteins, suggesting that these heterologous M proteins contain conserved brain-cross-reactive epitopes. Using synthetic peptides from several serotypes of M proteins, the conserved brain-cross-reactive epitopes were localized to a decapeptide contained within the covalent structure of the B repeat region of type 6 M protein. These peptides also inhibited brain-cross-reactive antibodies in the serum of a patient with active Sydenham's chorea. Our data indicate that streptococcal M proteins contain brain-cross-reactive epitopes that could potentially be involved in the pathogenesis of Sydenham's chorea.
authors.affiliation: Department of Veterans Affairs Medical Center, Memphis, TN.
authors.forename: M S
authors.initials: MS
authors.lastname: Bronze
authors.forename: J B
authors.initials: JB
authors.lastname: Dale
mesh_terms: D000208:Acute Disease; D000595:Amino Acid Sequence; D000818:Animals; D000907:Antibodies, Bacterial / Q000276:immunology*; D000942:Antigens, Bacterial / Q000276:immunology*; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000276:immunology*; D001921:Brain / Q000276:immunology*; D002352:Carrier Proteins; D002819:Chorea / Q000209:etiology; D003429:Cross Reactions; D000939:Epitopes; D006801:Humans; D008969:Molecular Sequence Data; D009206:Myocardium / Q000276:immunology; D011817:Rabbits; D012213:Rheumatic Fever / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D000939:Epitopes; C014689:streptococcal M protein