The aim of this research is to develop a safe and effective multivalent vaccine against strains of group A streptococci that trigger acute rheumatic fever and rheumatic heart disease. For this purpose, the chemistry and immunology of the protective as opposed to heart cross-reactive epitopes of streptococcal M protein will be studied in detail. Specific efforts will be directed toward: (1) identifying the protective M protein epitopes predominating among strains of group A streptococci collected from populations in which attacks of rheumatic fever remain high, (2) isolating, purifying and immunochemically analyzing M protein polypeptide fragments for protective and heart cross-reactive epitopes, (3) determining the covalent structure of the aminoterminal and common protective regions of relevant M proteins, (4) synthesizing peptide copies of the amino-terminal regions of selected M proteins, and testing the protective and heart cross-reactive immunogenicity of the peptides conjugated to various carriers in laboratory animals, (5) synthesizing and analyzing tandem hybrids of peptides containing protective epitopes of different M serotypes, and (6) carefully testing the immunogenicity of selected pep M proteins and synthetic peptides as guided by the foregoing studies in human volunteers. The predominant protective epitopes will be determined by M typing, opsonophagocytic and mouse protection tests, and Southern hybridization of the DNA of streptococcal strains with probes prepared from the structural genes encoding M protein under varying conditions of stringency. Purified peptic extracts of rheumatogenic streptococci will be tested for protective and heart cross-reactive immunogenicity in rabbits and mice. The covalent structures of the amino-terminus of the relevant M proteins will be determined by automated sequence analysis. Overlapping peptides will be synthesized, conjugated to various carriers, including pepM24, which has been shown to be devoid of heart cross-reactive epitopes, and tested for type-specific, cross protective and tissue-cross-reactive immunogenicity. Some of the peptides from different M serotypes will be synthesized in tandem in an attempt to produce multivalent hybrid peptides with protective immunogenicity against many serotypes of streptococci. Based on the results obtained in the foregoing studies, the synthetic peptides will be carefully evaluated in humans for protective immunogenicity. These studies should provide fundamental information on the chemistry and immunology of M protein as they relate to protective immunity against rheumatogenic streptococci.
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