Epitope-specific protective immunogenicity of chemically synthesized 13-, 18-, and 23-residue peptide fragments of streptococcal M protein.
The ability of chemically synthesized subpeptides of type 24 streptococcal M protein to evoke protective antibodies in rabbits was investigated. We synthesized copies of the COOH-terminal 13, 18, and 23 amino acid residues of cyanogen bromide fragment 7 (CB7) of pepsin-extracted type 24 M protein, except that methionine was substituted for homoserine as the COOH-terminal residue. An additional residue of cysteine was added at the COOH terminus of the 13-residue peptide. Each of the peptides, designated S-CB7-(23-35)-Cys, S-CB7-(18-35), and S-CB7-(13-35), when conjugated to lysylated tetanus toxoid with glutaraldehyde, was capable of stimulating formation of protective anti-type 24 M protein antibodies in rabbits. The smallest peptide, S-CB7-(23-35)-Cys, elicited immune responses equally as strong, if not stronger, than those to the longer peptides. A single Lys/Gly substitution in this 13-residue peptide resulted in its failure to stimulate protective antibodies. None of the antisera reacted with heterologous serotypes of M protein and none reacted with frozen sections of human heart tissue. These results indicate that a chemically synthesized peptide fragment corresponding to as few as 13 amino acid residues of streptococcal M protein is capable of evoking protective anti-streptococcal antibodies without evoking antibodies crossreactive with cardiac tissue.
D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000302:isolation & purification; D000917:Antibody Formation; D000942:Antigens, Bacterial / Q000276:immunology*; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000276:immunology*; D002352:Carrier Proteins; D004797:Enzyme-Linked Immunosorbent Assay; D005779:Immunodiffusion; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000276:immunology*; D011817:Rabbits; D013329:Structure-Activity Relationship; D013745:Tetanus Toxoid / Q000276:immunology
D000906:Antibodies; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D010446:Peptide Fragments; D013745:Tetanus Toxoid; C014689:streptococcal M protein