Allergic encephalomyelitis. Isolation of an encephalitogenic peptide active in the monkey.

A 17-residue peptide (Peptide Y) was isolated from the COOH-terminal end of the basic protein of bovine myelin by peptic digestion. This peptide induced experimental allergic encephalomyelitis in the rhesus monkey. Treatment of Peptide Y with cyanogen bromide released three amino acids from the COOH-terminal end and resulted in a tetradecapeptide (Peptide M) which was also encephalitogenic in the rhesus monkey. The sequence of Peptide M is: Phe-Lys-LEU-Gly-Gly-Arg-Asp-Ser-Arg-Ser-Gly-Ser-Pro-Met. Thus a major disease-inducing site active in the rhesus monkey is contained within a 14-residue peptide localized near the COOH-terminal end of the protein. This peptide differs markedly in location and sequence from the 9-residue peptide shown to contain the encephalitogenic determinant for the guinea pig.