Suppression and reversal of allergic encephalomyelitis in guinea pigs with a non-encephalitogenic analogue of the tryptophan region of the myelin basic protein.

The administration of synthetic peptide S42 leads to suppression and reversal of experimental allergic encephalomyelitis (EAE) induced in guinea pigs by myelin basic protein. Peptide S42 contains a linear sequence of 21 amino acid residues, H-Phe-Ser-Trp-Gln-Lys-Phe-Ser-Trp-Gln-Lys-Phe-Ser-Trp-Gln-Lys-Phe-Ser-Trp-Gln-Lys-Gly-OH, made up of four repeating unit sequences of H-Phe-Ser-Trp-Gln-Lys-OH in addition to a C-terminal glycine. Injected at relatively high doses, peptide S42 is non-encephalitogenic. It induces delayed-type hypersensitivity which is not followed by EAE, and elicits delayed-type hypersensitivity responses in peptide S42, encephalitogenic trytophan peptide, or BP-challenged animals for either of the three antigens. The repeating unit sequence of peptide S42 is analogous to the encephalitogenic tryptophan region of the BP molecules . The sequence homology is responsible for cellular recognition of this antigen by the skin test assay and suggests in vivo interaction between peptide S42 and EAE-inducing cells leading to suppression and reversal of disease.