IDENTIFICATION OF METH-A SARCOMA-DERIVED CLASS-I MAJOR HISTOCOMPATIBILITY COMPLEX-ASSOCIATED PEPTIDES RECOGNIZED BY A SPECIFIC CD8(-LYMPHOCYTE() CYTOTOXIC T)

The finding that class I major histocompatibility complex (MHC)-restri cted cytotoxic T lymphocytes (CTL) recognize peptide antigens (epitope s) bound to class I MHC molecules has accelerated efforts to identify CTL-defined tumor peptides for the development of peptide-based cancer immunotherapy. The Meth A sarcoma is probably one of the best studied of all murine tumors, It is extremely lethal unless protective immuni ty is induced. We recently reported the characterization of a cloned H -2K(d)-restricted, CD8(+) anti-Meth A CTL line (CTLMA-9C; Frassanito e t al., Cancer Res., 54: 4424-4429, 1994), The cytotoxic reactivity of this CTL was shown to be restricted to Meth A sarcoma, and the results of the analysis of the immunogenicity of the CTL-resistant variant of Meth A, designated Meth A4R, indicate that the CTL-defined epitope is functional in tumor rejection, Here we have isolated class I MHC-asso ciated peptides from Meth A sarcoma by mild acid treatment and resolve d them into sixty fractions by reverse phase-HPLC. These fractions wer e then tested for their ability to sensitize the DBA/2 mastocytoma P81 5 to cytolysis by the anti-Meth A CTL, A single fraction, fraction 27, has been repeatedly identified as containing the CTL-defined epitope, Peptides eluted from the CTL-resistant variant, Meth A4R, failed to s ensitize P815 to cytolysis by the anti-Meth A CTL, while fraction 27 d erived from Meth A sensitized Meth A4R to lysis by the CTL, These find ings confirm the peptide nature of the epitope recognized by CTL on th e surface of Meth A, Our future efforts will focus on the identificati on and sequence analysis of the tumor peptides and the development of a tumor peptide-based vaccine model for immunotherapy.