IDENTIFICATION OF HUMAN-MELANOMA PEPTIDES RECOGNIZED BY CLASS-I RESTRICTED TUMOR-INFILTRATING T-LYMPHOCYTES

Using a newly described pH 3.3 acid elution technique, peptides were e xtracted by denaturation of class I molecules on the surface of human melanomas. HPLC fractionation of this material revealed six T cell epi topes (termed P1-P6) recognized by HLA-A2-restricted, melanoma-specifi c tumor infiltrating lymphocyte (TIL) lines. Three of these fractions (P1, P2, and P4) appeared to represent shared/immunodominant melanoma Ag recognized in the context of HLA-A2 because they were expressed by 4/4 HLA-A2+ melanoma cell lines and were each recognized by all four o ligoclonal HLA-A2-restricted TIL lines examined. Interestingly, P1 and P2 (but not P3-P6) could also be recognized by these same TIL when pr esented by the HLA-Aw69 class I molecule, which is closely related to HLA-A2. P3, P5, and P6 displayed more restricted expression and were d ifferentially recognized by the four oligoclonal TIL lines. These resu lts suggest that synthetic peptide derived from P1, P2, and P4 sequenc es (when deduced) may form the basis of effective prophylactic or ther apeutic melanoma vaccines by stimulating CD8+ CTL in HLA-A2+ individua ls. This approach of identifying T cell epitopes presented by class I molecules should prove generally applicable to the study of other tumo rs recognized by class I-restricted CTL.