MULTIPLE MELANOMA-ASSOCIATED EPITOPES RECOGNIZED BY HLA-A3-RESTRICTEDCTLS AND SHARED BY MELANOMAS BUT NOT MELANOCYTES

The molecular characterization of melanoma-associated Ags allowed the definition of several HLA class I-presented peptides recognized by T c ells. However, no HLA-A3.1-restricted melanoma epitopes have been iden tified to date, To gain insight into the HLA-A3.1-restricted T cell ep itope repertoire of human melanoma, we analyzed the immunologic reacti vity of CTLs isolated from tumor-involved or tumor-free lymph nodes in two HLA-A3.1(+) melanoma patients, Three CTL lines, clonal or highly oligoclonal in their TCR composition, and two CTL clones were selected for HLA class I-restricted lysis of the autologous tumor and then tes ted for the recognition of HLA-A3(+) and HLA-A3(-) normal or neoplasti c cells of the melanocyte lineage, One CTL recognized a unique HLA-A3. 1-restricted Ag expressed only by the autologous tumors, while all the other CTLs defined three HLA-A3.1 epitopes shared by melanomas, but n ot by melanocytes, Moreover, the epitopes of two CTL lines with differ ent specificity were reconstituted by nonoverlapping fractions of HLA- A3(+) melanoma-derived peptides resolved by reverse phase-HPLC, indica ting that distinct naturally processed peptides were specifically reco gnized on melanoma cells in association with HLA-A3.1 molecules. These novel lineage-unrelated HLA-A3.1-restricted melanoma epitopes do not derive from MAGE, BAGE, or GAGE gene families, as evaluated by the COS -7 transfection assay, Our data show that CTLs may recognize HLA-A3.1- class I complexes presenting melanoma (but not melanocyte)-associated epitopes that are either unique to a given patient's tumor or that are shared between multiple melanomas.