707-AP PEPTIDE RECOGNIZED BY HUMAN-ANTIBODY INDUCES HUMAN-LEUKOCYTE ANTIGEN A2-RESTRICTED CYTOTOXIC T-LYMPHOCYTE KILLING OF MELANOMA

We recently identified a tumor-associated antigen that was recognized by human monoclonal antibody L94. The antibody-reactive 707-AP sequenc e RVAALARDAP, cloned from a melanoma cDNA library, was also found to b e recognized by peripheral blood lymphocytes (PBLs) from melanoma pati ents, In this study, 707-AP was used to stimulate melanoma patients' P BLs for the establishment of peptide-specific CTL cell lines, CTL cell lines derived from 258 melanoma patients of different human leukocyte antigen (HLA)-A and HLA-B allele expressions were assessed by a Cr-51 cytotoxicity assay against the peptide-pulsed autologous B lymphoblas toid cells and T2 HLA-A2 antigen-presenting cells and autologous and a llogeneic melanoma cell lines, The analysis of 707-AP CTL activity dem onstrated that only HLA-A2 patients' PBLs could be stimulated with 707 -AP, 707-AP CTLs were able to specifically lyse HLA-AZ autologous and allogeneic melanoma cell lines, This verified the endogenous processin g and presentation of 707-AP by melanoma cells, 707-AP CTL cytotoxicit y against peptide-pulsed autologous HLA-A2 B lymphoblastoid cells and T2 HLA-AZ cells was also demonstrated, The killing activity of HLA-AZ 707-AP CTL cell lines (CD8+ CD3+) was inhibited by anti-HLA class and anti-HLA-A2 monoclonal antibodies. The amino acid substitution or dele tion analysis of the 707-AP sequence in CTL stimulation and recognitio n confirmed that position 2, amino acid V and position 9, amino acid A were essential, Both positions are known as supermotif anchors for HL A-A2 peptide sequences, Our studies demonstrated that 707-AP is a pote nt stimulator of CTLs that can induce peptide-specific HLA-A2 melanoma cell killing, The recognition of 707-AP by both antibody and CTLs sug gests its potential significance as a peptide immunotherapeutic.