T-cell clones from melanoma patients immunized against an anchor- modified gp100 peptide display discordant effector phenotypes

PURPOSE: The modified peptide epitope gp100-209-217 (210M), referred to as g209-2M, of the gp100 melanocyte differentiation protein, when administered to melanoma patients by subcutaneous injection in incomplete Freund's adjuvant, is capable of generating HLA-A2-restricted CD8⁺ lymphocytes that specifically recognize the native gp100:209-217 (g209) peptide as well as gp100-expressing tumor cells. To evaluate the suitability of cloned lymphocytes from immunized patients for use in adoptive transfer therapy protocols, the functional and phenotypic variation of individual CD8⁺ T cell dunes comprising the antitumor immune response was evaluated. METHODS: T-cell clones from melanoma patients who received g209-2M immunization were isolated and expanded, and their specific antitumor functional phenotypes were characterized. RESULTS: g209-specific CD8⁺ lymphocytes that specially recognized gp100-expressing tumor cells were readily obtained from g209-2M-immunized patients. There was substantial variation in the absolute levels of cytokine secretion and target cell lysis by g209-specific clones from each patient. Furthermore, individual clones demonstrated discordant secretion of different proinflammatory cytokines. These clonal phenotypes were stable, even after large expansions in cell number. DISCUSSION: These results indicate that g209-2M peptide immunization of melanoma patients leads to a functionally diverse population of T cells, many of which are capable of expansion ex vivo to cell numbers appropriate for adoptive immunotherapy. However, the selection of a particular antigen- specific T-cell clone for treatment should be based on multiple functional criteria.