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 clones 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 specifically 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.