High avidity melanoma-reactive cytotoxic T lymphocytes are efficiently induced from peripheral blood lymphocytes on stimulation by peptide-pulsed melanoma cells.

To design an efficient procedure to expand high avidity melanoma reactive T cells and to perform immunotherapies, we compared conditions of peripheral blood lymphocyte (PBL) stimulation by Melan-A/MART-1 peptides. Avidity of induced CTLs was evaluated by measuring their lysis and cytokine secretion to peptide-pulsed transporter-associated protein-deficient cells and to melanoma cells. In side-by-side experiments, we show that melanoma cells, either allogeneic or autologous, induced the growth of high avidity Melan-A-reactive CTLs from all donors, whereas essentially low avidity T cells were induced by peptide-pulsed PBLs. We also show that at least two cytokines, interleukin-6 and interleukin-2, were required to promote the growth of high avidity CTLs. Once sorted by tetramer labeling or cloning, the specificity and reactivity to tumor cells of peptide-specific T cells induced by allogeneic melanoma cells were confirmed. We then describe a relatively simple and efficient procedure that allowed us to obtain systematically high amounts (in the range of billion) of high avidity Melan-A/ MART-1-specific T cells from the PBLs of HLA-A2 melanoma patients and healthy donors in 3 months. Because this antigen is expressed by most melanoma tumors, this procedure should be useful for checking the efficiency of adoptive immunotherapy of melanoma tumors and using functionally well-defined Melan-A/MART-1-specific CTLs in a large group of patients.