Pilot study of granulocyte-macrophage colony-stimulating factor and interleukin-2 as immune adjuvants for a melanoma peptide vaccine

Thus far, peptide vaccines used to stimulate tumor-specific immune responses in patients with melanoma have been largely unsuccessful. Granulocyte-macrophage colony-stimulating factor and interleukin-2 are immune-potentiating cytokines that have improved vaccine responses in preclinical models. We hypothesized that higher doses of granulocyte-macrophage colony-stimulating factor and addition of low-dose interleukin-2 might augment responses to vaccine antigens. Patients with resected stage II, III, or IV melanoma were treated with vaccines containing three melanoma-associated peptides [MART-1a, gp100(207-217), and survivin], along with 300 or 500 mcg granulocyte-macrophage colony-stimulating factor in Montanide ISA. Cohorts of patients received low-dose subcutaneous interleukin-2 on days 7-20 after vaccination. Induction of a response was defined as either doubling of cytotoxic T lymphocyte frequency from baseline or increase in frequency from undetectable (<0.05%) to detectable. Leukocyte subsets and plasma cytokines were analyzed before and after vaccination. Cytotoxic T lymphocyte responses to MART-1a, gp100(207-217), and survivin were induced in 11, 16, and 14 of 19 patients, respectively. Responses were not higher in patients receiving 500 mcg granulocyte-macrophage colony-stimulating factor or low-dose interleukin-2 than in patients receiving 300 mcg granulocyte-macrophage colony-stimulating factor only. Interleukin-2 treatment (in nine patients) led to increases in natural killer cells and T regulatory cells compared with no interleukin-2 treatment (nine patients). Multiple plasma cytokines were transiently induced during vaccination. Neither increasing the dose of granulocyte-macrophage colony-stimulating factor nor addition of low-dose interleukin-2 resulted in an increase in the frequency of vaccine-specific cytotoxic T lymphocytes to a melanoma peptide vaccine. The increase in T regulatory cells associated with interleukin-2 treatment suggests that interleukin-2 may be immunosuppressive in this setting.