Induction of broad repertoire of melanoma associated antigen-specific CD4+ T cells by dendritic cell vaccine loaded with killed allogeneic melanoma cells in patients with metastatic melanoma

3029 Background: Tumor-specific CD4+ T cells play an important role in antitumor immunity. CD4+ T cells recognizing melanoma associated antigens can be spontaneously generated in patients with metastatic melanoma as demonstrated by the infiltration of such cells at tumor sites; however, they are often dysfunctional. We analyzed tumor-specific CD4+ T cell repertoires in the blood of metastatic melanoma patients, and examined whether dendritic cell (DC) vaccine loaded with killed allogeneic melanoma cells administered to metastatic melanoma patients can induce and/or improve melanoma-specific CD4+ T cell immunity. Methods: PBMCs were obtained from ten metastatic melanoma patients who received at least four monthly DC vaccine injections (GM-IL-4 DC vaccine loaded with killed allogeneic melanoma cells, matured with CD40L and TNFa). Melanoma-specific T cell repertoires at baseline and after vaccinations were assessed with EPIMAX approach using overlapping peptide libraries spanning MART-1, gp100, and TRP-1 ant...