Interleukin 18 transfection enhances antitumor immunity induced by dendritic cell-tumor cell conjugates

Dendritic cell (DC)-based tumor vaccine represents a promising approach to the immunotherapy of malignant tumors. We prepared a novel type of DC-based vaccine, stable conjugates of DCs and EL4 cells transduced with cDNA of OVA (E.G7). Immunization with DC-E.G7 conjugates led to generation of T helper (Th) 1 cytokine-producing cells, antigen-specific CD8(+) T cells, and strong antitumor immunity that is dependent on both CD4(+) T cells and CD8(+) T cells. To further increase the potency of the vaccine, interleukin 18-transfected DCs were used to prepare the IL18DC-E.G7 conjugates. Immunization with such conjugates significantly increased the production of Th1 cytokine-producing cells and the number of antigen-specific CD8(+) T cells, as well as stronger antitumor immunity. Furthermore, the increased Th1 cytokine production and stronger antitumor effect were not observed in mice depleted of IFN-gamma. These data indicated that DC-tumor cell conjugates are a potent tumor vaccine. Interleukin 18 can be administrated using gene-transfected cells and enhances antitumor immunity, which is mainly mediated by IFN-gamma.