Increased Tumor-Specific CD8+ T Cell Induction by Dendritic Cells Matured with a Clinical Grade TLR-Agonist in Combination with IFN-γ

The limited response rate of cancer patients treated with dendritic cell (DC)-based vaccines indicates that vast improvements remain necessary. In many murine tumour models it has been demonstrated that the use of innate triggers (e.g. TLR triggers) in the maturation of DC results in higher efficacy. However, as few of these innate triggers are generated clinical grade, there remains a great necessity to fill the gap between fundamental mouse studies and a clinical trial in humans. In the present study we used a TLR2/4-agonist (FMKp which is available clinical grade) in combination with IFN-γ (FI-cocktail) in the maturation of elutriated monocyte-derived DC and compared it with the most used DC in current clinical trials (TNF-α/PGE-2, i.e. TP-cocktail). In addition to the assessment of CD4+ T cell polarizing capacity, we compared the quantity and intrinsic quality of induced CD8+ T cells of 2 different DC maturation protocols with all cells from the same donor. Besides differences in the cytokine profile, which could be coupled to increased Th1 and Th17 polarization, we demonstrate in this study that FMKp/IFN-γ matured DC are twice as effective in inducing cytotoxic T cells against known tumor antigens. Both DCs induced phenotypically equivalent effector memory CD8+ T cells that did not show a significant difference in their intrinsic capacity to kill tumor cells. These findings point to the therapeutic applicability of FI-DC as superior inducers of functional antigen-specific T cells. Their increased chemokine secretion is suggestive of a mechanism by which these DC may compensate for the limited migration observed for all ex vivo cultured DC when applied in patients.