Comparison of α-Type-1 polarizing and standard dendritic cell cytokine cocktail for maturation of therapeutic monocyte-derived dendritic cell preparations from cancer patients

The current “gold standard” for generation of dendritic cell (DC) used in DC-based cancer vaccine studies is maturation of monocyte-derived DCs with tumor necrosis factor-α (TNF-α)/IL-1β/IL-6 and prostaglandin E2 (PGE2). Recently, a protocol for producing so-called α-Type-1 polarized dendritic cells (αDC1) in serum-free medium was published based on maturation of monocyte-derived DCs with TNF-α/IL-1-β/polyinosinic:polycytidylic acid (poly-I:C)/interferon (IFN)-α and IFN-γ. This DC maturation cocktail was described to fulfill the criteria for optimal DC generation and to be superior to the standard DC (sDC) cocktail as it induced fully mature DCs with potent IL-12p70 secretion together with CCR7 expression which is necessary for priming of a TH1 response and for migration to the draining lymph node, respectively. In this study, we tested the adaptation of αDC1 maturation cocktail to a protocol for clinical grade DC generation from cancer patients performed in X-VIVO 15 medium. We showed that αDC1 in this protocol induce lower up-regulation of CD83 and several other maturation markers, co-stimulatory molecules and CCR7 together with higher up-regulation of inhibitory molecules such as PD-L1, ILT2, ILT3 as compared to sDC. Although αDC1 matured DCs secreted more IL-12p70 and IL-23 these DCs had lower or similar stimulatory capacity compared to sDCs when used as stimulating cells in mixed lymphocyte reaction (MLR) or for induction of autologous influenza antigen specific T lymphocytes. Thus, our observations underline that αDC1 maturation cannot be directly adapted to alternative protocols for DC generation. Also, this study indicates the necessity for further investigation of correlation between in vitro DC parameters and their in vivo efficacy in clinical vaccination trials.