An accelerated, clinical-grade protocol to generate high yields of type 1-polarizing messenger RNA loaded dendritic cells for cancer vaccination

Abstract Background Many efforts have been devoted to improve the performance of dendritic cell (DC)–based cancer vaccines. Ideally, a DC vaccine should induce robust type 1–polarized T-cell responses and efficiently expand antigen (Ag)-specific cytotoxic T-cells, while being applicable regardless of patient human leukocyte antigen (HLA) type. Production time should be short, while maximally being good manufacturing practice (GMP)–compliant. We developed a method that caters to all of these demands and demonstrated the superiority of the resulting product compared with DCs generated using a well-established “classical” protocol. Methods Immunomagnetically purified monocytes were cultured in a closed system for 3 days in GMP-compliant serum-free medium and cytokines, and matured for 24 h using monophosphoryl lipid A (MPLA)+ interferon-gamma (IFN-γ). Mature DCs were electroporated with messenger RNA (mRNA) encoding full-length antigen and cryopreserved. “Classical” DCs were cultured for 8 days in flasks, with one round of medium and cytokine supplementation, and matured with tumor necrosis factor alpha (TNF-α) + prostaglandin E2 (PGE2) during the last 2 days. Results Four-day MPLA/IFN-γ–matured DCs were superior to 8-day TNF-α/PGE2–matured DCs in terms of yield, co-stimulatory/co-inhibitory molecule expression, resilience to electroporation and cryopreservation and type 1–polarizing cytokine and chemokine release after cell thawing. Electroporated and cryopreserved DCs according to our protocol efficiently present epitopes from tumor antigen-encoding mRNA, inducing a strong expansion of antigen-specific CD8+ T-cells with full cytolytic capacity. Conclusion We demonstrate using a GMP-compliant culture protocol the feasibility of generating high yields of mature DCs in a short time, with a superior immunogenic profile compared with 8-day TNF-α/PGE2–matured DCs, and capable of inducing vigorous cytotoxic T-cell responses to antigen from electroporated mRNA. This method is now being applied in our clinical trial program.