In an attempt to capitalize on the strong inflammatory state induced by alloreactivity, Fotaki et al. infected monocyte-derived dendritic cells (DCs) with an infection-enhanced adenoviral vector (which could be used to encode a target antigen) and matured them with polyI:C, R848, and IFNγ. These DCs released pro-inflammatory cytokines and, when co-cultured with PBMCs, promoted the maturation of bystander DCs capable of cross-presenting a target antigen to CD8+ T cells, effectively activated T and NK cells, and promoted cytotoxic function.
Accumulating evidence support an important role for endogenous bystander dendritic cells (DCs) in the efficiency of autologous patient-derived DC-vaccines, as bystander DCs take up material from vaccine-DCs, migrate to draining lymph node and initiate antitumor T-cell responses. We examined the possibility of using allogeneic DCs as vaccine-DCs to activate bystander immune cells and promote antigen-specific T-cell responses. We demonstrate that human DCs matured with polyI:C, R848 and IFN-gamma (denoted COMBIG) in combination with an infection-enhanced adenovirus vector (denoted Ad5M) exhibit a pro-inflammatory state. COMBIG/Ad5M-matured allogeneic DCs (alloDCs) efficiently activated T-cells and NK-cells in allogeneic co-culture experiments. The secretion of immunostimulatory factors during the co-culture promoted the maturation of bystander-DCs, which efficiently cross-presented a model-antigen to activate antigen-specific CD8+ T-cells in vitro. We propose that alloDCs, in combination with Ad5M as loading vehicle, may be a cost-effective and logistically simplified DC vaccination strategy to induce anti-tumor immune responses in cancer patients.
