Induction of antigen-specific CD8+ cytotoxic T cells by dendritic cells co-electroporated with a dsRNA analogue and tumor antigen mRNA.

The maturation state of dendritic cells (DCs) is an important determinant for the initiation and regulation of adaptive immune responses. In this study, we wanted to assess whether functional activation of human monocyte-derived DCs can be achieved by electroporation of an activation signal in the form of double-stranded (ds) RNA and whether simultaneous electroporation of the dsRNA with tumor antigen encoding mRNA can lead to the induction of a cytotoxic T-lymphocyte (CTL) response. Electroporation of immature DCs with poly(I:C(12)U), a dsRNA analogue, resulted in phenotypic as well as functional changes, indicative of DC maturation. Co-electroporation of DCs with both poly(I:C(12)U) and Melan-A/MART-1 encoding mRNA induced strong anti-Melan-A/MART-1 CD8(+) T-cell responses in vitro. Higher numbers of Melan-A/MART-1-specific CTLs were consistently obtained with poly(I:C(12)U)-activated DCs compared to DCs matured in the presence of an inflammatory cytokine cocktail. These results indicate that DC co-electroporation with both dsRNA and tumor antigen encoding mRNA induces fully activated and antigen-loaded DCs that promote antigen-specific CTL responses and may provide the basis for future immunotherapeutic strategies.