Delivery of mRNA into Dendritic Cells Using Novel Transfer Peptides Leads to Prolonged Antigen Expression and Potent Immune Responses In Vivo.

We have previously shown that vaccination with RNA-transfected DC is a potent strategy to stimulate CTL and antitumor immunity in cancer patients. In this study, we investigated whether novel transfer peptides derived from the RNA-binding region of the HIV-1 nucleocapsid protein could be utilized for effective delivery of mRNA into human monocyte-derived dendritic cells (DC). Here we show that both peptide-mediated mRNA delivery and electroporation of DC with mRNA resulted in efficient gene transfer. However, the use of transfer peptides led to prolonged antigen expression and did not negatively affect the viability of DC, the migratory capacity of matured DC, and the production of cytokines by these cells in vitro. In murine studies, DC loaded with transfer peptide-mRNA complexes were clearly superior, compared to mRNA-electroporated DC, in stimulating antigen-specific CTL, CD4+ T cell, and antibody responses. Importantly, no transfer peptide-specific cellular or humoral immune responses were detected in vaccinated mice. Our data suggest that vaccination with transfer peptide-mRNA-loaded DC may represent a promising strategy to stimulate potent anti-tumor immune responses in a vaccination setting.