A cationic peptide consists of ornithine and histidine repeats augments gene transfer in dendritic cells.

Condensing the plasmid with high molecular weight cationic polymers such as poly-L-lysine (PLL) and poly-L-ornithine (PLO) can enhance antigen-specific immunity generated from genetic vaccination with naked DNA encoding antigens. While these high molecular weight polymers are clearly effective in transfection experiments, clinical applications are limited by their physical heterogeneity and toxicity. Three chemically defined low molecular weight cationic peptides, K(16), K(10)H(6), and O(10)H(6), were examined in the context of DNA binding, toxicity, and efficiency of gene transfer in dendritic cells (DC). The results showed that while all three peptides can bind to a plasmid encoding a reporter gene with similar efficiency, in vitro transfection with DNA complexed with O(10)H(6) complexed resulted in the highest level of gene expression. Moreover, free O(10)H(6) was not toxic to DC, while the lysine-based peptides caused significant cell death in DC cultures. We also showed that DC transfected ex vivo with DNA complexed with O(10)H(6) was capable of eliciting antigen-specific INFgamma production in vivo. Taken together, these results indicate ornithine and histidine repeats are suitable building blocks of non-viral gene transfer vector for DC.