Efficient nonviral transfection of dendritic cells and their use for in vivo immunization

Immunization with dendritic cells (DCs) transfected with genes encoding tum or-associated antigens (TAAs) is a highly promising approach to cancer immu notherapy. We have developed a system, using complexes of plasmid DNA expre ssion constructs with the cationic peptide CL22, that transfects human mono cyte-derived DCs much more efficiently than alternative nonviral agents, Af ter CL22 transfection, DCs expressing antigens stimulated autologous T cell s in vitro and elicited primary immune responses in syngeneic mice, in an a ntigen-specific manner. Injection of CL22-transfected DCs expressing a TAA, but not DCs pulsed with a TAA-derived peptide, protected mice from lethal challenge with tumor cells in an aggressive model of melanoma, The CL22 sys tem is a fast and efficient alternative to viral vectors for engineering DC s for use in immunotherapy and research.