CL22 - a novel cationic peptide for efficient transfection of mammalian cells.

Condensing peptide-DNA complexes have great potential as nonviral agents for gene delivery. To date, however, such complexes have given transfection activities greatly inferior to adenovirus and somewhat inferior to cationic lipid-DNA complexes, even for cell lines and primary cells in vitro. We report here the identification of a novel condensing peptide, CL22, which forms DNA complexes that efficiently transfect many cell lines, as well as primary dendritic and endothelial cells. We report studies with sequence and structure variants that define some properties of the peptide that contribute to efficient transfection. We demonstrate that the superior transfection activity of CL22 compared with other DNA condensing peptides is conferred at a step after uptake of the complexes into cells. We show that CL22-DNA complexes have transfection activity that is at least equivalent to the best available nonviral agents.

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

Immunization with dendritic cells (DCs) transfected with genes encoding tumor-associated antigens (TAAs) is a highly promising approach to cancer immunotherapy. We have developed a system, using complexes of plasmid DNA expression constructs with the cationic peptide CL22, that transfects human monocyte-derived DCs much more efficiently than alternative nonviral agents. After CL22 transfection, DCs expressing antigens stimulated autologous T cells in vitro and elicited primary immune responses in syngeneic mice, in an antigen-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 system is a fast and efficient alternative to viral vectors for engineering DCs for use in immunotherapy and research.