Branched amphiphilic peptides: An alternate non-viral gene delivery system

Success for gene therapy clinical protocols depends on the design of safe and efficient gene carriers. Nature had already designed efficient DNA or RNA delivery devices, namely virus particles. However, the risk of insertional mutagenesis has limited their clinical use. Alternatively, safer approaches involving non-viral carriers have been and continue to be developed. While they have been reported to be less efficient than viral vectors, adding genome editing elements to pDNA makes the integration of corrective sequence site specific moving non-viral gene delivery systems closer to clinical applications. Over the last decade, peptides have emerged as a new family of potential carriers in gene therapy. Peptides are easy to synthesize, quite stable and expected to produce minimally immunogenic and inflammatory responses. We recently reported on a new class of Branched Amphiphilic Peptides Capsules (BAPCs) that self-assemble into extremely stable nano-spheres. BAPCs display a uniform size of ∼20 nm if they are incubated at 4°C and they retain their size at elevated temperatures. In the presence of DNA, they can act as cationic nucleation centers around which DNA winds generating peptide-DNA complexes with a size ranging from 50nm to 100nm. However, if BACPs are not incubated at 4°C, the pattern of interaction with DNA differs. Depending of the peptide/DNA ratios, the peptides either coat the plasmid surface forming nano-fibers (0.5-1 muM in length) or condense the plasmid into nano-sized structures (100-400nm). Different gene delivery efficiencies are observed for the three types of assemblies. The structure where the DNA wraps around BAPCs display much higher transfection efficiencies in HeLa cells in comparison to the other two morphologies and the commercial lipid reagent LipofectinRTM. As a proof of concept, pDNA was delivered in vivo, as a vaccine DNA encoding E7 oncoprotein of HPV-16. It elicited an immune response activating CD8 + T cells and provided anti-tumor protection in a murine model.