Liposome delivery systems

Liposomal delivery systems for nucleic acids fall within the larger class of non-viral delivery vehicles. Chronologically, liposomal systems designed to encapsulate pDNA were among the first non-viral systems to demonstrate gene delivery. Plasmid DNA by itself has transfection activity in some systems. The enhancement in transfection efficiencies of these delivery systems over those of liposomes is imparted by the fusion properties of viral envelopes, such as the F protein of Sendai virus. The haemagglutinating virus of Japan system has also been used successfully to deliver antisense oligonucleotides in vivo to inhibit neointimal hyperplasia in a model of restenosis. The immune advantage of purely cationic lipid systems is offset somewhat by the lower potency of these delivery systems compared with viral systems. DC-Choi was used to deliver a plasmid containing the B7 co-stimulatory molecule as part of an immune system stimulation protocol designed to attack melanoma cells.