Development of liposomes and pseudovirions with fusion activity for efficient gene delivery

For efficient gene delivery, chimeric vectors combining non-viral vectors with viral components have been developed. In particular, increasing attention has been paid to viral fusion activity. HVJ (hemagglutinating virus of Japan; Sendai virus) fuses with the cell membrane at neutral pH, and HN and F, fusion proteins of the virus, contribute to the cell fusion. For fusion-mediated gene transfer, DNA-loaded liposomes were fused with UV-inactivated HVJ to form the fusion liposome, HVJ-liposome. Fusion-mediated delivery protects the molecules incorporated in the liposome from degradation in endosomes and lysosomes before reaching the cytoplasm. Reconstituted pseudovirions of fusion-competent viruses such as HVJ and influenza virus have been also developed by a detergent-lysis and-removal method. A more direct and practical approach is the conversion of fusion-competent virions to non-viral gene delivery particles. Based on this concept, the HVJ envelope vector was developed using inactivated particles of HVJ and has been utilized for gene therapy experiments and functional screening for therapeutic genes. A tissue-targeting HVJ envelope vector was also constructed.