Efficient gene transfer into mammalian cells using fusogenic liposome.

Fusogenic liposome (FL) based on Sendai virus constitutes a unique system that delivers the content efficiently into animal cells in vitro and in vivo. In this study we characterized unilamellar FL as a gene transfer vector in comparison with cationic lipid (CL)-DNA complex. FL transferred genes efficiently into cultured cells even when incubated for as little as 10 min, while CL-DNA complex required at least 30 min to reach the same level of gene expression. FL was also much less cytotoxic than CL-DNA complex under the conditions that resulted in the same level of gene expression. In addition, FL maintained 70% of the transfection activity even in the presence of 40% fetal calf serum (FCS), while CL-DNA complex almost completely lost their activity in the presence of 5% FCS. Furthermore, we found that FL could introduce and express luciferase gene into mouse ascites tumor cells in vivo, but CL-DNA complex could not even at higher concentrations of DNA. We conclude that unilamellar FL is a unique and efficient nonviral vector for gene transfer in vitro and in vivo.