An efficient liposomal gene delivery vehicle using Sendai F/HN proteins and protamine.

By means of a simple mixing procedure, we have constructed cationic Sendai virosomes consisting of fusogenic viral F/HN proteins and cationic lipids. Sendai virus F/HN proteins were purified by Triton X-100 treatment and sequential centrifugation, and then quantitatively added to cationic liposomes. The presence of HN proteins is essential for hemolytic activity of Sendai virus as well as efficient gene transfection. The amount of detergent added for purification of F/HN proteins was also crucial for hemolytic activity. The relevance of F/HN proteins in the gene-transfer capability of the cationic Sendai F/HN virosomes (CSVs) was verified by heat inactivation of the F/HN proteins, and cell-binding competition. DNA condensation by protamine sulfate was able to further enhance the transfection efficiency and serum resistance of CSV. The enhanced transfection efficiency of protamine-condensed DNA-encapsulating cationic Sendai F/HN virosomes (PCSVs) may result from specific and efficient cell binding mediated by F/HN proteins and efficient DNA encapsulation by protamine. The DNA condensation by protamine was crucial for systemic in vivo gene transfer by CSVs. The PCSVs exhibited a higher gene expression in various organs, especially the liver, compared to DOTAP/Chol lipoplexes. These results demonstrate the potential for the use of PCSV as gene delivery vehicles for systemic gene transfer.