341. Nucleic Acid Delivery Using Vesicular Stomatitis Virus-Based Vesicles

Gene delivery methods are essential to understand fundamental cellular mechanisms and to develop new therapies. Recombinant viruses are efficient to transfer nucleic acids but their safety is a concern. In addition, some commercial transfection reagents (including lipids and cationic polymers) and electroporation methods are cytotoxic. Interestingly, the sole expression of G envelope protein of the vesicular stomatitis virus (VSV) in mammalian cells can lead to the formation of VSV-G pseudotyped vesicles (V-VSV-G). In presence of polybrene, these vesicles are able to transfer plasmids in a large panel of animal cells. Unfortunately, the production of V-VSV-G and their use for nucleic acid delivery is poorly documented. Here we propose to improve this promising method of transfection. At first we developed a V-VSV-G production process by transient transfection of HEK-293 cells using polyethylenimine (PEI). Three modes of production were compared: cells cultivated in adherence, in suspension and on micro-carriers. Also we demonstrated that the quantity of vesicles produced depends on the VSV-G sequence used. The harvest of V-VSV-G from cell culture media was also optimized. Then, several parameters potentially involved in the formation and the transfer efficiency of V-VSV-G/DNA complex were studied: polybrene concentration, order of addition of mix transfection components, incubation time of the complexes, medium of transfection, etc. Stability studies also demonstrated that V-VSV-G are robust particles: DNA transfer capacity of V-VSV-G is efficient after 10 freezing and thawing cycles and V-VSV-G can be stored for long term at +4 °C, -20 °C and -80 °C. Finally, V-VSV-G/DNA ratio was optimized for three different cell types. Transfection efficiency of 70 % and 55 % were obtained for HEK-293 and HeLa cells respectively, with 1 µg of V-VSV-G and 0.4 µg of DNA. Transfection of refractory cells such as human myoblasts, reached 25 % with 5 µg of V-VSV-G and 0.8 µg of DNA. V-VSV-G can also deliver large plasmids (18 kb). Furthermore, no cytotoxicity was observed in cells transfected with these complexes. Presently, the potential of V-VSV-G to transfer siRNA is investigated. In conclusion, V-VSV-G is a powerful tool for nucleic acid delivery which could be useful for several applications oriented toward cell and gene therapies.