Highly efficient gene transfer into murine liver achieved by intravenous administration of naked Epstein-Barr virus (EBV)-based plasmid vectors

Naked plasmid DNA (pDNA) injection could become an alternative procedure to viral and nonviral gene delivery systems. We have previously shown that Epstein-Barr virus (EBV)-based plasmid vectors containing the EBV nuclear antigen 1 (EBNA 1) gene and the oriP sequence enable quite high and long-lasting expression in various in vitro and in vivo transfection systems. The EBV-based plasmids were intravenously injected into mice via their tail vein under high pressure. A large amount of the marker gene product was expressed in the liver, as much as 320 mug of luciferase was demonstrated per gram of liver at 8 to 24 h after a single injection with 10 mug of DNA. More than 70% of liver cells stained with X-gal when beta -gal gene was transferred. The expression level was significantly higher than that obtained by conventional pDNA lacking the EBNA 1 gene and oriP. On day 35 after the transfection, the expression from the EBV-based plasmid was approximately 100-fold stronger than the conventional pDNA gene expression. Both the EBNA1 gene and oriP are a prerequisite for the augmentation of the transfection efficiency. These results suggest that the intravascular transfection with naked EBV-based plasmid may provide a quite efficient, simple and convenient means to transduce therapeutic genes in vivo into the liver.