The efficacy and safety of gene transfer into the porcine liver in vivo by HVJ (sendai virus) liposome

Background. Gene transfer systems using viral vectors are efficient; however, most viral vectors also tend to evoke immunologic reactions, thereby clinically causing serial side effects. HVJ-liposome vector is a hybrid vector consisting of liposome and an inactivated Sendai virus (Hemmagglutinating Virus of Japan [HVJ]), which has been reported to be less immunogenic and can also be repeatedly administered. We examined the usefulness of this vector for hepatic gene therapy in a pig model. Methods. Genes encoding β-galactosidase and luciferase were used as reporter genes. The pigs were injected with the reporter gene loaded-HVJ-liposome into the portal vein under total vascular exclusion of the liver. The transfection efficiencies were then assessed by β-galactosidase staining, a luciferase assay, and RT-PCR for LacZ mRNA. Biochemical and histologic analyses were performed to evaluate tissue toxicity after gene transfer. Results. The luciferase gene expression in the liver reached its highest level at 7 days after transfection. It continued to be detected up to 28 days after transfection, while all pigs remained healthy throughout the observation period. The transfection efficiency was 15% in the hepatocytes according to (3-galactosidase staining. Extrahepatic transgene expression was slightly observed in the lung and kidney, but not in the spleen or ovary. Conclusions. These data suggest for the first time that the use of the HVJ-liposome vector is a safe and feasible modality for liver-directed gene transfer in pigs, and it might therefore be suitable for clinical gene therapy trials.