In SituRetrovirus-Mediated Gene Transfer into Dog Liver

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Abstract
Dogs were used as a large animal model to assess the feasibility and safety of a surgical method for gene transfer into hepatocytes in vivo. This method, which we previously described in rats, consists of a partial hepatectomy aimed at inducing liver regeneration, followed by the selective in situ perfusion of the remnant liver parenchyme with a retrovirus preparation. Isolation of the liver was obtained by clamping the afferent and efferent blood vessels, a procedure that prevented retroviral vector dissemination and genetic modification of nonhepatic organs. A helper-free retrovirus vector encoding β-galactosidase targeted to the nucleus was perfused in the liver of 5 golden retriever dogs. Volumes up to 1,650 ml of fresh or concentrated vector stocks were perfused and the procedure was well tolerated. Gene transfer, observed in 3 of 5 treated dogs when documented on liver biopsy fragments obtained at day 4, involved 0.15–0.6% hepatocytes and persisted at equivalent levels at the time of sacrifice, 6 weeks later. No propagation of the vector to other tissues was detected. These observations suggest that the selective perfusion of the regenerating liver might be considered an alternative to liver transplantation for the treatment of certain severe genetic liver disorders, or for the delivery of a therapeutic protein into the serum. The treatment of genetic deficiencies of liver functions, as well as the delivery of a therapeutic protein in the serum, could be achieved by gene transfer into hepatocytes. A technique for in vivo targeting of gene transfer into the liver has been described by the authors, which includes a partial liver resection followed by the selective perfusion of the remnant parenchyme with a retrovirus vector preparation. The present paper reports feasibility and safety data obtained in dogs, with a view toward future human trials.