Gene Transfer into Hepatocytes and Human Liver Tissue by Baculovirus Vectors

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Abstract
Gene therapy of liver diseases requires the development of efficient vectors for gene transfer in vivo. Retroviral and adenoviral vectors have been shown to deliver genes efficiently into hepatocytes in vitro and in vivo. However, these vectors do not allow for exclusive infection of the liver which would be highly advantageous for in vivo gene therapy strategies. We have recently demonstrated that genetically modified baculoviruses (Autographa californica nuclear polyhedrosis virus) efficiently deliver genes into cultured cells and have a strong preference for hepatocytes of different origin. Baculoviral gene transduction efficiency into human hepatocytes was determined to approach 100% and expression levels are high, provided that gene expression is controlled by mammalian promoters. In this report, we present further properties of baculoviruses regarding their use for hepatocyte gene transfer. Baculovirus-mediated gene expression declines rapidly in the hepatocellular carcinoma cell line Huh7 and more slowly in primary cultures of mouse hepatocytes. Direct application of baculoviruses for gene delivery to the liver in vivo is hampered by serum components, presumably by complement. However, we demonstrate here that baculoviral gene transfer is feasible in ex vivo perfused human liver tissue. This result suggests the development of a strategy using baculoviral vectors for liver-directed gene therapy. This study evaluates baculoviruses for their use in liver gene therapy. We demonstrate that baculovirus-mediated gene delivery is efficient and specific for human hepatocytes in vitro. The kinetics of gene expression mediated by baculovirus vectors are presented for dividing hepatocyte cell lines and nondividing primary cultures of hepatocytes. We describe potential limitations for the application of baculovirus vectors in vivo mainly caused by complement. Strategies of ex vivo perfusion of human liver tissue are feasible.