Amphotropic Retroviral Vectors Displaying Hepatocyte Growth Factor-Envelope Fusion Proteins Improve Transduction Efficiency of Primary Hepatocytes

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Abstract
The development of retroviral vectors with cell-specific targeting capabilities will be an important step toward successful in vitro gene therapy. This article describes the generation of a retroviral vector with enhanced binding abilities for cells bearing the c-Met receptor: the Madin-Darby canine kidney (MDCK) cell line and primary hepatocytes. The human hepatocyte growth factor (HGF) was displayed on murine amphotropic retroviral vectors by fusion to the viral transmembrane envelope glycoprotein (TM). The resulting chimeric envelope HGF-TM was expressed in an amphotropic packaging cell line producing viral particles that display both HGF-TM and the wild-type envelope. These modified viral particles had a titer equivalent to that of unmodified particles. Modified particles infected MDCK cells more efficiently than did unmodified amphotropic retrovirus. Adding anti-HGF antibodies to the viral vector particle supernatant prior to infection confirmed that the increased infection was mediated by the HGF moiety. The chimeric viruses also infected primary mouse and nonhuman primate fetal hepatocytes more effectively. Furthermore, these cells could be induced to proliferate by the modified HGF-TM viruses. Since exogenous HGF is primarily taken up by the liver, these results may have implications for retroviral vector design for liver-directed human gene therapy.