Hepatocyte-specific gene expression from integrated lentiviral vectors

Abstract Background For many applications, efficient gene therapy will require long‐term, organ‐specific therapeutic gene expression. Lentiviral vectors based on HIV‐1 are promising gene delivery vehicles due to their ability to integrate transgenes into non‐dividing cells. Many experimental vectors express transgenes under the control of the cytomegalovirus (CMV) immediate‐early gene promoter. Although this promoter directs strong gene expression in vitro , it may be shut off rapidly in vivo . This study explores the potential of HIV‐1‐based vectors to transduce hepatocytes and compares gene expression from different promoters in integrated vectors. Methods HIV‐1‐based vector plasmids expressing the green fluorescent protein (GFP) under the control of the CMV promoter, the alpha‐1 antitrypsin gene promoter or promoters derived from the hepatitis B virus (HBV) genome were used to compare expression in transfected and transduced cell lines. Results Hepatocyte cell lines differed strikingly in their transfectability. Transduction with replication‐deficient HIV‐1‐based vector particles incorporating the different promoter elements was uniformly effective in hepatocyte and non‐hepatocyte lines. However, in hepatocytes, only the CMV, alpha‐1 antitrypsin and HBV core but not HBV surface promoters were able to produce GFP expression. Addition of the HBV enhancer 2 element improved the transducing ability of the HBV surface promoter and suppressed expression in non‐hepatocytes increasing specificity for hepatocytes. Conclusions Integrated lentiviral vectors can be used to direct transgene expression in liver cells both promiscuously and specifically. Promoters derived from the alpha‐1 antitrypsin gene or HBV are alternatives to the CMV promoter. Inclusion of the HBV enhancer 2 permits strong liver‐specific gene expression in vitro. Copyright © 2004 John Wiley & Sons, Ltd.