A transient three-plasmid expression system for the production of hepatocytes targeting retroviral vectors.

Targeting of retroviral vectors to specific cells was attempted through modifying the surface protein of the murine leukemia viruses (MLVs), but in many cases the protein function was affected, and it is difficult to achieve the targeted delivery. In this study, we have tried to engineer ecotropic Moloney murine leukemia viruses (MoMLV)-based retroviral vectors to transduce hepatocytes. A chimeric envelope (Env) expression plasmid was constructed containing the hepatitis B virus PreS2 peptide fused to aa +1 at the N-terminus of Env. Following simultaneous transfection of pgag-pol, pLEGFP and chimeric env plasmids into 293T cells, helper-free retrovirus stocks with the titer of approximately 10(4) infectious units/ml were achieved at 48 h post-transfection. These pseudotype vectors showed the normal host range of retrovirus, infecting host NIH 3T3 cells, although the efficiency was reduced compared with that of virions carrying wild-type ecotropic MoMLV envelope. In addition, the resultant pseudotype viruses could transduce human hepatoma cells mediated by polymerized human serum albumin with relatively high titers in comparison with those transductions without polymerized human serum albumin. This approach can be used to target hepatocytes selectively.