The effect of virus-factor exposure time to HepG2 hepatocytes on transduction. HepG2 cells were infected with AdCTL or AdKO1 in the presence of FIX or FX for varying times (indicated) in serumfree media. Following extensive washing, cells were cultured in serum containing media and harvested at 72 hours after transduction and levels of β-galactosidase determined by X-Gal staining and quantitative analysis. ^*P < .05 versus virus alone.