hIFN-α was efficiently expressed in hepatocytes transfected with recombinant pSecTagB-IFN-α vector. HepG2 and HepG2.2.15 cells were transfected with pSecTagB-IFN-α or empty plasmid at a final concentration of 1 μg/mL and 1.6 μg/mL, respectively. (A) After 48 h, RNAs were isolated as described in Materials and Methods, and RT-PCR analysis was performed to evaluate pSecTagB-IFN-α transfection efficiency. One representative of three independent experiments was shown. (B) The supernatants were harvested after 24 h, 48 h and 72 h. The level of IFN-α was measured by ELISA. Data are expressed as the mean ± SD from at least three independent experiments.