FIG. 2.

Type I IFN inhibits the replication of vK1L⁻C7L⁻/GFP⁺. (A) Replication of vK1L⁻C7L⁻/GFP⁺ is inhibited by hIFN-β in a dose-dependent manner. Huh7 cells were pretreated with hIFN-β at concentrations of 0, 2, 20, 200, or 2,000 U/ml for 24 h at 37°C, infected by the indicated viruses at an MOI of 5, and harvested at 24 hpi. The viral yields at 24 hpi were determined as described in the legend to Fig. 1B. (B) Replication of vK1L⁻C7L⁻/GFP⁺ is inhibited by at least seven hIFN-α subtypes. The experiment was performed as described for panel A except that the cells were pretreated with 200 U/ml of hIFN-α or hIFN-γ. (C) vK1L⁻C7L⁻/GFP⁺ replicates abortively in hIFN-β-treated Huh7 cells. The cells were treated with 200 U/ml of hIFN-β for 24 h and infected with the indicated viruses at an MOI of 5 PFU/cell, and the GFP-expressing cells (shown as white) were photographed at 24 hpi. (D) Growth curves of WT-GFP⁺ and vK1L⁻C7L⁻/GFP⁺ in hIFN-β-treated Huh7 cells. The cells were treated with 200 U/ml of hIFN-β for 24 h and then infected at either high (5 PFU/cell) or low (0.05 PFU/cell) MOIs. Virus yields at 0, 24, and 48 hpi were determined by plaque assay.