FIG. 5.

Inhibition of IFN-β-induced PKR expression by PPMO does not affect SARS-CoV replication. (A) A total 4 × 10⁴ 293/ACE2 cells were treated with the indicated PPMO for 72 h and then with (+) or without (−) 10,000 IU of IFN-β for 24 h before infection with SARS-CoV at an MOI of 0.01. After the inoculum was removed, DMEM with 2% FCS and without or with 20 μM of the indicated PPMO was added to the cells. At 24 h p.i., cells were harvested and subjected to SDS-polyacrylamide gel electrophoresis. The levels of phosphorylated and total PKR (panel 1 from top), phosphorylated and total eIF2α (panel 2), phosphorylated and total PERK (panel 3), phosphorylated and total GCN2 (panel 4), and SARS-CoV nucleoprotein were determined by Western blot analysis. (B) Virus titers were determined by TCID₅₀ assays. Standard deviations are shown. Student's t test revealed that the viral titer differences between samples receiving IFN-β-treatment were not statistically significant (P > 0.100). The experiments were performed three times with similar outcomes.