FIG. 2.

Effect of PKR on RVFV replication in cell culture. (A and B) Virus growth on a kidney cell line derived from C57BL/6 and PKR^−/− mice (C57BL/6 background). Approximately 10⁶ cells were seeded per six-well cavity and then treated with 1,000 U of IFN-α/ml or left untreated. After 16 h, the cells were infected with either Clone 13 or wt RVFV at an MOI of 0.01 (A) or an MOI of 5 (B), and IFN-α treatment was continued. To exclude unwanted effects mediated by virus-induced IFN, all untreated cells were supplemented with medium containing saturating amounts of a neutralizing antibody against the murine IFNAR1 receptor. The graph shows the virus titers in the supernatant at 24 h postinfection as determined by plaque assay on IFNAR^−/− cells. Columns A to H show means ± the standard deviations (n = 3). (C) Summary of the statistical analysis of the data presented in panels A and B. (D) Virus growth on doxycycline-inducible Flp-In T-Rex cells expressing either GFP or PKR. Cells were treated with doxycycline or left untreated for 36 h, infected at an MOI of 0.01, and evaluated 24 h later as described above. Columns show means ± the standard deviations (n = 3). A two-tailed paired Student t test was performed to compare titers of untreated and doxycycline-treated cells. P values are indicated in the figure where P is <0.05.