FIG 2.

NS4 modulates IFN synthesis in infected cells. (A) In vitro replication kinetics of BTV8wt and BTV8ΔNS4 in primary ovEC and human A549 cells. The cells were infected with BTV8wt (red) and BTV8ΔNS4 (blue) at an MOI of 0.01, and the supernatants were titrated at the indicated time points as described in Materials and Methods. Experiments were performed independently three times. Two-way ANOVA, P < 0.01. *, P < 0.05; **, P < 0.01 (Bonferroni posttests). (B) Upregulation of IFN-β synthesis in BTV8-infected cells (IFN protection assay). Primary ovEC were mock infected or infected with the indicated viruses (MOI = 4). Supernatants were then collected at 16 h p.i. and inactivated by UV treatment, and the amount of IFN released in the supernatants was determined in biological assays as described in Materials and Methods. The error bars represent standard deviations. One-way ANOVA, P = 0.002. ***, P < 0.001 (Tukey's multiple-comparison test).