Figure 2. Results of sensitivity testing of BRBV to type I IFN–induced antiviral state in cell culture. A) Vero, Huh7, A549, and HeLa cells was infected with BRBV (multiplicity of infection [MOI] 0.001). At the indicated time points, the supernatants were harvested and viral titers determined. B) Huh7 or A549 were infected (MOI 0.25) with BRBV or DHOV for 16 h. Whole RNA was extracted and IFN-β and actin transcripts detected by real-time reverse transcription PCR. Changes in IFN-β transcripts were calculated in comparison to mock-treated cells. A conventional reverse transcription PCR assay with panspecific primers for viral segment 2 (PB1) was performed to control the infection. C, D) Defects in IFN induction or signaling enhancing BRBV propagation. Parental A549 and A549 cells stably expressing Npro of bovine viral diarrhea virus or the V protein of simian virus 5 (C), as well as (D) human skin fibroblast control cultures or with a defect in STAT2 infected with BRBV (MOI 0.001). Culture supernatants were collected and viral titers determined. Shown are the arithmetic means (+SD) of log-transformed values of 3 independent experiments. Statistical analyses were performed with a 1-way analysis of variance (Tukey multiple comparison test) (C) or a 2-tailed t-test (D). BRBV, Bourbon virus; CTRL, control; DHOV, Dhori virus; IFN, interferon; NS, nonsignificant; ∅, mock-treated (control). ***p<0.001; **p<0.01; *p<0.05.