Fig 1. VEEV is resistant to a pre-established anti-viral state and to individual overexpressed IFN effectors.

(A and B) Vero cells mock-treated or pre-treated with 5000 IU human leukocyte IFN for 24h were infected in triplicate with indicated viruses (M.O.I. = 2.5). Supernatants were collected at 6h (A) and 24h (B) p.i. and virus replication was quantified using plaque assays. ****, P<0.0005 using t-test. Data is representative of two independent experiments. (C) Tet-inducible mouse embryonic fibroblasts (MEFs) stably expressing IFIT1, ISG20 and GFP (control) were infected in triplicate with indicated viruses (M.O.I. = 1). Cell lysates were collected at 24h p.i and viral RNA levels were measured using RT PCR as described in Materials and Methods. Data is viral RNA levels from IFIT1 or ISG20 expressing cells as a fold change of viral RNA levels from GFP expressing cells. ****, P<0.0001; ***, P<0.001 using One-way ANOVA. All error bars are standard deviations. (D) MEF cells were mock-treated or pre-treated with 1000 IU mouse IFN for 24h and infected with indicated replicons (equal dilution). Lysates were collected in passive lysis buffer at 16h p.i. and luciferase activity was measured. Data is RLUs per μg total protein expressed as a fold change over no IFN for each replicon. Fold change for Vrep was set as 100% and all replicons were compared to Vrep. Infection was performed in triplicate. ****, P<0.0001; ***, P<0.0003 using t-test.