FIG 2.

Inhibition of poly(I·C)-induced activation of the IFN-β promoter by PRRSV proteins. (A) PRRSV nonstructural and structural protein expression vectors and pcDNA3.1 were cotransfected into HeLa cells with pGL3-IFN-β-Luc and pRL-TK, a control for transfection efficiency. Twenty-four hours later, cells were transfected with poly(I·C) for 8 h, and cell lysates were analyzed for luciferase activities. (B) HeLa cells were cotransfected with pGL3-IFN-β-Luc, pRL-TK, and nsp4 expression plasmids at different doses (0.1, 0.3, or 0.5 μg). Cells were transfected with poly(I·C) for 8 h, and luciferase activities were measured. (C) CRL-2843 cells were transfected with control vector or nsp4 expression plasmid. Cells were treated with or without poly(I·C) (10 μg/ml) for 6 h, and IFN-β expression was analyzed using qPCR. Data are means and SD from three independent experiments. Differences were evaluated by Student's t test. *, P < 0.05; **, P < 0.01; ***, P < 0.001.