DEV UL41 inhibits IFN-β production induced by interferon-stimulatory and viral DNA. (A) DEFs were transfected with UL41-Flag expression plasmid or empty vector for 24 h and then transfected with interferon-stimulatory DNA (ISD); the mRNA levels of IFN-β, IL-6, Mx, and OASL were measured by qPCR 6 h and 12 h later. UL41 expression was examined by Western blotting at 12 h after ISD transfection. (B) DEFs were transfected with UL41-Flag expression plasmid or empty vector for 24 h and then transfected with poly(dA·dT); the mRNA levels of IFN-β, IL-6, Mx, and OASL were measured by qPCR 6 h and 12 h later. UL41 expression was examined by Western blotting at 12 h after poly(dA·dT) transfection. (C) DEFs were transfected with UL41-Flag expression plasmid or empty vector and then left uninfected or infected with DEV (MOI = 0.01). The mRNA levels of IFN-β and Mx in these cells were measured by qPCR at 12 h postinfection, and UL41 expression was detected by Western blotting. (D) DEFs were transfected with UL41-Flag expression plasmid or empty vector and then left uninfected or infected with HVT (MOI = 0.01). The mRNA levels of IFN-β and Mx in these cells were measured by qPCR at 12 h postinfection, and UL41 expression was detected by Western blotting. (E) DEFs transfected with UL41-Flag plasmid or empty vector were infected with DEV at various MOIs (0.01 or 0.001). The viral titer was tested by qPCR at 24 and 48 hpi, and UL41 expression was examined by Western blotting at 48 hpi. (F) DEFs transfected with UL41-Flag plasmid or empty vector were infected with HVT at various MOIs (0.01 or 0.001). The viral titer was tested by qPCR at 24 and 48 hpi, and UL41 expression was examined by Western blotting at 48 hpi. The relative amount of IFN-β, IL-6, Mx, and OASL mRNA was normalized to β-actin mRNA levels in each sample, and the relative amount of DEV and HVT genomic DNA was normalized to GAPDH levels in each sample. All controls and treated groups were performed and examined in triplicate. *, P < 0.05; **, P < 0.01; ns, no significant difference.