FIG. 5.

Viral defects in counteracting IFN-β induction and JAK/STAT signaling. (A) HEK 293T cells were transfected with the IFN-β promoter-controlled plasmid p125-Luc and infected at an MOI of 3. FL expression was determined using the dual luciferase reporter system (Promega) at 24 h p.i. Both IRES-controlled RVs activate the IFN-β promoter more efficiently than wt RV SAD L16. SAD ΔPLP is a gene shift control virus expressing trace amounts of P (7). (B) Inhibition of IFN-stimulated gene expression by the indicated RV was analyzed in IFN-negative BSR T7/5 cells. Cells infected at an MOI of 1 and transfected 6 h later with the ISRE promoter-controlled reporter plasmid pISRE-Luc and pCMV-RL for normalization were treated 24 h p.i. with the indicated doses of IFN-α A/D. FL and RL activities were determined 48 h p.i. Only wt RV SAD L16 was able to almost completely abolish FL expression. Error bars indicate standard deviations from at least three parallel experiments.