Antagonizing of IFN signaling by NS proteins from five DENV1 strains.

(A-D) Overexpression of NS2A (A), 2B (B), 4A (C) and 4B (D) from DENV1 A-E suppressed RIG-I directed IFNβ-promoter activation. 293T cells were transfected with RIG-I-N, IFNβ-Luciferase reporter, together with plasmids encoding NS proteins or vector control. IFNβ-promoter activations were determined by Dual luciferase assay. (The mean values of the activated control groups were normalized as “100”). The expressions of indicated NS proteins were shown by Western Blots in the lower panels. (E) Co-expressing of four NS proteins (2A+2B+4A+4B) from DENV1A to E suppressed IFNβ mRNA production in RIG-I-N transfected 293T cells. (F-G) Co-expressing NS proteins (2A+2B+4A+4B) from DENV1A to E suppressed RIG-I-N (F) or IFNα (G) induced ISRE promoter activation. (H-I) Co-expressing NS proteins from DENV1A to E impaired ISG mRNA production from RIG-I-N (F) or IFNα (G) stimulated 293T cells. The relative mRNA expression levels of typical ISG genes IFIT1 and Cig5 were determined by qRT-PCRs. (A-I, Results were shown as Mean±SEM, * pppp<0.001, ANOVA test) The data shown are representative of at least 3 independent experiments.