FIG. 5.

Conserved NS4B function among flaviviruses. (A) An immunoblot shows levels of expression of DEN, WNV, and YFV NS4B in Vero cells transfected with the indicated plasmids. (B) Induction of ISRE-9-27-CAT after treatment with IFN-β. Vero cells were transfected with each of the indicated plasmids. At 24 h posttransfection, cells were treated with 1,000 U of human IFN-β. The CAT activities were normalized to the corresponding luciferase activities to determine CAT induction. CAT activities were determined as mean values from two independent experiments (P values of 0.02 to 0.04). (C) Vero cells simultaneously expressing YFV or WNV NS4B (red) and GFP-STAT1 (green) were treated with IFN-β. HA-labeled protein was detected by fluorescence microscopy after incubation with polyclonal antibodies to HA and Texas red-labeled secondary antibody.