FIG. 4.
Induction of IFN-α/β by the WT and NS2A/A30P mutated WNVKUN in mice. Groups of 5-week-old Swiss outbred mice (n = 3) were inoculated i.p. with 104 infectious units per mouse of the WT or NS2A/A30P-mutated WNVKUN. Sera were collected at day 1 and day 2 postinfection, pooled, UV inactivated to eliminate infectious virus, and analyzed for the presence of IFN-α/β by bioassay on L929 cells as described in Materials and Methods. IFN-α/β depletion was performed by preincubating sera with 400 units of each rabbit antibody against mouse IFN-α and IFN-β (IFN-α/β antibodies) prior to the bioassay. The results shown on the y axis represent percentages of L929 cells protected against challenge with SFV at an MOI of 0.5 by pretreatment with IFN-α/β-depleted (+) or with intact (−) sera from WNVKUN-infected mice. Each assay was performed in duplicate; the error bars represent standard deviations.