FIG 4.
Stability and safety of WNV-ΔNS1. (A) IFA detection of WNV-ΔNS1 virus at different passages using the 4G2 monoclonal antibody. WNV-ΔNS1 viruses were blind passaged for 15 rounds in VeroNS1 cells. The viruses at passages 0, 5, 10, and 15 were used to infect naive VeroNS1 cells and Vero cells. (B) Detection of the Gluc activities in cell lysates at different time points after WNV-ΔNS1-Gluc infection. Naive VeroNS1 cells and Vero cells were infected with WNV-ΔNS1-Gluc reporter virus at an MOI of 100, and the cell lysates collected at the indicated time points were subjected to the luciferase assay. Data represent the mean ± standard deviation of triplicate measurements in a representative experiment. (C and D) Morbidity (C) and survival (D) analyses of IFNAR−/− mice after inoculation with WT and WNV-ΔNS1 viruses. Six-week-old IFNAR−/− female mice were inoculated i.p. with 102 IU of WT WNV or 2 × 108 IU of WNV-ΔNS1. All mice (n = 5 for each group) were monitored for morbidity and death for 28 days. Two experiments were performed independently. The asterisks denote statistical differences between the indicated groups. ***, P < 0.001.