Figure 4.

Vaccine protection against challenge in Ifnar1^−/− mice. (A–D) Ifnar1^−/− mice were immunized with 10¹⁰ vp of Ad4-prM-E (n = 9), Ad5-prM-E (n = 10), or sham PBS (n = 10) via the i.m. route according to the timeline in (A). Two experimental replicates were performed. Mice were boosted with the same vaccine and dose at week 3 and then challenged with 10⁶ FFU of mouse-adapted ZIKV strain 41519 at week 7. Weight loss was monitored (B) and mice were sacrificed when a 25% weight loss was reached (C). Asterisks indicate significance in weight compared to PBS sham vaccinated mice as determined by two-way ANOVA (p < 0.05). Survival data was analyzed using a log rank test (^***p < 0.001, ^****p < 0.0001). Blood was sampled at 4 days post infection (d.p.i) to determine the viral load in the sera using RT-qPCR (D) (^**p < 0.01; ^****p < 0.0001; one-way ANOVA). To determine immune correlates in Ifnar1^−/− mice, groups (n = 5) were immunized with 10¹⁰ vp of the indicated Ad vaccine and sacrificed 2 weeks later. Sera was used to determine anti-ZIKV IgG (E) and neutralizing antibodies (F). In addition, an ELISPOT was performed to determine spot-forming cells per million splenocytes against the immunodominant E_4–12 epitope (G). ELISA, PRNT50, and ELISPOT are analyzed with one-way ANOVA (^**p < 0.01, ^****p < 0.0001). Data are expressed as the mean with standard error (SEM).