Fig. 1.

ZIKV-3′UTR-∆10-LAV protects pregnant C57BL/6 mice and their developing fetuses. a Scheme of immunization of wild-type (WT) C57BL/6 female mice with 10⁵ FFU of ZIKV-3′UTR-∆10-LAV (∆10; n = 12) or PBS sham (n = 16). b Serum was collected at day 28 post immunization and analyzed for neutralizing activity using an mCherry infectious ZIKV. Representative neutralization curves are shown. Error bars denote the SD of duplicate technical replicates. c NT₅₀ values of neutralizing antibodies were measured for individual animals. The dashed lines indicate the limit of detection (LOD) of the assay. d–g At day 35 post immunization, vaccinated female mice were mated with WT C57BL/6 males. A subset of the female mice developed vaginal plugs. Pregnant mice (n = 8 pooled from two independent experiments) were administered 2 mg of anti-Ifnar1 blocking antibody on E5, and 1 day later (E6), challenged with 10⁵ FFU of a pathogenic, mouse adapted ZIKV Dakar 41519 strain. On E13, animals were euthanized; maternal spleen (d), maternal brain (e), placenta (f), and fetal heads (g) were harvested and quantified for viral RNA levels. Median viral RNA levels are indicated for each group. Asterisks indicate significant differences (Mann–Whitney test: ****P-value < 0.0001). All negative samples are plotted at the half value of LOD. The results in the Figure are pooled from two independent experiments