ZIKV infection of pregnant C57BL/6J mice results in fetal demise caused by live infectious virus.

<p>(<b>A</b>) Scheme of infection and the follow up analyses. For <b>B</b> and <b>C</b>, pregnant dams at embryonic day 9.5 (E9.5) were infected with 3.4 × 10⁵ PFU of ZIKV by intravenous route. Control mice were left untreated (uninfected), or inoculated with Vero cell culture supernatant (Mock) or 3.4 × 10⁵ PFU-equivalent of heat-inactivated ZIKV (Inact. ZIKV). For <b>D</b> and <b>E</b>, ZIKV was left untreated (ZIKV) or pretreated with mouse IgG2a isotype (Isotype), the neutralizing anti-ZIKV mAb (mAb ZK-67), or the immune serum harvested from ZIKV-infected adult mice (ZIKV immune serum). Pregnant dams at E9.5 were then infected with 3.4 × 10⁵ PFU-equivalent of treated ZIKV by intravenous route. Control mice were inoculated with Vero cell culture supernatant (Mock). Mice were sacrificed 8 days post infection (dpi) at E17.5, and maternal tissues, placentas and embryos were harvested and examined. (<b>B</b>) Representative images of E17.5 uteri. The uteri of ZIKV-infected mice showed complete or partial fetal demise. Arrows indicate the placental residues of resorbed embryos. Arrowheads indicate the remaining intact embryos. (<b>C</b>) Impact of ZIKV infection on dams and embryos at E17.5. The percentage of dams showing abnormal pregnancy (i.e. at least one embryo in the litter showed morphological abnormality or suffered demise/resorption) is shown in the left panel. The percentage of embryos that were affected (i.e. had undergone demise/resorption, or exhibited any sign of growth restriction, malformation, or anatomical developmental defect by gross morphological examination) is shown in the right panel. Numbers on bars indicate normal pregnancy/embryo (top) or abnormal pregnancy/affected embryo (bottom). (ns, not significant; **** p<0.0001 compared with numbers in uninfected group by Fisher’s exact test). (<b>D</b>) Representative images of uteri and embryos or placental residues carried by dams infected with pretreated ZIKV. The uteri and embryos of dams infected with mAb- or immune serum-treated ZIKV showed no abnormality compared with those of mock infection. (<b>E</b>) Impact of infection with pretreated ZIKV on dams and embryos at E17.5, as described in (C). (ns, not significant; ** p<0.01; **** p<0.0001 compared with numbers in Mock group by Fisher’s exact test). Data for all panels are pooled from 5 (B and C) or 2 (D and E) independent experiments.