Downregulation of transcriptional activity, increased inflammation, and damage in the placenta following in utero Zika virus infection is associated with adverse pregnancy outcomes.

Zika virus (ZIKV) infection during pregnancy causes serious adverse outcomes to the developing fetus, including fetal loss and birth defects known as congenital Zika syndrome (CZS). The mechanism by which ZIKV infection causes these adverse outcomes and specifically, the interplay between the maternal immune response and ZIKV replication has yet to be fully elucidated. Using an immunocompetent mouse model of transplacental ZIKV transmission and adverse pregnancy outcomes, we have previously shown that Asian lineage ZIKV disrupts placental morphology and induces elevated secretion of IL-1β. In the current manuscript, we characterized placental damage and inflammation during in utero African lineage ZIKV infection. Within 48 hours after ZIKV infection at embryonic day 10, viral RNA was detected in placentas and fetuses from ZIKA infected dams, which corresponded with placental damage and reduced fetal viability as compared with mock infected dams. Dams infected with ZIKV had reduced proportions of trophoblasts and endothelial cells and disrupted placental morphology compared to mock infected dams. While placental IL-1β was increased in the placenta, but not the spleen, within 3 hours post infection, this was not caused by activation of the NLRP3 inflammasome. Using bulk mRNAseq from placentas of ZIKV and mock infected dams, ZIKV infection caused profound downregulation of the transcriptional activity of genes that may underly tissue morphology, neurological development, metabolism, cell signaling and inflammation, illustrating that in utero ZIKV infections causes disruption of pathways associated with CZS in our model.