Vertical transmission of African-lineage Zika virus through the fetal membranes in a rhesus macaque (Macaca mulatta) model

Abstract

Zika virus (ZIKV) can be transmitted vertically from mother to fetus during pregnancy, resulting in a range of outcomes including severe birth defects and fetal/infant death. Potential pathways of vertical transmission in utero have been proposed but remain undefined. Identifying the timing and routes of vertical transmission of ZIKV may help us identify when interventions would be most effective. Furthermore, understanding what barriers ZIKV overcomes to effect vertical transmission may help improve models for evaluating infection by other pathogens during pregnancy. To determine the pathways of vertical transmission, we inoculated 12 pregnant rhesus macaques with an African-lineage ZIKV at gestational day 30 (term is 165 days). Eight pregnancies were surgically terminated at either seven or 14 days post-maternal infection. Maternal-fetal interface and fetal tissues and fluids were collected and evaluated for ZIKV using RT-qPCR, in situ hybridization, immunohistochemistry, and plaque assays. Four additional pregnant macaques were inoculated and terminally perfused with 4% paraformaldehyde at three, six, nine, or ten days post-maternal inoculation. For these four cases, the entire fixed pregnant uterus was evaluated with in situ hybridization for ZIKV RNA. We determined that ZIKV can reach the MFI by six days after infection and infect the fetus by ten days. Infection of the chorionic membrane and the extraembryonic coelomic fluid preceded infection of the fetus and the mesenchymal tissue of the placental villi. We did not find evidence to support a transplacental route of ZIKV vertical transmission via infection of syncytiotrophoblasts or villous cytotrophoblasts. The pattern of infection observed in the maternal-fetal interface provides evidence of paraplacental vertical ZIKV transmission through the chorionic membrane, the outer layer of the fetal membranes.

Nanoparticle-mediated delivery of placental gene therapy via uterine artery catheterization in a pregnant rhesus macaque

“…Steroid hormones in serum were assessed by the Wisconsin National Primate Research Center's Assay Services Unit using a Roche Cobas e411 analyzer as previously described 15 .…”

Decidual leukocytes respond to African lineage Zika virus infection with mild anti-inflammatory changes during acute infection in rhesus macaques

“…A strong pro-inflammatory response to infection mounted by decidual leukocytes could contribute to adverse pregnancy outcomes. In vivo and ex vivo studies have demonstrated that ZIKV readily infects the decidua ( 28 – 36 ). The acute decidual response to ZIKV infection remains essentially unstudied in vivo .…”

“…showed that African-lineage ZIKV can be vertically transmitted through the fetal membranes during early pregnancies in rhesus macaques ( 36 ). African-lineage ZIKV was used in that study because it consistently produced a high rate of vertical transmission, an ideal result for a macaque model with limited animal numbers ( 36 ). Koenig et al.…”

“…Koenig et al. showed that the decidua was consistently infected with ZIKV ( 36 ). Furthermore, infection of the decidua was shown to play an important role bridging the pathway between ZIKV infection of maternal blood and the infection the fetal membranes ( 36 ).…”

“…showed that the decidua was consistently infected with ZIKV ( 36 ). Furthermore, infection of the decidua was shown to play an important role bridging the pathway between ZIKV infection of maternal blood and the infection the fetal membranes ( 36 ). Because the decidua is readily infected by both African and Asian ZIKV and pathological inflammation is proposed to play a role in APOs, we believe that further investigation of the effect that ZIKV has on the decidual immune environment is warranted.…”