Zika virus (ZIKV) infection during pregnancy is linked to severe birth defects, but mother-to-fetus transmission routes are unknown. We infected different primary cell types from mid- and late-gestation placentas and explants from first-trimester chorionic villi with the prototype Ugandan and a recently-isolated Nicaraguan ZIKV strain. ZIKV infects primary human placental cells and explants – cytotrophoblasts, endothelial cells, fibroblasts and Hofbauer cells in chorionic villi and amniotic epithelial cells, and trophoblast progenitors in amniochorionic membranes expressing Axl, Tyro3 and/or TIM1 viral entry cofactors. ZIKV produced NS3 and E proteins and generated higher viral titers in amniotic epithelial cells from mid-gestation compared to late-gestation placentas. Duramycin, a peptide that binds phosphatidylethanolamine in enveloped virions and precludes TIM1 binding, reduced ZIKV infection in placental cells and explants. Our results suggest that ZIKV spreads from basal and parietal decidua to chorionic villi and amniochorionic membranes, and targeting TIM1 could suppress infection at the uterine-placental interface.

Human cytomegalovirus (CMV) is the leading cause of prenatal viral infection. Affected infants may suffer intrauterine growth retardation and serious neurologic impairment. Analysis of spontaneously aborted conceptuses shows that CMV infects the placenta before the embryo or fetus. In the human hemochorial placenta, maternal blood directly contacts syncytiotrophoblasts that cover chorionic villi and cytotrophoblasts that invade uterine vessels, suggesting possible routes for CMV transmission. To test this hypothesis, we exposed first-trimester chorionic villi and isolated cytotrophoblasts to CMV in vitro. In chorionic villi, syncytiotrophoblasts did not become infected, although clusters of underlying cytotrophoblasts expressed viral proteins. In chorionic villi that were infected with CMV in utero, syncytiotrophoblasts were often spared, whereas cytotrophoblasts and other cells of the villous core expressed viral proteins. Isolated cytotrophoblasts were also permissive for CMV replication in vitro; significantly, infection subsequently impaired the cytotrophoblasts' ability to differentiate and invade. These results suggest two possible routes of CMV transmission to the fetus: (i) across syncytiotrophoblasts with subsequent infection of the underlying cytotrophoblasts and (ii) via invasive cytotrophoblasts within the uterine wall. Furthermore, the observation that CMV infection impairs critical aspects of cytotrophoblast function offers testable hypotheses for explaining the deleterious effects of this virus on pregnancy outcome.

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How human cytomegalovirus (CMV) reaches the fetus across the placenta is unknown. The major viral cause of congenital disease, CMV infects the uterine-placental interface with varied outcomes depending on the strength of maternal humoral immunity and gestational age. Covering the surface of villi that float in blood, syncytiotrophoblasts express the neonatal Fc receptor (FcRn) that transports IgG for passive immunity. Immunohistochemical analysis of early-gestation biopsy specimens showed an unusual pattern of CMV replication proteins in underlying villus cytotrophoblasts, whereas syncytiotrophoblasts were spared. Found in placentas with low to moderate CMV-neutralizing antibody titers, this pattern suggested virion transcytosis across the surface. In contrast, syncytiotrophoblasts from placentas with high neutralizing titers contained viral DNA and caveolin-1-positive vesicles in which IgG and CMV glycoprotein B co-localized. In villus explants, IgG-virion transcytosis and macrophage uptake were blocked with trypsin-treatment and soluble protein A. Quantitative analysis in polarized epithelial cells showed that FcRn-mediated transcytosis was blocked by the Fc fragment of IgG, but not F(ab')(2). Our results suggest that CMV virions could disseminate to the placenta by co-opting the receptor-mediated transport pathway for IgG. These findings could explain the efficacy of hyperimmune IgG for treatment of primary CMV infection during gestation and support vaccination.

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In an earlier paper (Morse et al., J. Virol. 24:231-248, 1977) we reported on the provenance of the DNA sequences in 26 herpes simplex virus type 1 (HSV-1) x HSV-2 recombinants as determined from analyses of their DNAs with at least five restriction endonucleases. This report deals with the polypeptides specified by the recombinants and by their HSV-1 and HSV-2 parents. We have identified (i) the corresponding HSV-1 and HSV-2 polypeptides with molecular weights ranging from 20,000 to more than 200,000, (ii) the polypeptides that undergo rapid post-translational processing, and (iii) polypeptides that vary intratypically in apparent molecular weight. By comparing the segregation patterns of the polypeptides with those of the DNA sequence of the recombinants, we have mapped the templates specifying 26 polypeptides and several viral functions on the physical map of HSV DNA. The data show the following: (i) a polypeptides map at the termini of the L and S components of the HSV DNA. Although a ICP 27 maps entirely within the reiterated region of the L component, the template for a ICP 4 may lie only in part within the reiterated sequences of the S component. Of note is the finding that cells infected with a recombinant that contains both HSV-1 and HSV-2 DNA sequences in the S component produced a ICP 4 of both HSV-1 and HSV-2. (ii) Templates specifying,8 and y polypeptides map in the L component and appear to be randomly distributed. (iii) Thymidine kinase and resistance to phosphonoacetic acid mapped in the L component. In addition, we have taken advantage of the rapid inhibition of host protein synthesis characteristic of HSV-2 infections and syncytial plaque morphology to also map the template(s) responsible for these functions in the L component. The implications of the template arrangement in HSV DNA are discussed. In this paper we report the location, in the are the following data: (i) Honess and Roizman DNAs of herpes simplex virus types 1 and 2 (13) reported that HSV-1 specifies in infected (human herpesviruses 1 and 2; HSV-1 and HSV-cells at least 48 polypeptides ranging from 20,00 2), of the templates specifying 26 polypeptides to greater than 200,000 in molecular weight. and several viral functions. The experimental Several additional polypeptides less than 20,000 design used in these studies was similar to that in molecular weight were reported by Marsden used in mapping adenovirus templates (9, 25) et al. (24). A similar list of HSV-2 polypeptides and consisted of comparing the segregation patwas reported by Powell and Courtney (30). Studterns of polypeptides specified by HSV-1 x ies by Courtney and Powell (3), Pereira et al. HSV-2 intertypic recombinants with their DNA (29), Gibson and Roizman (8), and Cassai et al. sequence arrangements. The DNA sequence ar-(2) showed that many HSV-1 and HSV-2 virion rangements of the intertypic recombinants used polypeptides and infected-cell polypeptides in these studies were reported in a previous (ICP) differ in electrophoretic mobility, but only paper in this serie...

Human placentation entails the remarkable integration of fetal and maternal cells into a single functional unit. In the basal plate region (the maternal-fetal interface) of the placenta, fetal cytotrophoblasts from the placenta invade the uterus and remodel the resident vasculature and avoid maternal immune rejection. Knowing the molecular bases for these unique cell-cell interactions is important for understanding how this specialized region functions during normal pregnancy with implications for tumor biology and transplantation immunology. Therefore, we undertook a global analysis of the gene expression profiles at the maternal-fetal interface. Basal plate biopsy specimens were obtained from 36 placentas (14-40 wk) at the conclusion of normal pregnancies. RNA was isolated, processed, and hybridized to HG-U133A&B Affymetrix GeneChips. Surprisingly, there was little change in gene expression during the 14- to 24-wk interval. In contrast, 418 genes were differentially expressed at term (37-40 wk) as compared with midgestation (14-24 wk). Subsequent analyses using quantitative PCR and immunolocalization approaches validated a portion of these results. Many of the differentially expressed genes are known in other contexts to be involved in differentiation, motility, transcription, immunity, angiogenesis, extracellular matrix dissolution, or lipid metabolism. One sixth were nonannotated or encoded hypothetical proteins. Modeling based on structural homology revealed potential functions for 31 of these proteins. These data provide a reference set for understanding the molecular components of the dialogue taking place between maternal and fetal cells in the basal plate as well as for future comparisons of alterations in this region that occur in obstetric complications.

Why certain viruses cross the physical barrier of the human placenta but others do not is incompletely understood. Over the past 20 years, we have gained deeper knowledge of intrauterine infection and routes of viral transmission. This review focuses on human viruses that replicate in the placenta, infect the fetus, and cause birth defects, including rubella virus, varicella-zoster virus, parvovirus B19, human cytomegalovirus (CMV), Zika virus (ZIKV), and hepatitis E virus type 1. Detailed discussions include ( a) the architecture of the uterine-placental interface, ( b) studies of placental explants ex vivo that provide insights into the infection and spread of CMV and ZIKV to the fetal compartment and how these viruses undermine early development, and ( c) novel treatments and vaccines that limit viral replication and have the potential to reduce dissemination, vertical transmission and the occurrence of congenital disease.