Sodium-dependent phosphate transporter PiT1/SLC20A1 as the receptor for the endogenous retroviral envelope syncytin-B involved in mouse placenta formation.

Syncytins are envelope genes of retroviral origin that play a critical role in the formation of a syncytial structure at the fetomaternal interface via their fusogenic activity. The mouse placenta is unique among placental mammals since the fetomaternal interface comprises two syncytiotrophoblast layers (ST-I and ST-II) instead of one observed in all other hemochorial placentae. Each layer specifically expresses a distinct mouse syncytin, namely syncytin-A (SynA) for ST-I and syncytin-B (SynB) for ST-II, which have been shown to be essential to placentogenesis and embryonic development. The cellular receptor for SynA has been identified as the membrane protein LY6E and is not the receptor for SynB. Here, by combining a cell-cell fusion assay with the screening of a human ORFeome-derived expression library, we identified the transmembrane multipass sodium-dependent phosphate transporter 1 PiT1/SLC20A1 as the receptor for SynB. Transfection of cells with the cloned receptor, but not the closely related PiT2/SLC20A2, leads to their fusion with cells expressing SynB, with no cross-reactive fusion activity with SynA. The interaction between the two partners was further demonstrated by immunoprecipitation. PiT1/PiT2 chimera and truncation experiments identified the PiT1 N-terminus as the major determinant for SynB-mediated fusion. RT-qPCR analysis of PiT1 expression on a panel of mouse adult and fetal tissues revealed a concomitant increase of PiT1 and SynB specifically in the developing placenta. Finally, electron microscopy analysis of the placenta of PiT1 null embryo before they die (E11.5) disclosed default of ST-II formation with lack of syncytialization, as previously observed in cognate SynB null placenta, and consistent with the present identification of PiT1 as the SynB partner.IMPORTANCESyncytins are envelope genes of endogenous retroviruses, coopted for a physiological function in placentation. They are fusogenic proteins that mediate cell-cell fusion by interacting with receptors present on the partner cells. Here, by devising an in vitro fusion assay that enables the screening of an ORFeome-derived expression library, we identified the long-sought receptor for syncytin-B (SynB), a mouse syncytin responsible for syncytiotrophoblast formation at the fetomaternal interface of the mouse placenta. This protein - PiT1/SLC20A1 - is a multipass transmembrane protein, also known as the receptor for a series of infectious retroviruses. Its profile of expression is consistent with a role in both ancestral endogenization of a SynB founder retrovirus and present-day mouse placenta formation, with evidence-in PiT1 knockout mice-of unfused cells at the level of the cognate placental syncytiotrophoblast layer.

The Relationship between HERV, Interleukin, and Transcription Factor Expression in ZIKV Infected versus Uninfected Trophoblastic Cells.

Zika virus (ZIKV) is an arbovirus with maternal, sexual, and TORCH-related transmission capabilities. After 2015, Brazil had the highest number of ZIVK-infected pregnant women who lost their babies or delivered them with Congenital ZIKV Syndrome (CZS). ZIKV triggers an immune defense in the placenta. This immune response counts with the participation of interleukins and transcription factors. Additionally, it has the potential involvement of human endogenous retroviruses (HERVS). Interleukins are immune response regulators that aid immune tolerance and support syncytial structure development in the placenta, where syncytin receptors facilitate vital cell-to-cell fusion events. HERVs are remnants of ancient viral infections that integrate into the genome and produce syncytin proteins crucial for placental development. Since ZIKV can infect trophoblast cells, we analyzed the relationship between ZIKV infection, HERV, interleukin, and transcription factor modulations in the placenta. To investigate the impact of ZIKV on trophoblast cells, we examined two cell types (BeWo and HTR8) infected with ZIKV-MR766 (African) and ZIKV-IEC-Paraíba (Asian-Brazilian) using Taqman and RT2 Profiler PCR Array assays. Our results indicate that early ZIKV infection (24-72 h) does not induce differential interleukins, transcription factors, and HERV expression. However, we show that the expression of a few of these host defense genes appears to be linked independently of ZIKV infection. Future studies involving additional trophoblastic cell lineages and extended infection timelines will illuminate the dynamic interplay between ZIKV, HERVs, interleukins, and transcription factors in the placenta.

Fetal MAVS and type I IFN signaling pathways control ZIKV infection in the placenta and maternal decidua.

The contribution of placental immune responses to congenital Zika virus (ZIKV) syndrome remains poorly understood. Here, we leveraged a mouse model of ZIKV infection to identify mechanisms of innate immune restriction exclusively in the fetal compartment of the placenta. ZIKV principally infected mononuclear trophoblasts in the junctional zone, which was limited by mitochondrial antiviral-signaling protein (MAVS) and type I interferon (IFN) signaling mechanisms. Single nuclear RNA sequencing revealed MAVS-dependent expression of IFN-stimulated genes (ISGs) in spongiotrophoblasts but not in other placental cells that use alternate pathways to induce ISGs. ZIKV infection of Ifnar1-/- or Mavs-/- placentas was associated with greater infection of the adjacent immunocompetent decidua, and heterozygous Mavs+/- or Ifnar1+/- dams carrying immunodeficient fetuses sustained greater maternal viremia and tissue infection than dams carrying wild-type fetuses. Thus, MAVS-IFN signaling in the fetus restricts ZIKV infection in junctional zone trophoblasts, which modulates dissemination and outcome for both the fetus and the pregnant mother.

Comprehensive analytics for virus-cell and cell-cell multinucleation system.

Cell-fusion mediated generation of multinucleated syncytia represent critical feature during viral infection and in development. Efficiency of syncytia formation is usually illustrated as fusion efficiency under given condition by quantifying total number of nuclei in syncytia normalized to total number of nuclei (both within syncytia and unfused cell nuclei) in unit field of view. However heterogeneity in multinucleated syncytia sizes poses challenge in quantification of cell-fusion multinucleation under diverse conditions. Taking in-vitro SARS-CoV-2 spike-protein variants mediated virus-cell fusion model and placenta trophoblast syncytialization as cell-cell fusion model; herein we emphasize wide application of simple unbiased detailed measure of virus-cell and cell-cell multinucleation using experiential cumulative distribution function (CDF) and fusion number events (FNE) approaches illustrating comprehensive metrics for syncytia interpretation.

Human Cytomegalovirus Dysregulates Cellular Dual-Specificity Tyrosine Phosphorylation-Regulated Kinases and Sonic Hedgehog Pathway Proteins in Neural Astrocyte and Placental Models.

Human cytomegalovirus (CMV) infection is the leading non-genetic cause of congenital malformation in developed countries, causing significant fetal injury, and in some cases fetal death. The pathogenetic mechanisms through which this host-specific virus infects then damages both the placenta and the fetal brain are currently ill-defined. We investigated the CMV modulation of key signaling pathway proteins for these organs including dual-specificity tyrosine phosphorylation-regulated kinases (DYRK) and Sonic Hedgehog (SHH) pathway proteins using human first trimester placental trophoblast (TEV-1) cells, primary human astrocyte (NHA) brain cells, and CMV-infected human placental tissue. Immunofluorescence demonstrated the accumulation and re-localization of SHH proteins in CMV-infected TEV-1 cells with Gli2, Ulk3, and Shh re-localizing to the CMV cytoplasmic virion assembly complex (VAC). In CMV-infected NHA cells, DYRK1A re-localized to the VAC and DYRK1B re-localized to the CMV nuclear replication compartments, and the SHH proteins re-localized with a similar pattern as was observed in TEV-1 cells. Western blot analysis in CMV-infected TEV-1 cells showed the upregulated expression of Rb, Ulk3, and Shh, but not Gli2. In CMV-infected NHA cells, there was an upregulation of DYRK1A, DYRK1B, Gli2, Rb, Ulk3, and Shh. These in vitro monoculture findings are consistent with patterns of protein upregulation and re-localization observed in naturally infected placental tissue and CMV-infected ex vivo placental explant histocultures. This study reveals CMV-induced changes in proteins critical for fetal development, and identifies new potential targets for CMV therapeutic development.

Exosomes-mediated transmission of standard bovine viral diarrhea strain OregonC24Va in bovine trophoblast cells.

Bovine viral diarrhoea virus (BVDV) can infect cows on days 30-110 of gestation and crossing the placental barrier, resulting in persistently infected (PI) and causing significant economic losses to dairy farming. Bovine placental trophoblast cells (BTCs) are the major cells in the early chorionic tissue of the placenta and play important roles in placental resistance to viral transmission. In this study, we have confirmed that BTCs is among a groups of cell types those could be infected by BVDV in vivo, and BVDV infection stimulates the autophagic responses in BTCs and promotes the release of exosomes. Meanwhile, the exosomes derived from BTCs can be used by BVDV to spread between placental trophoblast cells, and this mode of transmission cannot be blocked by antibodies against the BVDV E2 protein, whereas the replication and spread of BVDV in BTCs can be blocked by inhibiting autophagy and exosomogenesis. Our study provides a theoretical and practical basis for scientific prediction and intervention of reproductive disorders caused by BVDV infection in cows of different gestation periods from a novel perspective.

Influenza A virus infection disrupts the function of syncytiotrophoblast cells and contributes to adverse pregnancy outcomes.

Pregnancy heightens susceptibility to influenza A virus (IAV) infection, thereby increasing the risk of severe pneumonia and maternal mortality. It also raises the chances of adverse outcomes in offspring, such as fetal growth restriction, preterm birth, miscarriage, and stillbirth in offsprings. However, the underlying mechanisms behind these effects remain largely unknown. Syncytiotrophoblast cells, crucial in forming the placental barrier, nutrient exchange and hormone secretion, have not been extensively studied for their responses to IAV. In our experiment, we used Forskolin-treated BeWo cells to mimic syncytiotrophoblast cells in vitro, and infected them with H1N1, H5N1 and H7N9 virus stains. Our results showed that syncytiotrophoblast cells, with their higher intensity of sialic acid receptors, strongly support IAV infection and replication. Notably, high-dose viral infection and prolonged exposure resulted in a significant decrease in fusion index, as well as gene and protein expression levels associated with trophoblast differentiation, ß-human chorionic gonadotropin secretion, estrogen and progesterone biosynthesis, and nutrient transport. In pregnant BALB/c mice infected with the H1N1 virus, we observed significant decreases in trophoblast differentiation and hormone secretion gene expression levels. IAV infection also resulted in preterm labor, fetal growth restriction, and increased maternal and fetal morbidity and mortality. Our findings indicate that IAV infection in syncytiotrophoblastic cells can result in adverse pregnancy outcomes by altering trophoblast differentiation, suppressing of ß-hCG secretion, and disrupting placental barrier function.

Pan-microscopic examination of monkeypox virus in trophoblasts cells reveals new insights into virions release through filopodia-like projections.

Vertical transmission has been described following monkeypox virus (MPXV) infection in pregnant women. The presence of MPXV has been reported in the placenta from infected women, but whether pathogens colonize placenta remains unexplored. We identify trophoblasts as a target cell for MPXV replication. In a pan-microscopy approach, we decipher the specific infectious cycle of MPXV and inner cellular structures in trophoblasts. We identified the formation of a specialized region for viral morphogenesis and replication in placental cells. We also reported infection-induced cellular remodeling. We found that MPXV stimulates cytoskeleton reorganization with intercellular extensions for MPXV cell spreading specifically to trophoblastic cells. Altogether, the specific infectious cycle of MPXV in trophoblast cells and these protrusions that were structurally and morphologically similar to filopodia reveal new insights into the infection of MPXV.

Characterization of the endogenous retrovirus-derived placenta-specific soluble protein EnvV-Fca from domestic cats.

Endogenous retroviruses (ERVs) are remnants of ancestral viruses in the host genome. The present study identified the expression of a defective retroviral env gene belonging to the ERV group V member Env (EnvV) in Felis catus (EnvV-Fca). EnV-Fca was specifically detected in the placental trophoblast syncytiotrophobic layer and expressed as a secreted protein in cultured cells. Genetic analyses indicated that EnvV2 genes are widely present in vertebrates and are under purifying selection among carnivores, suggesting a potential benefit for the host. This study suggests that birds, bats, and rodents carrying EnvV2 may play significant roles as intermediate vectors in spreading or cross-transmitting viruses among species. Our findings provide valuable insights into the evolution of ERV in vertebrate hosts.

Human trophoblast stem cells restrict human cytomegalovirus replication.

Placental infection plays a central role in the pathogenesis of congenital human cytomegalovirus (HCMV) infections and is a cause of fetal growth restriction and pregnancy loss. HCMV can replicate in some trophoblast cell types, but it remains unclear how the virus evades antiviral immunity in the placenta and how infection compromises placental development and function. Human trophoblast stem cells (TSCs) can be differentiated into extravillous trophoblasts (EVTs), syncytiotrophoblasts (STBs), and organoids, and this study assessed the utility of TSCs as a model of HCMV infection in the first-trimester placenta. HCMV was found to non-productively infect TSCs, EVTs, and STBs. Immunofluorescence assays and flow cytometry experiments further revealed that infected TSCs frequently only express immediate early viral gene products. Similarly, RNA sequencing found that viral gene expression in TSCs does not follow the kinetic patterns observed during lytic infection in fibroblasts. Canonical antiviral responses were largely not observed in HCMV-infected TSCs and TSC-derived trophoblasts. Rather, infection dysregulated factors involved in cell identity, differentiation, and Wingless/Integrated signaling. Thus, while HCMV does not replicate in TSCs, infection may perturb trophoblast differentiation in ways that could interfere with placental function. IMPORTANCE: Placental infection plays a central role in human cytomegalovirus (HCMV) pathogenesis during pregnancy, but the species specificity of HCMV and the limited availability and lifespan of primary trophoblasts have been persistent barriers to understanding how infection impacts this vital organ. Human trophoblast stem cells (TSCs) represent a new approach to modeling viral infection early in placental development. This study reveals that TSCs, like other stem cell types, restrict HCMV replication. However, infection perturbs the expression of genes involved in differentiation and cell fate determination, pointing to a mechanism by which HCMV could cause placental injury.

Immune rebalancing at the maternal-fetal interface of maternal SARS-CoV-2 infection during early pregnancy.

The current coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus (SARS-CoV-2) remains a threat to pregnant women. However, the impact of early pregnancy SARS-CoV-2 infection on the maternal-fetal interface remains poorly understood. Here, we present a comprehensive analysis of single-cell transcriptomics and metabolomics in placental samples infected with SARS-CoV-2 during early pregnancy. Compared to control placentas, SARS-CoV-2 infection elicited immune responses at the maternal-fetal interface and induced metabolic alterations in amino acid and phospholipid profiles during the initial weeks post-infection. However, subsequent immune cell activation and heightened immune tolerance in trophoblast cells established a novel dynamic equilibrium that mitigated the impact on the maternal-fetal interface. Notably, the immune response and metabolic alterations at the maternal-fetal interface exhibited a gradual decline during the second trimester. Our study underscores the adaptive immune tolerance mechanisms and establishment of immunological balance during the first two trimesters following maternal SARS-CoV-2 infection.

Targeting first trimester trophoblast cell metabolism modulates its susceptibility to Zika virus infection.

In the last 15 years Zika virus (ZIKV) caused several outbreaks of increasing scale in Micronesia, South Pacific islands, and more recently in the Caribbean and South America. The severity of the clinical presentation in neonates from pregnant women infected with ZIKV during the last outbreak supports the relevance of unraveling the mechanism of infection and viral persistence in the placenta with local viral isolates. Here, we investigated the relevance of trophoblast metabolic rewiring for viral multiplication and the role of the vasoactive intestinal peptide (VIP) as an endogenous factor associated with placental restriction to ZIKV infection at early pregnancy. Our in vitro model demonstrated that ZIKV triggers metabolic rewiring in first trimester cytotrophoblast-derived cells by increasing glucose utilization as fuel to sustain its replication, decreasing long-chain polyunsaturated fatty acid uptake, and promoting lipid droplets accumulation to favor its multiplication. Of note, variations in nutrient availability modulated viral spread in trophoblast cultures. The presence of VIP during trophoblast infection impaired ZIKV infective particle production and viral replication, restoring cell migration and metabolism. Moreover, the blockade of endogenous VIP signaling increased viral particle production and the viral entry receptor AXL expression. These results highlight the potential role of VIP as an endogenous antiviral factor related to trophoblast cell permissiveness to ZIKV infection at early pregnancy.

Placental SARS-CoV-2 distribution correlates with level of tissue oxygenation in COVID-19-associated necrotizing histiocytic intervillositis/perivillous fibrin deposition.

INTRODUCTION: Recent evidence supports the - rare - occurrence of vertical transplacental SARS-CoV-2 transmission. We previously determined that placental expression of angiotensin-converting enzyme 2 (ACE2), the SARS-CoV-2 receptor, and associated viral cell entry regulators is upregulated by hypoxia. In the present study, we utilized a clinically relevant model of SARS-CoV-2-associated chronic histiocytic intervillositis/massive perivillous fibrin deposition (CHIV/MPFVD) to test the hypothesis that placental hypoxia may facilitate placental SARS-CoV-2 infection. METHODS: We performed a comparative immunohistochemical and/or RNAscope in-situ hybridization analysis of carbonic anhydrase IX (CAIX, hypoxia marker), ACE2 and SARS-CoV-2 expression in free-floating versus fibrin-encased chorionic villi in a 20-weeks' gestation placenta with SARS-CoV-2-associated CHIV/MPVFD. RESULTS: The levels of CAIX and ACE2 immunoreactivity were significantly higher in trophoblastic cells of fibrin-encased villi than in those of free-floating villi, consistent with hypoxia-induced ACE2 upregulation. SARS-CoV-2 showed a similar preferential localization to trophoblastic cells of fibrin-encased villi. DISCUSSION: The localization of SARS-CoV-2 to hypoxic, fibrin-encased villi in this placenta with CHIV/MPVFD suggests placental infection and, therefore, transplacental SARS-CoV-2 transmission may be promoted by hypoxic conditions, mediated by ACE2 and similar hypoxia-sensitive viral cell entry mechanisms. Understanding of a causative link between placental hypoxia and SARS-CoV-2 transmittability may potentially lead to the development of alternative strategies for prevention of intrauterine COVID-19 transmission.

The S100A10-AnxA2 complex is associated with the exocytosis of hepatitis B virus in intrauterine infection.

Mother-to-child transmission (MTCT) is the major cause of chronic infection of hepatitis B virus (HBV) in patients. However, whether and how HBV crosses the placenta to cause infection in utero remains unclear. In this study, we investigate the mechanism as to how the HBV virions pass through layers of the trophoblast. Our data demonstrate the exocytosis of virions from the trophoblast after exposure to HBV where the endocytosed HBV virions co-localized with an S100A10/AnxA2 complex and LC3, an autophagosome membrane marker. Knockdown of either AnxA2 or S100A10 in trophoblast cells led to a reduction of the amount of exo-virus in Transwell assay. Immunohistochemistry also showed a high expression of AnxA2 and S100A10 in the placental tissue samples of HBV-infected mothers with congenital HBV-positive infants (HBV+/+). We conclude that in HBV intrauterine infection and mother-to-child transmission, a proportion of HBV hijacks autophagic protein secretion pathway and translocate across the trophoblast via S100A10/AnxA2 complex and multivesicular body (MVB)-mediated exocytosis. Our study provides a potential target for the interference of the mechanisms of HBV intrauterine infection and mother-to-child transmission.

Murine Trophoblast Stem Cells and Their Differentiated Cells Attenuate Zika Virus In Vitro by Reducing Glycosylation of the Viral Envelope Protein.

Zika virus (ZIKV) infection during pregnancy can cause devastating fetal neuropathological abnormalities, including microcephaly. Most studies of ZIKV infection in pregnancy have focused on post-implantation stage embryos. Currently, we have limited knowledge about how a pre-implantation stage embryo deals with a viral infection. This study investigates ZIKV infection on mouse trophoblast stem cells (TSCs) and their in vitro differentiated TSCs (DTSCs), which resemble the cellular components of the trophectoderm layer of the blastocyst that later develops into the placenta. We demonstrate that TSCs and DTSCs are permissive to ZIKV infection; however, ZIKV propagated in TSCs and DTSCs exhibit substantially lower infectivity, as shown in vitro and in a mouse model compared to ZIKV that was generated in Vero cells or mouse embryonic fibroblasts (MEFs). We further show that the low infectivity of ZIKV propagated in TSCs and DTSCs is associated with a reduced level of glycosylation on the viral envelope (E) proteins, which are essential for ZIKV to establish initial attachment by binding to cell surface glycosaminoglycans (GAGs). The decreased level of glycosylation on ZIKV E is, at least, partially due to the low-level expression of a glycosylation-related gene, Hexa, in TSCs and DTSCs. Furthermore, this finding is not limited to ZIKV since similar observations have been made as to the chikungunya virus (CHIKV) and West Nile virus (WNV) propagated in TSCs and DTSCs. In conclusion, our results reveal a novel phenomenon suggesting that murine TSCs and their differentiated cells may have adapted a cellular glycosylation system that can limit viral infectivity by altering the glycosylation of viral envelope proteins, therefore serving as a unique, innate anti-viral mechanism in the pre-implantation stage embryo.

Rift Valley Fever Virus Propagates in Human Villous Trophoblast Cell Lines and Induces Cytokine mRNA Responses Known to Provoke Miscarriage.

The mosquito-borne Rift Valley fever (RVF) is a prioritised disease that has been listed by the World Health Organization for urgent research and development of counteraction. Rift Valley fever virus (RVFV) can cause a cytopathogenic effect in the infected cell and induce hyperimmune responses that contribute to pathogenesis. In livestock, the consequences of RVFV infection vary from mild symptoms to abortion. In humans, 1-3% of patients with RVFV infection develop severe disease, manifested as, for example, haemorrhagic fever, encephalitis or blindness. RVFV infection has also been associated with miscarriage in humans. During pregnancy, there should be a balance between pro-inflammatory and anti-inflammatory mediators to create a protective environment for the placenta and foetus. Many viruses are capable of penetrating that protective environment and infecting the foetal-maternal unit, possibly via the trophoblasts in the placenta, with potentially severe consequences. Whether it is the viral infection per se, the immune response, or both that contribute to the pathogenesis of miscarriage remains unknown. To investigate how RVFV could contribute to pathogenesis during pregnancy, we infected two human trophoblast cell lines, A3 and Jar, representing normal and transformed human villous trophoblasts, respectively. They were infected with two RVFV variants (wild-type RVFV and RVFV with a deleted NSs protein), and the infection kinetics and 15 different cytokines were analysed. The trophoblast cell lines were infected by both RVFV variants and infection caused upregulation of messenger RNA (mRNA) expression for interferon (IFN) types I-III and inflammatory cytokines, combined with cell line-specific mRNA expression of transforming growth factor (TGF)-ß1 and interleukin (IL)-10. When comparing the two RVFV variants, we found that infection with RVFV lacking NSs function caused a hyper-IFN response and inflammatory response, while the wild-type RVFV suppressed the IFN I and inflammatory response. The induction of certain cytokines by RVFV infection could potentially lead to teratogenic effects that disrupt foetal and placental developmental pathways, leading to birth defects and other pregnancy complications, such as miscarriage.

SARS-CoV-2 can infect and propagate in human placenta explants.

The ongoing SARS-CoV-2 pandemic continues to lead to high morbidity and mortality. During pregnancy, severe maternal and neonatal outcomes and placental pathological changes have been described. We evaluate SARS-CoV-2 infection at the maternal-fetal interface using precision-cut slices (PCSs) of human placenta. Remarkably, exposure of placenta PCSs to SARS-CoV-2 leads to a full replication cycle with infectious virus release. Moreover, the susceptibility of placental tissue to SARS-CoV-2 replication relates to the expression levels of ACE2. Viral proteins and/or viral RNA are detected in syncytiotrophoblasts, cytotrophoblasts, villous stroma, and possibly Hofbauer cells. While SARS-CoV-2 infection of placenta PCSs does not cause a detectable cytotoxicity or a pro-inflammatory cytokine response, an upregulation of one order of magnitude of interferon type III transcripts is measured. In conclusion, our data demonstrate the capacity of SARS-CoV-2 to infect and propagate in human placenta and constitute a basis for further investigation of SARS-CoV-2 biology at the maternal-fetal interface.

Morphometric Parameters of Placental Villi in Parturient Women with COVID-19.

We performed a comparative morphological analysis of placental villi in parturient women with mild and moderate COVID-19 infection. The area and perimeter of terminal villi, their capillaries, and syncytiotrophoblast were assessed on immunohistochemical preparations with antibodies to CD31 using an image analysis system; the parameters of fetal vascular component in the placental villi were also assessed. Changes in the studied parameters differed in parturient women with mild and moderate COVID-19 infection. The observed increase in the total perimeter with a simultaneous decrease in the total capillary area and the degree of vascularization of the placental villi in parturient women with COVID-19 indicates impairment of circulation in the fetal compartment and the development of placental hypoxia, which can be the cause of unfavorable neonatal outcomes.

Limited replication of human cytomegalovirus in a trophoblast cell line.

Several viruses, including human cytomegalovirus (HCMV), are thought to replicate in the placenta. However, there is little understanding of the molecular mechanisms involved in HCMV replication in this tissue. We investigated replication of HCMV in the extravillous trophoblast cell line SGHPL-4, a commonly used model of HCMV replication in the placenta. We found limited HCMV protein expression and virus replication in SGHPL-4 cells. This was associated with a lack of trophoblast progenitor cell protein markers in SGHPL-4 cells, suggesting a relationship between trophoblast differentiation and limited HCMV replication. We proposed that limited HCMV replication in trophoblast cells is advantageous to vertical transmission of HCMV, as there is a greater opportunity for vertical transmission when the placenta is intact and functional. Furthermore, when we investigated the replication of other vertically transmitted viruses in SGHPL-4 cells we found some limitation to replication of Zika virus, but not herpes simplex virus. Thus, limited replication of some, but not all, vertically transmitted viruses may be a feature of trophoblast cells.

COVID-19 in pregnancy: placental pathological patterns and effect on perinatal outcome in five cases.

INTRODUCTION: COVID-19, the disease caused by the novel coronavirus SARS-CoV-2, is a severe systemic thrombotic syndrome that emerged in 2019, with an ensuing pandemic. To evaluate the impact of this disease on placental tissue and perinatal outcome, histological, immunohistochemical and ultrastructural analyses of placental tissue were performed for five cases of pregnant women with COVID-19. CASE REPORTS: All five pregnant women in this series developed COVID-19 in late pregnancy. Two patients experienced respiratory distress, and computed tomography revealed signs of pneumonia, with bilateral involvement, multiple lobular and subsegmental areas of consolidation and ground-glass opacities. Histological studies of placental tissue revealed the presence of slight signs of maternal vascular underperfusion (MVUs) or foetal vascular underperfusion (FVUs) lesions and mild inflammatory lesions. CD15 immunoreactivity in the placental tissue was low in all cases, demonstrating that in these cases there was not severe foetal hypoxia/asphyxia risk for newborns or distal vascular immaturity. In all cases examined, ultrastructural analyses showed spherical-like coronavirus particles with an electron intermediate-density core as well as projections from the surface as spike-like structures in the syncytiotrophoblasts. At term, all of the women delivered newborns who were negative for SARS-CoV-2 by nasopharyngeal testing in their first day of life. All newborns were exclusively breastfed and were discharged on the 3rd day of life. CONCLUSIONS: In conclusion, placental patterns in pregnancy due to COVID-19 in the late stage of gestation indicate no evidence of vertical trans-placental SARS-CoV-2 transmission or a significant impact on the perinatal outcome of newborns, in both mild and more severe cases.