Cellular and molecular mechanisms of viral infection in the human placenta

Melatonin: the placental antioxidant and anti-inflammatory

Melatonin (N-acetyl-5-methoxytryptamine) is an indolamine hormone with many physiological and biological roles. Melatonin is an antioxidant, anti-inflammatory, free radical scavenger, circadian rhythm regulator, and sleep hormone. However, its most popular role is the ability to regulate sleep through the circadian rhythm. Interestingly, recent studies have shown that melatonin is an important and essential hormone during pregnancy, specifically in the placenta. This is primarily due to the placenta's ability to synthesize its own melatonin rather than depending on the pineal gland. During pregnancy, melatonin acts as an antioxidant and anti-inflammatory, which is necessary to ensure a stable environment for both the mother and the fetus. It is an essential antioxidant in the placenta because it reduces oxidative stress by constantly scavenging for free radicals, i.e., maintain the placenta's integrity. In a healthy pregnancy, the maternal immune system is constantly altered to accommodate the needs of the growing fetus, and melatonin acts as a key anti-inflammatory by regulating immune homeostasis during early and late gestation. This literature review aims to identify and summarize melatonin's role as a powerful antioxidant and anti-inflammatory that reduces oxidative stress and inflammation to maintain a favorable homeostatic environment in the placenta throughout gestation.

Perinatal Outcomes of Newborns of COVID-19-Infected Pregnant Women: An Updated Systematic Review and Meta-Analysis

In this systematic review and meta-analysis, we aimed to review the characteristics and outcomes of the newborns of Coronavirus disease 2019 (COVID-19) infected pregnant women. We conducted an online bibliographic search using the following electronic databases: MEDLINE via PubMed, Scopus, Web of Science, and Cochrane Central. Studies were deemed eligible if they recruited newborns from mothers with confirmed COVID-19 and reported the perinatal outcomes of neonatal COVID-19 cases. A total of 20 studies were included. Neonates born to mothers with positive COVID-19 results have been shown to have significantly lower birth weights (mean difference, MD = -48.54 g, p = 0.04), increased risks of fetal distress (odds ratio, OR = 1.76, p < 0.00001), respiratory distress (OR = 1.96, p = 0.006), premature birth (OR = 2.08, p < 0.00001), neonatal death (OR = 2.20, p = 0.004), and a lower 5-minute Apgar score (OR = 1.44, p = 0.02). Additionally, they were more likely to be admitted to the neonatal intensive care unit (NICU) (OR = 2.25, p = 0.007) and test positive for COVID-19 themselves (OR = 9.88, p = 0.03). However, other parameters, such as risks for malformations, mechanical ventilation, hypoglycemia, and sepsis, appeared to be comparable between the two groups. Maternal infection with COVID-19 during pregnancy is associated with several neonatal outcomes, some of which are adverse and others that do not show significant deviation from norms. While our meta-analysis clearly illustrates heightened risks associated with premature birth, reduced neonatal weight, and other challenges, it also emphasizes that not all neonatal outcomes can be directly attributed to maternal SARS-CoV-2 infection.

Transmission, seroprevalence, and maternal-fetal impact of lymphocytic choriomeningitis virus

Congenital infections can have devastating short- and long-term impacts on the developing fetus. Lymphocytic choriomeningitis virus (LCMV) is a zoonotic pathogen of concern that causes a severe congenital syndrome but is under-recognized and under-studied. Herein we review data on the natural animal reservoirs of LCMV, modes of transmission to humans, seroprevalence of LCMV worldwide in both pregnant and non-pregnant individuals, mechanisms of viral dissemination to placenta and fetus, and impact of climate change on viral transmission. We highlight opportunities to enhance awareness of congenital LCMV and provide recommendations for prevention and monitoring among at-risk pregnant people. IMPACT: Key message of the article: LCMV is a zoonotic virus that poses a major threat to maternal-fetal health. Adds to the existing literature: We comprehensively address transmission of LCMV from the natural reservoir to the pregnant individual, placenta, and fetus. Impact: Available data call for enhanced patient and provider awareness about congenital LCMV during pregnancy, as well as a need for efforts to better define the seroprevalence and impact of congenital LCMV worldwide.

Common pathways targeted by viral hemorrhagic fever viruses to infect the placenta and increase the risk of stillbirth

Viral hemorrhagic fevers (VHF) are endemic to Africa, South America and Asia and contribute to significant maternal and fetal morbidity and mortality. Viruses causing VHFs are typically zoonotic, spreading to humans through livestock, wildlife, or mosquito vectors. Some of the most lethal VHF viruses also impart a high-risk of stillbirth including ebolaviruses, Marburg virus (MARV), Lassa virus (LASV), and Rift Valley Fever Virus (RVFV). Large outbreaks and epidemics are common, though the impact on the mother, fetus and placenta is understudied from a public health, clinical and basic science perspective. Notably, these viruses utilize ubiquitous cellular surface entry receptors critical for normal placental function to enable viral invasion into multiple key cell types of the placenta and set the stage for maternal-fetal transmission and stillbirth. We employ insights from molecular virology and viral immunology to discuss how trophoblast expression of viral entry receptors for VHF viruses may increase the risk for viral transmission to the fetus and stillbirth. As the frequency of VHF outbreaks is expected to increase with worsening climate change, understanding the pathogenesis of VHF-related diseases in the placenta is paramount to predicting the impact of emerging viruses on the placenta and perinatal outcomes.

The effects of COVID-19 on placental morphology

The impact of the COVID-19 infection, caused by Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), during the pandemic has been considerably more severe in pregnant women than non-pregnant women. Therefore, a review detailing the morphological alterations and physiological changes associated with COVID-19 during pregnancy and the effect that these changes have on the feto-placental unit is of high priority. This knowledge is crucial for these mothers, their babies and clinicians to ensure a healthy life post-pandemic. Hence, we review the placental morphological changes due to COVID-19 to enhance the general understanding of how pregnant mothers, their placentas and unborn children may have been affected by this pandemic. Based on current literature, we deduced that COVID-19 pregnancies were oxygen deficient, which could further result in other pregnancy-related complications like preeclampsia and IUGR. Therefore, we present an up-to-date review of the COVID-19 pathophysiological implications on the placenta, covering the function of the placenta in COVID-19, the effects of this virus on the placenta, its functions and its link to other gestational complications. Furthermore, we highlight the possible effects of COVID-19 therapeutic interventions on pregnant mothers and their unborn children. Based on the literature, we strongly suggest that consistent surveillance for the mothers and infants from COVID-19 pregnancies be prioritised in the future. Though the pandemic is now in the past, its effects are long-term, necessitating the monitoring of clinical manifestations in the near future.

Fetal effects of mild maternal COVID-19 infection: metabolomic profiling of cord blood

INTRODUCTION

The impact of maternal coronavirus disease 2019 (COVID-19) infection on fetal health remains to be precisely characterized.

OBJECTIVES

Using metabolomic profiling of newborn umbilical cord blood, we aimed to investigate the potential fetal biological consequences of maternal COVID-19 infection.

METHODS

Cord blood plasma samples from 23 mild COVID-19 cases (mother infected/newborn negative) and 23 gestational age-matched controls were analyzed using nuclear magnetic spectroscopy and liquid chromatography coupled with mass spectrometry. Metabolite set enrichment analysis (MSEA) was used to evaluate altered biochemical pathways due to COVID-19 intrauterine exposure. Logistic regression models were developed using metabolites to predict intrauterine exposure.

RESULTS

Significant concentration differences between groups (p-value < 0.05) were observed in 19 metabolites. Elevated levels of glucocorticoids, pyruvate, lactate, purine metabolites, phenylalanine, and branched-chain amino acids of valine and isoleucine were discovered in cases while ceramide subclasses were decreased. The top metabolite model including cortisol and ceramide (d18:1/23:0) achieved an Area under the Receiver Operating Characteristics curve (95% CI) = 0.841 (0.725-0.957) for detecting fetal exposure to maternal COVID-19 infection. MSEA highlighted steroidogenesis, pyruvate metabolism, gluconeogenesis, and the Warburg effect as the major perturbed metabolic pathways (p-value < 0.05). These changes indicate fetal increased oxidative metabolism, hyperinsulinemia, and inflammatory response.

CONCLUSION

We present fetal biochemical changes related to intrauterine inflammation and altered energy metabolism in cases of mild maternal COVID-19 infection despite the absence of viral infection. Elucidation of the long-term consequences of these findings is imperative considering the large number of exposures in the population.

Type VII Aplasia Cutis Congenita in Neonates Related to Maternal HBV Infection? Case Report and Literature Review

Aplasia cutis congenita (ACC) is a rare disease with an unclear pathogenic mechanism. ACC has been suggested to result from the disrupted development or degeneration of skin in the uterus. This study describes two cases that may have underlying pathogenic cause that have not been previously reported. Two neonates who were admitted to the neonatal intensive care unit due to "skin lesions on the limbs" without other deformities or complications were diagnosed with type VII ACC by dermatologist. The mothers showed positivity for hepatitis B virus (HBV) surface antigen and elevated level of HBV DNA copies, which may be related to ACC. But this association could be a coincidence. Both neonates were treated with antibacterial dressings and achieved satisfactory healing.

Feto-placental Unit: From Development to Function

The placenta is an intriguing organ that allows us to survive intrauterine life. This essential organ connects both mother and fetus and plays a crucial role in maternal and fetal well-being. This chapter presents an overview of the morphological and functional aspects of human placental development. First, we describe early human placental development and the characterization of the cell types found in the human placenta. Second, the human placenta from the second trimester to the term of gestation is reviewed, focusing on the morphology and specific pathologies that affect the placenta. Finally, we focus on the placenta's primary functions, such as oxygen and nutrient transport, and their importance for placental development.

PREGNANT WOMEN WITH COVID-19 AND PLACENTA ANGIOGENESIS

OBJECTIVE

Aim of our research was to conduct a clinical and laboratory analysis of the impact of COVID-19 on pregnancy and the condition of the fetus.

PATIENTS AND METHODS

Materials and Methods: At the first stage, we conducted a retrospective examination of 50 pregnant women treated at Ternopil Municipal Hospital No.2 (Ukraine) between November 2020 and January 2022 with the history of COVID-19, confirmed by PCR test, and 25 pregnant COVID-19 negative pregnant women (control group). At the second stage, we performed prospective cohort study and involved 40 pregnant women treated with the history of COVID-19, confirmed by PCR, and 10 pregnant COVID-19 negative women with a physiological course of pregnancy as a control group.Women were divided into the following groups: group I -10 women diagnosed with COVID-19 during the first trimester of pregnancy: group II-15 women diagnosed during the second trimester; group III-15 women diagnosed during the third trimester. Ultrasound examination and cardiotocograms were performed to assess fetus status. Blood samples were collected at delivery. To determine whether COVID-19 could alter placental angiogenesis, vascular endothelial growth factor A (VEGFA), PlGF and interleuin-32-α were assessed.

RESULTS

Results: We identified that concentration of VEGFA was 95.30±5.65 pg/ml in control group. In women who had COVID-19 in first trimester, this index was 1.3 times higher, in second trimester 1.63 times higher and in third trimester by 2 times compared to control group. PlGF concentration was only 27,4 percent in group I, 16 percent in group II and 30 percent in group III,compared to control group. Concentration of interleuin-32-α was 67.27±5.63 pg/ml in control group and increased to 167 percent in group I, by 2.8 times in group II and by 6.3 times in group III compared to control group.

CONCLUSION

Conclusions: COVID-19 has a negative impact on placental angiogenesis, including VEGFA and PlGF. Fetal post-COVID-19 syndrome requires timely diagnosis of disorders and further study. Post-COVID-19 syndrome is an immune-dependent pathology in which the processes of protracted cytokine activation occur in the body of a pregnant woman.

COVID-19 and pregnancy: clinical outcomes; mechanisms, and vaccine efficacy

As the COVID-19 pandemic continues into its third year, emerging data indicates increased risks associated with SARS-CoV-2 infection during pregnancy, including pre-eclampsia, intrauterine growth restriction, preterm birth, stillbirth, and risk of developmental defects in neonates. Here, we review clinical reports to date that address different COVID-19 pregnancy complications. We also document placental pathologies induced by SARS-CoV-2 infection, entry mechanisms in placental cells, and immune responses at the maternal-fetal interface. Since new variants of SARS-CoV-2 are emerging with characteristics of higher transmissibility and more effective immune escape strategies, we also briefly highlight the genomic and proteomic features of SARS-CoV-2 investigated to date. Vector and mRNA-based COVID-19 vaccines continue to be rolled out globally. However, because pregnant individuals were not included in the vaccine clinical trials, some pregnant individuals have safety concerns and are hesitant to take these vaccines. We describe the recent studies that have addressed the effectiveness and safety of the current vaccines during pregnancy. This review also sheds light on important areas that need to be carefully or more fully considered with respect to understanding SARS-CoV-2 disease mechanisms of concern during pregnancy.

Monkeypox in pregnancy: virology, clinical presentation, and obstetric management

The 2022 monkeypox outbreak, caused by the zoonotic monkeypox virus, has spread across 6 World Health Organization regions (the Americas, Africa, Europe, Eastern Mediterranean, Western Pacific, and South-East Asia) and was declared a public health emergency of international concern on July 23, 2022. The global situation is especially concerning given the atypically high rate of person-to-person transmission, which suggests viral evolution to an established human pathogen. Pregnant women are at heightened risk of vertical transmission of the monkeypox virus because of immune vulnerability and natural depletion of population immunity to smallpox among reproductive-age women, and because orthopoxviral cell entry mechanisms can overcome the typically viral-resistant syncytiotrophoblast barrier within the placenta. Data on pregnancy outcomes following monkeypox infection are scarce but include reports of miscarriage, intrauterine demise, preterm birth, and congenital infection. This article forecasts the issues that maternity units might face and proposes guidelines to protect the health of pregnant women and fetuses exposed to the monkeypox virus. We review the pathophysiology and clinical features of monkeypox infection and discuss the obstetrical implications of the unusually high prevalence of anogenital lesions. We describe the use of real-time polymerase chain reaction tests from mucocutaneous and oropharyngeal sites to confirm infection, and share an algorithm for the antenatal management of pregnant women with monkeypox virus exposure. On the basis of the best available knowledge from prenatal orthopoxvirus infections, we discuss the sonographic features of congenital monkeypox and the role of invasive testing in establishing fetal infection. We suggest a protocol for cesarean delivery to avoid the horizontal transmission of the monkeypox virus at birth and address the controversy of mother-infant separation in the postpartum period. Obstetrical concerns related to antiviral therapy with tecovirimat and vaccinia immune globulin are highlighted, including the risks of heart rate-corrected QT-interval prolongation, inaccuracies in blood glucose monitoring, and the predisposition to iatrogenic venous thromboembolism. The possibility of monkeypox vaccine hesitancy during pregnancy is discussed, and strategies are offered to mitigate these risks. Finally, we conclude with a research proposal to address knowledge gaps related to the impact of monkeypox infection on maternal, fetal, and neonatal health.

Vertical Transmission of SARS-CoV-2 Infection and Miscarriage in the Second Trimester: Report of an Immunohistochemically Proven Case

It is an acknowledged fact that SARS-CoV-2 exhibits tropism for the human placenta. A possible mechanism of SARS-CoV-2 entry into host cells is via angiotensin-converting enzyme 2 (ACE2) receptors, which are expressed in trophoblasts, endothelial cells, and macrophages. The present study describes a case of spontaneous miscarriage in the 20th gestational week after maternal SARS-CoV-2 infection. The placenta and various fetal organs were examined for structural alterations and expression of the viral nucleocapsid protein and several immune cell markers via immunohistochemistry (IHC). Histopathological examination of the placenta revealed acute chorioamnionitis, acute subamnionic placentitis, multiple intervillous thrombi, increased fibrinoid deposition, and necrotic changes of the chorionic villi. Immunohistochemistry confirmed the presence of SARS-CoV-2 nucleocapsid protein regions predominantly in the syncytiotrophoblast. Staining of the placental tissue for different markers helped elucidate the distribution of immune cells. Pathomorphological examination of the fetal organs demonstrated changes in microcirculation with the presence of sludge phenomenon and diapedesis haemorrhages, mostly in the lungs, brain, and myocardium. IHC staining of fetal organs revealed expression of SARS-CoV-2 nucleocapsid protein, which was detected to the highest extent in the brain, lungs, and liver. The findings of the present report support the hypothesis of possible vertical transmission of SARS-CoV-2 from mother to fetus.

Coronavirus disease 2019 and the placenta: A literature review

Coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus has been implicated in the clinical pathology of multiple organs and organ systems. Due to the novelty of the disease, there is a need to review emerging literature to understand the profile of SARS-CoV-2 in the placenta. This review sought to evaluate the literature on the mediators, mechanism of entry, pathogenesis, detection, and pathology of SARS-CoV-2 in the placenta. Systematic literature searches found 96 eligible studies. Our review revealed that SARS-CoV-2 canonical mediators, angiotensin-converting enzyme-2 (ACE2), and transmembrane serine protease-2 (TMPRSS2) are variably expressed in various placenta compartments, including the villous cytotrophoblasts, syncytiotrophoblasts (STBs), and extravillous trophoblasts (EVTs) throughout pregnancy. Placental SARS-CoV-2 and coronavirus-associated receptors and factors (SCARFs), including basigin (BSG/CD147), dipeptidyl peptidase-4 (DPP4/CD26), cathepsin B/L (CTL B/L), furin, interferon-induced transmembrane protein (IFITM1-3), and lymphocyte antigen 6E (LY6E) may increase or reduce the permissiveness of the placenta to SARS-CoV-2. EVTs express genes that code for proteins that may drive viral pathogenesis in the placenta. Viral RNA, proteins, and particles were detected primarily in the STBs by in situ hybridization, immunohistochemistry, electron microscopy, and polymerase chain reaction. Placental pathology in SARS-CoV-2-infected placentas included maternal and fetal vascular malperfusion and a generally nonspecific inflammatory-immune response. The localization of SARS-CoV-2 receptors, proteases, and genes involved in coding proteins that drive viral pathogenesis in the placenta predisposes the placenta to SARS-CoV-2 infection variably in all pregnancy trimesters, with antecedent placental pathology. There is a need for further studies to explicate the mechanism of entry and pathogenesis of SARS-CoV-2 in the placenta.

Maternal HPV Infection and the Estimated Risks for Adverse Pregnancy Outcomes—A Systematic Review

Background: Human Papilloma Virus (HPV) represents the most prevalent genital infection in young women of reproductive age. Objective: This systematic review aims to estimate the effect of HPV infection during pregnancy and assess the correlation between HPV and adverse pregnancy outcomes. Materials and methods: The search strategy has been developed based on the PICOS framework: Population (pregnant women infected with HPV), Intervention (HPV infection confirmed by molecular tests), Comparator (pregnant women without HPV infection), Outcomes (adverse pregnancy outcomes) and Study design (observational studies). We searched PubMed, Web of Science, and Scopus databases on 8 January 2022 by using the following keywords: “HPV”, “prematurity”, “preterm birth”, “miscarriage”, “premature rupture of membranes”, “adverse pregnancy outcome”, “low birth weight”, “fetal growth restriction”, “pregnancy-induced hypertensive disorders”, “preeclampsia”. Selection criteria were HPV infection confirmed within maximum 2 years before pregnancy with a molecular test and adverse pregnancy outcomes. (Results: Although numerous studies are conducted on this topic, data are still controversial regarding identifying maternal HPV infection as a risk factor for adverse pregnancy outcomes. More prospective large cohort studies are needed to prove a causative relationship.

Zika virus vertical transmission in interferon receptor1-antagonized Rag1-/- mice results in postnatal brain abnormalities and clinical disease

The mechanisms by which vertically transmitted Zika virus (ZIKV) causes postnatal brain development abnormalities and congenital disease remain poorly understood. Here, we optimized the established anti-IFNAR1 treated, Rag1^-/- (AIR) mouse model of ZIKV infection to examine the consequence of vertical transmission on neonate survival and postnatal brain development. We found that modulating the infectious dose and the frequency of anti-IFNAR1 treatment of pregnant mice (termed AIR^low mice) prolonged neonatal survival allowing for pathogenesis studies of brain tissues at critical postnatal time points. Postnatal AIR^low mice all had chronic ZIKV infection in the brain that was associated with decreased cortical thickness and cerebellar volume, increased gliosis, and higher levels of cell death in many brain areas including cortex, hippocampus and cerebellum when compared to controls. Interestingly, despite active infection and brain abnormalities, the neurodevelopmental program remained active in AIR^low mice as indicated by elevated mRNA expression of critical neurodevelopmental genes in the brain and enlargement of neural-progenitor rich regions of the cerebellum at a developmental time point analogous to birth in humans. Nevertheless, around the developmental time point when the brain is fully populated by neurons, AIR^low mice developed neurologic disease associated with persistent ZIKV infection in the brain, gliosis, and increased cell death. Together, these data show that vertically transmitted ZIKV infection in the brain of postnatal AIR^low mice strongly influences brain development resulting in structural abnormalities and cell death in multiple regions of the brain.

Potential role of viral infections in miscarriage and insights into the underlying molecular mechanisms

Intrauterine viruses can infect the decidua and placenta and cause adverse effects on the fetus during gestation. This review discusses the contribution of various viral infections to miscarriage and the molecular mechanisms by which viruses can cause devastating effects on healthy fetuses and induce miscarriage. Severe acute respiratory syndrome coronavirus 2 as newly emerged coronavirus was considered here, due to the concerns about its role during pregnancy and inducing miscarriage, as well. In this narrative review, an extensive literature search was conducted to find all studies investigating viral infections in miscarriage and their molecular mechanisms published over the past 20 years. The results of various studies investigating the roles of 20 viral infections in miscarriage are presented. Then, the mechanisms of pregnancy loss in viral infections were addressed, including alteration of trophoblast invasion and placental dysfunction, inducing excessive maternal immune response, and inducing apoptosis in the placental tissue. Viruses may cause pregnancy loss through different mechanisms and our knowledge about these mechanisms can be helpful for controlling or preventing viral infections and achieving a successful pregnancy.

OUP accepted manuscript

STUDY QUESTION

Does maternal infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the first trimester affect the risk of miscarriage before 13 week’s gestation?

SUMMARY ANSWER

Pregnant women with self-reported diagnosis of SARS-CoV-2 in the first trimester had a higher risk of early miscarriage.

WHAT IS KNOWN ALREADY

Viral infections during pregnancy have a broad spectrum of placental and neonatal pathology. Data on the effects of the SARS-CoV-2 infection in pregnancy are still emerging. Two systematic reviews and meta-analyses reported an increased risk of preterm birth, caesarean delivery, maternal morbidity and stillbirth. Data on the impact of first trimester infection on early pregnancy outcomes are scarce. This is the first study, to our knowledge, to investigate the rates of early pregnancy loss during the SARS-CoV-2 outbreak among women with self-reported infection.

STUDY DESIGN, SIZE, DURATION

This was a nationwide prospective cohort study of pregnant women in the community recruited using social media between 21 May and 31 December 2020. We recruited 3545 women who conceived during the SARS-CoV-2 pandemic who were <13 week’s gestation at the time of recruitment.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The COVID-19 Contraception and Pregnancy Study (CAP-COVID) was an on-line survey study collecting longitudinal data from pregnant women in the UK aged 18 years or older. Women who were pregnant during the pandemic were asked to complete on-line surveys at the end of each trimester. We collected data on current and past pregnancy complications, their medical history and whether they or anyone in their household had symptoms or been diagnosed with SARS-CoV-2 infection during each trimester of their pregnancy. RT-PCR-based SARS-CoV-2 RNA detection from respiratory samples (e.g. nasopharynx) is the standard practice for diagnosis of SARS-CoV-2 in the UK. We compared rate of self-reported miscarriage in three groups: ‘presumed infected’, i.e. those who reported a diagnosis with SARS-CoV-2 infection in the first trimester; ‘uncertain’, i.e. those who did not report a diagnosis but had symptoms/household contacts with symptoms/diagnosis; and ‘presumed uninfected’, i.e. those who did not report any symptoms/diagnosis and had no household contacts with symptoms/diagnosis of SARS-CoV-2.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 3545 women registered for the CAP-COVID study at <13 weeks gestation and were eligible for this analysis. Data for the primary outcome were available from 3041 women (86%). In the overall sample, the rate of self-reported miscarriage was 7.8% (238/3041 [95% CI, 7–9]). The median gestational age (GA) at miscarriage was 9 weeks (interquartile range 8–11). Seventy-seven women were in the ‘presumed infected’ group (77/3041, 2.5% [95% CI 2–3]), 295/3041 were in the uncertain group (9.7% [95% CI 9–11]) and the rest in the ‘presumed uninfected’ (87.8%, 2669/3041 [95% CI 87–89]). The rate of early miscarriage was 14% in the ‘presumed infected’ group, 5% in the ‘uncertain’ and 8% in the ‘presumed uninfected’ (11/77 [95% CI 6–22] versus 15/295 [95% CI 3–8] versus 212/2669 [95% CI 7–9], P = 0.02). After adjusting for age, BMI, ethnicity, smoking status, GA at registration and the number of previous miscarriages, the risk of early miscarriage appears to be higher in the ‘presumed infected’ group (relative rate 1.7, 95% CI 1.0–3.0, P = 0.06).

LIMITATIONS, REASONS FOR CAUTION

We relied on self-reported data on early pregnancy loss and SARS-CoV-2 infection without any means of checking validity. Some women in the ‘presumed uninfected’ and ‘uncertain’ groups may have had asymptomatic infections. The number of ‘presumed infected’ in our study was low and therefore the study was relatively underpowered.

WIDER IMPLICATIONS OF THE FINDINGS

This was a national study from the UK, where infection rates were one of the highest in the world. Based on the evidence presented here, women who are infected with SARS-CoV-2 in their first trimester may be at an increased risk of a miscarriage. However, the overall rate of miscarriage in our study population was 8%. This is reassuring and suggests that if there is an effect of SARS-CoV-2 on the risk of miscarriage, this may be limited to those with symptoms substantial enough to lead to a diagnostic test. Further studies are warranted to evaluate a causal association between SARS-CoV-2 infection in early pregnancy and miscarriage risk. Although we did not see an overall increase in the risk of miscarriage, the observed comparative increase in the presumed infected group reinforces the message that pregnant women should continue to exercise social distancing measures and good hygiene throughout their pregnancy to limit their risk of infection

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by a grant from the Elizabeth Garrett Anderson Hospital Charity (G13-559194). The funders of the study had no role in study design, data collection, data analysis, data interpretation or writing of the report. J.A.H. is supported by an NIHR Advanced Fellowship. A.L.D. is supported by the National Institute for Health Research University College London Hospitals Biomedical Research Centre. All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf and declare: support to J.A.H. and A.L.D. as above; no financial relationships with any organizations that might have an interest in the submitted work in the previous 3 years; no other relationships or activities that could appear to have influenced the submitted work.

TRIAL REGISTRATION NUMBER

N/A.

Human papillomavirus (HPV) in pregnancy - An update

Human papilloma viruses (HPV) are small epitheliotropic DNA viruses, of which there are 200 genotypes, 40 of which are known to cause genital infections and are also oncogenic. HPV is the most common sexually transmitted infection. Clinical features vary from asymptomatic (identified at routine cervical cancer screening) to large lesions on the vulva, vagina, cervix and some extragenital sites. Its prevalence in pregnancy varies from 5.5% to 65% depending on age, geography and gestational age (increasing with gestational age). Infection in pregnancy has been associated with adverse outcomes such as spontaneous miscarriage, preterm birth, placental abnormalities and fetal growth restriction. However, the evidence for these adverse outcomes is varied. Besides being oncogenic (and thus associated with cancer of the cervix in pregnancy), vertical transmission to the fetus/neonate can cause neonatal infections, especially juvenile-onset recurrent oral and respiratory papillomatosis (JORRP). Where there are very large lesions on the vulva, delivery may be obstructed. Diagnosis in pregnancy is mainly by viral PCR or from the clinical appearance of the characteristic lesions on the vulva. Treatment is local by either surgical or laser excision or application of trichloroacetic acid. Podophyllin/podophyllotoxin is contraindicated in pregnancy. HPV Infection is not an indication for caesarean delivery as this has not been shown to prevent vertical transmission. For those diagnosed at routine cervical cancer screening, management should follow guidelines for cervical cancer screening in pregnancy. Vaccination is currently not recommended for pregnant women, although studies on those inadvertently vaccinated in pregnancy have not shown any adverse effects on either the fetus or mother.

[Impact of SARS-CoV-2/COVID-19 on the placenta]

Ein besonderes Augenmerk bei der durch das Severe-acute-respiratory-syndrome-Coronavirus‑2 (SARS-CoV-2) hervorgerufenen Coronaviruskrankheit 2019 (COVID-19) wurde von Beginn an auf die Gruppe der Schwangeren gelegt.

Nach einer Einführung zur Immunabwehr der Plazenta und viralen plazentaren Infektionen, beschreiben wir die morphologischen Veränderungen der Plazenta bei SARS-CoV-2-Infektion der Mutter, ziehen Vergleiche zur SARS-Epidemie und diskutieren die Frage der vertikalen Transmission von SARS-CoV‑2 von der Mutter auf das Neugeborene.

Die häufigsten pathologischen Befunde der Plazenta bestehen in Zeichen der maternalen und auch fetalen Malperfusion sowie immunologisch bzw. thromboinflammatorisch vermittelten Veränderungen. Es finden sich Infarkte, deziduale Vaskulopathie sowie Thromben im fetalen Kreislauf und Vermehrung avaskulärer Villi. Daneben zeigen sich in einigen Fällen Entzündungsreaktionen mit Villitis und Intervillositis sowie eine Vaskulitis fetaler Gefäße. Zudem konnte der Nachweis erbracht werden, dass SARS-CoV‑2 die Plazenta direkt infizieren kann. Somit ist auch eine vertikale Transmission möglich.

Ein COVID-19-spezifisches Schädigungsmuster der Plazenta liegt bislang nicht vor, obwohl der Nachweis von fetaler Thrombovaskulitis, Villitis und Intervillositis sowie einer fetalen und maternalen Malperfusion in Analogie zu der bereits bekannten allgemeinen Pathophysiologie von COVID-19 (Entzündungsreaktion und Mikrozirkulationsstörung) interpretiert werden könnte. Der Nachweis viraler RNA in den fetalen Kompartimenten der Plazenta/der Nabelschnur zeugt von der vertikalen SARS-CoV‑2 Transmission.

Cytomegalovirus Infection and Inflammation in Developing Brain

Human cytomegalovirus (HCMV) is a highly prevalent herpesvirus that can cause severe disease in immunocompromised individuals and immunologically immature fetuses and newborns. Most infected newborns are able to resolve the infection without developing sequelae. However, in severe cases, congenital HCMV infection can result in life-threatening pathologies and permanent damage of organ systems that possess a low regenerative capacity. Despite the severity of the problem, HCMV infection of the central nervous system (CNS) remains inadequately characterized to date. Cytomegaloviruses (CMVs) show strict species specificity, limiting the use of HCMV in experimental animals. Infection following intraperitoneal administration of mouse cytomegalovirus (MCMV) into newborn mice efficiently recapitulates many aspects of congenital HCMV infection in CNS. Upon entering the CNS, CMV targets all resident brain cells, consequently leading to the development of widespread histopathology and inflammation. Effector functions from both resident cells and infiltrating immune cells efficiently resolve acute MCMV infection in the CNS. However, host-mediated inflammatory factors can also mediate the development of immunopathologies during CMV infection of the brain. Here, we provide an overview of the cytomegalovirus infection in the brain, local immune response to infection, and mechanisms leading to CNS sequelae.

The Immunological Role of the Placenta in SARS-CoV-2 Infection-Viral Transmission, Immune Regulation, and Lactoferrin Activity

A pandemic of acute respiratory infections, due to a new type of coronavirus, can cause Severe Acute Respiratory Syndrome 2 (SARS-CoV-2) and has created the need for a better understanding of the clinical, epidemiological, and pathological features of COVID-19, especially in high-risk groups, such as pregnant women. Viral infections in pregnant women may have a much more severe course, and result in an increase in the rate of complications, including spontaneous abortion, stillbirth, and premature birth-which may cause long-term consequences in the offspring. In this review, we focus on the mother-fetal-placenta interface and its role in the potential transmission of SARS-CoV-2, including expression of viral receptors and proteases, placental pathology, and the presence of the virus in neonatal tissues and fluids. This review summarizes the current knowledge on the anti-viral activity of lactoferrin during viral infection in pregnant women, analyzes its role in the pathogenicity of pandemic virus particles, and describes the potential evidence for placental blocking/limiting of the transmission of the virus.

Central role of the placenta during viral infection: Immuno-competences and miRNA defensive responses

Pregnancy is a unique immunological condition in which an "immune-diplomatic" dialogue between trophoblasts and maternal immune cells is established to protect the fetus from rejection, to create a privileged environment in the uterus and to simultaneously be alert to any infectious challenge. The maternal-placental-fetal interface (MPFI) performs an essential role in this immunological defense. In this review, we will address the MPFI as an active immuno-mechanical barrier that protects against viral infections. We will describe the main viral infections affecting the placenta and trophoblasts and present their structure, mechanisms of immunocompetence and defensive responses to viral infections in pregnancy. In particular, we will analyze infection routes in the placenta and trophoblasts and the maternal-fetal outcomes in both. Finally, we will focus on the cellular targets of the antiviral microRNAs from the C19MC cluster, and their effects at both the intra- and extracellular level.

Fetal and placental infection with SARS-CoV-2 in early pregnancy

To date, mother‐to‐fetus transmission of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), responsible for the coronavirus disease 2019 (COVID‐19) pandemic, remains controversial. Although placental COVID‐19 infection has been documented in some cases during the second‐ and third‐trimesters, no reports are available for the first trimester of pregnancy, and no SARS‐CoV‐2 protein has been found in fetal tissues. We studied the placenta and fetal organs from an early pregnancy miscarriage in a COVID‐19 maternal infection by immunohistochemical, reverse transcription quantitative real‐time polymerase chain reaction, immunofluorescence, and electron microscopy methods. SARS‐CoV‐2 nucleocapsid protein, viral RNA, and particles consistent with coronavirus were found in the placenta and fetal tissues, accompanied by RNA replication revealed by double‐stranded RNA (dsRNA) positive immunostain. Prominent damage of the placenta and fetal organs were associated with a hyperinflammatory process identified by histological examination and immunohistochemistry. The findings provided in this study document that congenital SARS‐CoV‐2 infection is possible during the first trimester of pregnancy and that fetal organs, such as lung and kidney, are targets for coronavirus. The infection and multi‐organic fetal inflammation produced by SARS‐CoV‐2 during early pregnancy should alert clinicians in the assessment and management of pregnant women for possible fetal consequences and adverse perinatal outcomes.

Placental Immune Responses to Viruses: Molecular and Histo-Pathologic Perspectives

As most recently demonstrated by the SARS-CoV-2 pandemic, congenital and perinatal infections are of significant concern to the pregnant population as compared to the general population. These outcomes can range from no apparent impact all the way to spontaneous abortion or fetal infection with long term developmental consequences. While some pathogens have developed mechanisms to cross the placenta and directly infect the fetus, other pathogens lead to an upregulation in maternal or placental inflammation that can indirectly cause harm. The placenta is a temporary, yet critical organ that serves multiple important functions during gestation including facilitation of fetal nutrition, oxygenation, and prevention of fetal infection in utero. Here, we review trophoblast cell immunology and the molecular mechanisms utilized to protect the fetus from infection. Lastly, we discuss consequences in the placenta when these protections fail and the histopathologic result following infection.

Respiratory viral infections during pregnancy: effects of SARS-CoV-2 and other related viruses over the offspring

Little is known about the consequences of viral infection for pregnant woman or for the fetus. This issue became important with the appearance of the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2). The infection with SARS-CoV-2 causes a respiratory syndrome known as COVID-19. The fast spreading around the world and the fact that without a treatment or vaccine humans are completely exposed, converts emerging viral diseases in a significant risk for pregnant women and their infants. At this time, during SARS-CoV-2 pandemics pregnant women are not considered as a risk population and little is known about the effects of viral infections over the offspring although the amount of emerging evidence showing detrimental effects for the mother and the fetus. This issue highlights the importance to understand the effects of viral infections during pregnancy. In this work, we analyze the effects of viral infections, like SARS-CoV-2 and other related viruses during pregnancy over the mother and the consequences for the offspring.

Critical Role of the Maternal Immune System in the Pathogenesis of Autism Spectrum Disorder

Autism spectrum disorders (ASD) are a group of neurodevelopmental disorders characterised by impairments in communication, social interaction, and the presence of restrictive and repetitive behaviours. Over the past decade, most of the research in ASD has focused on the contribution of genetics, with the identification of a variety of different genes and mutations. However, the vast heterogeneity in clinical presentations associated with this disorder suggests that environmental factors may be involved, acting as a “second hit” in already genetically susceptible individuals. To this regard, emerging evidence points towards a role for maternal immune system dysfunctions. This literature review considered evidence from epidemiological studies and aimed to discuss the pathological relevance of the maternal immune system in ASD by looking at the proposed mechanisms by which it alters the prenatal environment. In particular, this review focuses on the effects of maternal immune activation (MIA) by looking at foetal brain-reactive antibodies, cytokines and the microbiome. Despite the arguments presented here that strongly implicate MIA in the pathophysiology of ASD, further research is needed to fully understand the precise mechanisms by which they alter brain structure and behaviour. Overall, this review has not only shown the importance of the maternal immune system as a risk factor for ASD, but more importantly, has highlighted new promising pathways to target for the discovery of novel therapeutic interventions for the treatment of such a life-changing disorder.

Placental Pathology of COVID-19 with and without Fetal and Neonatal Infection: Trophoblast Necrosis and Chronic Histiocytic Intervillositis as Risk Factors for Transplacental Transmission of SARS-CoV-2

The mechanism(s) by which neonates testing positive for coronavirus disease 2019 (COVID-19) acquire their infection has been largely unknown. Transmission of the etiological agent, SARS-CoV-2, from mother to infant has been suspected but has been difficult to confirm. This communication summarizes the spectrum of pathology findings from pregnant women with COVID-19 based upon the infection status of their infants and addresses the potential interpretation of these results in terms of the effects of SARS-CoV-2 on the placenta and the pathophysiology of maternal-fetal infection. Placentas from pregnant women with COVID-19 and uninfected neonates show significant variability in the spectrum of pathology findings. In contrast, placentas from infected maternal-neonatal dyads are characterized by the finding of mononuclear cell inflammation of the intervillous space, termed chronic histiocytic intervillositis, together with syncytiotrophoblast necrosis. These placentas show prominent positivity of syncytiotrophoblast by SARS-CoV-2, fulfilling the published criteria for transplacental viral transmission as confirmed in fetal cells through identification of viral antigens by immunohistochemistry or viral nucleic acid using RNA in situ hybridization. The co-occurrence of chronic histiocytic intervillositis and trophoblast necrosis appears to be a risk factor for placental infection with SARS-CoV-2 as well as for maternal-fetal viral transmission, and suggests a potential mechanism by which the coronavirus can breach the maternal-fetal interface.

Placental barrier against COVID-19

Vertical transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and possible induction of pregnancy complications, including miscarriage, fetal malformations, fetal growth restriction and/or stillbirth, are serious concerns for pregnant individuals with COVID-19. According to clinical information, the incidence of vertical transmission of SARS-CoV-2 is limited to date. However, even if a neonate tests negative for SARS-CoV-2, frequent abnormal findings, including fetal and maternal vascular malperfusion, have been reported in cases of COVID-19-positive mothers. Primary receptor of SARS-CoV-2 is estimated as angiotensin-converting enzyme 2 (ACE2). It is highly expressed in maternal-fetal interface cells, such as syncytiotrophoblasts, cytotrophoblasts, endothelial cells, and the vascular smooth muscle cells of primary and secondary villi. However other route of transplacental infection cannot be ruled out. Pathological examinations have demonstrated that syncytiotrophoblasts are often infected with SARS-CoV-2, but fetuses are not always infected. These findings suggest the presence of a placental barrier, even if it is not completely effective. As the frequency and molecular mechanisms of intrauterine vertical transmission of SARS-CoV-2 have not been determined to date, intensive clinical examinations by repeated ultrasound and fetal heart rate monitoring are strongly recommended for pregnant women infected with COVID-19. In addition, careful investigation of placental samples after delivery by both morphological and molecular methods is also strongly recommended.

COVID-19 in pregnancy: Placental and neonatal involvement

Since December 2019, severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) has caused over 12 million infections and more than 550 000 deaths.¹ Morbidity and mortality appear partly due to host inflammatory response.² Despite rapid, global research, the effect of SARS‐CoV‐2 on the developing fetus remains unclear. Case reports indicate that vertical transmission is uncommon; however, there is evidence that placental and fetal infection can occur.^3‐7 Placentas from infected patients show inflammatory, thrombotic, and vascular changes that have been found in other inflammatory conditions.^8,9 This suggests that the inflammatory nature of SARS‐CoV‐2 infection during pregnancy could cause adverse obstetric and neonatal events. Exposure to intrauterine inflammation and placental changes could also potentially result in long‐term, multisystemic defects in exposed infants. This review will summarize the known literature on the placenta in SARS‐CoV‐2 infection, evidence of vertical transmission, and possible outcomes of prenatal exposure to the virus.

Lights and Shadows of TORCH Infection Proteomics

Congenital abnormalities cause serious fetal consequences. The term TORCH is used to designate the most common perinatal infections, where: (T) refers to toxoplasmosis, (O) means "others" and includes syphilis, varicella-zoster, parvovirus B19, zika virus (ZIKV), and malaria among others, (R) refers to rubella, (C) relates to cytomegalovirus infection, and (H) to herpes simplex virus infections. Among the main abnormalities identified in neonates exposed to congenital infections are central nervous system (CNS) damage, microcephaly, hearing loss, and ophthalmological impairment, all requiring regular follow-up to monitor its progression. Protein changes such as mutations, post-translational modifications, abundance, structure, and function may indicate a pathological condition before the onset of the first symptoms, allowing early diagnosis and understanding of a particular disease or infection. The term "proteomics" is defined as the science that studies the proteome, which consists of the total protein content of a cell, tissue or organism in a given space and time, including post-translational modifications (PTMs) and interactions between proteins. Currently, quantitative bottom-up proteomic strategies allow rapid and high throughput characterization of complex biological mixtures. Investigating proteome modulation during host-pathogen interaction helps in elucidating the mechanisms of infection and in predicting disease progression. This "molecular battle" between host and pathogen is a key to identify drug targets and diagnostic markers. Here, we conducted a survey on proteomic techniques applied to congenital diseases classified in the terminology "TORCH", including toxoplasmosis, ZIKV, malaria, syphilis, human immunodeficiency virus (HIV), herpes simplex virus (HSV) and human cytomegalovirus (HCVM). We have highlighted proteins and/or protein complexes actively involved in the infection. Most of the proteomic studies reported have been performed in cell line models, and the evaluation of tissues (brain, muscle, and placenta) and biofluids (plasma, serum and urine) in animal models is still underexplored. Moreover, there are a plethora of studies focusing on the pathogen or the host without considering the triad mother-fetus-pathogen as a dynamic and interconnected system.

A Message from the Human Placenta: Structural and Immunomodulatory Defense against SARS-CoV-2

The outbreak of the coronavirus disease 2019 (COVID-19) pandemic has caused a global public health crisis. Viral infections may predispose pregnant women to a higher rate of pregnancy complications, including preterm births, miscarriage, and stillbirth. Despite reports of neonatal COVID-19, definitive proof of vertical transmission is still lacking. In this review, we summarize studies regarding the potential evidence for transplacental transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), characterize the expression of its receptors and proteases, describe the placental pathology and analyze virus-host interactions at the maternal-fetal interface. We focus on the syncytium, the barrier between mother and fetus, and describe in detail its physical and structural defense against viral infections. We further discuss the potential molecular mechanisms, whereby the placenta serves as a defense front against pathogens by regulating the interferon type III signaling, microRNA-triggered autophagy and the nuclear factor-κB pathway. Based on these data, we conclude that vertical transmission may occur but rare, ascribed to the potent physical barrier, the fine-regulated placental immune defense and modulation strategies. Particularly, immunomodulatory mechanisms employed by the placenta may mitigate violent immune response, maybe soften cytokine storm tightly associated with severely ill COVID-19 patients, possibly minimizing cell and tissue damages, and potentially reducing SARS-CoV-2 transmission.

Placental Myeloid Cells Protect against Zika Virus Vertical Transmission in a Rag1-Deficient Mouse Model

The ability of Zika virus (ZIKV) to cross the placenta and infect the fetus is a key mechanism by which ZIKV causes microcephaly. How the virus crosses the placenta and the role of the immune response in this process remain unclear. In the current study, we examined how ZIKV infection affected innate immune cells within the placenta and fetus and whether these cells influenced virus vertical transmission (VTx). We found myeloid cells were elevated in the placenta of pregnant ZIKV-infected Rag1-/- mice treated with an anti-IFNAR Ab, primarily at the end of pregnancy as well as transiently in the fetus several days before birth. These cells, which included maternal monocyte/macrophages, neutrophils, and fetal myeloid cells contained viral RNA and infectious virus, suggesting they may be infected and contributing to viral replication and VTx. However, depletion of monocyte/macrophage myeloid cells from the dam during ZIKV infection resulted in increased ZIKV infection in the fetus. Myeloid cells in the fetus were not depleted in this experiment, likely because of an inability of liposome particles containing the cytotoxic drug to cross the placenta. Thus, the increased virus infection in the fetus was not the result of an impaired fetal myeloid response or breakdown of the placental barrier. Collectively, these data suggest that monocyte/macrophage myeloid cells in the placenta play a significant role in inhibiting ZIKV VTx to the fetus, possibly through phagocytosis of virus or virus-infected cells.

Cytoplasmic m1A reader YTHDF3 inhibits trophoblast invasion by downregulation of m1A-methylated IGF1R

N1-methyladenosine (m1A) is one of the important post-transcriptional modifications in RNA and plays an important role in promoting translation or decay of m1A-methylated messenger RNA (mRNA), but the "reader" protein and the exact biological role of m1A remain to be determined. Here, we identified that nine potential m1A "reader" proteins including YTH domain family and heterogeneous nuclear ribonucleoprotein by mass spectrometry, and among them, YTH domain-containing protein 3 (YTHDF3), could bind directly to m1A-carrying RNA. YTHDF3 was then identified to negatively regulate invasion and migration of trophoblast. Mechanistically, we found that the m1A "reader" YTHDF3 bound to certain m1A-methylated transcripts, such as insulin-like growth factor 1 receptor (IGF1R), with the combination of iCLIP-seq (individual-nucleotide resolution ultraviolet crosslinking and immunoprecipitation high-throughput sequencing) and m1A-seq. Furthermore, YTHDF3 could promote IGF1R mRNA degradation and thus inhibit IGF1R protein expression along with its downstream matrix metallopeptidase 9 signaling pathway, consequently decreasing migration and invasion of trophoblast. Thus, we demonstrated that YTHDF3 as an m1A reader decreased invasion and migration of trophoblast by inhibiting IGF1R expression. Our study outlines a new m1A epigenetic way to regulate the trophoblast activity, which suggests a novel therapeutic target for trophoblast-associated pregnancy disorders.

Recent Updates on Research Models and Tools to Study Virus-Host Interactions at the Placenta

The placenta is a unique mixed organ, composed of both maternal and fetal tissues, that is formed only during pregnancy and serves as the key physiological and immunological barrier preventing maternal-fetal transmission of pathogens. Several viruses can circumvent this physical barrier and enter the fetal compartment, resulting in miscarriage, preterm birth, and birth defects, including microcephaly. The mechanisms underlying viral strategies to evade the protective role of placenta are poorly understood. Here, we reviewed the role of trophoblasts and Hofbauer cells in the placenta and have highlighted characteristics of vertical and perinatal infections caused by a wide range of viruses. Moreover, we explored current progress and future opportunities in cellular targets, pathogenesis, and underlying biological mechanisms of congenital viral infections, as well as novel research models and tools to study the placenta.

The Dual Role of the Immune Response in Reproductive Organs During Zika Virus Infection

Zika virus is a mosquito-borne viral disease that emerged as a significant health problem in the Americas after an epidemic in 2015. Especially concerning are cases where Zika is linked to the development of brain abnormalities in newborns. Unlike other flaviviruses, Zika can be transmitted sexually, increasing the potential for intraspecies infection. Several reports show that the virus can persist for months in the testis of males after clearance of viremia, and that females are highly susceptible to infection via sexual transmission. The most common route of sexual transmission is male-to-female, which suggests that the mechanism driving persistence of Zika in the testis is essential for dissemination. The immune system plays an essential role in Zika infection. In females, a robust response inhibits the virus to control the infection. In males, however, the immunological response to Zika infection correlates with viral persistence. Thus, the immune system may have a dual role in sexually transmitted pathogenesis. The mechanism by which the immune system allows the virus to enter an immune-privileged site while continuing to disseminate is unclear. In this mini-review, we highlight advances in our knowledge of sexually transmitted Zika virus pathogenesis and the possible mechanisms mounted by the immune system that control or exacerbate the infection.

A Stillborn Multiple Organs' Investigation from a Maternal DENV-4 Infection: Histopathological and Inflammatory Mediators Characterization

Dengue virus (DENV) is an emerging virus involved in outbreaks in Brazil. The association between the virus and vertical transmission, with disorders in the placenta, has raised a worldwide concern. On the 29th gestational week, a pregnant woman presented severe complications due to a DENV infection leading to maternal and fetus death. Postmortem analysis of fetal organs demonstrated the presence of DENV using reverse transcriptase polymerase chain reaction (RT-PCR) in the fetal brain and DENV non-structural protein 3 (NS3) staining in placenta and several peripheral fetal tissues, such as the brain, liver, lungs, and spleen. Histological analysis of the placenta and fetal organs revealed different types of tissue abnormalities, which included inflammation, hemorrhage, edema, and necrosis in placenta and tissue disorganization in the fetus, such as spongiform parenchyma, microglial inflammation, steatosis, hyalinose arteriolar, inflammatory cells in the alveolar septa, and disorganization of the lymphoid follicle. Increased cellularity (macrophage, Hofbauer cells and TCD8+ lymphocytes) and up-regulation of inflammatory mediators such as IFN-γ, TNF-α, RANTES/CCL5, MCP1/CCL2, and VEGF/R2 were detected in the liver, lung, spleen, brain, and placenta, supporting placental and fetus peripheral tissues inflammation. Maternal infection leading to the production of those vascular mediators may alter the vascular permeability, facilitating the virus entry and tissue and barrier dysfunction.

The BeWo cell line derived from a human placental choriocarcinoma is permissive for respiratory syncytial virus infection

The respiratory syncytial virus (RSV) is the main pathogen associated with upper respiratory tract infections during early childhood. Vertical transmission of this virus has been suggested in humans, based on observations recorded during animal studies that revealed an association of RSV with persistent structural and functional changes in the developing lungs of the offspring. However, human placentas have not yet been evaluated for susceptibility to RSV infection. In this study, we examined the capacity of RSV to infect a human trophoblast model, the BeWo cell line. Our results suggest that BeWo cells are susceptible to RSV infection since they allow RNA viral replication, viral protein translation, leading to the production of infectious RSV particles. In this report, we demonstrate that a human placenta model system, consisting of BeWo cells, is permissive to RSV infection. Thus, the BeWo cell line may represent a useful model for studies that aim to characterize the events of a possible RSV infection at the human maternal-fetal interface.

Cross-Reactivity of Virus-Specific CD8+ T Cells Against Allogeneic HLA-C: Possible Implications for Pregnancy Outcome

Heterologous immunity of virus-specific T cells poses a potential barrier to transplantation tolerance. Cross-reactivity to HLA-A and -B molecules has broadly been described, whereas responses to allo-HLA-C have remained ill defined. In contrast to the transplant setting, HLA-C is the only polymorphic HLA molecule expressed by extravillous trophoblasts at the maternal-fetal interface during pregnancy. Uncontrolled placental viral infections, accompanied by a pro-inflammatory milieu, can alter the activation status and stability of effector T cells. Potential cross-reactivity of maternal decidual virus-specific T cells to fetal allo-HLA-C may thereby have detrimental consequences for the success of pregnancy. To explore the presence of cross-reactivity to HLA-C and the other non-classical HLA antigens expressed by trophoblasts, HLA-A and -B-restricted CD8+ T cells specific for Epstein-Barr virus, Cytomegalovirus, Varicella-Zoster virus, and Influenza virus were tested against target cells expressing HLA-C, -E, and -G molecules. An HLA-B^*08:01-restricted EBV-specific T cell clone displayed cross-reactivity against HLA-C^*01:02. Furthermore, cross-reactivity of HLA-C-restricted virus-specific CD8+ T cells was observed for HCMV HLA-C^*06:02/TRA CD8+ T cell lines and clones against HLA-C^*03:02. Collectively, these results demonstrate that cross-reactivity against HLA-C can occur and thereby may affect pregnancy outcome.