Differential expression of the coxsackievirus and adenovirus receptor regulates adenovirus infection of the placenta

Gestational Viral Infections: Role of Host Immune System

Viral infections in pregnancy are major causes of maternal and fetal morbidity and mortality. Infections can develop in the neonate transplacentally, perinatally, or postnatally (from breast milk or other sources) and lead to different clinical manifestations, depending on the viral agent and the gestational age at exposure. Viewing the peculiar tolerogenic status which characterizes pregnancy, viruses could exploit this peculiar immunological status to spread or affect the maternal immune system, adopting several evasion strategies. In fact, both DNA and RNA virus might have a deep impact on both innate and acquired immune systems. For this reason, investigating the interaction with these pathogens and the host's immune system during pregnancy is crucial not only for the development of most effective therapies and diagnosis but mostly for prevention. In this review, we will analyze some of the most important DNA and RNA viruses related to gestational infections.

Adenoviral Infections in Neonates: A Case-Based Literature Review

Adenoviral infections in neonates are associated with high rates of mortality due to the lack of humoral immunity. A comprehensive search of published literature in PubMed, Google Scholar, and Science Direct electronic databases was conducted for case reports published between the years 1990 and 2021. The aim of our study is to investigate the risk factors, clinical manifestations, treatment, and outcomes of adenoviral infections in neonates. In our study, 36 cases were included. The most common type of infection was disseminated one (14/36, 38.8%), followed by adenoviral pneumonia (13/36, 36.1%). Cidofovir was administered in seven cases (19.4%), and death was reported in six of them. One preterm low birthweight neonate with disseminated adenoviral infection was treated with a combination of cidofovir, intravenous immune globulin, and haploidentical virus-specific T lymphocytes (VSTs) and survived. In this review, we found a statistically significant difference in the outcome based on the type of adenoviral infection (p=0.001). Disseminated infection and pneumonia are associated with the worst prognosis. In addition, mortality was observed to be higher in neonates with disseminated disease in contrast to neonates with localized infection (p=0.002). However, the antiviral treatment had no statistically significant effect on the mortality rate (p=0.137). There is a necessity for further investigation and randomized studies to validate the results of the present study.

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.

The Immunology of Syncytialized Trophoblast

Multinucleate syncytialized trophoblast is found in three forms in the human placenta. In the earliest stages of pregnancy, it is seen at the invasive leading edge of the implanting embryo and has been called primitive trophoblast. In later pregnancy, it is represented by the immense, multinucleated layer covering the surface of placental villi and by the trophoblast giant cells found deep within the uterine decidua and myometrium. These syncytia interact with local and/or systemic maternal immune effector cells in a fine balance that allows for invasion and persistence of allogeneic cells in a mother who must retain immunocompetence for 40 weeks of pregnancy. Maternal immune interactions with syncytialized trophoblast require tightly regulated mechanisms that may differ depending on the location of fetal cells and their invasiveness, the nature of the surrounding immune effector cells and the gestational age of the pregnancy. Some specifically reflect the unique mechanisms involved in trophoblast cell–cell fusion (aka syncytialization). Here we will review and summarize several of the mechanisms that support healthy maternal–fetal immune interactions specifically at syncytiotrophoblast interfaces.

Coxsackievirus B3 Infection Early in Pregnancy Induces Congenital Heart Defects Through Suppression of Fetal Cardiomyocyte Proliferation

Background Coxsackievirus B (CVB) is the most common cause of viral myocarditis. It targets cardiomyocytes through coxsackie and adenovirus receptor, which is highly expressed in the fetal heart. We hypothesized CVB3 can precipitate congenital heart defects when fetal infection occurs during critical window of gestation. Methods and Results We infected C57Bl/6 pregnant mice with CVB3 during time points in early gestation (embryonic day [E] 5, E7, E9, and E11). We used different viral titers to examine possible dose-response relationship and assessed viral loads in various fetal organs. Provided viral exposure occurred between E7 and E9, we observed characteristic features of ventricular septal defect (33.6%), abnormal myocardial architecture resembling noncompaction (23.5%), and double-outlet right ventricle (4.4%) among 209 viable fetuses examined. We observed a direct relationship between viral titers and severity of congenital heart defects, with apparent predominance among female fetuses. Infected dams remained healthy; we did not observe any maternal heart or placental injury suggestive of direct viral effects on developing heart as likely cause of congenital heart defects. We examined signaling pathways in CVB3-exposed hearts using RNA sequencing, Kyoto Encyclopedia of Genes and Genomes enrichment analysis, and immunohistochemistry. Signaling proteins of the Hippo, tight junction, transforming growth factor-β1, and extracellular matrix proteins were the most highly enriched in CVB3-infected fetuses with ventricular septal defects. Moreover, cardiomyocyte proliferation was 50% lower in fetuses with ventricular septal defects compared with uninfected controls. Conclusions We conclude prenatal CVB3 infection induces congenital heart defects. Alterations in myocardial proliferate capacity and consequent changes in cardiac architecture and trabeculation appear to account for most of observed phenotypes.

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.

The Vaginal Virome-Balancing Female Genital Tract Bacteriome, Mucosal Immunity, and Sexual and Reproductive Health Outcomes?

Besides bacteria, fungi, protists and archaea, the vaginal ecosystem also contains a range of prokaryote- and eukaryote-infecting viruses, which are collectively referred to as the "virome". Despite its well-described role in the gut and other environmental niches, the vaginal virome remains understudied. With a focus on sexual and reproductive health, we summarize the currently known components of the vaginal virome, its relationship with other constituents of the vaginal microbiota and its association with adverse health outcomes. While a range of eukaryote-infecting viruses has been described to be present in the female genital tract (FGT), few prokaryote-infecting viruses have been described. Literature suggests that various vaginal viruses interact with vaginal bacterial microbiota and host immunity and that any imbalance thereof may contribute to the risk of adverse reproductive health outcomes, including infertility and adverse birth outcomes. Current limitations of vaginal virome research include experimental and analytical constraints. Considering the vaginal virome may represent the missing link in our understanding of the relationship between FGT bacteria, mucosal immunity, and adverse sexual and reproductive health outcomes, future studies evaluating the vaginal microbiome and its population dynamics holistically will be important for understanding the role of the vaginal virome in balancing health and disease.

Adenoviral mediated expression of anti-inflammatory progranulin by placental explants modulates endothelial cell activation by decrease of ICAM-1 expression

INTRODUCTION

Functional disorders of the villous trophoblast may result in preeclampsia through the release of endothelial activating substances. Progranulin is an anti-inflammatory, pro-angiogenic cytokine with TNF-α antagonizing activity. The trophoblastic expression of progranulin is increased during preeclampsia. The aim of the study was to investigate the impact of placental progranulin synthesis on endothelial cell activation.

METHODS

Placental progranulin expression was modified by transduction of an adenoviral vector. Primary isolated human umbilical venous endothelial cells (HUVECs) were incubated with conditioned medium of first trimester placental explants. Functional studies on HUVECs included assays for proliferation, viability, cytotoxicity and analyzes of Intercellular adhesion molecule-1 (ICAM-1) and E-selectin expression.

RESULTS

Placental progranulin expression was more than 10-fold higher by using an adenoviral-mediated overexpression system (Ad.PGRN) compared to control vector (Ad.CTRL) and untreated controls. Incubation of HUVECs with conditioned placental medium revealed a dose-dependent increase of cytotoxicity, reduced cell proliferation and viability and resulted in an increase of ICAM-1 and E-selectin expression. Overexpression of progranulin (Ad.PGRN) antagonized the ICAM-1 expression induced by conditioned medium. However progranulin did not influence the effects on cell proliferation, viability, cytotoxicity and E-selectin expression in HUVECs.

DISCUSSION

Regulation of gene expression in human placental explants is possible by usage of an adenoviral vector system. The increase of endothelial ICAM-1 expression following the incubation with placental conditioned medium was partly reversed by overexpression of placental progranulin. It is suggested that up-regulation of the placental progranulin expression is an endogenous anti-inflammatory mechanism that partially antagonizes the endothelial cell activation during preeclampsia.

In Vitro Human Placental Studies to Support Adenovirus-Mediated VEGF-DΔNΔC Maternal Gene Therapy for the Treatment of Severe Early-Onset Fetal Growth Restriction

Severe fetal growth restriction (FGR) affects 1 in 500 pregnancies, is untreatable, and causes serious neonatal morbidity and death. Reduced uterine blood flow (UBF) is one cause. Transduction of uterine arteries in normal and FGR animal models using an adenovirus (Ad) encoding VEGF isoforms increases UBF and improves fetal growth in utero. Understanding potential adverse consequences of this therapy before first-in-woman clinical application is essential. The aims of this study were to determine whether Ad.VEGF-D^ΔNΔC (1) transfers across the human placental barrier and (2) affects human placental morphology, permeability and primary indicators of placental function, and trophoblast integrity. Villous explants from normal term human placentas were treated with Ad.VEGF-D^ΔNΔC (5 × 10^7-10 virus particles [vp]/mL), or virus formulation buffer (FB). Villous structural integrity (hematoxylin and eosin staining) and tissue accessibility (LacZ immunostaining) were determined. Markers of endocrine function (human chorionic gonadotropin [hCG] secretion) and cell death (lactate dehydrogenase [LDH] release) were assayed. Lobules from normal and FGR pregnancies underwent ex vivo dual perfusion with exposure to 5 × 10¹⁰ vp/mL Ad.VEGF-D^ΔNΔC or FB. Perfusion resistance, para-cellular permeability, hCG, alkaline phosphatase, and LDH release were measured. Ad.VEGF-D^ΔNΔC transfer across the placental barrier was assessed by quantitative polymerase chain reaction in DNA extracted from fetal-side venous perfusate, and by immunohistochemistry in fixed tissue. Villous explant structural integrity and hCG secretion was maintained at all Ad.VEGF-D^ΔNΔC doses. Ad.VEGF-D^ΔNΔC perfusion revealed no effect on placental permeability, fetoplacental vascular resistance, hCG secretion, or alkaline phosphatase release, but there was a minor elevation in maternal-side LDH release. Viral vector tissue access in both explant and perfused models was minimal, and the vector was rarely detected in the fetal venous perfusate and at low titer. Ad.VEGF-D^ΔNΔC did not markedly affect human placental integrity and function in vitro. There was limited tissue access and transfer of vector across the placental barrier. Except for a minor elevation in LDH release, these test data did not reveal any toxic effects of Ad.VEGF-D^ΔNΔC on the human placenta.

Cellular and molecular mechanisms of viral infection in the human placenta

The placenta is a highly specialized organ that is formed during human gestation for conferring protection and generating an optimal microenvironment to maintain the equilibrium between immunological and biochemical factors for fetal development. Diverse pathogens, including viruses, can infect several cellular components of the placenta, such as trophoblasts, syncytiotrophoblasts and other hematopoietic cells. Viral infections during pregnancy have been associated with fetal malformation and pregnancy complications such as preterm labor. In this minireview, we describe the most recent findings regarding virus-host interactions at the placental interface and investigate the mechanisms through which viruses may access trophoblasts and the pathogenic processes involved in viral dissemination at the maternal-fetal interface.

Risks associated with viral infections during pregnancy

Despite the prevalence of viral infections in the American population, we still have a limited understanding of how they affect pregnancy and fetal development. Viruses can gain access to the decidua and placenta by ascending from the lower reproductive tract or via hematogenous transmission. Viral tropism for the decidua and placenta is then dependent on viral entry receptor expression in these tissues as well as on the maternal immune response to the virus. These factors vary by cell type and gestational age and can be affected by changes to the in utero environment and maternal immunity. Some viruses can directly infect the fetus at specific times during gestation, while some only infect the placenta. Both scenarios can result in severe birth defects or pregnancy loss. Systemic maternal viral infections can also affect the pregnancy, and these can be especially dangerous, because pregnant women suffer higher virus-associated morbidity and mortality than do nonpregnant counterparts. In this Review, we discuss the potential contributions of maternal, placental, and fetal viral infection to pregnancy outcome, fetal development, and maternal well-being.

Pregnancy loss following coxsackievirus b3 infection in mice during early gestation due to high expression of coxsackievirus-adenovirus receptor (CAR) in uterus and embryo

Coxsackieviruses are important pathogens in children and the outcomes of neonatal infection can be serious or fatal. However, the outcomes of coxsackievirus infection during early gestation are not well defined. In this study, we examined the possibility of vertical transmission of coxsackievirus B3 (CVB3) and the effects of CVB3 infection on early pregnancy of ICR mice. We found that the coxsackievirus and adenovirus receptor (CAR) was highly expressed not only in embryos but also in the uterus of ICR mice. CVB3 replicated in the uterus 1 to 7 days post-infection (dpi), with the highest titer at 3 dpi. The pregnancy loss rate in mice infected with CVB3 during early gestation was 38.3%, compared to 4.7% and 2.7% in mock-infected and UV-inactivated-CVB3 infected pregnant mice, respectively. These data suggest that the uterus and embryo, which express abundant CAR, are important targets of CVB3 and that the vertical transmission of CVB3 during early gestation induces pregnancy loss.

Animal models for prenatal gene therapy: choosing the right model

Testing in animal models is an essential requirement during development of prenatal gene therapy for -clinical application. Some information can be derived from cell lines or cultured fetal cells, such as the efficiency of gene transfer and the vector dose that might be required. Fetal tissues can also be maintained in culture for short periods of time and transduced ex vivo. Ultimately, however, the use of animals is unavoidable since in vivo experiments allow the length and level of transgene expression to be measured, and provide an assessment of the effect of the delivery procedure and the gene therapy on fetal and neonatal development. The choice of animal model is determined by the nature of the disease and characteristics of the animal, such as its size, lifespan, and immunology, the number of fetuses and their development, parturition, and the length of gestation and the placentation. The availability of a disease model is also critical. In this chapter, we discuss the various animal models that can be used and consider how their characteristics can affect the results obtained. The projection to human application and the regulatory hurdles are also presented.

Monitoring for potential adverse effects of prenatal gene therapy: use of large animal models with relevance to human application

Safety is an absolute prerequisite for introducing any new therapy, and the need to monitor the consequences of administration of both vector and transgene to the fetus is particularly important. The unique features of fetal development that make it an attractive target for gene therapy, such as its immature immune system and rapidly dividing populations of stem cells, also mean that small perturbations in pregnancy can have significant short- and long-term consequences. Certain features of the viral vectors used, the product of the delivered gene, and sometimes the invasive techniques necessary to deliver the construct to the fetus in utero have the potential to do harm. An important goal of prenatal gene therapy research is to develop clinically relevant techniques that could be applied to cure or ameliorate human disease in utero on large animal models such as sheep or nonhuman primates. Equally important is the use of these models to monitor for potential adverse effects of such interventions. These large animal models provide good representation of individual patient-based investigations. However, analyses that require defined genetic backgrounds, high throughput, defined variability and statistical analyses, e.g. for initial studies on teratogenic and oncogenic effects, are best performed on larger groups of small animals, in particular mice. This chapter gives an overview of the potential adverse effects in relation to prenatal gene therapy and describes the techniques that can be used experimentally in a large animal model to monitor the potential adverse consequences of prenatal gene therapy, with relevance to clinical application. The sheep model is particularly useful to allow serial monitoring of fetal growth and well-being after delivery of prenatal gene therapy. It is also amenable to serially sampling using minimally invasive and clinically relevant techniques such as ultrasound-guided blood sampling. For more invasive long-term monitoring, we describe telemetric techniques to measure the haemodynamics of the mother or fetus, for example, that interferes minimally with normal animal behaviour. Implanted catheters can also be used for serial fetal blood sampling during gestation. Finally, we describe methods to monitor events around birth and long-term neonatal follow-up that are important when considering human translation of this therapy.

Gene targeting in primary human trophoblasts

Studies in primary human trophoblasts provide critical insights into placental function in normal and complicated pregnancies. Mechanistic studies in these cells require experimental tools to modulate gene expression. Lipid-based methods to transfect primary trophoblasts are fairly simple to use and allow for the efficient delivery of nucleic acids, but potential toxic effects limit these methods. Viral vectors are versatile transfection tools of native trophoblastic or foreign cDNAs, providing high transfection efficiency, low toxicity and stable DNA integration into the trophoblast genome. RNA interference (RNAi), using small interfering RNA (siRNA) or microRNA, constitutes a powerful approach to silence trophoblast genes. However, off-target effects, such as regulation of unintended complementary transcripts, inflammatory responses and saturation of the endogenous RNAi machinery, are significant concerns. Strategies to minimize off-target effects include using multiple individual siRNAs, elimination of pro-inflammatory sequences in the siRNA construct and chemical modification of a nucleotide in the guide strand or of the ribose moiety. Tools for efficient gene targeting in primary human trophoblasts are currently available, albeit not yet extensively validated. These methods are critical for exploring the function of human trophoblast genes and may provide a foundation for the future application of gene therapy that targets placental trophoblasts.

When are amniotic fluid viral PCR studies indicated in prenatal diagnosis?

OBJECTIVE

To determine which prenatal ultrasound findings indicate the need to also obtain PCR studies for viral genome in women undergoing midtrimester amniocentesis.

METHODS

This was a retrospective observational study on women that underwent amniotic fluid karyotyping and viral PCR testing for history or ultrasound based indication. Amniotic fluid was tested for adenovirus, cytomegalovirus, respiratory syncytial virus, enterovirus, Epstein-Barr virus, and parvovirus B19 using multiplex PCR study with multiple appropriate controls. Ultrasound findings were coded as normal or abnormal with 34 categories of ultrasound abnormality stratified into 18 subgroups. Relationships between these subgroups and karyotype/PCR results were tested by Pearson chi-square method or Fisher's exact test and overall logistic regression analysis.

RESULTS

Amniotic fluid samples from 1191 patients were obtained for the study. Abnormal karyotype was detected in 5.4% of cases (64/1191), and PCR was positive in 6.5% of cases (77/1191). Abnormal fetal ultrasonographic findings were observed in 28.4% of cases (338/1191). There was an association between intrauterine growth restriction, nonimmune hydrops fetalis, hand/foot anomalies or neural tube defects (NTDs), and PCR positivity. NTDs were associated with PCR positivity in fetuses with normal karyotype and nuchal thickening, cardiac or ventral wall defects were specifically associated with aneuploidy.

CONCLUSION

Amniotic fluid viral PCR testing should be considered for fetuses with intrauterine growth restriction, nonimmune hydrops fetalis, hand/foot anomalies, or NTDs. After aneuploidy is excluded, NTDs are associated with PCR positivity.

Pre-eclampsia: connecting angiogenic and metabolic pathways

Pre-eclampsia is a hypertensive disease of pregnancy with a worldwide incidence of 5-8%. This review focuses on recent developments in pre-eclampsia research related to angiogenesis and metabolism. We first address the 'angiogenic imbalance' theory, which hypothesizes that pre-eclampsia results from an imbalance of factors that promote or antagonize angiogenesis, such as soluble fms-like tyrosine kinase (sFlt1), 2-methoxyestradiol (2-ME) and catechol-O-methyltransferase (COMT). Next, we analyze the association between pre-eclampsia and dysfunctional metabolism of both homocysteine and placental glycogen. We hope that illuminating some of the various connections existing between angiogenesis and metabolism in pre-eclampsia will facilitate the update or reconsideration of old models of pathogenesis.

TLR-mediated preterm birth in response to pathogenic agents

The incidence of preterm birth in developed countries has risen in the past decades. Underlying causes for this enigmatic pregnancy complication are numerous, yet infectious agents that induce dysregulation of immunity at the maternal-fetal interface pose one of the most probable causes of preterm birth. This paper highlights two factors regarding maternal infections that trigger unscheduled inflammatory sequences that are deleterious to the maternal-fetal balance necessary to maintain pregnancy. Firstly, we discuss the role of Toll-like receptors (TLRs) as sentinels of uterine immunity in the context of response to pathogens. We highlight the idea that particular TLR activations lead to differential immune cascades that induce preterm birth. Secondly, two alternative routes of pathogenic entry may prove to be critical for inducing preterm birth via a cytokine storm or a secondary and currently unknown cell-mediated mechanism of uterine inflammation. This paper summarizes pathways that underlie activation of adverse and diverse immune responses to foreign agents that may result in preterm birth.

H3N2 influenza A virus replicates in immortalized human first trimester trophoblast cell lines and induces their rapid apoptosis

PROBLEM

Epidemiological data suggested that pandemic influenza increased the risks of spontaneous abortion and premature labor, while seasonal influenza also increased the risk of schizophrenia in adolescence. However, their pathogenesis is so far unknown.

METHOD OF STUDY

The first trimester trophoblast cell lines, namely, Swan71 and HTR8 cells were challenged with A/Udorn/72 influenza virus (H3N2). At indicated time points, cells were examined for expression of influenza proteins. Viral replication in culture media, apoptosis and the expression of human leukocyte antigen (HLA)-G were also examined.

RESULTS

Intracellular localization of viral proteins was observed. Twenty-four hours after inoculation, virus was detected in culture media while most cells fell into apoptosis. During apoptosis, expression of HLA-G was unchanged.

CONCLUSION

We revealed replication of low pathogenic influenza virus in the first trimester trophoblast cell lines. Placental damages are likely to be induced by direct cytopathic effects of influenza virus and subsequent apoptosis rather than down regulation of HLA-G expression and subsequent rejection by maternal immune system.

Perinatal outcomes after second trimester detection of amniotic fluid viral genome in asymptomatic patients

OBJECTIVE

Symptomatic fetal viral infection can affect placental and fetal development and may lead to non-immune hydrops or fetal death. All infections are not detectable by clinical history or ultrasound and a background positivity rate exists in asymptomatic patients. We investigated if intraamniotic presence of viral genome at the time of genetic amniocentesis in asypmtomatic patients affects perinatal outcome.

STUDY DESIGN

Six-hundred and eighty-six pregnancies referred for second trimester genetic amniocentesis with a normal ultrasound and fetal karyotype had amniotic fluid multiplex polymerase chain reaction for adeno-, cytomegalo-, Ebstein-Barr-, entero- and parvovirus. Forty asymptomatic patients that were positive for viral genome were matched 2:1 with negative controls. Perinatal outcomes were compared between these groups.

RESULTS

Pregnancy complications and perinatal outcomes were similar in the two groups.

CONCLUSION

Asymptomatic fetal viral infection at the time of second trimester amniocentesis does not increase the risk for adverse perinatal outcome.

Viruses and other infections in stillbirth: what is the evidence and what should we be doing?

In Australia, as in other developed countries, approximately 40-50% of stillbirths are of unknown aetiology. Emerging evidence suggests stillbirths are often multifactorial. The absence of a known cause leads to uncertainty regarding the risk of recurrence, which can cause extreme anguish for parents that may manifest as guilt, anger or bewilderment. Further, clinical endeavours to prevent recurrences in future pregnancies are impaired by lack of a defined aetiology. Therefore, efforts to provide an aetiological diagnosis of stillbirth impact upon all aspects of care of the mother, and inform many parts of clinical decision making. Despite the magnitude of the problem, that is 7 stillbirths per 1000 births in Australia, diagnostic efforts to discover viral aetiologies are often minimal. Viruses and other difficult to culture organisms have been postulated as the aetiology of a number of obstetric and paediatric conditions of unknown cause, including stillbirth. Reasons forwarded for testing stillbirth cases for infectious agents are non-medical factors, including addressing all parents' need for diagnostic closure, identifying infectious agents as a sporadic cause of stillbirth to reassure parents and clinicians regarding risk for future pregnancies, and to reduce unnecessary testing. It is clear that viral agents including rubella, human cytomegalovirus (CMV), parvovirus B19, herpes simplex virus (HSV), lymphocytic choriomeningitis virus (LCMV), and varicella zoster virus (VZV) may cause intrauterine deaths. Evidence for many other agents is that minimal or asymptomatic infections also occur, so improved markers of adverse outcomes are needed. The role of other viruses and difficult-to-culture organisms in stillbirth is uncertain, and needs more research. However, testing stillborn babies for some viral agents remains a useful adjunct to histopathological and other examinations at autopsy. Modern molecular techniques such as multiplex PCR, allow searches for multiple agents. Now that such testing is available, it is important to assess the clinical usefulness of such testing.

Placenta and fetal growth restriction

The placenta, as the vector for all maternal-fetal oxygen and nutrient exchange, is a principal influence on birthweight. Placental weight summarizes laterally expanding growth of the chorionic disc, and villous arborization yielding the nutrient exchange surface. These different growth dimensions alter fetoplacental weight ratio and ponderal index, and thus may modify placental functional efficiency. The placenta may show a range of histopathologies, some of which are also associated with fetal growth restriction. Different fetal intrinsic abilities to compensate for gross and histo-pathology may clarify the imperfect relationships between fetal growth and both intrauterine pathology, and the long-term health risks associated with poor fetal growth.

Multidrug resistance proteins affect drug transmission across the placenta

OBJECTIVE

We studied the role of multidrug resistance proteins in regulating transplacental transmission of corticosteroids and protease inhibitors.

STUDY DESIGN

We performed quantitative polymerase chain reaction and FACS analyses to study MDR1 (encodes P-glycoprotein) and MRP-1 expression in extravillous (HTR-8/SVneo) and villous (BeWo) trophoblast cells treated with saquinavir, a multidrug resistance protein substrate. We measured H3-dexamethasone and H3-ritonavir transfer across confluent, syncytialized BeWo cells before and after treatment with agents that inhibit multidrug resistance proteins.

RESULTS

Compared with baseline expression, messenger RNA and protein levels were increased significantly in trophoblast cells after treatment with saquinavir. H3-dexamethasone and H3-ritonavir levels increased in BeWo cells after treatment with anti-P-glycoprotein antibodies or cyclosporine A. Transfer of H3-labeled drugs from the apical (eg, maternal) to basolateral (eg, fetal) side of the syncytialized BeWo cell monolayer was increased significantly when cells were pretreated with anti-P-glycoprotein antibodies.

CONCLUSION

Multidrug resistance proteins regulate drug levels in trophoblast cells and may mediate transmission of therapeutic agents across the placenta.

The effect of over-expression of sFlt-1 on blood pressure and the occurrence of other manifestations of preeclampsia in unrestrained conscious pregnant mice

OBJECTIVE

It has been shown that the level of soluble fms-like tyrosine kinase-1 (sFlt-1) is elevated in pregnant women who are destined to have preeclampsia, and a role for sFlt-1 in its pathogenesis has been suggested. Our objective was to determine the effect of the over-expression of sFlt-1 on blood pressure and the occurrence of other manifestations of preeclampsia in pregnant mice.

STUDY DESIGN

At day 8 of gestation CD-1 mice were allocated randomly to an injection of an adenovirus carrying sFlt-1 (10(9) plaque-forming units; sFlt-1 group), adenovirus carrying the murine immunoglobulin G2alpha Fc fragment (10(9) plaque-forming units; mFc group used as a control for the virus) or saline solution (100 microL; saline group). At day 10 of gestation, blood pressure catheters were inserted through the left carotid artery into the aortic arch and tunneled to a telemetric transmitter. Blood pressure was monitored continuously in the conscious unrestrained animals until day 18. Blood was collected from the pregnant mice at different gestational times, and plasma sFlt-1 was measured by enzyme-linked immunosorbent assay. Pups and placentae were weighed, and maternal platelet counts were determined at death on day 18.

RESULTS

Plasma levels of sFlt-1 increased significantly in the sFlt-1 mice and were significantly higher than the 2 control groups. The mean blood pressure in the sFlt-1 mice was significantly higher on days 17 and 18 of gestation, compared with the mFc and saline solution groups. The time-course of blood pressure rise mirrored that of the sFlt-1 levels. The average pup weight, placental weight, and maternal platelet counts were significantly lower in the sFlt-1 group, compared with the controls.

CONCLUSION

SFlt-1 induces hypertension and fetal growth restriction in pregnant mice, which supports its hypothesized role in the pathogenesis of preeclampsia. This animal model minimizes the need for manipulation or the administration of various compounds to induce the condition.

Adeno-associated virus-2 (AAV-2) causes trophoblast dysfunction, and placental AAV-2 infection is associated with preeclampsia

Shallow invasion by extravillous trophoblast cells into the uterine wall reduces placental perfusion and causes placental dysfunction, but the one or more causes of shallow placental invasion are unknown. We hypothesized that infection with adeno-associated virus-2 (AAV-2) inhibits trophoblast invasion and is associated with preeclampsia, which is a common obstetric complication resulting from placental dysfunction. We determined that transformed extravillous trophoblast (HTR-8/SVneo) cells were susceptible to AAV-2 infection in the presence or absence of adenovirus, which provides helper function for AAV-2 replication, and that AAV-2 infection reduced invasion of HTR-8/SVneo cells through an extracellular matrix before cytopathic effects were detected. In a case-control study, AAV-2 DNA was found more frequently in trophoblast cells from cases of severe preeclampsia (22/40) than from normal term deliveries (5/27, P = 0.002). These results indicate that AAV-2 infection is a previously unidentified cause of placental dysfunction. Additional studies to determine the susceptibility of extravillous trophoblast to other viruses, and the mechanisms by which viral infection impairs placental function, are warranted.

West Nile virus infection of the placenta

Intrauterine infection of fetuses with West Nile virus (WNV) has been implicated in cases of women infected during pregnancy. Infection of timed-pregnant mice on 5.5, 7.5, and 9.5 days post-coitus (dpc) resulted in fetal infection. Infection of dams on 11.5 and 14.5 dpc resulted in little and no fetal infection, respectively. Pre-implantation embryos in culture were also infected with WNV after the blastocyst stage and the formation of trophectoderm. Green fluorescent protein (GFP) expression was observed in a trophoblast stem (TS) cell line after infection with a GFP-expressing WNV construct. However, no fluorescence was observed in differentiated trophoblast giant cell (TGC) cultures. GFP fluorescence was present in TGC cultures if infected TS cells were induced to differentiate. These results suggest that embryos are susceptible to WNV infection after the formation of the trophectoderm around 3.5 dpc through the formation of the functional placenta around 10.5 dpc.

Efficient Gene Transfer into Differentiated Human Trophoblast Cells with Adenovirus Vector Containing RGD Motif in the Fiber Protein

Previously we reported fiber-modified adenovirus (Ad) vectors containing the Arg-Gly-Asp (RGD) motif on the HI loop of the fiber knob (Ad-RGD vectors) have high gene transfer efficacy into some human trophoblast cell lines. In the current study, we investigate transgene activity of Ad-RGD during differentiation of human cytotrophoblast BeWo cells into syncytiotrophoblast-like cells. Although cellular differentiation into syncytiotrophoblast cells was followed by a decrease in the coxsackievirus and adenovirus receptor levels on the cell membrane, the alphaVbeta3 and alphaVbeta5 integrin levels did not change. Conventional adenovirus vector had lower transduction activity in the differentiated cells than non-differentiated cells. In contrast, Ad-RGD vector had no influence on differentiation and had a ca. 2-5 fold higher transduction activity than that of the conventional Ad vector. Thus, Ad-RGD vector can be a powerful tool for gene transfer experiments in syncytiotrophoblast cells.

Comparison of transgene expression mediated by several Fiber-modified adenovirus vectors in trophoblast cells

The transfer of genes of interest is a useful method for studying placental biology. Recombinant adenovirus (Ad) vector is an efficient vector for transgene expression. An interaction between the fiber of Ad and the coxsackievirus and adenovirus receptor on the cell membrane is the first step in infection. We previously developed fiber-modified Ad vectors and showed that they improved transgene activity in several cell lines when compared to wild-type vector. In the present study, we examined the ability of three fiber-modified Ad vectors to transduce human choriocarcinoma cell lines (JEG-3, JAR and BeWo) and rat trophoblast cell lines (Rcho-1, TR-TBT 18d-1 and TR-TBT 18d-2). We compared the transgene efficacy of wild-type Ad-L2 vector, Ad-RGD(HI)-L2 vector containing an Arg-Gly-Asp motif, Ad-K7(C)-L2 vector containing a 7-tandem lysine motif, and Ad-RGD(HI)K7(C)-L2 vector containing both motifs in the fiber. We used the luciferase gene as a reporter gene. In the human and rodent trophoblast cell lines, Ad-RGD(HI)-L2 had the greatest infectious potential, followed by Ad-RGD(HI)K7(C)-L2, Ad-K7(C)-L2 and Ad-L2. Compared to the amount of luciferase produced by wild-type vector, Ad-RGD(HI)-L2 mediated 8.1-fold the amount of luciferase in JEG-3 cells, 13.5-fold in JAR cells, 76.8-fold in BeWo cells, 5.0-fold in Rcho-1, 19.4-fold in TR-TBT 18d-1 and 15.0-fold in TR-TBT 18d-2. These results indicate that Ad-RGD(HI) is a potential recombinant Ad vector for transgene expression in some trophoblast cell lines.

Coxsackievirus-adenovirus receptor (CAR) is essential for early embryonic cardiac development

The coxsackievirus-adenovirus receptor (CAR) is a cell contact protein on various cell types with unknown physiological function. It belongs to a subfamily of the immunoglobulin-superfamily of which some members are junctional adhesion molecules on epithelial and/or endothelial cells. CAR is dominantly expressed in the hearts and brains of mice until the newborne phase after which it becomes mainly restricted to various epithelial cells. To understand more about the physiological function of CAR, we have generated CAR-deficient mice by gene targeting. We found that these mice die between E11.5 and E13.5 of embryonal development. Ultrastructural analysis of cardiomyocytes revealed that the density of myofibrils was reduced and that their orientation and bundling was disorganized. In addition, mitochondria were enlarged and glycogen storage strongly enriched. In line with these defects, we observed pericardial edema formation as a clear sign of insufficient heart function. Developmental abnormalities likely to be secondary effects of gene ablation were the persistent singular cardial atrio-ventricular canal and dilatations of larger blood vessels such as the cardinal veins. The secondary nature of these defects was supported by the fact that CAR was not expressed on vascular cells or on cells of the vascular wall. No obvious signs for alterations of the histological organization of the placenta were observed. We conclude that CAR is required for embryonal heart development, most likely due to its function during the organization of myofibrils in cardiomyocytes.

Detection of viral deoxyribonucleic acid in amniotic fluid: association with fetal malformation and pregnancy abnormalities

OBJECTIVE

To first test the hypothesis that the presence of viral nucleic acid in amniotic fluid (AF) is associated with an abnormal pregnancy outcome, and second, to determine if the overall rate of polymerase chain reaction (PCR) positivity and the distribution of virus types vary geographically.

STUDY DESIGN

Cytomegalovirus (CMV), parvovirus B19, adenovirus, enterovirus, herpes simplex virus, Epstein-Barr virus, and respiratory syncytial virus nucleic acids were sought in 423 AF samples obtained for clinical indications: 284 from the East Coast (EC) and 139 from the Midwest (MW).

RESULTS

Gestational age at sampling was 19.1 weeks for EC and 20.1 weeks for MW. 13.5% of karyotypically normal singleton pregnancies (57/423) had a positive AF PCR. 11% of AF PCR from the EC while 18% of AF PCR from the MW were positive (p = 0.06). The most commonly detected viruses were adenovirus (77%), enterovirus (12%), and CMV and parvovirus B19 (5% each). Twenty-four percent of sonographically abnormal pregnancies (33/136) had a positive AF PCR compared to only 8.4% (24/287) of normal pregnancies (p < 0.001).

CONCLUSION

A positive AF PCR is associated with an increased rate of fetal structural malformations, intrauterine growth restriction, hydrops and other fetal abnormalities. There were no significant geographic differences in the incidence of AF viral PCR positivity.

Is adenovirus a fetal pathogen?

OBJECTIVES

The purpose of this study was to test the relationship between adenovirus genetic material in the amniotic fluid and adverse pregnancy outcome.

STUDY DESIGN

This was a prospective, observational study of women who were referred in the second trimester of gestation for either genetic amniocentesis or evaluation of fetal malformation. A 2-mL aliquot of amniotic fluid was subjected to multiplex polymerase chain reaction for a panel of viruses that included adenovirus and human genome controls. Fetuses with an abnormal karyotype were excluded from analysis.

RESULTS

The prevalence of adenovirus was similar in normal (39/652) and anomalous fetuses (23/364; chi(2) test, P=.376). There was significant seasonal variation in the prevalence in both normal and anomalous fetuses (chi(2) exact test, P<.001), but no significant difference between groups. The monthly proportion of patients who underwent amniocentesis remained constant throughout the year (mean, 8.3%; chi(2) test, P=.67). Central nervous system anomalies and echogenic liver foci were significantly more common among fetuses with positive amniotic fluid polymerase chain reaction results for adenovirus (P<.005, respectively).

CONCLUSION

Adenovirus is found in a similar prevalence and seasonal variation in sonographically normal and abnormal pregnancies. Although a specific fetal presentation was not identified, echogenic liver lesions with or without hydrops and neural tube defects were significantly more common in the presence of adenovirus. The significance of these findings deserves further study.

Placental extravillous cytotrophoblasts persistently express class I major histocompatibility complex molecules after human cytomegalovirus infection

Human cytomegalovirus (HCMV) downregulates the class I major histocompatibility complexes (MHCs), HLA-A and -B, in infected fibroblasts to escape from antigen-specific cytotoxic T lymphocytes. The HCMV genes responsible for the downregulation of MHCs are US2, US3, US6, and US11, which encode type I membrane proteins working at the endoplasmic reticulum (ER). However, it is largely unknown whether HCMV downregulates the class I MHC molecules in placental extravillous cytotrophoblasts (EVT), which express HLA-C, -E, and -G to protect a semiallogenic fetus from maternal natural killer (NK) cells at the fetomaternal interface. Here, we report that differentiated EVT prepared from human first-trimester chorionic villi persistently express class I MHC molecules upon HCMV infection. When these US proteins were expressed in uninfected EVT, they were localized at the ER in the entire cytoplasm. However, subsequent HCMV infection resulted in dissociation of these US proteins from the ER, which relocated toward the cell membrane. In fibroblasts, these US proteins were localized at the ER before and after HCMV infection. These results suggest that the US gene products are not integrated into ER of HCMV-infected EVT and fail to downregulate class I MHC molecules.

Prevalence of viral DNA in amniotic fluid of low-risk pregnancies in the second trimester

AIM

The association between fetal viral infection and adverse pregnancy outcome is well documented. However, the prevalence of common viral pathogens in the amniotic fluid of normal pregnancies is not established. The purpose of this study was to determine this prevalence in asymptomatic patients.

METHODS

This was a prospective observational study of patients at low risk for viral infection who were referred for second-trimester genetic amniocentesis. In patients with normal fetal anatomy on ultrasound and a normal fetal karyotype, a 2-ml aliquot of amniotic fluid obtained at amniocentesis was analyzed by multiplex polymerase chain reaction for cytomegalovirus (CMV), parvovirus B19, adenovirus, enterovirus, herpes simplex virus (HSV), respiratory syncytial virus (RSV) and Epstein-Barr virus (EBV).

RESULTS

Among 686 patients, advanced maternal age was the most common indication for genetic testing (n = 469, 68.4%), followed by elevated aneuploidy risk on triple screen (n = 164, 23.9%), elevated maternal serum alpha-fetoprotein (n = 20, 2.9%), previous aneuploidy (n = 16, 2.3%) and family history of inheritable disease (n = 14, 2.1%). Forty-four (6.4%) amniotic fluid samples were positive for viral genome. A single genome was amplified in 41 samples (93%). In three samples, two viral genomes were identified. Adenovirus was most frequently identified (37/44), followed by CMV (5/44), EBV (2/44), enterovirus (2/44) and RSV (1/44). Parvovirus and HSV were not identified. There was a bimodal seasonal variation in prevalence, with the highest prevalence during the summer and late winter.

CONCLUSION

Viral genome is commonly found in amniotic fluid with a sonographically normal fetus, and the prevalence follows a seasonal pattern. The mechanism, significance and effects of this asymptomatic viral presence require further study.

Viral infection of the trophoblast: time to take a serious look at its role in abnormal implantation and placentation?

Fragmentary evidence suggests that trophoblast viral infection may play a role in placental dysfunction, leading to complications including spontaneous miscarriage, preeclampsia, fetal growth restriction and preterm birth. Here, we review the mechanisms underlying differentiation and gestational age-dependent infection of trophoblast cells and the consequences of in vitro infection on trophoblast function. The relationship between trophoblast infection by common viruses and pregnancy outcomes is also analyzed. We conclude that there is sufficient evidence linking placental infection by common viruses, including viruses thought to be non-pathogenic or to have low pathogenicity, to indicate that this effect contributes to poor pregnancy outcome.

The mechanisms of placental viral infection

The placenta is a dynamic organ whose structure and function change throughout pregnancy. There is compelling evidence that the placenta plays an integral role in the vertical transmission of viruses, such as cytomegalovirus and human immunodeficiency virus, from the mother to the fetus. Although the sequelae of congenital viral infection (i.e., fetal anomalies, intrauterine fetal death, and persistent postnatal infection) may be devastating, very little is known about the passage of viruses across the placenta and the pathologic consequences of placental viral infection. We postulate that the syncytiotrophoblast, which forms a continuous barrier between the maternal and fetal circulation, is relatively resistant to viral infection. In support of this hypothesis, we observed that the susceptibility of trophoblast cells to infection by adenovirus and herpes simplex virus and the expression of viral receptors were reduced as trophoblast cells terminally differentiated into syncytiotrophoblast. Conversely, we observed that undifferentiated, extravillous trophoblast cells, which are susceptible to adenovirus infection, underwent pathologic changes (i.e., apoptosis) when infected by adenovirus in the presence of decidual lymphocytes (which were used to simulate the maternal immune response to viral infection). Based on these findings, we speculate that viral infection of extravillous trophoblast cells may negatively impact the process of placental invasion and predispose the mother and fetus to adverse reproductive outcomes that result from placental dysfunction.