Viral ssRNA induces first trimester trophoblast apoptosis through an inflammatory mechanism

Antiphospholipid-exposed trophoblast-derived extracellular vesicles express elevated levels of TLR7/8-activating microRNAs and induce endometrial endothelial activation, in part, through TLR7

Women with antiphospholipid syndrome (APS) are at high risk for miscarriage and preeclampsia. Unlike pro-thrombotic systemic APS, obstetric APS is associated with insufficient placentation, as well as inflammation and vascular dysfunction at the maternal-fetal interface. Antiphospholipid antibodies (aPL) can target the placental trophoblast and induce inflammation. We reported that aPL trigger trophoblast cells to produce elevated levels of IL-8 through activation of Toll-like receptor 4 (TLR4). Downstream of TLR4, we found this IL-8 response is mediated by a TLR8-activating microRNA (miR), miR-146a-3p, which is also released by the trophoblast via extracellular vesicles (EVs). Since endothelial dysfunction is a feature of obstetric APS, we sought to determine if other miRs that can activate the RNA sensors, TLR7 and/or TLR8, are released by the trophoblast via EVs after exposure to aPL, and if these EVs can activate human endometrial endothelial cells (HEECs). Using a human first trimester extravillous trophoblast cell line we found that aPL elevated their release of small EVs (<150 nm). These extracellular vesicles released from trophoblast cells exposed to aPL expressed elevated levels of TLR7/8-activating miR-21a and miR-29a, in addition to the previously reported miR-146a-3p. Extracellular vesicles from aPL-exposed human trophoblast cells triggered human endometrial endothelial cells to generate an inflammatory IL-8 response, in part through TLR7. This study highlights EVs as a mode of communication between the placenta and the maternal vasculature, as well as a potential role for TLR7/8-activating miRs in contributing to inflammation at the maternal-fetal interface in obstetric APS.

Implication of viruses in the etiology of preeclampsia

Preeclampsia is one of the most common disorders that poses threat to both mothers and neonates and a major contributor to perinatal morbidity and mortality worldwide. Viral infection during pregnancy is not typically considered to cause preeclampsia; however, syndromic nature of preeclampsia etiology and the immunomodulatory effects of viral infections suggest that microbes could trigger a subset of preeclampsia. Notably, SARS-CoV-2 infection is associated with an increased risk of preeclampsia. Herein, we review the potential role of viral infections in this great obstetrical syndrome. According to in vitro and in vivo experimental studies, viral infections can cause preeclampsia by introducing poor placentation, syncytiotrophoblast stress, and/or maternal systemic inflammation, which are all known to play a critical role in the development of preeclampsia. Moreover, clinical and experimental investigations have suggested a link between several viruses and the onset of preeclampsia via multiple pathways. However, the results of experimental and clinical research are not always consistent. Therefore, future studies should investigate the causal link between viral infections and preeclampsia to elucidate the mechanism behind this relationship and the etiology of preeclampsia itself.

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.

Potential genetic robustness of Prnp and Sprn double knockout mouse embryos towards ShRNA-lentiviral inoculation

The Shadoo and PrP prion protein family members are thought to be functionally related, but previous knockdown/knockout experiments in early mouse embryogenesis have provided seemingly contradictory results. In particular, Shadoo was found to be indispensable in the absence of PrP in knockdown analyses, but a double-knockout of the two had little phenotypic impact. We investigated this apparent discrepancy by comparing transcriptomes of WT, Prnp^0/0 and Prnp^0/0Sprn^0/0 E6.5 mouse embryos following inoculation by Sprn- or Prnp-ShRNA lentiviral vectors. Our results suggest the possibility of genetic adaptation in Prnp^0/0Sprn^0/0 mice, thus providing a potential explanation for their previously observed resilience.

Interferon epsilon and preterm birth subtypes; a new piece of the type I interferon puzzle during pregnancy?

PROBLEM

Interferon epsilon (IFNε) is a unique type I IFN that is expressed in response to sex steroids. Studies suggest that type I IFNs regulate inflammation-induced preterm birth (PTB), but no study has examined the role of IFNε in human pregnancy.

METHOD OF STUDY

We used stored vaginal swabs between 8 and 26 weeks of gestation from the Global Alliance to Prevent Prematurity and Stillbirth (GAPPS) biobank and measured IFNε by enzyme-linked immunosorbent assay (ELISA). A total of 29 women with spontaneous preterm births, 34 women with medically indicated preterm births, and 134 women with term births were included. Secondary outcomes included a preterm birth with chorioamnionitis and preeclampsia with a preterm birth. Logistic regression calculated odds ratios (OR) and 95% confidence intervals (CI) adjusting for maternal age, race, body mass index, prior pregnancy complications, lower genital tract infections, chronic health conditions, and gestational age at blood draw.

RESULTS AND CONCLUSIONS

There was no significant association between IFNε and spontaneous preterm birth (OR_adj 1.0, 0.8-1.3) or chorioamnionitis (OR_adj 1.6, 0.7-3.5). A trend toward increased odds of medically indicated preterm birth (OR_adj . 1.3, 1.0-1.8) was observed. This was likely due to elevated IFNε among women with preterm preeclampsia (OR_adj . 2.0, 95% CI 1.3-3.2). While exploratory, our novel findings suggest that larger longitudinal studies of IFNε across human pregnancy may be warranted.

Placenta-derived interferon-stimulated gene 20 controls ZIKA virus infection

Zika virus is a positive-sense single-stranded RNA virus, which can be transmitted across the placenta and has adverse effects on fetal development during pregnancy. The severity of these complications highlights the importance of prevention and treatment. However, no vaccines or drugs are currently available. In this study, we characterize the IFNβ-mediated anti-viral response in trophoblast cells in order to identify critical components that are necessary for the successful control of viral replication and determine whether components of the IFN-induced response can be used as a replacement therapy for ZIKA virus infection during pregnancy. We identify and characterize interferon-stimulated gene 20 (ISG20) as playing a central role in controlling Zika virus infection in trophoblast cells and successfully establish a recombinant ISG20-Fc protein that effectively decreases viral titers in vitro and in vivo by maintaining its exonuclease activity and displaying potential immune modulatory functions. Recombinant ISG20-Fc has thus the potential to be further developed as an anti-viral treatment against ZIKA viral infection in high-risk populations, particularly in pregnant women.

Breast cancer resistance protein (Bcrp/Abcg2) is selectively modulated by lipopolysaccharide (LPS) in the mouse yolk sac

Bacterial infection alters placental ABC transporters expression. These transporters provide fetal protection against circulating xenobiotics and environmental toxins present in maternal blood. We hypothesized that lipopolysaccharide (LPS-bacterial mimic) alters the yolk sac morphology and expression of key ABC transporters in a gestational-age dependent manner. Yolk sac samples from C57BL/6 mice were obtained at gestational ages (GD) 15.5 and GD18.5, 4 or 24 h after LPS exposure (150ug/kg; n = 8/group). Samples underwent morphometrical, qPCR and immunohistochemistry analysis. The volumetric proportions of the histological components of the yolk sac did not change in response to LPS. LPS increased Abcg2 expression at GD15.5, after 4 h of treatment (p < 0.05). No changes in Abca1, Abcb1a/b, Abcg1, Glut1, Snat1, Il-1β, Ccl2 and Mif were observed. Il-6 and Cxcl1 were undetectable in the yolk sac throughout pregnancy. Abca1, breast cancer resistance protein (Bcrp, encoded by Abcg2) and P-glycoprotein (P-gp/ Abcb1a/b) were localized in the endodermal (uterine-facing) epithelium and to a lesser extent in the mesothelium (amnion-facing), whereas Abca1 was also localized to the endothelium of the yolk sac blood vessels. LPS increased the labeling area and intensity of Bcrp in the yolk sac's mesothelial cells at GD15.5 (4 h), whereas at GD18.5, the area of Bcrp labeling in the mesothelium (4 and 24 h) was decreased (p < 0.05). Bacterial infection has the potential to change yolk sac barrier function by affecting Bcrp and Abcg2 expression in a gestational-age dependent-manner. These changes may alter fetal exposure to xenobiotics and toxic substances present in the maternal circulation and in the uterine cavity.

Eutherian-Specific Gene TRIML2 Attenuates Inflammation in the Evolution of Placentation

Evolution of highly invasive placentation in the stem lineage of eutherians and subsequent extension of pregnancy set eutherians apart from other mammals, that is, marsupials with short-lived placentas, and oviparous monotremes. Recent studies suggest that eutherian implantation evolved from marsupial attachment reaction, an inflammatory process induced by the direct contact of fetal placenta with maternal endometrium after the breakdown of the shell coat, and shortly before the onset of parturition. Unique to eutherians, a dramatic downregulation of inflammation after implantation prevents the onset of premature parturition, and is critical for the maintenance of gestation. This downregulation likely involved evolutionary changes on maternal as well as fetal/placental side. Tripartite-motif family-like2 (TRIML2) only exists in eutherian genomes and shows preferential expression in preimplantation embryos, and trophoblast-derived structures, such as chorion and placental disc. Comparative genomic evidence supports that TRIML2 originated from a gene duplication event in the stem lineage of Eutheria that also gave rise to eutherian TRIML1. Compared with TRIML1, TRIML2 lost the catalytic RING domain of E3 ligase. However, only TRIML2 is induced in human choriocarcinoma cell line JEG3 with poly(I:C) treatment to simulate inflammation during viral infection. Its knockdown increases the production of proinflammatory cytokines and reduces trophoblast survival during poly(I:C) stimulation, while its overexpression reduces proinflammatory cytokine production, supporting TRIML2’s role as a regulatory inhibitor of the inflammatory pathways in trophoblasts. TRIML2’s potential virus-interacting PRY/SPRY domain shows significant signature of selection, suggesting its contribution to the evolution of eutherian-specific inflammation regulation during placentation.

Peli1 signaling blockade attenuates congenital zika syndrome

Zika virus (ZIKV) infects pregnant women and causes devastating congenital zika syndrome (CZS). How the virus is vertically transmitted to the fetus and induces neuronal loss remains unclear. We previously reported that Pellino (Peli)1, an E3 ubiquitin ligase, promotes p38MAPK activation in microglia and induction of lethal encephalitis by facilitating the replication of West Nile virus (WNV), a closely related flavivirus. Here, we found that Peli1 expression was induced on ZIKV-infected human monocytic cells, peripheral blood mononuclear cells, human first-trimester placental trophoblasts, and neural stem cell (hNSC)s. Peli1 mediates ZIKV cell attachment, entry and viral translation and its expression is confined to the endoplasmic reticulum. Moreover, Peli1 mediated inflammatory cytokine and chemokine responses and induced cell death in placental trophoblasts and hNSCs. ZIKV-infected pregnant mice lacking Peli1 signaling had reduced placental inflammation and tissue damage, which resulted in attenuated congenital abnormalities. Smaducin-6, a membrane-tethered Smad6-derived peptide, blocked Peli1-mediated NF-κB activation but did not have direct effects on ZIKV infection. Smaducin-6 reduced inflammatory responses and cell death in placental trophoblasts and hNSCs, and diminished placental inflammation and damage, leading to attenuated congenital malformations in mice. Collectively, our results reveal a novel role of Peli1 in flavivirus pathogenesis and suggest that Peli1 promotes ZIKV vertical transmission and neuronal loss by mediating inflammatory cytokine responses and induction of cell death. Our results also identify Smaducin-6 as a potential therapeutic candidate for treatment of CZS.

We previously reported that Pellino (Peli)1, an E3 ubiquitin ligase mediates p38MAPK activation in microglia and induces lethal encephalitis by facilitating replication of a mosquito -borne flavivirus, West Nile virus (WNV). Zika virus (ZIKV), a closely related flavivirus, causes devastating congenital zika syndrome (CZS) in pregnant women. How ZIKV is vertically transmitted to the fetus and induces neuronal loss remains unclear. Here, we found that Peli1 expression was enhanced in human monocytic cells, peripheral blood mononuclear cells, first-trimester placental trophoblasts and neural stem cell (hNSC)s following ZIKV infection. Peli1 expression colocalized with the endoplasmic reticulum and double-stranded RNA in ZIKV-infected cells and was required for ZIKV cell attachment and replication. Peli1 knockdown in placental trophoblasts inhibited ZIKV replication and decreased inflammatory cytokine responses and cell death. ZIKV-infected pregnant mice lacking Peli1 signaling showed reduced placental inflammation and tissue damage, which resulted in attenuated congenital abnormalities. Furthermore, Smaducin-6, a membrane-tethered Smad6-derived peptide, blocked Peli1-mediated NF-κB activation, but not ZIKV replication. Smaducin 6 inhibited Peli1-mediated inflammatory cytokine responses and cell death in placental trophoblasts and hNSCs, and attenuated congenital malformations in mice. Collectively, our results reveal a novel role of Peli1 in flavivirus pathogenesis and suggest that Peli1 promotes ZIKV vertical transmission and neuronal loss by mediating inflammatory cytokine responses and induction of cell death.

Human Chorionic Gonadotropin modulates CXCL10 Expression through Histone Methylation in human decidua

The process of implantation, trophoblast invasion and placentation demand continuous adaptation and modifications between the trophoblast (embryonic) and the decidua (maternal). Within the decidua, the maternal immune system undergoes continued changes, as the pregnancy progress, in terms of the cell population, phenotype and production of immune factors, cytokines and chemokines. Human chorionic gonadotropin (hCG) is one of the earliest hormones produced by the blastocyst and has potent immune modulatory effects, especially in relation to T cells. We hypothesized that trophoblast-derived hCG modulates the immune population present at the maternal fetal interface by modifying the cytokine profile produced by the stromal/decidual cells. Using in vitro models from decidual samples we demonstrate that hCG inhibits CXCL10 expression by inducing H3K27me3 histone methylation, which binds to Region 4 of the CXCL10 promoter, thereby suppressing its expression. hCG-induced histone methylation is mediated through EZH2, a functional member of the PRC2 complex. Regulation of CXCL10 expression has a major impact on the capacity of endometrial stromal cells to recruit CD8 cells. We demonstrate the existence of a cross talk between the placenta (hCG) and the decidua (CXCL10) in the control of immune cell recruitment. Alterations in this immune regulatory function, such as during infection, will have detrimental effects on the success of the pregnancy.

Fetal-Derived MyD88 Signaling Contributes to Poor Pregnancy Outcomes During Gestational Malaria

Placental malaria (PM) remains a severe public health problem in areas of high malaria transmission. Despite the efforts to prevent infection poor outcomes in Plasmodium endemic areas, there is still a considerable number of preterm births and newborns with low birth weight resulting from PM. Although local inflammation triggered in response to malaria is considered crucial in inducing placental damage, little is known about the differential influence of maternal and fetal immune responses to the disease progression. Therefore, using a PM mouse model, we sought to determine the contribution of maternal and fetal innate immune responses to PM development. For this, we conducted a series of cross-breeding experiments between mice that had differential expression of the MyD88 adaptor protein to obtain mother and correspondent fetuses with distinct genetic backgrounds. By evaluating fetal weight and placental vascular spaces, we have shown that the expression of MyD88 in fetal tissue has a significant impact on PM outcomes. Our results highlighted the existence of a distinct contribution of maternal and fetal immune responses to PM onset. Thus, contributing to the understanding of how inflammatory processes lead to the dysregulation of placental homeostasis ultimately impairing fetal development.

Relevance of placental type I interferon beta regulation for pregnancy success

Pregnancy is a unique immunologic and microbial condition that requires an adequate level of awareness to provide a fast and protective response against pathogens as well as to maintain a state of tolerance to paternal antigens. Dysregulation of inflammatory pathways in the placenta triggered by pathogens is one of the main factors responsible for pregnancy complications. Type I IFNs are key molecules modulating immune responses at the level of the placenta and are crucial for protection of the pregnancy via their antiviral and immune modulatory properties. In this study, we elucidate the mechanisms controlling the basal expression of IFNβ and its negative feedback. Using in vitro and in vivo animal models, we found that TLR signaling maintains basal IFNβ levels through the TLR4-MyD88-independent TBK/IRF3 signaling pathway. We describe the role of the TAM receptor Axl in the regulation of IFNβ function in human and mouse trophoblast cells. The absence of TAM receptors in vivo is associated with fetal demise due to dysregulation of IFNβ expression and its pro-apoptotic downstream effectors. Collectively, our data describe a feedback signaling pathway controlling the expression and function of IFNβ in the trophoblast that is essential for an effective response during viral and microbial infections.

Zika, dengue and yellow fever viruses induce differential anti-viral immune responses in human monocytic and first trimester trophoblast cells

Zika virus (ZIKV) is a mosquito-borne flavivirus associated with severe neonatal birth defects, but the causative mechanism is incompletely understood. ZIKV shares sequence homology and early clinical manifestations with yellow fever virus (YFV) and dengue virus (DENV) and are all transmitted in urban cycles by the same species of mosquitoes. However, YFV and DENV have been rarely reported to cause congenital diseases. Here, we compared infection with a contemporary ZIKV strain (FSS13025) to YFV17D and DENV-4 in human monocytic cells (THP-1) and first-trimester trophoblasts (HTR-8). Our results suggest that all three viruses have similar tropisms for both cells. Nevertheless, ZIKV induced strong type 1 IFN and inflammatory cytokine and chemokine production in monocytes and peripheral blood mononuclear cells. Furthermore, ZIKV infection in trophoblasts induced lower IFN and higher inflammatory immune responses. Placental inflammation is known to contribute to the risk of brain damage in preterm newborns. Inhibition of toll-like receptor (TLR)3 and TLR8 each abrogated the inflammatory cytokine responses in ZIKV-infected trophoblasts. Our findings identify a potential link between maternal immune activation and ZIKV-induced congenital diseases, and a potential therapeutic strategy that targets TLR-mediated inflammatory responses in the 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.

Immune Regulation in Pregnancy: A Matter of Perspective?

The maternal immune system is complex and governed by multiple hormonal and metabolic factors, including those provided to the mother via the fetus. Understanding of the balance between maternal tolerance and protection of the fetus may require thinking from multiple theoretical approaches to the general problem of immune activation and tolerance. This article provides a brief review of the immune system, with aspects relevant to pregnancy. The references include reviews that expand on the elements discussed. The article also uses different models of immune system activation and tolerance to provide a theoretical understanding of the problem of maternal tolerance.

Immune Regulation in Pregnancy: A Matter of Perspective?

The maternal immune system is complex and governed by multiple hormonal and metabolic factors, including those provided to the mother via the fetus. Understanding of the balance between maternal tolerance and protection of the fetus may require thinking from multiple theoretical approaches to the general problem of immune activation and tolerance. This article provides a brief review of the immune system, with aspects relevant to pregnancy. The references include reviews that expand on the elements discussed. The article also uses different models of immune system activation and tolerance to provide a theoretical understanding of the problem of maternal tolerance.

Trophoblast-microbiome interaction: a new paradigm on immune regulation

The immunologic paradigm of pregnancy led to the conceptualization of pregnancy as an organ transplant that requires, for its success, suppression of the maternal immune system. Growing scientific evidence suggests that in many ways the placenta functions as a tumor rather than a transplant and the immune regulation of the maternal-fetal interface is the result of the coordinated interaction between all its cellular components, including bacteria. Examining the role of microbiota in reproduction is in its infancy, but there is growing literature that supports its relevance. We discuss a potential normal function of bacteria in the establishment of immune tolerance and compelling evidence that a viral infection might be the underlying cause of perturbation of homeostasis. There is compelling evidence that many infectious diseases of human beings are caused by >1 microorganism and are defined as polymicrobial infections. We propose that pregnancy complications, such as preterm birth, are the result of polymicrobial infections. We examine the potential cellular and molecular mechanisms by which a viral infection of the placenta might disrupt the normal interaction between the cellular component of the implantation site and bacteria. As we better understand the normal homeostasis among the maternal immune system, placenta, and commensal, we will be able to elucidate pathogenic conditions and design better approaches to treat pregnancy complications associated with infection.

Hepatitis C Virus Sensing by Human Trophoblasts Induces Innate Immune Responses and Recruitment of Maternal NK Cells: Potential Implications for Limiting Vertical Transmission

Hepatitis C virus (HCV) is the world's most common blood-borne viral infection for which there is no vaccine. The rates of vertical transmission range between 3 and 6% with odds 90% higher in the presence of HIV coinfection. Prevention of vertical transmission is not possible because of lack of an approved therapy for use in pregnancy or an effective vaccine. Recently, HCV has been identified as an independent risk factor for preterm delivery, perinatal mortality, and other complications. In this study, we characterized the immune responses that contribute to the control of viral infection at the maternal-fetal interface (MFI) in the early gestational stages. In this study, we show that primary human trophoblast cells and an extravillous trophoblast cell line (HTR8), from first and second trimester of pregnancy, express receptors relevant for HCV binding/entry and are permissive for HCV uptake. We found that HCV-RNA sensing by human trophoblast cells induces robust upregulation of type I/III IFNs and secretion of multiple chemokines that elicit recruitment and activation of decidual NK cells. Furthermore, we observed that HCV-RNA transfection induces a proapoptotic response within HTR8 that could affect the morphology of the placenta. To our knowledge, for the first time, we demonstrate that HCV-RNA sensing by human trophoblast cells elicits a strong antiviral response that alters the recruitment and activation of innate immune cells at the MFI. This work provides a paradigm shift in our understanding of HCV-specific immunity at the MFI as well as novel insights into mechanisms that limit vertical transmission but may paradoxically lead to virus-related pregnancy complications.

Placenta-on-a-chip: a novel platform to study the biology of the human placenta

OBJECTIVE

Studying the biology of the human placenta represents a major experimental challenge. Although conventional cell culture techniques have been used to study different types of placenta-derived cells, current in vitro models have limitations in recapitulating organ-specific structure and key physiological functions of the placenta. Here we demonstrate that it is possible to leverage microfluidic and microfabrication technologies to develop a microengineered biomimetic model that replicates the architecture and function of the placenta.

MATERIALS AND METHODS

A "Placenta-on-a-Chip" microdevice was created by using a set of soft elastomer-based microfabrication techniques known as soft lithography. This microsystem consisted of two polydimethylsiloxane (PDMS) microfluidic channels separated by a thin extracellular matrix (ECM) membrane. To reproduce the placental barrier in this model, human trophoblasts (JEG-3) and human umbilical vein endothelial cells (HUVECs) were seeded onto the opposite sides of the ECM membrane and cultured under dynamic flow conditions to form confluent epithelial and endothelial layers in close apposition. We tested the physiological function of the microengineered placental barrier by measuring glucose transport across the trophoblast-endothelial interface over time. The permeability of the barrier study was analyzed and compared to that obtained from acellular devices and additional control groups that contained epithelial or endothelial layers alone.

RESULTS

Our microfluidic cell culture system provided a tightly controlled fluidic environment conducive to the proliferation and maintenance of JEG-3 trophoblasts and HUVECs on the ECM scaffold. Prolonged culture in this model produced confluent cellular monolayers on the intervening membrane that together formed the placental barrier. This in vivo-like microarchitecture was also critical for creating a physiologically relevant effective barrier to glucose transport. Quantitative investigation of barrier function was conducted by calculating permeability coefficients and metabolic rates in varying conditions of barrier structure. The rates of glucose transport and metabolism were consistent with previously reported in vivo observations.

CONCLUSION

The "Placenta-on-a-Chip" microdevice described herein provides new opportunities to simulate and analyze critical physiological responses of the placental barrier. This system may be used to address the major limitations of existing placenta model systems and serve to enable research platforms for reproductive biology and medicine.

Induction of an embryonic mouse innate immune response following inoculation in utero with minute virus of mice

We used an embryonic-infection model system to show that MVMp, the prototypic minute virus of mice (MVM) serotype and a member of the genus Protoparvovirus, triggers a comprehensive innate immune response in the developing mouse embryo. Direct inoculation of the midtrimester embryo in utero with MVMp results in a widespread, productive infection. During a 96-h infection course, embryonic beta interferon (IFN-β) and IFN-γ transcription were induced 90- and 60-fold, respectively. IFN-β levels correlated with the embryo viral burden, while IFN-γ levels first increased and then decreased. Production of proinflammatory cytokines, interleukin 1β (IL-1β) and tumor necrosis factor alpha (TNF-α), also increased, but by smaller amounts, approximately 7-fold each. We observed increased levels of downstream antiviral effector molecules, PKR and phosphorylated STAT2. Finally, we showed that there is an immune cell response to the virus infection. Infected tissues in the embryo exhibited an increased density of mature leukocytes compared to the same tissues in uninfected embryos. The responses we observed were almost completely restricted to the infected embryos. Uninfected littermates routinely exhibited small increases in innate immune components that rarely reached statistical significance compared to negative controls. Similarly, the placentae of infected embryos did not show any significant increase in transcription of innate immune cytokines. Since the placenta has both embryonic and maternal components, we suggest there is minimal involvement of the dam in the response to infection.

IMPORTANCE

Interaction between the small single-stranded vertebrate DNA viruses, the protoparvoviruses, and the host innate immune system has been unclear. The issue is important practically given the potential use of these viruses as oncotherapeutic agents. The data reported here stand in contrast to studies of innate immune response during protoparvovirus infection of adult hosts, which invariably reported no or minimal and sporadic induction of an interferon response during infection. We conclude that under conditions of robust and productive MVM infection, a normal murine host is able to mount a significant and broad innate immune response.

Viral single stranded RNA induces a trophoblast pro-inflammatory and antiviral response in a TLR8-dependent and -independent manner

Interest is growing in the role of viral infections and their association with adverse pregnancy outcomes. The trophoblast is permissive to viruses, but little is known about their impact on the placenta. We previously established that viral single stranded RNA (ssRNA), a Toll-like receptor 8 (TLR8) agonist, induces a restricted trophoblast pro-inflammatory cytokine/chemokine response by upregulating the secretion of interleukin (IL)-6 and IL-8. In parallel, the type I interferon, IFNbeta, is produced and acts back on the cell in an autocrine/paracrine manner to trigger caspase-3-dependent apoptosis. In this study, we sought to extend these findings by determining the mechanisms involved, examining whether viral ssRNA could induce a trophoblast antiviral response, and evaluating the influence of viral ssRNA on pregnancy outcome using a mouse model. Viral ssRNA induced human first-trimester trophoblast inflammation, type I interferon production, an antiviral response, and apoptosis in both a TLR8/MyD88-dependent and -independent manner. Furthermore, administration of viral ssRNA to pregnant mice induced placental caspase-3 activation, a pro-inflammatory cytokine/chemokine, type I interferon, and antiviral response as well as immune cell infiltration. Thus, ssRNA viral infections may compromise pregnancy by altering placental trophoblast survival and function through both TLR8 and non-TLR8 signaling pathways, leading to immune changes at the maternal-fetal interface.

New insights into the relationship between viral infection and pregnancy complications

A recent study by McDonnold and coinvestigators published in Am J Obstet Gynecol reports an association between human papillomavirus (HPV) infection and preeclampsia. The investigation was based on the hypothesis that HPV trophoblast infection results in failed trophoblast invasion, and placental dysfunction and hypoxia. The findings from this study along with previous data addressing the relationship between viral infection and obstetrical complications highlight the relevance of viral infection during pregnancy. A better understanding of mechanisms via which virus leads to pregnancy complications will drive us closer to finding a strategy to prevent adverse outcomes.

Endoglin in amniotic fluid as a risk factor for the subsequent development of bronchopulmonary dysplasia

OBJECTIVE

Cross-talk between inflammation and angiogenesis pathways has been recently reported. The objectives of this study were to: (i) examine whether amniotic fluid (AF) concentrations of soluble endoglin (sEng), a protein with anti-angiogenic properties, change during pregnancy, parturition, or intra-amniotic infection and/or inflammation (IAI); (ii) determine whether an increase in sEng in the AF of patients with preterm labor (PTL) and preterm prelabor rupture of membranes (PROM) is associated with adverse neonatal outcomes; and (iii) investigate potential sources of sEng in AF.

STUDY DESIGN

A cross-sectional study was conducted to include patients in the following groups: (i) mid-trimester (n = 20); (ii) PTL with term delivery (n = 95); (iii) PTL leading to preterm delivery with (n = 40) and without IAI (n = 46); (iv) preterm PROM with (n = 37) and without IAI (n = 37); (v) term in labor (n = 48) and not in labor (n = 44). AF concentrations of sEng were determined by enzyme-linked immunosorbent assay. Chorioamniotic membranes, umbilical cord blood, and AF macrophages were examined for the expression of endoglin.

RESULTS

(i) Patients with IAI had a higher median AF concentration of sEng than those without IAI (P = 0.02 for PTL and 0.06 for preterm PROM); (ii) AF concentrations of sEng in the 3rd and 4th quartiles were associated with IAI (OR 2.5 and 7.9, respectively); (iii) an AF sEng concentration ≥779.5 pg/mL was associated with bronchopulmonary dysplasia (BPD) (OR 7.9); (iv) endoglin was co-localized with CD14+ macrophages in AF pellets of patients with IAI by immunofluorescence and flow cytometry; and (v) the concentration of sEng in the supernatant was significantly increased after the treatment of macrophages with endotoxin or TNF-α.

CONCLUSIONS

Soluble endoglin participates in the host response against IAI. Activated macrophages may be a source of sEng concentrations in the AF of patients with IAI. An increase of sEng in the AF is associated with BPD and adverse neonatal outcomes.

Viral invasion of the amniotic cavity (VIAC) in the midtrimester of pregnancy

INTRODUCTION

The prevalence of viral infections in the amniotic fluid (AF) has not yet been ascertained. The aim of this study was to determine the prevalence of specific viral nucleic acids in the AF and its relationship to pregnancy outcome.

STUDY DESIGN

From a cohort of 847 consecutive women undergoing midtrimester amniocentesis, 729 cases were included in this study after exclusion of documented fetal anomalies, chromosomal abnormalities, unavailability of AF specimens and clinical outcomes. AF specimens were tested by quantitative real-time PCR for the presence of genome sequences of the following viruses: adenoviruses, herpes simplex virus (HSV), varicella zoster virus (VZV), human herpesvirus 6 (HHV6), human cytomegalovirus (HCMV), Epstein-Barr virus (EBV), parvovirus B19 and enteroviruses. Viral nucleic acid testing was also performed in maternal blood and cord blood in the population of women in whom AF was positive for viruses and in a control group of 29 women with AF negative for viral nucleic acids. The relationship between the presence of viruses and pregnancy and neonatal outcome was examined. The correlation between the presence of nucleic acids of viruses in the AF and the concentration of the cytokine interleukin-6 (IL-6) and the T cell chemokine CXCL-10 (or IP-10) in AF and maternal blood were analyzed.

RESULTS

Viral genome sequences were found in 16 of 729 (2.2%) AF samples. HHV6 was the most commonly detected virus (7 cases, 1.0%), followed by HCMV (6 cases, 0.8%), parvovirus B19 (2 cases, 0.3%) and EBV (1 case, 0.1%), while HSV, VZV, enteroviruses and adenoviruses were not found in this cohort. Corresponding viral DNA was also detected in maternal blood of six out of seven women with HHV6-positive AF and in the umbilical cord plasma, which was available in one case. In contrast, viral DNA was not detected in maternal blood of women with AF positive for parvovirus B19, HCMV, EBV or of women with AF negative for viruses. HHV6 genome copy number in AF and maternal blood was consistent with genomic integration of viral DNA and genetic infection in all women. There was no significant difference in the AF concentration of IL-6 and IP-10 between patients with and without VIAC. However, for HCMV, there was a significant relationship between viral copy number and IP-10 concentration in maternal blood and AF. The group of women with AF positive for viral DNA delivered at term healthy neonates without complications in 14 out of 16 cases. In one case of HHV6 infection in the AF, the patient developed gestational hypertension at term, and in another case of HHV6 infection in the AF, the patient delivered at 33 weeks after preterm premature rupture of membranes (PPROM).

CONCLUSION

Viral nucleic acids are detectable in 2.2% of AF samples obtained from asymptomatic women in the midtrimester. HHV6 was the most frequently detected virus in AF. Adenoviruses were not detected. Vertical transmission of HHV6 was demonstrated in one case.

Placental Toll-like receptor 3 and Toll-like receptor 7/8 activation contributes to preeclampsia in humans and mice

Preeclampsia (PE) is a pregnancy-specific hypertensive syndrome characterized by excessive maternal immune system activation, inflammation, and endothelial dysfunction. Toll-like receptor (TLR) 3 activation by double-stranded RNA (dsRNA) and TLR7/8 activation by single-stranded RNA (ssRNA) expressed by viruses and/or released from necrotic cells initiates a pro-inflammatory immune response; however it is unknown whether viral/endogenous RNA is a key initiating signal that contributes to the development of PE. We hypothesized that TLR3/7/8 activation will be evident in placentas of women with PE, and sufficient to induce PE-like symptoms in mice. Placental immunoreactivity and mRNA levels of TLR3, TLR7, and TLR8 were increased significantly in women with PE compared to normotensive women. Treatment of human trophoblasts with the TLR3 agonist polyinosine-polycytidylic acid (poly I:C), the TLR7-specific agonist imiquimod (R-837), or the TLR7/8 agonist CLO97 significantly increased TLR3/7/8 levels. Treatment of mice with poly I:C, R-837, or CLO97 caused pregnancy-dependent hypertension, endothelial dysfunction, splenomegaly, and placental inflammation. These data demonstrate that RNA-mediated activation of TLR3 and TLR7/8 plays a key role in the development of PE.

Pathogens and the placental fortress

Placental infections are major causes of maternal and fetal disease. This review introduces a new paradigm for placental infections based on current knowledge of placental defenses and how this barrier can be breached. Transmission of pathogens from mother to fetus can occur at two sites of direct contact between maternal cells and specialized fetal cells (trophoblasts) in the human placenta: firstly, maternal immune and endothelial cells juxtaposed to extravillous trophoblasts in the uterine implantation site and secondly, maternal blood surrounding the syncytiotrophoblast (SYN). Recent findings suggest that the primary vulnerability is in the implantation site. We explore evidence that the placental SYN evolved as a defense against pathogens, and that inflammation-mediated spontaneous abortion may benefit mother and pathogen.

Immunomodulator expression in trophoblasts from the feline immunodeficiency virus (FIV)-infected cat

Background

FIV infection frequently compromises pregnancy under experimental conditions and is accompanied by aberrant expression of some placental cytokines. Trophoblasts produce numerous immunomodulators that play a role in placental development and pregnancy maintenance. We hypothesized that FIV infection may cause dysregulation of trophoblast immunomodulator expression, and aberrant expression of these molecules may potentiate inflammation and compromise pregnancy. The purpose of this project was to evaluate the expression of representative pro-(TNF-α, IFN-γ, IL-1β, IL-2, IL-6, IL-12p35, IL-12p40, IL-18, and GM-CSF) and anti-inflammatory cytokines (IL-4, IL-5, and IL-10); CD134, a secondary co-stimulatory molecule expressed on activated T cells (FIV primary receptor); the chemokine receptor CXCR4 (FIV co-receptor); SDF-1α, the chemokine ligand to CXCR4; and FIV gag in trophoblasts from early-and late-term pregnancy.

Methods

We used an anti-cytokeratin antibody in immunohistochemistry to identify trophoblasts selectively, collected these cells using laser capture microdissection, and extracted total RNA from the captured cell populations. Real time, reverse transcription-PCR was used to quantify gene expression.

Results

We detected IL-4, IL-5, IL-6, IL-1β, IL-12p35, IL-12p40, and CXCR4 in trophoblasts from early-and late-term pregnancy. Expression of cytokines increased from early to late pregnancy in normal tissues. A clear, pro-inflammatory microenvironment was not evident in trophoblasts from FIV-infected queens at either stage of pregnancy. Reproductive failure was accompanied by down-regulation of both pro-and anti-inflammatory cytokines. CD134 was not detected in trophoblasts, and FIV gag was detected in only one of ten trophoblast specimens collected from FIV-infected queens.

Conclusion

Feline trophoblasts express an array of pro-and anti-inflammatory immunomodulators whose expression increases from early to late pregnancy in normal tissues. Non-viable pregnancies were associated with decreased expression of immunomodulators which regulate trophoblast invasion in other species. The detection of FIV RNA in trophoblasts was rare, suggesting that the high rate of reproductive failure in FIV-infected queens was not a direct result of viral replication in trophoblasts. The influence of placental immune cells on trophoblast function and pregnancy maintenance in the FIV-infected cat requires additional study.

Viral infection of the placenta leads to fetal inflammation and sensitization to bacterial products predisposing to preterm labor

Pandemics pose a more significant threat to pregnant women than to the nonpregnant population and may have a detrimental effect on the well being of the fetus. We have developed an animal model to evaluate the consequences of a viral infection characterized by lack of fetal transmission. The experiments described in this work show that viral infection of the placenta can elicit a fetal inflammatory response that, in turn, can cause organ damage and potentially downstream developmental deficiencies. Furthermore, we demonstrate that viral infection of the placenta may sensitize the pregnant mother to bacterial products and promote preterm labor. It is critical to take into consideration the fact that during pregnancy it is not only the maternal immune system responding, but also the fetal/placental unit. Our results further support the immunological role of the placenta and the fetus affecting the global response of the mother to microbial infections. This is relevant for making decisions associated with treatment and prevention during pandemics.