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

Transplacental delivery of factor IX Fc-fusion protein ameliorates bleeding phenotype of newborn hemophilia B mice

Hemophilia B is an inherited hemorrhagic disorder characterized by a deficiency of blood coagulation factor IX (FIX) that results in abnormal blood coagulation. The blood coagulation is already evident in hemophiliacs at the fetal stage, and thus intracranial hemorrhage and other bleeding complications can occur at birth, leading to sequelae. Therefore, it is important to develop effective treatments for hemophiliacs in utero. In this study, in order to transplacentally deliver FIX from pregnant mice to their fetuses, an improved adenovirus (Ad) vector expressing human FIX fused with the IgG Fc domain (FIX Fc fusion protein), which plays a crucial role in neonatal Fc receptor (FcRn)-mediated transcytosis across the placenta, was intravenously administered to E13.5 pregnant mice. Significant levels of FIX Fc fusion protein were detected in 0-day-old newborn mice whose mothers were administered an Ad vector expressing FIX Fc fusion protein. Wild-type FIX overexpressed in the pregnant mice was not delivered to the fetuses. Plasma FIX levels in the newborn mice were relatively well correlated with those in their mothers, although transplacental delivery efficiencies of FIX Fc fusion protein were slightly reduced when the FIX Fc fusion protein was highly expressed in the mother mice. Plasma FIX levels in the newborn mice were about 3.6-6.4% of those in their mothers, Transplacental delivery of FIX Fc fusion protein to their fetuses successfully improved the blood clotting ability in the newborn mice.

Deep metagenomic characterization of the gut virome in pregnant women with preeclampsia

Preeclampsia (PE), a pregnancy-specific syndrome, has been associated with the gut bacteriome. Here, to investigate the impact of the gut virome on the development of PE, we identified over 8,000 nonredundant viruses from the fecal metagenomes of 40 early-onset PE and 37 healthy pregnant women and profiled their abundances. Comparison and correlation analysis showed that PE-enriched viruses frequently connected to Blautia species enriched in PE. By contrast, bacteria linked to PE-depleted viruses were often the Bacteroidaceae members such as Bacteroides spp., Phocaeicola spp., Parabacteroides spp., and Alistipes shahii. In terms of viral function, PE-depleted viruses had auxiliary metabolic genes that participated in the metabolism of simple and complex polysaccharides, sulfur metabolism, lipopolysaccharide biosynthesis, and peptidoglycan biosynthesis, while PE-enriched viruses had a gene encoding cyclic pyranopterin monophosphate synthase, which seemed to be special, that participates in the biosynthesis of the molybdenum cofactor. Furthermore, the classification model based on gut viral signatures was developed to discriminate PE patients from healthy controls and showed an area under the receiver operating characteristic curve of 0.922 that was better than that of the bacterium-based model. This study opens up new avenues for further research, providing valuable insights into the PE gut virome and offering potential directions for future mechanistic and therapeutic investigations, with the ultimate goal of improving the diagnosis and management of PE.IMPORTANCEThe importance of this study lies in its exploration of the previously overlooked but potentially critical role of the gut virome in preeclampsia (PE). While the association between PE and the gut bacteriome has been recognized, this research takes a pioneering step into understanding how the gut virome, represented by over 8,000 nonredundant viruses, contributes to this condition. The findings reveal intriguing connections between PE-enriched viruses and specific gut bacteria, such as the prevalence of Blautia species in individuals with PE, contrasting with bacteria linked to PE-depleted viruses, including members of the Bacteroidaceae family. These viral interactions and associations provide a deeper understanding of the complex dynamics at play in PE.

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.

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.

Activation of the Interferon Pathway in Trophoblast Cells Productively Infected with SARS-CoV-2

SARS-CoV-2 infection during pregnancy has been associated with poor maternal and neonatal outcomes and placental defects. The placenta, which acts as a physical and immunological barrier at the maternal-fetal interface, is not established until the end of the first trimester. Therefore, localized viral infection of the trophoblast compartment early in gestation could trigger an inflammatory response resulting in altered placental function and consequent suboptimal conditions for fetal growth and development. In this study, we investigated the effect of SARS-CoV-2 infection in early gestation placentae using placenta-derived human trophoblast stem cells (TSCs), a novel in vitro model, and their extravillous trophoblast (EVT) and syncytiotrophoblast (STB) derivatives. SARS-CoV-2 was able to productively replicate in TSC-derived STB and EVT, but not undifferentiated TSCs, which is consistent with the expression of SARS-CoV-2 entry host factors, ACE2 (angiotensin-converting enzyme 2) and TMPRSS2 (transmembrane cellular serine protease) in these cells. In addition, both TSC-derived EVT and STB infected with SARS-CoV-2 elicited an interferon-mediated innate immune response. Combined, these results suggest that placenta-derived TSCs are a robust in vitro model to investigate the effect of SARS-CoV-2 infection in the trophoblast compartment of the early placenta and that SARS-CoV-2 infection in early gestation activates the innate immune response and inflammation pathways. Therefore, placental development could be adversely affected by early SARS-CoV-2 infection by directly infecting the developing differentiated trophoblast compartment, posing a higher risk for poor pregnancy outcomes.

Adeno-associated virus infection and its impact in human health: an overview

Discovered as a contaminant of adenovirus stocks in the 1960s, adeno-associated virus (AAV) is a mono-stranded DNA virus that depends on helper factors to replicate. Even though AAV is endemic in the human population (35-80%), it is remarkable that many issues concerning the natural infection by this virus remain unanswered. In this study, we reflect on the main basic aspects of AAV biology and provide an overview of the studies exploring the impact of AAV infection on human health, focusing on three major research areas including, (i) cervical and (ii) liver cancer, and (iii) reproductive system disorders. Conflicting results have been obtained into the association of AAV infection with the occurrence of adverse reproductive outcomes, such as placental complications, spontaneous abortion, and fertility disorders, or with a protective role in HPV-related cervical carcinogenesis. Noteworthy, recent reports have identified AAV insertional mutagenesis as a novel risk factor for the development of hepatocellular carcinoma. This latest finding raises concern regarding the widespread usage of AAV vectors in liver-targeted gene therapy.

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.

SARS-CoV-2 infection during pregnancy and risk of preeclampsia: a systematic review and meta-analysis

OBJECTIVE

To examine the relationship between SARS-CoV-2 infection during pregnancy and the risk for preeclampsia.

DATA SOURCES

MEDLINE, Embase, POPLINE, CINAHL, LILACS, and the World Health Organization COVID-19, Chinese, and preprint databases (all from December 1, 2019, to May 31, 2021). Google Scholar, bibliographies, and conference proceedings were also searched.

STUDY ELIGIBILITY CRITERIA

Observational studies that assessed the association between SARS-CoV-2 infection during pregnancy and preeclampsia and that reported unadjusted and/or adjusted risk estimates and 95% confidence intervals or data to calculate them.

STUDY APPRAISAL AND SYNTHESIS METHODS

The primary outcome was preeclampsia. Secondary outcomes included preeclampsia with severe features, preeclampsia without severe features, eclampsia, and hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome. Two reviewers independently reviewed studies for inclusion, assessed their risk of bias, and extracted data. Pooled unadjusted and adjusted odds ratios with 95% confidence intervals, and 95% prediction interval were calculated. Heterogeneity was quantified using the І2 statistic, for which І2≥30% indicated substantial heterogeneity. Subgroup and sensitivity analyses were performed to test the robustness of the overall findings.

RESULTS

A total of 28 studies comprising 790,954 pregnant women, among which 15,524 were diagnosed with SARS-CoV-2 infection, met the inclusion criteria. The meta-analysis of unadjusted odds ratios showed that the odds of developing preeclampsia were significantly higher among pregnant women with SARS-CoV-2 infection than among those without SARS-CoV-2 infection (7.0% vs 4.8%; pooled odds ratio, 1.62; 95% confidence interval, 1.45-1.82; P<.00001; І2=17%; 26 studies; 95% prediction interval of the odds ratio, 1.28-2.05). The meta-analysis of adjusted odds ratios also showed that SARS-CoV-2 infection during pregnancy was associated with a significant increase in the odds of preeclampsia (pooled odds ratio, 1.58; 95% confidence interval, 1.39-1.80; P<.0001; І2=0%; 11 studies). There was a statistically significant increase in the odds of preeclampsia with severe features (odds ratio, 1.76; 95% confidence interval, 1.18-2.63; І2=58%; 7 studies), eclampsia (odds ratio, 1.97; 95% confidence interval, 1.01-3.84; І2=0%, 3 studies), and HELLP syndrome (odds ratio, 2.10; 95% confidence interval, 1.48-2.97; 1 study) among pregnant women with SARS-CoV-2 infection when compared to those without the infection. Overall, the direction and magnitude of the effect of SARS-CoV-2 infection during pregnancy on preeclampsia was consistent across most prespecified subgroup and sensitivity analyses. Both asymptomatic and symptomatic SARS-CoV-2 infections significantly increased the odds of developing preeclampsial; however, it was higher among patients with symptomatic illness (odds ratio, 2.11; 95% confidence interval, 1.59-2.81) than among those with asymptomatic illness (odds ratio, 1.59; 95% confidence interval, 1.21-2.10).

CONCLUSION

SARS-CoV-2 during pregnancy is associated with higher odds of preeclampsia.

Role of GRK2 in Trophoblast Necroptosis and Spiral Artery Remodeling: Implications for Preeclampsia Pathogenesis

Impaired invasion of extravillous trophoblasts and severe oxidative stress manifest the poor placentation in preeclampsia, which is life-threatening and more than a hypertensive disease of pregnancy. Previous studies have reported that G protein-coupled receptor kinases (GRKs) play a key role in initiating hypertension and hypertensive renal damage, yet little evidence so far suggests a link between GRKs and preeclampsia-related hypertension. Here, we demonstrate GRK2 expression is significantly downregulated (P < 0.0001) in preeclamptic placentae compared to normotensive controls. Knockdown or inhibition of GRK2 in placentae caused insufficient arterial remodeling and elevated trophoblast necroptosis in vivo. These further induced preeclampsia-like phenotype in mice: hypertension, proteinuria, and elevated pro-angiogenic cytokines. By human extra-villous invasive trophoblast cell line (HTR8/SVneo cells), we revealed the knockdown or inhibition of GRK2 triggered excessive death with typical necroptotic characteristics: nuclear envelope rupture and the activation of RIPK1, RIPK3, and MLKL. Necrostatin-1, an inhibitor of RIPK1, is able to restore the survival of trophoblasts. Together, our findings demonstrated that insufficient GRK2 activity compromises spiral artery remodeling and initiates necrotic events in placentae, thereby leading to preeclampsia. These findings advance our understanding of GRK2 in the pathogenesis of preeclampsia and could shed light on a potential treatment for preeclampsia.

Metagenomic profiling of placental tissue suggests DNA virus infection of the placenta is rare

It is widely recognized that pathogens can be transmitted across the placenta from mother to foetus. Recent re-evaluation of metagenomic studies indicates that the placenta has no unique microbiome of commensal bacteria. However, viral transmission across the placenta, including transmission of DNA viruses such as the human herpesviruses, is possible. A fuller understanding of which DNA virus sequence can be found in the placenta is required. We employed a metagenomic analysis to identify viral DNA sequences in placental metagenomes from full-term births (20 births), pre-term births (13 births), births from pregnancies associated with antenatal infections (12 births) or pre-term births with antenatal infections (three births). Our analysis found only a small number of DNA sequences corresponding to the genomes of human herpesviruses in four of the 48 metagenomes analysed. Therefore, our data suggest that DNA virus infection of the placenta is rare and support the concept that the placenta is largely free of pathogen infection.

Cadmium exposure reduces invasion of the human trophoblast-derived HTR-8/SVneo cells by inhibiting cell adhesion and matrix metalloproteinase-9 secretion

Preeclampsia and intrauterine growth restriction, multisystemic disorders characterized by a shallow trophoblast invasion, have been associated with maternal cadmium (Cd) exposure. The molecular mechanisms of this association remain unknown. Cell adhesion and matrix metalloproteinase production are essential for an adequate trophoblast invasion. Thus, the aim of this study was to determine the effect of Cd exposure on invasion, adhesion, and matrix metalloproteinase-9 (MMP-9) production in the trophoblast-derived HTR-8/SVneo cell line. Cultured HTR-8/SVneo trophoblast cells were incubated with different concentrations of CdCl₂ for 6 h. Cell invasion was determined by the transwell assay, while cell adhesion was examined on collagen type I. MMP-9 release and activity were measured by ELISA and zymography, respectively. MMP-9 mRNA expression was detected by reverse-transcription polymerase chain reaction, while intracellular MMP-9 protein was assessed by Western blotting. Cd exposure significantly decreased the invasion and adhesion of HTR-8/SVneo cells. Also, MMP-9 levels and activity in the culture medium were significantly reduced after Cd incubation. In contrast, MMP-9 mRNA expression and intracellular protein levels were significantly increased. These data indicate that Cd reduces trophoblast cells invasiveness by inhibiting cell adhesion and MMP-9 secretion.

Immunology of the Placenta

In this article, the authors provide a general overview of the major immune cells present at the maternal-fetal interface, describe the key mechanisms used by the placenta to promote maternal immune regulation, tolerance, and adaptation, and discuss how dysregulation of these pathways could lead to obstetric complications such as pregnancy loss and preeclampsia. Finally, they conclude with a description of the innate immune properties of the human placenta that not only serve to protect the pregnancy from infection but also contribute to pregnancy complications such as preterm birth.

Antiviral Inflammation during Early Pregnancy Reduces Placental and Fetal Growth Trajectories

Many viruses are detrimental to pregnancy and negatively affect fetal growth and development. What is not well understood is how virus-induced inflammation impacts fetal-placental growth and developmental trajectories, particularly when inflammation occurs in early pregnancy during nascent placental and embryo development. To address this issue, we simulated a systemic virus exposure in early pregnant rats (gestational day 8.5) by administering the viral dsRNA mimic polyinosinic:polycytidylic acid (PolyI:C). Maternal exposure to PolyI:C induced a potent antiviral response and hypoxia in the early pregnant uterus, containing the primordial placenta and embryo. Maternal PolyI:C exposure was associated with decreased expression of the maternally imprinted genes Mest, Sfrp2, and Dlk1, which encode proteins critical for placental growth. Exposure of pregnant dams to PolyI:C during early pregnancy reduced fetal growth trajectories throughout gestation, concomitant with smaller placentas, and altered placental structure at midgestation. No detectable changes in placental hemodynamics were observed, as determined by ultrasound biomicroscopy. An antiviral response was not evident in rat trophoblast stem (TS) cells following exposure to PolyI:C, or to certain PolyI:C-induced cytokines including IL-6. However, TS cells expressed high levels of type I IFNR subunits (Ifnar1 and Ifnar2) and responded to IFN-⍺ by increasing expression of IFN-stimulated genes and decreasing expression of genes associated with the TS stem state, including Mest IFN-⍺ also impaired the differentiation capacity of TS cells. These results suggest that an antiviral inflammatory response in the conceptus during early pregnancy impacts TS cell developmental potential and causes latent placental development and reduced fetal growth.

Molecular Detection of Adeno-Associated Virus DNA in Cases of Spontaneous and Therapeutic Abortion

BACKGROUND

Adeno-associated viruses (AAVs) have been found in human blood cells, cervical biopsies, and epithelial cell brushings, endometrium, and abortion material, which suggest their possible roles in the induction of miscarriage.

OBJECTIVE

In this case control study, the presence of AAV DNA in placental tissue of spontaneous and therapeutic abortions was compared.

METHOD

Placenta samples were evaluated for AAV DNA by hemi-nested PCR in miscarriages occurring in the first 24 weeks of pregnancy from therapeutic and spontaneous abortions.

RESULTS

Eighty-one therapeutic abortions (control group) and 83 spontaneous abortions (case group) were evaluated. Sixty-two (38.2%) of 164 abortions were AAV positive, including 35 (21.6%) spontaneous abortions and 27 (16.6%) therapeutic abortions.

CONCLUSION

There was no statistically significant difference between the presence of the AAV genome in spontaneous and therapeutic abortions. This observation was consistent with other studies in this area.

Genetic and non-genetic risk factors for pre-eclampsia: umbrella review of systematic reviews and meta-analyses of observational studies

OBJECTIVE

To summarize evidence from the literature on genetic and non-genetic risk factors associated with pre-eclampsia (PE), assess the presence of statistical bias in the studies and identify risk factors for which there is robust evidence supporting their association with PE.

METHODS

PubMed and ISI Web of Science were searched from inception to October 2016, to identify systematic reviews and meta-analyses of observational studies examining associations between genetic or non-genetic risk factors and PE. For each meta-analysis, the summary-effect size was estimated using random-effects and fixed-effects models, along with 95% CIs and the 95% prediction interval. Between-study heterogeneity was expressed using the I2 statistic, and evidence of small-study effects (large studies had significantly more conservative results than smaller studies) and evidence of excess significance bias (too many studies with statistically significant results) were estimated.

RESULTS

Fifty-eight eligible meta-analyses were identified, which included 1466 primary studies and provided data on 130 comparisons of risk factors associated with PE, covering a wide range of comorbid diseases, genetic factors, exposure to environmental agents and biomarkers. Sixty-five (50%) associations had nominally statistically significant findings at P < 0.05, while 16 (12%) were significant at P < 10-6 . Sixty-five (50%) associations had large or very large heterogeneity. Evidence for small-study effects and excess significance bias was found in 10 (8%) and 26 (20%) associations, respectively. The only non-genetic risk factor with convincing evidence for an association with PE was oocyte donation vs spontaneous conception, which had a summary odds ratio of 4.33 (95% CI, 3.11-6.03), was supported by 2712 cases with small heterogeneity (I2  = 26%) and 95% prediction intervals excluding the null value, and without hints of small-study effects (P for Egger's test > 0.10) or excess of significance (P > 0.05). Of the statistically significant (P < 0.05) genetic risk factors for PE, only PAI-1 4G/5G (recessive model) polymorphism was supported by strong evidence for a contribution to the pathogenesis of PE. Eleven factors (serum iron level, pregnancy-associated plasma protein-A, chronic kidney disease, polycystic ovary syndrome, mental stress, bacterial and viral infections, cigarette smoking, oocyte donation vs assisted reproductive technology, obesity vs normal weight, severe obesity vs normal weight and primiparity) presented highly suggestive evidence for an association with PE.

CONCLUSIONS

A large proportion of meta-analyses of genetic and non-genetic risk factors for PE have caveats that threaten their validity. Oocyte donation vs spontaneous conception and PAI-1 4G/5G polymorphism (recessive model) showed the strongest consistent evidence for an association with risk for PE. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Natural killer cells and T lymphocytes in pregnancy and pre-eclampsia

Although pre-eclampsia (PE), a hypertensive disorder of pregnancy, has significant maternal and fetal morbidity and mortality worldwide, the mechanisms contributing to this disease have not been fully elucidated. Studies in patients and experimental models have shown that changes in the number or function of immune cells of both the adaptive and innate immune systems contribute to the development and pathogenesis of PE. This commentary summarizes our current understanding of the role of the immune system in the pathogenesis of PE, specifically focussing on dysfunction of natural killer (NK) cells and T lymphocyte populations.

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.

Depletion of MHC class II invariant chain peptide or γ–δ T-cells ameliorates experimental preeclampsia

Excessive innate immune system activation and inflammation during pregnancy can lead to organ injury and dysfunction and preeclampsia (PE); however, the molecular mechanisms involved are unknown. We tested the hypothesis that Toll-like receptor (TLR) activation induces major histocompatibility complex (MHC) class II invariant chain peptide (CLIP) expression on immune cells, makes them pro-inflammatory, and are necessary to cause PE-like features in mice. Treatment with VG1177, a competitive antagonist peptide for CLIP in the groove of MHC class II, was able to both prevent and treat PE-like features in mice. We then determined that γ–δ T cells are critical for the development of PE-like features in mice since γ–δ T-cell knockout mice, like CLIP deficient mice, are resistant to developing PE-like features. Placentas from women with PE exhibit significantly increased levels of γ–δ T cells. These preclinical data demonstrate that CLIP expression and activated γ–δ T cells are responsible for the development of immunologic PE-like features and that temporarily antagonizing CLIP and/or γ–δ T cells may be a therapeutic strategy for PE.

Recent Advances in Immunity and Hypertension

Persistent immune system activation plays an important role in the development of various forms of hypertension. Activation of the innate immune system, inflammation, and subsequent adaptive immune system response causing end-organ injury and dysfunction ultimately leads to hypertension and its associated sequelae including coronary artery disease, heart failure, stroke, and chronic kidney disease. In this review, we will provide updates on the innate and adaptive immune cells involved in hypertension, the current understanding of how the immune system gets activated, and examine the recently discovered mechanisms involved in several forms of experimental hypertension.

Human infectious diseases and risk of preeclampsia: an updated review of the literature

BACKGROUND

Preeclampsia (PE) is one of the major causes of maternal and perinatal morbidity and mortality, especially in low- and middle-income countries. In recent years, a growing body of literatures suggests that infections by bacteria, viruses, and parasites and their related inflammations play an important role in the pathogenesis of PE.

METHODS

We searched PubMed, Google scholar, and Cochrane databases using the following search words: "infection and preeclampsia," "bacterial infection and preeclampsia," "viral infection and preeclampsia" and "parasitic infection and preeclampsia."

RESULTS

The literature review revealed that many bacteria including Helicobacter pylori, Chlamydia pneumonia, and those are involved in periodontal disease or urinary tract infections (UTIs) and some viral agents such as Cytomegalovirus, herpes simplex virus type-2, human immunodeficiency virus, and some parasites especially Plasmodium spp. and Toxoplasma gondii can be effective in development of PE. Inflammation responses against infections has major role in the inducement of PE. The shift of immunological cytokine profile of Th2 toward Th1 and high levels of pro-inflammatory cytokines (TNF-ɑ, IL-12, IFN-γ, etc.), increase of oxidative stress, increase of anti-angiogenic proteins, increase of vascular endothelial growth factor receptor 1 (sVEGFR1), and complement C5a are the main potential mechanisms related to infections and enhanced development of PE.

CONCLUSION

Thus, early diagnosis and treatment of bacterial, viral, and parasitic infections could be an effective strategy to reduce the incidence of PE.

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.

Placental transcriptome in development and pathology: expression, function, and methods of analysis

The placenta is the essential organ of mammalian pregnancy and errors in its development and function are associated with a wide range of human pathologies of pregnancy. Genome sequencing has led to methods for investigation of the transcriptome (all expressed RNA species) using microarrays and next-generation sequencing, and implementation of these techniques has identified many novel species of RNA including: micro-RNA, long noncoding RNA, and circular RNA. These species can physically interact with both each other and regulatory proteins to modify gene expression and messenger RNA to protein translation. Transcriptome analysis is actively used to investigate placental development and dysfunction in pathologies ranging from preeclampsia and fetal growth restriction to preterm labor. Genome-wide gene expression analysis is also being applied to identify prognostic and diagnostic biomarkers of these disorders. In this comprehensive review we summarize transcriptome biology, methods of isolation and analysis, application to placental development and pathology, and use in diagnostic analysis in maternal blood. Key information for analysis methods is organized into quick reference tables where current analysis techniques and tools are cited and compared. We have created this review as a practical guide and starting reference for those interested in beginning an investigation into the transcriptome of the placenta.

A Method for Remotely Silencing Neural Activity in Rodents During Discrete Phases of Learning

This protocol describes how to temporarily and remotely silence neuronal activity in discrete brain regions while animals are engaged in learning and memory tasks. The approach combines pharmacogenetics (Designer-Receptors-Exclusively-Activated-by-Designer-Drugs) with a behavioral paradigm (sensory preconditioning) that is designed to distinguish between different forms of learning. Specifically, viral-mediated delivery is used to express a genetically modified inhibitory G-protein coupled receptor (the Designer Receptor) into a discrete brain region in the rodent. Three weeks later, when designer receptor expression levels are high, a pharmacological agent (the Designer Drug) is administered systemically 30 min prior to a specific behavioral session. The drug has affinity for the designer receptor and thus results in inhibition of neurons that express the designer receptor, but is otherwise biologically inert. The brain region remains silenced for 2-5 hr (depending on the dose and route of administration). Upon completion of the behavioral paradigm, brain tissue is assessed for correct placement and receptor expression. This approach is particularly useful for determining the contribution of individual brain regions to specific components of behavior and can be used across any number of behavioral paradigms.

Large scale aggregate microarray analysis reveals three distinct molecular subclasses of human preeclampsia

Background

Preeclampsia (PE) is a life-threatening hypertensive pathology of pregnancy affecting 3–5% of all pregnancies. To date, PE has no cure, early detection markers, or effective treatments short of the removal of what is thought to be the causative organ, the placenta, which may necessitate a preterm delivery. Additionally, numerous small placental microarray studies attempting to identify “PE-specific” genes have yielded inconsistent results. We therefore hypothesize that preeclampsia is a multifactorial disease encompassing several pathology subclasses, and that large cohort placental gene expression analysis will reveal these groups.

Results

To address our hypothesis, we utilized known bioinformatic methods to aggregate 7 microarray data sets across multiple platforms in order to generate a large data set of 173 patient samples, including 77 with preeclampsia. Unsupervised clustering of these patient samples revealed three distinct molecular subclasses of PE. This included a “canonical” PE subclass demonstrating elevated expression of known PE markers and genes associated with poor oxygenation and increased secretion, as well as two other subclasses potentially representing a poor maternal response to pregnancy and an immunological presentation of preeclampsia.

Conclusion

Our analysis sheds new light on the heterogeneity of PE patients, and offers up additional avenues for future investigation. Hopefully, our subclassification of preeclampsia based on molecular diversity will finally lead to the development of robust diagnostics and patient-based treatments for this disorder.

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.

Interleukin-4 deficiency induces mild preeclampsia in mice

OBJECTIVE

Inflammation is necessary for successful pregnancy; however, excessive inflammation plays a central role in the development of the pregnancy-specific hypertensive disorder preeclampsia. Numerous anti-inflammatory cytokines are decreased in women with preeclampsia but the role of individual cytokines in blood pressure regulation during pregnancy is unknown. Therefore, we examined whether the lack of the potent anti-inflammatory cytokine interleukin-4 (IL-4) would be sufficient to elicit a preeclampsia-like syndrome in mice, and when coupled with immune system activation that these symptoms would be further augmented.

METHODS

Measures of splenic immune cells, placental inflammation, blood pressure, endothelial function, and urinary protein excretion were performed in pregnant IL-4-deficient mice as well as in pregnant IL-4-deficient mice treated with the Toll-like receptor 3 agonist polyinosinic:polycytidylic (poly I:C).

RESULTS

Pregnant IL-4-deficient mice exhibited altered splenic immune cell subsets, increased levels of pro-inflammatory cytokines, placental inflammation, mild hypertension, endothelial dysfunction, and proteinuria compared to pregnant control mice. Compared to pregnant control mice treated with poly I:C which exhibit preeclampsia-like symptoms, poly I:C-treated pregnant IL-4-deficient mice exhibited a further increase in pro-inflammatory cytokine levels, which was associated with augmented SBP and endothelial dysfunction.

CONCLUSION

Collectively, these data show that the absence of IL-4 is sufficient to induce mild preeclampsia-like symptoms in mice due to excessive inflammation. Thus, the anti-inflammatory effects of IL-4 are important in preventing hypertension during pregnancy.

TLR3-induced placental miR-210 down-regulates the STAT6/interleukin-4 pathway

Several clinical studies have reported increased placental miR-210 expression in women with PE compared to normotensive women, but whether miR-210 plays a role in the etiology of PE is unknown. We reported that activation of TLR3 produces the PE-like symptoms of hypertension, endothelial dysfunction, and proteinuria in mice only when pregnant, but whether TLR3 activation in pregnant mice and human cytotrophoblasts (CTBs) increases miR-210 and modulates its targets related to inflammation are unknown. Placental miR-210 levels were increased significantly in pregnant mice treated with the TLR3 agonist poly I:C (P-PIC). Both HIF-1α and NF-κBp50, known to bind the miR-210 promoter and induce its expression, were also increased significantly in placentas of P-PIC mice. Target identification algorithms and gene ontology predicted STAT6 as an inflammation-related target of miR-210 and STAT6 was decreased significantly in placentas of P-PIC mice. IL-4, which is regulated by STAT6 and increases during normotensive pregnancy, failed to increase in serum of P-PIC mice. P-PIC TLR3 KO mice did not develop hypertension and placental HIF-1α, NF-κBp50, miR-210, STAT6, and IL-4 levels were unchanged. To determine the placental etiology, treatment of human CTBs with poly I:C significantly increased HIF-1α, NF-κBp50, and miR-210 levels and decreased STAT6 and IL-4 levels. Overexpression of miR-210 in CTBs decreased STAT6 and IL-4 while inhibition of miR-210 increased STAT6 and IL-4. These findings demonstrate that TLR3 activation induces placental miR-210 via HIF-1α and NF-κBp50 leading to decreased STAT6 and IL-4 levels and this may contribute to the development of PE.

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.

Presence of DNA of adeno-associated virus in subfertile couples, but no association with fertility factors

BACKGROUND

Based on previous reports suggesting a role of adeno-associated virus (AAV) in miscarriage, the prevalence of AAV DNA in genital tracts of male and female partners of subfertile couples was determined to assess a potential association of AAV infection with clinically relevant parameters of male and female fertility.

METHODS

A prospective study was performed in the outpatient infertility clinic of a university-based hospital. Semen samples and endocervical material obtained from 146 male and 134 female partners of asymptomatic subfertile couples were analyzed for the presence of AAV DNA (using nested PCR). Patients' medical histories and details of clinical examinations were recorded. Semen quality, including sperm functional capacity and the presence of antisperm antibodies (ASA) and seminal white blood cells (WBC), was assessed in aliquots of the same ejaculate. Detailed examinations of the cervical factor and other variables of female subfertility were performed. Both partners were screened for bacterial infection.

RESULTS

The presence of AAV DNA in semen was not significantly related to semen quality, including sperm functional capacity or local ASA, nor was it coupled to the presence of AAV in the endocervical material of female partners. The presence of AAV DNA was not associated with the presence of other micro-organisms of the lower genital tract or with seminal WBC in men. AAV DNA in endocervical material was not related to a reduced quality of cervical mucus or to other female infertility factors.

CONCLUSIONS

The presence of AAV DNA in semen samples or endocervical swabs showed no significant association with clinically relevant infertility factors. However, longitudinal studies may clarify previous suggestions of an influence of AAV infection on early pregnancy problems.

Molecular detection of adeno-associated virus in cases of spontaneous and intentional human abortion

Pregnancy failure is a common event and often of unknown cause. Some viruses are thought to cause abortions including the adeno-associated viruses (AAV), viruses which are regarded as being without any definitive association to any human disease. This study investigated AAV infection in 81 human abortions, both spontaneous and intentional that occurred up to the 23rd week of gestation. Nucleic acid of AAV-2, 3, and 5 types from 118 decidual and chorionic tissues, collected from the patients in this study, was amplified by nested-PCR. In situ hybridization (ISH) was developed with a digoxigenin-labeled AAV probe in paraffin embedded tissues from the AAV positive cases. AAV was observed in 28.4% (23/81) of the cases, of which, 78.3% (18/23) were in the decidua and 21.7% (5/23) in the extravillous trophoblast, the chorionic plate, or chorionic villi fragments. AAV-2, the only type detected, occurred in 32.3% (22/68) and in 7.7% (1/13) of the spontaneous and intentional abortions, respectively. ISH revealed AAV in the decidua, chorionic tissue or chorionic plate and extravillous trophoblast. The detection of only AAV-2 type indicates that it is the most frequent in the population studied and/or shows tissue tropism. The presence of AAV in decidual or trophoblastic cells in cases of abortion, as observed by ISH, implies that the virus could jeopardize the pregnancy. The significant predominance in spontaneous cases suggests possibly a causal association between AAV and abortion.

Parvovirus infection-induced cell death and cell cycle arrest

The cytopathic effects induced during parvovirus infection have been widely documented. Parvovirus infection-induced cell death is often directly associated with disease outcomes (e.g., anemia resulting from loss of erythroid progenitors during parvovirus B19 infection). Apoptosis is the major form of cell death induced by parvovirus infection. However, nonapoptotic cell death, namely necrosis, has also been reported during infection of the minute virus of mice, parvovirus H-1 and bovine parvovirus. Recent studies have revealed multiple mechanisms underlying the cell death during parvovirus infection. These mechanisms vary in different parvoviruses, although the large nonstructural protein (NS)1 and the small NS proteins (e.g., the 11 kDa of parvovirus B19), as well as replication of the viral genome, are responsible for causing infection-induced cell death. Cell cycle arrest is also common, and contributes to the cytopathic effects induced during parvovirus infection. While viral NS proteins have been indicated to induce cell cycle arrest, increasing evidence suggests that a cellular DNA damage response triggered by an invading single-stranded parvoviral genome is the major inducer of cell cycle arrest in parvovirus-infected cells. Apparently, in response to infection, cell death and cell cycle arrest of parvovirus-infected cells are beneficial to the viral cell lifecycle (e.g., viral DNA replication and virus egress). In this article, we will discuss recent advances in the understanding of the mechanisms underlying parvovirus infection-induced cell death and cell cycle arrest.

Toll-like receptor 3 activation during pregnancy elicits preeclampsia-like symptoms in rats

BACKGROUND

Preeclampsia (PE), a pregnancy-specific hypertensive syndrome, is one of the leading causes of premature births as well as fetal and maternal death. There is strong evidence that maternal immune system activation, of which Toll-like receptors (TLRs) play a major role, contributes to the development of PE. Viral infections, sensed by TLR3, are associated with hypertensive disorders of pregnancy. We tested the hypothesis that TLR3 activation during pregnancy would cause hypertension, endothelial dysfunction, proteinuria, and intrauterine growth restriction in normal pregnant rats.

METHODS

We treated pregnant and nonpregnant rats with the viral mimetic polyinosinic:polycytidylic acid (poly I:C) or vehicle every other day beginning at day 10 of gestation and measured systolic blood pressure, aortic vasodilation, urinary protein concentration, fetal growth, and serum and placental cytokine levels.

RESULTS

Pregnant rats treated with poly I:C displayed significantly elevated systolic blood pressures compared to pregnant rats and nonpregnant rats treated with poly I:C on day 18 of gestation. Poly I:C-treated pregnant rats also exhibited significantly decreased aortic vasodilation, significantly increased urinary protein concentrations, and had more malformed pups/litter. Additionally, poly I:C-treated rats exhibited a significant increase in placental TLR3 expression and proinflammatory/anti-inflammatory cytokine ratio compared to vehicle-treated rats. Poly I:C treatment of nonpregnant control rats had no effect on systolic blood pressure, aortic vasodilation, or urinary protein concentrations.

CONCLUSION

These findings demonstrate that sustained maternal immune system activation via TLR3 during pregnancy causes PE-like symptoms in rats and suggest that viral infection during pregnancy may contribute to the development of PE.

Porphyromonas gingivalis invades human trophoblasts and inhibits proliferation by inducing G1 arrest and apoptosis

Porphyromonas gingivalis is an oral pathogen that is also associated with serious systemic conditions such as preterm delivery. Here we investigated the interaction between P. gingivalis and a cell line of extravillous trophoblasts (HTR-8) derived from the human placenta. P. gingivalis internalized within HTR-8 cells and inhibited proliferation through induction of arrest in the G1 phase of the cell cycle. G1 arrest was associated with decreased expression of cyclin D and of CDKs 2, 4 and 6. In addition, levels of CDK inhibitors p15, p16, p18 and p21 were increased following P. gingivalis infection. The amount of Rb was diminished by P. gingivalis, and transient overexpression of Rb, with concomitant upregulation of phospho-Rb, relieved P. gingivalis-induced G1 arrest. HTR-8 cells halted in the G1 phase became apoptotic, and apoptosis was accompanied by an increase in the ratio of Bax/Bcl-2 and increased activity of caspases 3, 7 and 9. HTR-8 cells infected with P. gingivalis also exhibited a sustained activation of ERK1/2, and knock-down of ERK1/2 activity with siRNA abrogated both G1 arrest and apoptosis. Thus, P. gingivalis can invade placental trophoblasts and induce G1 arrest and apoptosis through pathways involving ERK1/2 and its downstream effectors, properties that provide a mechanistic basis for pathogenicity in complications of pregnancy.

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.

Trophoblast infection with Chlamydia pneumoniae and adverse pregnancy outcomes associated with placental dysfunction

OBJECTIVE

We sought to determine whether Chlamydia pneumoniae impairs invasive trophoblast function and is associated with preeclampsia.

STUDY DESIGN

We conducted cell viability and invasion assays using primary extravillous trophoblast cells isolated from first-trimester placentas. We performed a case-control study to identify C pneumoniae in trophoblast cells dissected by laser capture microscopy from placentas in women with severe preeclampsia and control subjects who delivered at term.

RESULTS

Trophoblast cell viability and invasion through extracellular matrices were decreased after infection with C pneumoniae (both P < .05). C pneumoniae DNA was detected in trophoblast cells in 15/48 cases but only 3/30 controls (odds ratio, 4.1; P = .02). Positive and negative controls yielded expected results.

CONCLUSION

C pneumoniae infection can reduce trophoblast invasion into the uterine wall and is associated with preeclampsia. Further investigation of the mechanisms by which C pneumoniae induces trophoblast dysfunction, and the identification of therapies to prevent adverse outcomes attributed to trophoblast dysfunction, are warranted.

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.

Maternal TLR4 and NOD2 gene variants, pro-inflammatory phenotype and susceptibility to early-onset preeclampsia and HELLP syndrome

BACKGROUND

Altered maternal inflammatory responses play a role in the development of preeclampsia and the hemolysis, elevated liver enzymes and low platelets (HELLP) syndrome. We examined whether allelic variants of the innate immune receptors Toll-like receptor 4 (TLR4) and nucleotide-binding oligomerization domain 2 (NOD2), that impair the inflammatory response to endotoxin, are related to preeclampsia and HELLP syndrome.

METHODS AND FINDINGS

We determined five common mutations in TLR4 (D299G and T399I) and NOD2 (R702W, G908R and L1007fs) in 340 primiparous women with a history of early-onset preeclampsia, of whom 177 women developed HELLP syndrome and in 113 women with a history of only uneventful pregnancies as controls. In addition, we assessed plasma levels of pro-inflammatory biomarkers C-reactive protein, interleukin-6, soluble intercellular adhesion molecule-1, fibrinogen and von Willebrand factor in a subset of 214 women included at least six months after delivery. After adjustment for maternal age and chronic hypertension, attenuating allelic variants of TLR4 were more common in women with a history of early-onset preeclampsia than in controls (OR 2.9 [95% CI 1.2-6.7]). Highest frequencies for TLR4 variants were observed in women who developed HELLP syndrome (adjusted OR 4.1 [95% CI 1.7-9.8]). In addition, high levels of interleukin-6 and fibrinogen were associated with a history of early-onset preeclampsia. Combined positivity for any of the TLR4 and NOD2 allelic variants and high levels of interleukin-6 was 6.9-fold more common in women with a history of early-onset preeclampsia (95% CI 2.1-23.2) compared to controls.

CONCLUSIONS

We observed an association of common TLR4 and NOD2 gene variants, and pro-inflammatory phenotype with a history of early-onset preeclampsia and HELLP syndrome. These findings suggest involvement of the maternal innate immune system in severe hypertensive disorders of pregnancy.

Maternal infection and risk of preeclampsia: systematic review and metaanalysis

There are lingering questions regarding the association between maternal infection and preeclampsia. Systematic review and metaanalysis was conducted of observational studies that examined the relationship between maternal infection and preeclampsia. Forty-nine studies met the inclusion criteria. The risk of preeclampsia was increased in pregnant women with urinary tract infection (pooled odds ratio, 1.57; 95% CI, 1.45-1.70) and periodontal disease (pooled odds ratio, 1.76; 95% CI, 1.43-2.18). There were no associations between preeclampsia and presence of antibodies to Chlamydia pneumoniae, Helicobacter pylori, and cytomegalovirus, treated and nontreated HIV infection, and malaria. Individual studies did not find a relationship between herpes simplex virus type 2, bacterial vaginosis, and Mycoplasma hominis and preeclampsia. Urinary tract infection and periodontal disease during pregnancy are associated with an increased risk of preeclampsia. More studies are required to verify this as well as to explore whether or not such relationships are causal and, if so, the mechanisms involved.

Toll-like receptors in the uterus, cervix, and placenta: is pregnancy an immunosuppressed state?

OBJECTIVE

These studies were performed to elucidate the expression of Toll-like receptors (TLRs) in the uterus, cervix, and placenta in pregnancy and across gestation.

STUDY DESIGN

Message expressions of TLR-2, -3, -4, and -9 were investigated in nonpregnant mice and across gestation in CD-1 mice. Uterine, cervical, and placental tissues were harvested, and RNA was extracted. Quantitative polymerase chain reaction was performed.

RESULTS

Messenger RNA expression of TLRs is significantly upregulated in pregnant uterine and cervical tissues. There is differential TLR messenger RNA expression between the uterus, cervix, and placenta. In the placenta, TLR 4 is significantly downregulated.

CONCLUSION

These findings suggest that the innate immune system is a dynamic system during gestation. The concept of immunosuppression during pregnancy appears to be valid in the placenta only in regard to TLR expression. Research is warranted to determine whether the upregulation in the uterus and cervix during pregnancy is associated with an increased likelihood of responding to a pathogen or serve as a protective mechanism or both.

Association between maternal infections and preeclampsia: a systematic review of epidemiologic studies

OBJECTIVES

A growing body of evidence suggests an association between maternal infection and preeclampsia. To examine the strength of this association, we conducted a comprehensive review of studies published in peer-reviewed journals.

METHODS

Data collection for this review involved Medline, Embase, and Cochrane data base searches of published studies since 1964 on the relationship between maternal infection and preeclampsia. Data were abstracted according to predefined inclusion and exclusion criteria. Study population included women with preeclampsia and normotensive mothers with and without bacterial or viral infections. Altogether, thirty two original studies were identified and evaluated for methodological quality, preeclampsia diagnosis and adjustment for well-known preeclampsia confounders. Pooled odds ratios and 95% confidence intervals, according to infection status, were calculated using DerSimonian-Laird random-effects models. Publication bias was assessed with a funnel plot and Egger's regression asymmetry test.

RESULTS

Sixteen of the 32 studies evaluated were selected for inclusion in the meta-analysis. These studies showed that women with either a bacterial or viral infection were at higher risk of developing preeclampsia, compared to women without infection. Combined results for the 16 studies yielded an OR of 2.1 (95% CI 1.6-2.7). Separate pooled estimates for prospective (OR 2.3, 95% CI 1.7-3.0), case control and retrospective studies combined (OR 2.0, 95% CI 1.4-2.9) yielded similar results. Heterogeneity was significant across overall pooled estimates, case control and retrospective studies (Q(df=20) of 45.7, P = .001; Q(df=10) of 38.7, P < .005, respectively), but not prospective studies (Q(df=9) of 6.5 P = .69).

CONCLUSIONS

In our analysis, any infection (bacterial or viral) was associated with a two-fold higher risk of preeclampsia. This association may provide a potential explanation for preeclampsia-related inflammation.