SARS-CoV-2 Placentitis and Intraparenchymal Thrombohematomas Among COVID-19 Infections in Pregnancy

This cases series examines SARS-CoV-2 placentitis and intraparenchymal thrombohematomas among COVID-19 infections during pregnancy.

A standardized definition of placental infection by SARS-CoV-2, a consensus statement from the National Institutes of Health/Eunice Kennedy Shriver National Institute of Child Health and Human Development SARS-CoV-2 Placental Infection Workshop

Pregnant individuals infected with SARS-CoV-2 have higher rates of intensive care unit admission, oxygen requirement, need for mechanical ventilation, and death than nonpregnant individuals. Increased COVID-19 disease severity may be associated with an increased risk of viremia and placental infection. Maternal SARS-CoV-2 infection is also associated with pregnancy complications such as preeclampsia and preterm birth, which can be either placentally mediated or reflected in the placenta. Maternal viremia followed by placental infection may lead to maternal-fetal transmission (vertical), which affects 1% to 3% of exposed newborns. However, there is no agreed-upon or standard definition of placental infection. The National Institutes of Health/Eunice Kennedy Shriver National Institute of Child Health and Human Development convened a group of experts to propose a working definition of placental infection to inform ongoing studies of SARS-CoV-2 during pregnancy. Experts recommended that placental infection be defined using techniques that allow virus detection and localization in placental tissue by one or more of the following methods: in situ hybridization with antisense probe (detects replication) or a sense probe (detects viral messenger RNA) or immunohistochemistry to detect viral nucleocapsid or spike proteins. If the abovementioned methods are not possible, reverse transcription polymerase chain reaction detection or quantification of viral RNA in placental homogenates, or electron microscopy are alternative approaches. A graded classification for the likelihood of placental infection as definitive, probable, possible, and unlikely was proposed. Manuscripts reporting placental infection should describe the sampling method (location and number of samples collected), method of preservation of tissue, and detection technique. Recommendations were made for the handling of the placenta, examination, and sampling and the use of validated reagents and sample protocols (included as appendices).

Pregnancy alters interleukin-1 beta expression and antiviral antibody responses during severe acute respiratory syndrome coronavirus 2 infection

BACKGROUND

Severe acute respiratory syndrome coronavirus 2, the disease-causing pathogen of the coronavirus disease 2019 pandemic, has resulted in morbidity and mortality worldwide. Pregnant women are more susceptible to severe coronavirus disease 2019 and are at higher risk of preterm birth than uninfected pregnant women. Despite this evidence, the immunologic effects of severe acute respiratory syndrome coronavirus 2 infection during pregnancy remain understudied.

OBJECTIVE

This study aimed to assess the impact of severe acute respiratory syndrome coronavirus 2 infection during pregnancy on inflammatory and humoral responses in maternal and fetal samples and compare antibody responses to severe acute respiratory syndrome coronavirus 2 among pregnant and nonpregnant women.

STUDY DESIGN

Immune responses to severe acute respiratory syndrome coronavirus 2 were analyzed using samples from pregnant (n=33) and nonpregnant (n=17) women who tested either positive (pregnant, 22; nonpregnant, 17) or negative for severe acute respiratory syndrome coronavirus 2 (pregnant, 11) at Johns Hopkins Hospital. We measured proinflammatory and placental cytokine messenger RNAs, neonatal Fc receptor expression, and tetanus antibody transfer in maternal and cord blood samples. In addition, we evaluated antispike immunoglobulin G, antispike receptor-binding domain immunoglobulin G, and neutralizing antibody responses to severe acute respiratory syndrome coronavirus 2 in serum or plasma collected from nonpregnant women, pregnant women, and cord blood.

RESULTS

Pregnant women with laboratory-confirmed severe acute respiratory syndrome coronavirus 2 infection expressed more interleukin-1 beta, but not interleukin 6, in blood samples collected within 14 days vs >14 days after performing severe acute respiratory syndrome coronavirus 2 test. Pregnant women with laboratory-confirmed severe acute respiratory syndrome coronavirus 2 infection also had reduced antispike receptor-binding domain immunoglobulin G titers and were less likely to have detectable neutralizing antibody than nonpregnant women. Although severe acute respiratory syndrome coronavirus 2 infection did not disrupt neonatal Fc receptor expression in the placenta, maternal transfer of severe acute respiratory syndrome coronavirus 2 neutralizing antibody was inhibited by infection during pregnancy.

CONCLUSION

Severe acute respiratory syndrome coronavirus 2 infection during pregnancy was characterized by placental inflammation and reduced antiviral antibody responses, which may impact the efficacy of coronavirus disease 2019 treatment in pregnancy. In addition, the long-term implications of placental inflammation for neonatal health require greater consideration.

A Case Report of Fetal Thrombotic Vasculopathy in a COVID Placenta

COVID-19 has affected patients of all ages and demographics, not excluding pregnant women. The effects of COVID-19 on pregnant women are still largely unknown. Several adverse perinatal outcomes have been reported in COVID-19-positive pregnant women, including pre-eclampsia, miscarriage, pre-term labor, and stillbirth. Histopathological examination of COVID-19 placentas can contribute significant data regarding maternal and fetal health and can elucidate more findings in this novel disease. A 23-year-old female with morbid obesity and scant antenatal care presented to the emergency department complaining of shortness of breath and fever; she was found to be positive for COVID-19. Grossly, her placenta showed no abnormalities. Histological examination of her placenta showed chronic lymphoplasmacytic deciduitis, villous fibrosis, loss of capillarization, extravasation of erythrocytes, chorangiosis, and thrombosis of upstream stem vessels, including large fetal vessels on the chorionic plate. These changes were deemed to be consistent with fetal thrombotic vasculopathy (FTV). In conclusion, this case of FTV in the placenta of a patient with COVID-19 is a significant finding, as it can be critical to clinicians in the management of prenatal care for expecting mothers during this pandemic.This case was presented at the annual meeting of the Association of Clinical Scientists (ACS) on May 13, 2021.

Chronic villitis of unknown etiology: Investigations into viral pathogenesis

INTRODUCTION

Chronic villitis of unknown etiology (VUE) is a chronic inflammatory lesion of third trimester placenta, which contributes to major adverse obstetric outcomes. However, the inciting factors and mechanisms by which VUE contributes to adverse outcomes are poorly understood. This limits our ability to develop preventions or interventions. Our goals were to determine whether viruses can be detected in placental tissues with VUE and to determine whether gene expression profiles support an antiviral response.

METHODS

We extracted RNA and DNA from 20 placentas with high-grade chronic villitis and 20 control placentas without inflammation. Viruses were assessed using ViroCap viral nucleic acid enrichment coupled with metagenomic sequencing. RNA sequencing was used to evaluate the inflammatory gene expression profiles in each placenta.

RESULTS

We detected at least 1 virus in 50% of the samples tested. We found that herpesviruses, were found more frequently in cases compared with controls (P = 0.01). Antiviral pathways, including defense response to virus, interferon gamma response, and IFN alpha/beta response, were upregulated in cases. We observed two clusters of gene expression profiles in the VUE cases, suggesting multiple inflammatory profiles are associated with VUE.

DISCUSSION

These data support a viral etiology for some cases of VUE. Furthermore, gene expression profiles suggest the possibility of more than one cause or manifestation of VUE. Viral mechanisms should be explored as potential targets for prevention or intervention in VUE.

Placental infection by Zika virus in French Guiana

OBJECTIVES

To describe placental findings on prenatal ultrasound and anatomopathological examination in women with Zika virus (ZIKV) infection, and to assess their association with congenital ZIKV infection and severe adverse outcome, defined as fetal loss or congenital Zika syndrome (CZS).

METHODS

This was a prospective study of pregnancies undergoing testing for maternal ZIKV infection at a center in French Guiana during the ZIKV epidemic. In ZIKV-positive women, congenital infection was defined as either a positive reverse transcription polymerase chain reaction result or identification of ZIKV-specific immunoglobulin-M in at least one placental, fetal or neonatal sample. Placental ZIKV-infection status was classified as non-exposed (placentae from non-infected women), exposed (placentae from ZIKV-infected women without congenital infection) or infected (placentae from ZIKV-infected women with proven congenital infection). Placentae were assessed by monthly prenatal ultrasound examinations, measuring placental thickness and umbilical artery Doppler parameters, and by anatomopathological examination after live birth or intrauterine death in women with ZIKV infection. The association of placental thickness during pregnancy and anatomopathological findings with the ZIKV status of the placenta was assessed. The association between placental findings and severe adverse outcome (CZS or fetal loss) in the infected group was also assessed.

RESULTS

Among 291 fetuses/neonates/placentae from women with proven ZIKV infection, congenital infection was confirmed in 76 cases, of which 16 resulted in CZS and 11 resulted in fetal loss. The 215 remaining placentae from ZIKV-positive women without evidence of congenital ZIKV infection represented the exposed group. A total of 334 placentae from ZIKV-negative pregnant women represented the non-exposed control group. Placentomegaly (placental thickness > 40 mm) was observed more frequently in infected placentae (39.5%) than in exposed placentae (17.2%) or controls (7.2%), even when adjusting for gestational age at diagnosis and comorbidities (adjusted hazard ratio (aHR), 2.02 (95% CI, 1.22-3.36) and aHR, 3.23 (95% CI, 1.86-5.61), respectively), and appeared earlier in infected placentae. In the infected group, placentomegaly was observed more frequently in cases of CZS (62.5%) or fetal loss (45.5%) than in those with asymptomatic congenital infection (30.6%) (aHR, 5.43 (95% CI, 2.17-13.56) and aHR, 4.95 (95% CI, 1.65-14.83), respectively). Abnormal umbilical artery Doppler was observed more frequently in cases of congenital infection resulting in fetal loss than in those with asymptomatic congenital infection (30.0% vs 6.1%; adjusted relative risk (aRR), 4.83 (95% CI, 1.09-20.64)). Infected placentae also exhibited a higher risk for any pathological anomaly than did exposed placentae (62.8% vs 21.6%; aRR, 2.60 (95% CI, 1.40-4.83)).

CONCLUSIONS

Early placentomegaly may represent the first sign of congenital infection in ZIKV-infected women, and should prompt enhanced follow-up of these pregnancies. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Placental growth disorders and perinatal adverse outcomes in Brazilian HIV-infected pregnant women

Fetal and placental growth disorders are common in maternal human immunodeficiency virus (HIV) infection and can be attributed to both the infection and comorbidities not associated with HIV. We describe placental growth disorders and adverse reproductive outcomes in HIV-infected pregnant women whose delivery occurred between 2001-2014 in Vitoria, Brazil. Cases with gestational age (GA) ≥ than 22 weeks validated by ultrasonography, with placental and fetal weight dimensions at birth, were studied. Outcomes were summarized as proportions of small (SGA), appropriate (AGA), and large (LGA) for GA when the z-score values were below -1.28, between -1.28 and +1.28, or above +1.28, respectively. Of 187 fetal attachment requisitions, 122(65.2%) women and their newborns participated in the study. The median maternal age was 28 years and 81(66.4%) underwent ≥ 6 prenatal visits. A total of 81(66.4%) were diagnosed before current pregnancy; 68(55.7%) exhibited criteria for acquired immunodeficiency syndrome (AIDS); 64(52.4%) had detectable viral load; 25(20.5%) cases presented SGA placental weight and 6(4.9%) SGA placental thickness. SGA placental area was observed in 41(33.6%) cases, and among the SGA placental weight cases 12(48%) were also SGA fetal weight. Preterm birth (PTB) occurred in 15.6%(19/122) of cases; perinatal death in 4.1%(5/122) and HIV vertical transmission in 6 of 122 (4.9%). Women, ≥36 years old, were 5.7 times more likely to have PTB than those under 36. Also, patients with AIDS-defining criteria were 3.7 times more likely to have PTB. Prenatal care was inversely associated with PTB. Statistically significant associations were observed between AGA placental area and Protease Inhibitor usage and between SGA placental weight and SGA area. We found a prevalence of placental growth disorders in HIV-infected pregnant women and values higher than international reference values. The restriction of placental growth was a common disorder, possibly attributed to virus effects or a combination of antiretroviral regimens.

Zika Virus Infection during Pregnancy in Mice Causes Placental Damage and Fetal Demise

Zika virus (ZIKV) infection in pregnant women causes intrauterine growth restriction, spontaneous abortion, and microcephaly. Here, we describe two mouse models of placental and fetal disease associated with in utero transmission of ZIKV. Female mice lacking type I interferon signaling (Ifnar1(-/-)) crossed to wild-type (WT) males produced heterozygous fetuses resembling the immune status of human fetuses. Maternal inoculation at embryonic day 6.5 (E6.5) or E7.5 resulted in fetal demise that was associated with ZIKV infection of the placenta and fetal brain. We identified ZIKV within trophoblasts of the maternal and fetal placenta, consistent with a trans-placental infection route. Antibody blockade of Ifnar1 signaling in WT pregnant mice enhanced ZIKV trans-placental infection although it did not result in fetal death. These models will facilitate the study of ZIKV pathogenesis, in utero transmission, and testing of therapies and vaccines to prevent congenital malformations.

Distinct patterns of C4d immunoreactivity in placentas with villitis of unknown etiology, cytomegaloviral placentitis, and infarct

C4d deposition is considered to be evidence of antibody-mediated rejection. This study was conducted to compare C4d immunoreactivity between villitis of unknown etiology (VUE) and cytomegaloviral placentitis. C4d immunohistochemistry was performed in cases with VUE (n = 16) and cytomegaloviral placentitis (n = 5). Distinct, linear C4d immunoreactivity along the syncytiotrophoblast was found in all VUE cases. In cytomegaloviral placentitis, the intensity of C4d immunoreactivity along the syncytiotrophoblast was not prominent, but cytoplasmic C4d immunoreactivity of villous cytotrophoblasts was frequently observed. Further screening of the cases with placental infarcts (n = 5) demonstrated prominent C4d immunoreactivity in the chorionic villi adjacent to the infarct. We report the characteristic co-localization of VUE and C4d immunoreactivity. The overall findings in this study strongly suggest that the complement activation is a common mechanism of diverse placental injuries associated with rejection, infection, and ischemia.

[Clinical course and outcomes of influenza A (H1N1) 2009 in pregnant women]

AIM

Study of course of pregnancy, delivery, postpartum period and perinatal outcomes in pregnant women with influenza A (H1N1) 2009.

MATERIALS AND METHODS

Course of pregnancy and outcomes in 16 women, who had influenza A (H1N1) 2009, were analyzed. Influenza A (H1N1) 2009 virus was detected by PCR.

RESULTS

Influenza A (H1N1) 2009 had a severe course and high rates of complications: pneumonia (100%), respiratory distress syndrome (25%), placental deficiency (100%). Most of the neonates (87%) from mothers, who had influenza A (H1N1) 2009, had neonatal period disorders: congenital pneumonia--2 (12.5%), cerebral ischemia--10 (62.5%), hyperbilirubinemia--2 (12.5%), vegeto-visceral syndrome--4 (25%), hemorrhagic, convulsive and respiratory distress syndrome--1 (6.7%) each. Alteration in placenta was detected--influenza placentitis. Transplacental route of virus transmission was not detected.

CONCLUSION

Pregnant women are a high risk group for influenza and serious complications caused by the virus. Influenza A (H1N1) 2009 has a more severe course and a higher rate of complications in both mothers and neonates.

Placental viral infection sensitizes to endotoxin-induced pre-term labor: a double hit hypothesis

PROBLEM

Among pregnant women, acquired viral infections with a concurrent bacterial infection is a detrimental factor associated to poor prognosis. We evaluate the effect of a viral infection that does not lead to pre-term labor on the response to low doses of lipopolysaccharide (LPS). Our objectives were (i) to characterize the effect of a viral infection concurrent with exposure to microbial products on pregnancy outcome and (ii) to characterize the placental and fetal immune responses to the viral sensitization to LPS.

METHOD

C57B/6 wild-type mice were injected with murine gammaherpesvirus 68 (MHV68) at E8.5. Either PBS or LPS was injected i.p. at E15.5. Pregnancy outcome and cytokine/chemokine profile from implantation sites were analyzed by multiplex.

RESULTS

LPS treatment of MHV-68-infected animals induced pre-term delivery and fetal death in 100% of the mice. Pre-term labor was characterized by a upregulation of pro-inflammatory cytokines and chemokines in both placenta and decidua. Similar profiles were observed from MHV-68-infected human primary trophoblast and trophoblast cell lines in response to LPS.

CONCLUSION

We describe for the first time that a sub-clinical viral infection in pregnant mice might sensitize to a bacterial infection leading to pre-term delivery. We propose the 'Double Hit Hypothesis' where the presence of a viral infection enhances the effect of bacterial products during pregnancy leading not only to pre-term labor but likely larger adverse outcomes.

The importance of cytomegalovirus-specific antibodies for the prevention of fetal cytomegalovirus infection or disease

Primary maternal infection with cytomegalovirus (CMV) during or just before pregnancy is responsible for nearly all congenital infections where the baby is symptomatic at birth. If primary maternal CMV infection occurs during the first or second trimester, between one-third and one-half of fetuses become infected, and between one-half and one-third of infected fetuses go on to have symptoms at birth. Experiments using a guinea-pig model of CMV infection in pregnant dames (and subsequent observational studies in humans) indicate a beneficial effect is associated with administering high-titre CMV hyperimmunoglobulin (HIg) to pregnant women with primary CMV infection. HIg appears to be effective for treating and preventing fetal CMV infection; its mechanism of action probably includes reduced placental inflammation, viral neutralization associated with high-avidity antibodies and, possibly, downregulation of cytokine-mediated cellular immune responses.

Detection of bovine herpesvirus 4 in aborted bovine placentas

Diagnostic studies on aborted placentas of cattle usually do not determine any reason for abortions. In this paper, five bovine herpesviruses (BoHVs) and some bacteriological agents were investigated by several methods in 33 aborted bovine placentas. Inclusion bodies, PCR and in situ DNA hybridization proved the presence of BoHV-4 DNA in six (18.18%) tested placentas. Positive DNA hybridization signal localized BoHV-4 DNA to placental epithelial cells macrophages and lymphocytes. By destroying epithelial cells and provoking local immune response BoHV-4 infection may inhibit physiological functions of the placenta during gestation. This finding is a further sign that BoHV-4 plays an active role in reproductive disorders of cattle.

Placental enlargement in women with primary maternal cytomegalovirus infection is associated with fetal and neonatal disease

BACKGROUND

Serological testing for primary maternal cytomegalovirus (CMV) infection during pregnancy is not routine, but ultrasound studies are routine. Therefore, we evaluated placental thickening in women with primary CMV infection during pregnancy.

METHODS

The study included 92 women with primary CMV infection during pregnancy and 73 CMV-seropositive pregnant women without primary CMV infection. Neonatal CMV transmission was determined by CMV culture of urine samples. Thirty-two women were treated with CMV hyperimmune globulin to either prevent or treat intrauterine CMV infection. Maximal placental thickness was measured by longitudinal (nonoblique) scanning with the ultrasound beam perpendicular to the chorial dish. Programmed placental ultrasound evaluations were performed from 16 to 36 weeks of gestation.

RESULTS

At each measurement between 16 and 36 weeks of gestation, women with primary CMV infection who had a fetus or newborn with CMV disease had placentas that were significantly thicker than those of women with primary CMV infection who did not have a diseased fetus or newborn (P<.0001); the latter group, in turn, had placentas that were significantly thicker than those of seropositive control subjects (P<.0001). For both women with and women without diseased fetuses or newborns, receipt of hyperimmune globulin after primary CMV infection was associated with statistically significant reductions in placental thickness (P<.001). Placental vertical thickness values, which are predictive of primary maternal infection, were observed at each measurement from 16 to 36 weeks of gestation, and cutoff values ranged from 22 mm to 35 mm, with the best sensitivity and specificity at 28 and 32 weeks of gestation.

CONCLUSIONS

Primary maternal CMV infection and fetal or neonatal disease are associated with sonographically thickened placentas, which respond to administration of hyperimmune globulin. These observations suggest that many of the manifestations of fetal and neonatal disease are caused by placental insufficiency.

Correlates of placental infection with cytomegalovirus, parvovirus B19 or human herpes virus 7

Vertical transmission of viruses is an important cause of morbidity in the fetus and neonate. Placental viral infection indicates risk of vertical transmission, but not always transmission to, or disease of the fetus. Specimens from mothers and babies from three groups-two prospective and one retrospective cohort-were tested for pathogens of teratogenic potential using multiplex PCR. Placental infection was present in 13% of the 105 samples collected. Assessment of the prospective cohorts showed cytomegalovirus (CMV) detected in 4% of placentae from unselected women, parvovirus B19 in 1% and Ureaplasma parvum in 1% of placentae. In a retrospective cohort of women at high risk of transmitting congenital infection due to seroconversion during pregnancy, miscarriage or stillbirth, CMV was detected in 64% and human herpes virus type 7 in 9% of placentae. Of 14 PCR-positive placentae, two were associated with the birth of a living symptomatic infant, two with stillbirth, one with miscarriage, and two with elective terminations of pregnancy. Directed laboratory assessment of women at high risk of transmitting congenital infection, on the basis of clinical or laboratory markers, is important for accurate diagnosis of adverse outcomes of pregnancy. However, routine screening for viruses in the placentae from women with a low-risk serological profile for transmitting congenital infection is unlikely to result in significant numbers of additional diagnoses and is confounded by inadequacy of current diagnostic methods. The major pathogen detected in all cases of placental infection associated with fetal death was human CMV.

West Nile virus infection of the placenta

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

Patterns of human cytomegalovirus infection in term placentas: a preliminary analysis

BACKGROUND

Primary maternal CMV infection is the major risk factor for symptomatic congenital infection as maternal immunity reduces the risk of transmission to the fetus. Analysis of first trimester placentas showed that virus replicates in the uterus and is transmitted to the placenta causing focal infection.

OBJECTIVES AND STUDY DESIGN

We examined 78 term placentas from uncomplicated deliveries for the presence of CMV DNA and evaluated evidence of infection by means of immunohistological and serological analysis.

RESULTS

PCR analysis of villus biopsy samples and decidua showed that CMV DNA was present in 62% of tissues. Seven placentas with neutralizing titers were further examined by immunohistology for expression of viral proteins. In placentas with high levels of CMV DNA, fetal blood vessels in the villus core contained neutrophils with viral replication proteins, and macrophages/dendritic cells with glycoprotein B (gB). Cord blood samples from 1 of 11 placentas contained CMV DNA, an indication of replication in the fetal compartment. In placentas with low levels of viral DNA, macrophage/dendritic cells in the villus core contained CMV gB. This pattern was comparable to that seen in early gestation placentas from women with strong neutralizing antibodies.

CONCLUSIONS

The results show CMV replication proteins in focal areas of the placenta, implying virus transmission to the fetal circulation. These preliminary results suggest that the incidence of asymptomatic congenital CMV infection might be higher than currently estimated.

Vaccinia virus infection during murine pregnancy: a new pathogenesis model for vaccinia fetalis

Vaccinia fetalis, the vertical transfer of vaccinia virus from mother to fetus, is a relatively rare but often fatal complication of primary vaccinia virus vaccination during pregnancy. To date there has been no attempt to develop an animal model to study the pathogenesis of this acute viral infection in vivo. Here we report that infection of gestating BALB/c mice by either intravenous or intraperitoneal routes with the Western Reserve strain of vaccinia virus results in the rapid colonization of the placenta and vertical transfer of virus to the developing fetus. Systemic maternal infections during gestation lead to the death of all offspring prior to or very shortly after birth. Using in situ hybridization for vaccinia virus mRNA to identify infected cells, we show that the virus initially colonizes cells lining maternal lacunae within the trophospongium layer of the placenta. The study of this model will significantly enhance our understanding of the pathogenesis of fetal vaccinia virus infections and aid in the development of effective treatments designed to reduce the risk of vaccinia virus-associated complications during pregnancy.

Human cytomegalovirus transmission from the uterus to the placenta correlates with the presence of pathogenic bacteria and maternal immunity

Prenatal cytomegalovirus infection may cause pregnancy complications such as intrauterine growth restriction and birth defects. How virus from the mother traverses the placenta is unknown. PCR analysis of biopsy specimens of the maternal-fetal interface revealed that DNA sequences from cytomegalovirus were commonly found with those of herpes simplex viruses and pathogenic bacteria. Cytomegalovirus DNA and infected cell proteins were found more often in the decidua than in the placenta, suggesting that the uterus functions as a reservoir for infection. In women with low neutralizing titers, cytomegalovirus replicated in diverse decidual cells and placental trophoblasts and capillaries. In women with intermediate to high neutralizing titers, decidual infection was suppressed and the placenta was spared. Overall, cytomegalovirus virions and maternal immunoglobulin G were detected in syncytiotrophoblasts, villus core macrophages, and dendritic cells. These results suggest that the outcome of cytomegalovirus infection depends on the presence of other pathogens and coordinated immune responses to viral replication at the maternal-fetal interface.

Placental Malaria and Perinatal Transmission of Human Immunodeficiency Virus Type 1

Prevalence of placental malaria in human immunodeficiency virus (HIV) type 1-infected and -uninfected women and the effect of placental malaria on genital shedding and perinatal transmission of HIV-1 were examined. Genital samples for HIV-1 DNA RNA were collected during labor. Infants were tested for HIV-1 at 1 day and 6 weeks postpartum. Placental malaria was diagnosed by histopathological examination: 372 placentas of HIV-1-infected women and 277 of HIV-1-uninfected women were processed. A higher prevalence of placental malaria was seen in HIV-1-infected women. No association was found between placental malaria and either maternal virus load, genital HIV-1 DNA, or HIV-1 RNA. Placental malaria did not correlate with in utero or peripartal transmission of HIV-1.

Detection of cytomegalovirus DNA in human placenta

Although human cytomegalovirus (CMV) is one of the most common causes of viral intrauterine and perinatal infection, its distribution in the placenta is poorly understood. The purpose of this study was to determine the frequency of CMV DNA positivity in placentas, to demonstrate the localization of the viral genome, and to identify the clinical features related to placental CMV. A total of 254 placentas from 231 mothers were investigated, and the maternal serum CMV immunoglobulin antibodies were measured. Specimens from both the placental parenchyma and the placental membrane close to the ruptured site in each placenta were examined for the presence of CMV DNA using dot blot hybridization after PCR amplification. None of 57 placentas from seronegative mothers was positive for CMV DNA. Of 197 placentas from seropositive mothers, 60 (30.5%) had CMV DNA in either the parenchyma or the membrane by dot blot analysis. In situ hybridization was carried out on these 60 placentas, and the localization of the viral genome was established in 19; CMV DNA was localized mostly to the villi, including the mesenchyme and trophoblasts, extravillous trophoblasts, and decidual cells. The mean gestational age at delivery was significantly later in the CMV DNA-positive placentas than in the negative placentas (36.9 +/- 5.1 vs 34.7 +/- 6.2 weeks, P = 0.0059). CMV DNA was detected in only 6 of 33 placentas delivered in the second trimester, and all six were associated with either severe maternal nephritis or severe chorioamnionitis. These results suggest that the CMV genome is common in placentas at later gestational ages and in those of earlier gestational ages with certain maternal complications.

Placental inflammation and perinatal transmission of HIV-1

The effect of placental membrane inflammation on mother-to-child transmission (MTCT) of HIV-1 is reported. Placentas from HIV-1-infected women were examined as part of a perinatal HIV-1 project in Mombasa, Kenya. Polymerase chain reaction analysis was used to test for HIV-1 in the infants at birth and at 6 weeks. The maternal HIV-1 seroprevalence was 13.3% (298 of 2,235). The overall rate of MTCT of HIV-1 was 25.4%; polymerase chain reaction analysis revealed that of the 201 infants 6.0% (12) were already HIV-1-positive at birth (intrauterine transmission) and 19.4% (39) were infected during the peripartum period or in early neonatal life (perinatal transmission). The prevalence of acute chorioamnionitis was 8.8%, that of deciduitis was 10.8%, and that of villitis was 1.6%. Acute chorioamnionitis was independently associated with peripartum HIV-1 transmission but not with in utero MTCT (17.9% vs. 6.7%, respectively; adjusted odds ratio, 3.9; 95% confidence interval, 1.2-12.5; p =.025). Other correlates of perinatal MTCT were presence of HIV in the genital tract and in the baby's oral cavity and a high maternal viral load in peripheral blood. The adjusted population attributable fraction of 12.8% (95% confidence interval, 1.5%-22.8%) indicated that approximately 3% of MTCT could be prevented if acute chorioamnionitis was eliminated. We suggest that further research on the role of antimicrobial treatment in the prevention of chorioamnionitis and the reduction of peripartum MTCT needs to be performed.

Pathogenesis of transplacental virus infection: pestivirus replication in the placenta and fetus following respiratory infection

Although transplacental virus infections account for considerable morbidity and mortality in both animals and humans, very little is so far known about the pathways whereby virus reaches the conceptus, the subsequent virus-host interactions in the early phases of the infections, and the establishment of persistent non-lethal infection. Using a natural animal model we recently demonstrated that bovine pestivirus can spread from the site of infection to the ovine fetus within 72 h, despite the expression of interferon in the reproductive tract [1]. In the present study we demonstrate that pestivirus first establishes infection and spread within the allantoic and amniotic membranes and then the fetus, followed several days later by infection of the uterine glands. However, virus replication and spread within the fetus is, at least in part, controlled by fetal developmental factors. In fetuses less than 25 days of gestational age, the virus remains restricted to the bulbis cordis, the first brachial pouch and occasionally the aorta. Over the next few days the virus spreads to multiple tissues, in addition to becoming more widespread and pronounced within the initially infected tissues. A potential role for the binucleated cells of the allantochorion in the spread of the virus from the fetal to the maternal tissues was also found. These cells expressed high levels of viral antigen just prior to and during the time period in which virus antigen became detectable in the epithelial cells of the uterine glands, in endothelial cells of uterine vessels and in scattered macrophage-like cells in the uterine stroma. Most likely this relatively late virus transfer is inconsequential for the mother, since it occurs at a time when a maternal virus-specific antibody response is becoming measurable. This is in contrast to the fetus, where the infection will have established itself widely prior to the development of lymphoid tissues and a functional immune response, thus setting the scenario for development of specific tolerance to the persisting virus.

Coxsackie virus infection of the placenta associated with neurodevelopmental delays in the newborn

OBJECTIVE

To determine if viral infection of the placenta was associated with long-term neurodevelopmental delays in the newborn.

METHODS

Placental tissue from seven newborn infants with severe respiratory failure and subsequent neurodevelopmental abnormalities as well as ten normal controls and five cases of known placental infection (cytomegalovirus, herpes simplex virus, and parvovirus) were tested by in situ hybridization or reverse transcriptase in situ polymerase chain reaction (PCR) for adenovirus, coxsackie virus, cytomegalovirus, Epstein Barr virus, herpes simplex virus, influenza A virus, picornavirus, polyoma virus, parvovirus, respiratory syncytial virus, rotavirus, and varicella zoster virus.

RESULTS

Coxsackie virus RNA was detected in six of the seven cases, and in none of the ten normal controls or five cases with known viral infection. Viral RNA localized primarily to the Hofbauer cells and trophoblasts of the terminal villi. Immunohistochemical analysis for the coxsackie virus antigen VP1 yielded equivalent results.

CONCLUSIONS

In utero coxsackie virus of the placenta is associated with the development of severe respiratory failure and central nervous system sequelae in the newborn. This underscores the importance of detailed pathologic and viral examination of the placenta in cases of systemic illness in the newborn.

Measles virus infection in the placenta of monozygotic twins

We report a case of monozygotic twins whose mother was infected with measles at 19 weeks' gestation. One of the twins died in utero at 32 weeks' gestation. The placenta of the stillbirth showed massive fibrin deposition, and some residual trophoblasts contained many inclusion bodies positive for measles virus antigen. Fetal organs and cells other than a few splenic lymphocytes showed no evidence of measles virus infection. The placenta of the surviving infant showed focal intervillous fibrin deposits, and only a few syncytiotrophoblasts were positive for measles virus antigen. At present, 7 months after the delivery, the surviving infant has not developed any sign of measles virus infection. Postpartum course of the mother has been uneventful, although high titers of serum anti-measles virus IgM persisted for 6 months after delivery. This case is informative in the following respects: the villous trophoblasts had diagnostic inclusion bodies and ultrastructural evidence of measles virus infection, the degree of viral involvement within the monochorionic placenta was uneven, both of the twins were virtually free from measles virus infection despite the marked involvement of the placenta, and measles virus infection had persisted in the monochorionic placenta for approximately 13 weeks.

The mechanisms of placental viral infection

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

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

The molecular mechanisms and pathologic significance of placental viral infections are poorly understood. We investigated factors that regulate placental infection by adenovirus, which is the most common viral pathogen identified in fetal samples from abnormal pregnancies (i.e., fetal growth restriction, oligohydramnios, and nonimmune fetal hydrops). We also determined the pathologic significance of placental adenovirus infection. Northern hybridization, flow cytometry, and immunostaining revealed that placental expression of the coxsackievirus and adenovirus receptor (CAR) varied with gestational age and trophoblast phenotype. The CAR was continuously expressed in invasive or extravillous trophoblast cells but not in villous trophoblast cells. We postulate that the villous syncytiotrophoblast, which does not express CAR and is resistant to adenovirus infection, limits the transplacental transmission of viral pathogens, including adenovirus. Conversely, extravillous trophoblast cells underwent apoptosis when infected by adenovirus in the presence of decidual lymphocytes (which simulated the maternal immune response to viral infection). Thus, adenovirus infection and/or the maternal immune response to adenovirus infection induced the death of placental cell types that expressed CAR. Consequently, we speculate that adenovirus infection of extra-villous trophoblast cells may negatively impact the process of placental invasion and predispose the mother and fetus to adverse reproductive outcomes that result from placental dysfunction.

Growth retardation and microcephaly induced in mice by placental infection with murine cytomegalovirus

BACKGROUND

The placenta is regarded as a site of congenital cytomegalovirus (CMV) infection. The placental infection of fetuses with murine CMV (MCMV) was investigated in a mouse model.

METHODS

The placentas and fetuses were examined using the polymerase chain reaction (PCR) and Southern blotting for viral DNA and immunostaining for viral antigen. Since the transplacental infection rarely occurs, the placentas were directly injected with MCMV at day 12.5 of gestation; the embryos were then allowed to develop until day 18.5 of gestation.

RESULTS

Formation of infected foci at day 18. 5 of gestation was found in more than 60% of the injected placentas. Infection of about 50% of the embryos occurred from the infected placentas. The frequency of infection in the brain was 27%, which was the same as that in the liver and higher than that in the lungs. In the brains, infected cells were often observed in the ventricular zone of the cerebrum and sometimes in the cortical plate and the hippocampus. Developmental retardation with microcephaly was observed in about 25% of offspring exposed to infection in utero.

CONCLUSIONS

These results suggest that formation of infected foci in the placenta is important for embryonic congenital infection, and that the cerebral ventricular zone is one of the most susceptible sites for CMV infection in the embryonic stage.

HTLV-I transmission from mother to child

Human T-lymphotropic virus type I (HTLV-I), a causative agent of adult T-cell leukemia, (ATL) is transmitted from mother to child. ATL cells originate from the CD4 subset of peripheral T cells. The main route of mother-to-child transmission is postnatal breast-feeding. Refraining from breast-feeding or limiting the duration of breast-feeding can reduce the risk of mother-to-child transmission. Other than postnatal breast-feeding, there seem to be two routes of HTLV-I transmission from mother to child. One is intrauterine transmission, and the other is via saliva. Intrauterine transmission is rare, although proviral DNA is detected in cord blood samples. HTLV-I proviruses in the cord blood may be defective. HTLV-I proviral DNA and antibodies against HTLV-I are also detected in saliva. However, no report has been published so far which showed direct evidence of HTLV-I transmission via saliva. The placenta can be infected by HTLV-I, but infection does not reach the fetus, possibly apoptosis of placental villous cells because it is induced by HTLV-I infection.

Villitis of known origin: varicella and toxoplasma

Chronic villitis is a common condition in human placentae. In some cases an infectious cause can be demonstrated, such as infection with cytomegalovirus and rubella virus. Most often it is of unknown aetiology, the so-called VUE (villitis of unknown aetiology). We describe two cases with identification of specific infectious agents, each demonstrating previously unreported findings, i.e. persistent varicella antigen in the villi in case 1, and presence of toxoplasma cysts in Wharton's jelly in case 2. The identification of the pathogens, varicella virus and toxoplasma, would easily have been overlooked in routine study of the placenta and were possible because of clinical suspicion.

Determination of CMV placentitis. Diagnostic application of the polymerase chain reaction

Cytomegalovirus (CMV) infection constitutes an important cause of intrauterine death. In the present study CMV infection of placentas resulting from intrauterine deaths was assessed by immunohistochemistry and by the polymerase chain reaction (PCR). Among 32 cases of chronic villitis examined, 7 were found by PCR to be associated with CMV infection, although light microscopic examination revealed only 3 of them, while 4 had shown positive immunohistochemical staining. In conclusion, CMV may be considered to be a relatively common cause of placentitis, and PCR is a helpful tool in confirming the nature of the disease.

Placental examination in intrauterine coinfection with herpes simplex virus and cytomegalovirus

Intrauterine coinfections have rarely been reported. However, pregnancies exposed to multiple sexually transmitted infectious agents and drugs are likely to occur with increasing frequency and lead to complex pathology in the newborn. Often it will be difficult to establish a diagnosis, above all when this has to be done retrospectively. A premature (34 weeks) newborn presented with a complex clinical picture after exposure to multiple infectious and noninfectious teratogens during gestation. Immunocytochemical staining of the placental membranes and parenchyma suggested intrauterine coinfection by herpes simplex virus (HSV) type 2 and cytomegalovirus. This case illustrates the importance of careful placental investigation with modern techniques for the diagnosis of intrauterine HSV infection and coinfections.

[Ultrastructural analysis of placentas with villitis. Retrospective study]

A villitis is a focal or multifocal inflammatory reaction of chorionic villi with infiltration of mononuclear cells and usually is associated with fibrinoid necrosis. The aetiology of villitis could be a transplacental infection of the fetus, especially with virus (VIV), in normal placentae however, the presence of villitis is referred as villitis of unknown ethiology (VED). This study was designed to characterize villitis lesions of 11 placentae, four VIV and seven VED, ultrastructural descriptive comparisons of both types of villitis are discussed. Biopsies were processed with the conventional optic and electronic microscopy techniques. Our ultrastructural observations confirmed the presence of virus in four placentae whereas no virus or bacteria were found in seven placentae. Microvilli were absent or markedly diminished, this finding was associated to the presence of fibrinoid necrosis in the stroma and clinically to intrauterine growth retardation, 4 preterm pregnancies and one obitus. Trophoblast alterations were found in both types of villitis, basal membrane thickness, is some cases associated to electrodense material similar to calcium deposites, vascuolization and the presence of edema in the stroma was observed. In some cases we noted the presence of focal fibrin deposits associated to necrosis zones in the stroma, calcium precipitates and mielinic bodies. Fetal vessels obliteration and intravascular thrombi were found in the syncitiotrophoblast placentae with viral particles CMV or rubivirus associated to an increment in Hofbauer cells and basal membrane calcifications. From our ultrastructural observations, we conclude that both types of villitis are associated to a typic immunologic reaction that induce lose of trophoblast microvilli, mononuclear infiltration and edema. This placental alterations reduce dramatically the maternofetal exchange of gases, nutrients and other active peptides and could be the cause of fetal growth retardation, inmadurity or death.

Cytomegalovirus in the perfused human term placenta in vitro

Cytomegalovirus (CMV) is one of the most frequent causes of intrauterine-acquired infection in the human species. However, very little is known about the pathophysiology of the transplacental transmission of the virus from the mother to the fetus. In this study, the passage of CMV across the human term placenta, and the susceptibility of the human term trophoblast to infection with CMV was investigated. In vitro dual perfusion of human term placental lobules was performed. In five experiments the perfused tissue was exposed to high titres (10(4)-10(6) 50 per cent tissue culture infective doses) of CMV AD169 for up to 9.5 h. Monitoring included placental functional parameters, and virus titres in the perfused tissue, and in the fetal and maternal circuit. Immunocytochemistry with a monoclonal antibody against CMV immediate early antigen was used to search for placental infection. CMV AD169 did not cross the placenta even during many hours of perfusion, up to 9.5 h, and with exposure to high virus titres. No infected placental cells were detected by immunocytochemistry, although the virus cultures from perfused tissue samples were positive. The perfused human term placenta and the term trophoblast in vitro form an effective barrier to cell-free CMV AD169.

Characterization of the placental barrier to murine enterovirus infection

We performed studies to characterize the mechanisms responsible for development during gestation of a placental barrier to Theiler's murine encephalomyelitis virus (TMEV) in a murine model of gestational enterovirus infection. Electron microscopy of placentae infected in early gestation revealed TMEV-induced changes in the decidua, giant cell, spongiotrophoblast, and labyrinth layers; in contrast, placentae infected in middle and late pregnancy demonstrated degenerative changes in the decidua, giant cell, and spongiotrophoblast layers but not in the labyrinth. Immunohistochemistry and in situ hybridization of placentae infected in early or late gestation demonstrated accumulation of monocytes/macrophages in infected, histologically damaged labyrinths, but no infiltration of immune cells into infected but histologically normal placental regions. Silver staining of placentae from dams inoculated in late gestation with inert gold beads the size of TMEV virions revealed beads within the decidua, giant cell, and spongiotrophoblast layers, but restriction of beads from labyrinths, similar to the usual distribution of TMEV in placentae infected in late pregnancy. These experiments suggest that anatomical relationships, and not systemic immune response, appear to be a major contributor to the murine placental barrier to TMEV.

[Placentitis induced by hepatitis viruses]

The results of morphological studies of 66 placentas from women suffering from various forms of viral hepatitis and HBs antigen carriers as well as results of a pathomorphological study of a late abortion, 3 stillborns and 2 newborns are presented. 33 placentas showed lymphocytic infiltration of varying degree and vasculitis. Of most importance were cellular changes, particularly in the decidua, with the appearance in the nuclei of inclusions similar to those found in the liver affected with viral hepatitis. A correlation is observed in some cases between liver changes in the mother, placental alterations and changes in the child.