Timing of in utero malaria exposure influences fetal CD4 T cell regulatory versus effector differentiation

Regulatory T cell homing and activation is a signature of neonatal sepsis

Regulatory T cells (Treg) play a prominent role in utero tolerating non-inherited maternal antigens and in regulating immune responses against pathogens at birth. This study investigates Treg immunity in newborns in West Africa, where sepsis remains a major public health problem. Treg phenotypes on neonates subgroups with early-onset sepsis (EOS), presumed sepsis, and healthy newborn with and without prenatal risk factors were evaluated. Treg phenotypes varied according to prenatal conditions, with increase in Treg frequency and Foxp3 expression in healthy newborns with prenatal risk factors compared to those with none risk. Compared to healthy newborns with prenatal risk factors, EOS neonates had a significantly reduced frequency of Treg and Foxp3 expression. In the Treg pool, higher frequency of activated Treg was observed in EOS neonates, suggesting an in-utero activation upstream of the sepsis onset. Their migration to the infection site may explain the reduced frequency of circulating Integrin α4β1+ Treg suggestive of homing to the endothelial tissue. EOS neonates show increases expression of CTLA-4, PD-1 and CD39 on Treg, which negatively regulate the activation of effector T cells (Teff) corroborating by the lower frequency of Teff in EOS neonates. The higher frequency of CD39+ Treg and the lower frequency of integrinα4β1+ Treg in EOS non-survivor suggests that Treg exhaustement and endothelial homing are associated with outcome severity. Neonates developing EOS are born with an altered Treg phenotypic profile. Treg expression of CTLA-4, PD-1, CD39, and integrinα4β1 cell markers can be considered as early warning or diagnostic markers of EOS.

Immunophenotypes of Newborns From SARS-CoV-2-infected Mothers

BACKGROUND

Little is known about the neonatal immunologic response to a maternal SARS-CoV-2 infection present during childbirth. Here we analyze a cohort of 75 neonates from SARS-CoV-2-infected mothers.

METHODS

The SARS-CoV-2 infection status was laboratory assessed by real-time reverse transcription polymerase chain reaction on nasopharyngeal swabs (NPS) in both mothers during childbirth and neonates within 24 hours of life. Immunophenotypes of peripheral blood mononucleated cells and SARS-CoV-2 antispike IgA, IgM and IgG of the newborns were recorded. Ten (13.3%) of 75 neonates had positive NPS for SARS-CoV-2; 17 of 75 (23%) were SARS-CoV-2-IgG seropositive, of which one with positive NPS. All the newborns resulted seronegative for SARS-CoV-2 IgA and IgM and were asymptomatic. Our cohort of newborns was divided into groups according to IgG seropositivity (IgG+/-) and NPS results (NPS+/-).

RESULTS

The count and proportion of lymphocyte subsets (evaluated measuring CD3, CD4, CD8 and CD19 markers) and of natural killer cells (evaluated by measuring the CD3-/CD16+/CD56+ subset) were all in the normal range, with no statistical differences among groups. We found a significant expansion of the T cell (CD3+) subset in the IgG+ group interpreted as the result of immune effects triggered by trained immunity in these newborns, but a decrease in CD4+ T cells for NPS+ neonates. It is therefore difficult to conclude that the decrease in CD4 can certainly be caused by an infection.

CONCLUSIONS

A maternal SARS-CoV-2 infection resulted in an expansive effect of CD3+ T cells in IgG+ newborns; nonetheless, it seems not to affect structural and functional development of the newborn immune system.

Exposure to pesticides in utero impacts the fetal immune system and response to vaccination in infancy

The use of pesticides to reduce mosquito vector populations is a cornerstone of global malaria control efforts, but the biological impact of most pesticides on human populations, including pregnant women and infants, is not known. Some pesticides, including carbamates, have been shown to perturb the human immune system. We measure the systemic absorption and immunologic effects of bendiocarb, a commonly used carbamate pesticide, following household spraying in a cohort of pregnant Ugandan women and their infants. We find that bendiocarb is present at high levels in maternal, umbilical cord, and infant plasma of individuals exposed during pregnancy, indicating that it is systemically absorbed and trans-placentally transferred to the fetus. Moreover, bendiocarb exposure is associated with numerous changes in fetal immune cell homeostasis and function, including a dose-dependent decrease in regulatory CD4 T cells, increased cytokine production, and inhibition of antigen-driven proliferation. Additionally, prenatal bendiocarb exposure is associated with higher post-vaccination measles titers at one year of age, suggesting that its impact on functional immunity may persist for many months after birth. These data indicate that in utero bendiocarb exposure has multiple previously unrecognized biological effects on the fetal immune system.

Impact of Malaria in Pregnancy on Risk of Malaria in Young Children: Systematic Review and Meta-Analyses

BACKGROUND

Our objective was to quantify the risk of acquiring malaria among progeny of women with malaria during pregnancy.

METHODS

We searched MEDLINE, EMBASE, CINAHL, and the Cochrane Library for eligible prospective studies. The primary predictor was malaria during pregnancy defined as placental malaria, parasitemia, clinical malaria, or pregnancy-associated malaria. Primary outcomes were parasitemia or clinically defined malaria of young children. We performed meta-analyses to pool adjusted risk estimates using a random-effects model.

RESULTS

Nineteen of 2053 eligible studies met inclusion criteria for the systemic review. Eleven of these studies were quantitative and were included in the meta-analyses. The pooled adjusted odds ratio (aOR) or adjusted hazard ratio (aHR) of malaria during pregnancy for detection of parasitemia in young children were 1.94 (95% confidence interval [CI], 0.93-4.07; P = .08) and 1.46 (95% CI, 1.07-2.00; P < .001), respectively. The pooled aOR or aHR for clinically defined malaria in young children were 2.82 (95% CI, 1.82-4.38; P < .001) and 1.31 (95% CI, 0.96-1.79; P = .09), respectively.

CONCLUSIONS

Our results confirmed that malaria during pregnancy significantly increased the overall risk of malaria in young children via indeterminate mechanisms and emphasize the urgent need to implement safe and highly effective strategies to prevent malaria during pregnancy.

Seasonal variation in the non-specific effects of BCG vaccination on neonatal mortality: three randomised controlled trials in Guinea-Bissau

The BCG vaccine protects non-specifically against other diseases than tuberculosis. Three randomised controlled trials of early BCG in Guinea-Bissau found a 38% reduction in all-cause neonatal mortality. Little is known about the underlying mechanisms. In Guinea-Bissau, prevalent infectious diseases display distinct seasonality. Revisiting the three trials (>6500 infants) comparing early BCG versus no early BCG in low weight infants on all-cause neonatal mortality over 12 consecutive years, we explored the seasonal variation in BCG’s effect on mortality. In a subgroup of participants, adaptive and innate cytokine responses were measured 4 weeks after randomisation. Consistently over the course of the three trials and 12 years, the effect of BCG on all-cause neonatal mortality was particularly beneficial when administered in November to January, coincident with peaking malaria infections. During these months, BCG was also associated with stronger proinflammatory responses to heterologous challenge. Recent studies have suggested a protective effect of BCG against malaria. BCG may also ameliorate immune-compromising fatal effects of placental malaria in the newborn.

Using two phases of the CD4 T cell response to blood-stage murine malaria to understand regulation of systemic immunity and placental pathology in Plasmodium falciparum infection

Plasmodium falciparum infection and malaria remain a risk for millions of children and pregnant women. Here, we seek to integrate knowledge of mouse and human T helper cell (Th) responses to blood-stage Plasmodium infection to understand their contribution to protection and pathology. Although there is no complete Th subset differentiation, the adaptive response occurs in two phases in non-lethal rodent Plasmodium infection, coordinated by Th cells. In short, cellular immune responses limit the peak of parasitemia during the first phase; in the second phase, humoral immunity from T cell-dependent germinal centers is critical for complete clearance of rapidly changing parasite. A strong IFN-γ response kills parasite, but an excess of TNF compared with regulatory cytokines (IL-10, TGF-β) can cause immunopathology. This common pathway for pathology is associated with anemia, cerebral malaria, and placental malaria. These two phases can be used to both understand how the host responds to rapidly growing parasite and how it attempts to control immunopathology and variation. This dual nature of T cell immunity to Plasmodium is discussed, with particular reference to the protective nature of the continuous generation of effector T cells, and the unique contribution of effector memory T cells.

In utero priming of highly functional effector T cell responses to human malaria

Malaria remains a significant cause of morbidity and mortality worldwide, particularly in infants and children. Some studies have reported that exposure to malaria antigens in utero results in the development of tolerance, which could contribute to poor immunity to malaria in early life. However, the effector T cell response to pathogen-derived antigens encountered in utero, including malaria, has not been well characterized. Here, we assessed the frequency, phenotype, and function of cord blood T cells from Ugandan infants born to mothers with and without placental malaria. We found that infants born to mothers with active placental malaria had elevated frequencies of proliferating effector memory fetal CD4⁺ T cells and higher frequencies of CD4⁺ and CD8⁺ T cells that produced inflammatory cytokines. Fetal CD4⁺ and CD8⁺ T cells from placental malaria-exposed infants exhibited greater in vitro proliferation to malaria antigens. Malaria-specific CD4⁺ T cell proliferation correlated with prospective protection from malaria during childhood. These data demonstrate that placental malaria is associated with the generation of proinflammatory malaria-responsive fetal T cells. These findings add to our current understanding of fetal immunity and indicate that a functional and protective pathogen-specific T cell response can be generated in utero.

The immune response to malaria in utero

Malaria causes tremendous early childhood morbidity and mortality, providing an urgent impetus for the development of a vaccine that is effective in neonates. However, the infant immune response to malaria may be influenced by events that occur well before birth. Placental malaria infection complicates one quarter of all pregnancies in Africa and frequently results in exposure of the fetus to malaria antigens in utero, while the immune system is still developing. Some data suggest that in utero exposure to malaria may induce immunologic tolerance that interferes with the development of protective immunity during childhood. More recently, however, a growing body of evidence suggests that fetal malaria exposure can prime highly functional malaria-specific T- and B-cells, which may contribute to postnatal protection from malaria. In utero exposure to malaria also impacts the activation and maturation of fetal antigen presenting cells and innate lymphocytes, which could have implications for global immunity in the infant. Here, we review recent advances in our understanding of how various components of the fetal immune system are altered by in utero exposure to malaria, discuss factors that may tilt the critical balance between tolerance and adaptive immunity, and consider the implications of these findings for malaria prevention strategies.

Additional Screening and Treatment of Malaria During Pregnancy Provides Further Protection Against Malaria and Nonmalarial Fevers During the First Year of Life

Background

Although consensus exists that malaria in pregnancy (MiP) increases the risk of malaria in infancy, and eventually nonmalarial fevers (NMFs), there is a lack of conclusive evidence of benefits of MiP preventive strategies in infants.

Methods

In Burkina Faso, a birth cohort study was nested to a clinical trial assessing the effectiveness of a community-based scheduled screening and treatment of malaria in combination with intermittent preventive treatment with sulfadoxine-pyrimethamine (CSST/IPTp-SP) to prevent placental malaria. Clinical episodes and asymptomatic infections were monitored over 1 year of follow-up to compare the effect of CSST/IPTp-SP and standard IPTp-SP on malaria and NMFs.

Results

Infants born during low-transmission season from mothers receiving CSST/IPTp-SP had a 26% decreased risk of experiencing a first clinical episode (hazard ratio, 0.74 [95% confidence interval, .55-0.99]; P = .047). CSST/IPTp-SP interacted with birth season and gravidity to reduce the incidence of NMFs. No significant effects of CSST/IPTp-SP on the incidence of clinical episodes, parasite density, and Plasmodium falciparum infections were observed.

Conclusions

Our findings indicate that CSST/IPTp-SP strategy may provide additional protection against both malaria and NMFs in infants during the first year of life, and suggest that malaria control interventions during pregnancy could have long-term benefits in infants.

How does malaria in pregnancy impact malaria risk in infants?

Malaria in pregnancy not only exerts profound negative consequences on the health of the mother and developing fetus, but may also alter the risk of malaria during infancy. Although mechanisms driving this altered risk remain unclear, in utero exposure to malaria antigens may impact the development of fetal and infant innate immunity. In an article in BMC Medicine, Natama et al. describe an ambitious analysis of basal and TLR-stimulated cord blood responses among a birth cohort in Burkina Faso. Basal levels of several cytokines, chemokines, and growth factors were shown to be significantly lower in cord blood with histopathologic evidence of placental malaria. Additionally, following TLR7/8 stimulation, samples obtained from infants of mothers with placental malaria were hyper-responsive compared to those without evidence of prenatal malaria exposure. Furthermore, several responses impacted by placental malaria were associated with differential malaria risk in infancy. Understanding how malaria in pregnancy shapes immune responses in infants will provide critical insight into the rational design of malaria control strategies during pregnancy, including intermittent preventative treatment in pregnancy and vaccines.Please see related article: https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-018-1187-3.

Modulation of innate immune responses at birth by prenatal malaria exposure and association with malaria risk during the first year of life

BACKGROUND

Factors driving inter-individual differences in immune responses upon different types of prenatal malaria exposure (PME) and subsequent risk of malaria in infancy remain poorly understood. In this study, we examined the impact of four types of PME (i.e., maternal peripheral infection and placental acute, chronic, and past infections) on both spontaneous and toll-like receptors (TLRs)-mediated cytokine production in cord blood and how these innate immune responses modulate the risk of malaria during the first year of life.

METHODS

We conducted a birth cohort study of 313 mother-child pairs nested within the COSMIC clinical trial (NCT01941264), which was assessing malaria preventive interventions during pregnancy in Burkina Faso. Malaria infections during pregnancy and infants' clinical malaria episodes detected during the first year of life were recorded. Supernatant concentrations of 30 cytokines, chemokines, and growth factors induced by stimulation of cord blood with agonists of TLRs 3, 7/8, and 9 were measured by quantitative suspension array technology. Crude concentrations and ratios of TLR-mediated cytokine responses relative to background control were analyzed.

RESULTS

Spontaneous production of innate immune biomarkers was significantly reduced in cord blood of infants exposed to malaria, with variation among PME groups, as compared to those from the non-exposed control group. However, following TLR7/8 stimulation, which showed higher induction of cytokines/chemokines/growth factors than TLRs 3 and 9, cord blood cells of infants with evidence of past placental malaria were hyper-responsive in comparison to those of infants not-exposed. In addition, certain biomarkers, which levels were significantly modified depending on the PME category, were independent predictors of either malaria risk (GM-CSF TLR7/8 crude) or protection (IL-12 TLR7/8 ratio and IP-10 TLR3 crude, IL-1RA TLR7/8 ratio) during the first year of life.

CONCLUSIONS

These findings indicate that past placental malaria has a profound effect on fetal immune system and that the differential alterations of innate immune responses by PME categories might drive heterogeneity between individuals to clinical malaria susceptibility during the first year of life.

In utero exposure to fine particulate matter results in an altered neuroimmune phenotype in adult mice

Environmental exposure to air pollution has been linked to a number of health problems including organ rejection, lung damage and inflammation. While the deleterious effects of air pollution in adult animals are well documented, the long-term consequences of particulate matter (PM) exposure during animal development are uncertain. In this study we tested the hypothesis that environmental exposure to PM 2.5 μm in diameter in utero promotes long term inflammation and neurodegeneration. We evaluated the behavior of PM exposed animals using several tests and observed deficits in spatial memory without robust changes in anxiety-like behavior. We then examined how this affects the brains of adult animals by examining proteins implicated in neurodegeneration, synapse formation and inflammation by western blot, ELISA and immunohistochemistry. These tests revealed significantly increased levels of COX2 protein in PM2.5 exposed animal brains in addition to changes in synaptophysin and Arg1 proteins. Exposure to PM2.5 also increased the immunoreactivity for GFAP, a marker of activated astrocytes. Cytokine concentrations in the brain and spleen were also altered by PM2.5 exposure. These findings indicate that in utero exposure to particulate matter has long term consequences which may affect the development of both the brain and the immune system in addition to promoting inflammatory change in adult animals.

Malaria in pregnancy shapes the development of foetal and infant immunity

Malaria, particularly Plasmodium falciparum, continues to disproportionately affect pregnant women. In addition to the profoundly deleterious impact of maternal malaria on the health of the mother and foetus, malaria infection in pregnancy has been shown to affect the development of the foetal and infant immune system and may alter the risk of malaria and nonmalarial outcomes during infancy. This review summarizes our current understanding of how malaria infection in pregnancy shapes the protective components of the maternal immune system transferred to the foetus and how foetal exposure to parasite antigens impacts the development of foetal and infant immunity. It also reviews existing evidence linking malaria infection in pregnancy to malaria and nonmalarial outcomes in infancy and how preventing malaria in pregnancy may alter these outcomes. A better understanding of the consequences of malaria infection in pregnancy on the development of foetal and infant immunity will inform control strategies, including intermittent preventive treatment in pregnancy and vaccine development.

Management of malaria in pregnancy

Pregnant women are especially susceptible to malaria infection. Without existing immunity, severe malaria can develop requiring emergency treatment, and pregnancy loss is common. In semi-immune women, consequences of malaria for the mother include anaemia while stillbirth, premature delivery and foetal growth restriction affect the developing foetus. Preventive measures include insecticide-treated nets and (in some African settings) intermittent preventive treatment. Prompt management of maternal infection is key, using parenteral artemisinins for severe malaria, and artemisinin combination treatments (ACTs) in the second and third trimesters of pregnancy. ACTs may soon also be recommended as an alternative to quinine as a treatment in the first trimester of pregnancy. Monitoring the safety of antimalarials and understanding their pharmacokinetics is particularly important in pregnancy with the altered maternal physiology and the risks to the developing foetus. As increasing numbers of countries embrace malaria elimination as a goal, the special needs of the vulnerable group of pregnant women and their infants should not be overlooked.

Diagnostic accuracy of loop-mediated isothermal amplification (LAMP) for screening malaria in peripheral and placental blood samples from pregnant women in Colombia

Background

Pregnant women frequently show low-density Plasmodium infections that require more sensitive methods for accurate diagnosis and early treatment of malaria. This is particularly relevant in low-malaria transmission areas, where intermittent preventive treatment is not recommended. Molecular methods, such as polymerase chain reaction (PCR) are highly sensitive, but require sophisticated equipment and advanced training. Instead, loop mediated isothermal amplification (LAMP) provides an opportunity for molecular detection of malaria infections in remote endemic areas, outside a reference laboratory. The aim of the study is to evaluate the performance of LAMP for the screening of malaria in pregnant women in Colombia.

Methods

This is a nested prospective study that uses data and samples from a larger cross-sectional project conducted from May 2016 to January 2017 in three Colombian endemic areas (El Bagre, Quibdó, and Tumaco). A total of 531 peripheral and placental samples from pregnant women self-presenting at local hospitals for antenatal care visits, at delivery or seeking medical care for suspected malaria were collected. Samples were analysed for Plasmodium parasites by light microscopy (LM), rapid diagnostic test (RDT) and LAMP. Diagnostic accuracy endpoints (sensitivity, specificity, predictive values, and kappa scores) of LM, RDT and LAMP were compared with nested PCR (nPCR) as the reference standard.

Results

In peripheral samples, LAMP showed an improved sensitivity (100.0%) when compared with LM 79.5% and RDT 76.9% (p < 0.01), particularly in afebrile women, for which LAMP sensitivity was two-times higher than LM and RDT. Overall agreement among LAMP and nPCR was high (kappa value = 1.0). Specificity was similar in all tests (100%). In placental blood, LAMP evidenced a four-fold improvement in sensitivity (88.9%) when compared with LM and RDT (22.2%), being the only method, together with nPCR, able to detect placental infections in peripheral blood.

Conclusions

LAMP is a simple, rapid and accurate molecular tool for detecting gestational and placental malaria, being able to overcome the limited sensitivity of LM and RDT. These findings could guide maternal health programs in low-transmission settings to integrate LAMP in their surveillance systems for the active detection of low-density infections and asymptomatic malaria cases.

High production of pro-inflammatory cytokines by maternal blood mononuclear cells is associated with reduced maternal malaria but increased cord blood infection

Background

Increased susceptibility to malaria during pregnancy is not completely understood. Cellular immune responses mediate both pathology and immunity but the effector responses involved in these processes have not been fully characterized. Maternal and fetal cytokine and chemokine responses to malaria at delivery, and their association with pregnancy and childhood outcomes, were investigated in 174 samples from a mother and child cohort from Mozambique. Peripheral and cord mononuclear cells were stimulated with Plasmodium falciparum lysate and secretion of IL-12p70, IFN-γ, IL-2, IL-10, IL-8, IL-6, IL-4, IL-5, IL-1β, TNF, TNF-β was quantified in culture supernatants by multiplex flow cytometry while cellular mRNA expression of IFN-γ, TNF, IL-2, IL-4, IL-6, IL-10 and IL-13 was measured by quantitative PCR.

Results

Higher concentrations of IL-6 and IL-1β were associated with a reduced risk of P. falciparum infection in pregnant women (p < 0.049). Pro-inflammatory cytokines IL-6, IL-1β and TNF strongly correlated among themselves (ρ > 0.5, p < 0.001). Higher production of IL-1β was significantly associated with congenital malaria (p < 0.046) and excessive TNF was associated with peripheral infection and placental lesions (p < 0.044).

Conclusions

Complex network of immuno-pathological cytokine mechanisms in the placental and utero environments showed a potential trade-off between positive and negative effects on mother and newborn susceptibility to infection.

Electronic supplementary material

The online version of this article (10.1186/s12936-018-2317-2) contains supplementary material, which is available to authorized users.

Malaria incidence and prevalence during the first year of life in Nanoro, Burkina Faso: a birth-cohort study

Background

Infants are thought to be protected against malaria during the first months of life mainly due to passage of maternal antibodies. However, in high transmission settings, malaria in early infancy is not uncommon and susceptibility to the infections varies between individuals. This study aimed to determine malaria morbidity and infection during early childhood in rural Burkina Faso.

Methods

Malariometric indices were determined over 1-year follow-up in a birth cohort of 734 infants living in Nanoro health district. Clinical malaria episodes were determined by passive case detection at peripheral health centres while asymptomatic malaria infections were identified during  4 cross-sectional surveys at 3, 6, 9 and 12 months of age. Plasmodium falciparum infections were detected by rapid diagnostic test and/or light microscopy (LM) and quantitative PCR (qPCR).

Results

In total, 717 clinical episodes were diagnosed by qPCR over 8335.18 person-months at risk. The overall malaria incidence was 1.03 per child-year and increased from 0.27 per child-year at 0–3 months of age to 1.92 per child-year at 9–12 months of age. Some 59% of children experienced at least one clinical episode with a median survival time estimated at 9.9 months, while 20% of infants experienced the first episode before 6 months of age. The majority of the clinical episodes were attributable to microscopic parasitaemia (84.2%), and there was a positive correlation between parasite density and age (Spearman’s rho = 0.30; P < 0.0001). Prevalence of asymptomatic infections was similar at 3, 6 and 9 months of age (17.7–20.1%) and nearly 1.6 times higher at 12 months (31.3%). Importantly, gametocyte prevalence among the LM-positive study population was 6.7%, but increased to 10% among asymptomatic infections. In addition, 46% of asymptomatic infections were only detected by qPCR suggesting that infants below 1 year are a potential reservoir for sustaining malaria transmission. Both symptomatic and asymptomatic infections showed marked seasonal distribution with the highest transmission period (July to December) accounting for about 89 and 77% of those infections, respectively.

Conclusions

These findings indicate high and marked age and seasonal-dependency of malaria infections and disease during the first year of life in Nanoro, calling for intensified efforts to control malaria in rural Burkina Faso.

Hyperparasitaemia during clinical malaria episodes in infants aged 0-24 months and its association with in utero exposure to Plasmodium falciparum

Objective

Existing information has shown that infants who are prenatally exposed to P. falciparum are susceptible to subsequent malaria infections. However, the effect of prenatal exposure to P. falciparum on parasite density during clinical malaria episodes has not been fully elucidated. This study is a component of a prospective cohort study for which initial results have been published. This component was designed to determine the effect of prenatal exposure to P. falciparum on parasite density during clinical malaria episodes in the first 24 months of life. A total of 215 infants were involved and monitored for clinical malaria episodes defined by fever (≥ 37 °C) and parasitaemia. The geometric mean parasite counts between exposed and unexposed infants were compared using independent samples t test. The effect of in utero exposure to P. falciparum on parasite density was assessed using binary logistic regression.

Results

The geometric mean parasite count per µl of blood during clinical malaria episodes in exposed infants was 24,889 (95% CI 18,286–31,490) while in unexposed infants it was 14,035 (95% CI 12,111–15,960), P < 0.05. Prenatal exposure to P. falciparum was associated with hyperparasitaemia during clinical malaria episodes (OR 7.04, 95% CI 2.31–21.74), while other factors were not significantly associated (P > 0.05).

Placental implantation over prior cesarean scar causes activation of fetal regulatory T cells

Introduction

Maternal‐fetal chimerism is miniscule, a testament to the integrity of the uteroplacental interface. The soundness of this border region is potentially altered through cesarean delivery of prior babies with uncertain consequences for the following pregnancies.

Methods

Using multicolor flow cytometry and quantitative PCR of non‐inherited maternal antigens we performed a retrospective case control pilot study and formulated the null hypothesis that placental implantation over a prior uterine scar does not result in the presence of memory Treg (CD45RO+) in the fetus. We then performed a power calculation and performed a blinded, appropriately powered prospective case control study to test the null hypothesis.

Results

Fetuses born to mothers with prior uterine scar have a roughly five times higher maternal to fetal microchimerism when the placenta directly interacts with the uterine scar. Unlike exposure to antigens in adult life, in utero antigenic exposure induces tolerogenic (Treg) responses in fetuses and we here report the presence of fetal Treg with a memory phenotype (CD45RO+). However, we only find such CD45RO+ fetal Tregs when the placenta abuts the uterine scar (Risk Ratio = 5 [p < 0.05 CI:(1.448 to 17.27)]). These memory fetal Tregs are functionally highly suppressive compared to CD45RA‐expressing fetal Tregs, and have specificity for non‐inherited maternal antigens.

Conclusions

We found that uterine scars, in the case of our study these scars are from prior c‐sections, fundamentally impair uterine integrity allowing for increased antigen exposure of the fetus; with our appropriately powered study we rejected the null hypothesis and accepted the alternative hypothesis that placental implantation over a prior uterine scar results in the presence of memory Treg (CD45RO+) in the fetus. Thus, our study demonstrates a previously unappreciated role for uterine integrity in limiting fetal antigenic exposure, a key element to avoid the formation of inappropriate tolerances by the fundamentally tolerogenic fetal immune system.

Burden, pathology, and costs of malaria in pregnancy: new developments for an old problem

Over the past 10 years, knowledge of the burden, economic costs, and consequences of malaria in pregnancy has improved, and the prevalence of malaria caused by Plasmodium falciparum has declined substantially in some geographical areas. In particular, studies outside of Africa have increased the evidence base of Plasmodium vivax in pregnancy. Rapid diagnostic tests have been poor at detecting malaria in pregnant women, while PCR has shown a high prevalence of low density infection, the clinical importance of which is unknown. Erythrocytes infected with P falciparum that express the surface protein VAR2CSA accumulate in the placenta, and VAR2CSA is an important target of protective immunity. Clinical trials for a VAR2CSA vaccine are ongoing, but sequence variation needs to be carefully studied. Health system and household costs still limit access to prevention and treatment services. Within the context of malaria elimination, pregnant women could be used to monitor malaria transmission. This Series paper summarises recent progress and highlights unresolved issues related to the burden of malaria in pregnancy.

Relationships between infection with Plasmodium falciparum during pregnancy, measures of placental malaria, and adverse birth outcomes

Background

Malaria in pregnancy has been associated with maternal morbidity, placental malaria, and adverse birth outcomes. However, data are limited on the relationships between longitudinal measures of malaria during pregnancy, measures of placental malaria, and birth outcomes.

Methods

This is a nested observational study of data from a randomized controlled trial of intermittent preventive therapy during pregnancy among 282 participants with assessment of placental malaria and delivery outcomes. HIV-uninfected pregnant women were enrolled at 12–20 weeks of gestation. Symptomatic malaria during pregnancy was measured using passive surveillance and monthly detection of asymptomatic parasitaemia using loop-mediated isothermal amplification (LAMP). Placental malaria was defined as either the presence of parasites in placental blood by microscopy, detection of parasites in placental blood by LAMP, or histopathologic evidence of parasites or pigment. Adverse birth outcomes assessed included low birth weight (LBW), preterm birth (PTB), and small for gestational age (SGA) infants.

Results

The 282 women were divided into three groups representing increasing malaria burden during pregnancy. Fifty-two (18.4%) had no episodes of symptomatic malaria or asymptomatic parasitaemia during the pregnancy, 157 (55.7%) had low malaria burden (0–1 episodes of symptomatic malaria and < 50% of samples LAMP+), and 73 (25.9%) had high malaria burden during pregnancy (≥ 2 episodes of symptomatic malaria or ≥ 50% of samples LAMP+). Women with high malaria burden had increased risks of placental malaria by blood microscopy and LAMP [aRR 14.2 (1.80–111.6) and 4.06 (1.73–9.51), respectively], compared to the other two groups combined. Compared with women with no malaria exposure during pregnancy, the risk of placental malaria by histopathology was higher among low and high burden groups [aRR = 3.27 (1.32–8.12) and aRR = 7.07 (2.84–17.6), respectively]. Detection of placental parasites by any method was significantly associated with PTB [aRR 5.64 (1.46–21.8)], and with a trend towards increased risk for LBW and SGA irrespective of the level of malaria burden during pregnancy.

Conclusion

Higher malaria burden during pregnancy was associated with placental malaria and together with the detection of parasites in the placenta were associated with increased risk for adverse birth outcomes.

Trial Registration Current Controlled Trials Identifier NCT02163447

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-017-2040-4) contains supplementary material, which is available to authorized users.

Formidable Defenses In Utero

A developing human embryo encounters a multitude of threatening scenarios in the womb. How does the fetus defend itself throughout gestation? A new study by McGovern et al. provides remarkable insight into maternal-fetal immunotolerance.

PERIPHERAL PARASITAEMIA AND ITS ASSOCIATION WITH PLASMA CYTOKINES LEVELS IN MALARIA-INFECTED PREGNANT WOMEN IN ABA, ABIA STATE, NIGERIA

Background:

Cytokines in pregnant female may not be a normal phenomenon as malarial infection is often associated with strong CD4+ cell activation and up-regulation of pro-inflammatory cytokines. We investigated the relationship between peripheral parasitaemia and plasma levels of cytokines among malaria infected pregnant women in Aba, Abia State, Nigeria.

Materials and Methods:

A total of 206 non-HIV positive asymptomatic malaria parasitaemic (n=144) and non-parasitaemic (n=62) pregnant women were recruited for this study alongside 80 non-pregnant women who served as positive (n=40) and negative (n=40) controls. Blood samples were aseptically collected from each subject and tested for HIV and malaria parasites using standard methods. Also, plasma levels of cytokines were measured using Th1/Th2 human cytokine ELISA kits (Abcam, UK). Analysis of Variance and Student’s t-test were used for Comparison of groups while Pearson’s Correlation Coefficient was used for tests of association.

Results:

The results revealed a mean parasite density of 685.56±484.55 parasites/µl of blood. Malaria infected pregnant subjects showed significantly higher levels of IFN-γ, TNF-α, IL-4, IL-6 and IL-10 when compared with their non-infected counterparts (P< 0.05). The cytokines evaluated were higher in moderate parasitaemia than mild parasitaemia. Positive correlation existed between peripheral parasite density (PPD) and IL-4 (r= 0.24, P=0.004), PPD and IL-6 (r = 0.35, P = 0.001) as well as PPD and IL-10 (r = 0.29, P = 0.001).

Conclusion:

This study showed that increase in peripheral parasitaemia increased levels of some plasma cytokines (IL-4, IL-6 and IL-10) but not IFN-γ and TNF-α in the malaria infected pregnant women studied.

Sex Disparity in Cord Blood FoxP3+ CD4 T Regulatory Cells in Infants Exposed to Malaria In Utero

Sex differences in the immune response and in infectious disease susceptibility have been well described, although the mechanisms underlying these differences remain incompletely understood. We evaluated the frequency of cord blood CD4 T cell subsets in a highly malaria-exposed birth cohort of mother-infant pairs in Uganda by sex. We found that frequencies of cord blood regulatory T cell ([T_reg] CD4⁺CD25⁺FoxP3⁺CD127^lo/−) differed by infant sex, with significantly lower frequencies of T_regs in female than in male neonates (P = .006). When stratified by in utero malaria exposure status, this difference was observed in the exposed, but not in the unexposed infants.