Is Placental Malaria a Long-term Risk Factor for Mild Malaria Attack in Infancy? Revisiting a Paradigm

Risk of malaria in young children after periconceptional iron supplementation

This study in Burkina Faso investigated whether offspring of young mothers who had received weekly periconceptional iron supplementation in a randomised controlled trial were at increased risk of malaria. A child safety survey was undertaken in the peak month of malaria transmission towards the end of the trial to assess child iron biomarkers, nutritional status, anaemia and malaria outcomes. Antenatal iron biomarkers, preterm birth, fetal growth restriction and placental pathology for malaria and chorioamnionitis were assessed. Data were available for 180 babies surviving to the time of the survey when their median age was 9 months. Prevalence of maternal iron deficiency in the last trimester based on low body iron stores was 16%. Prevalence of active placental malaria infection was 24.8%, past infection 59% and chorioamnionitis 55.6%. Babies of iron supplemented women had lower median gestational age. Four out of five children ≥ 6 months were iron deficient, and 98% were anaemic. At 4 months malaria prevalence was 45%. Child iron biomarkers, anaemia and malaria outcomes did not differ by trial arm. Factors associated with childhood parasitaemia were third trimester C-reactive protein level (OR 2.1; 95% CI 1.1-3.9), active placental malaria (OR 5.8; 1.0-32.5, P = 0.042) and child body iron stores (OR 1.13; 1.04-1.23, P = 0.002). Chorioamnionitis was associated with reduced risk of child parasitaemia (OR 0.4; 0.1-1.0, P = 0.038). Periconceptional iron supplementation of young women did not alter body iron stores of their children. Higher child body iron stores and placental malaria increased risk of childhood parasitaemia.

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.

Increased Risk of Malaria During the First Year of Life in Small-for-Gestational-Age Infants: A Longitudinal Study in Benin

BACKGROUND

According to the Developmental Origins of Health and Diseases paradigm, the fetal period is highly vulnerable and may have profound effects on later health. Few studies assessed the effect of small-for-gestational age (SGA), a proxy for fetal growth impairment, on risk of malaria during infancy in Africa.

METHODS

We used data from a cohort of 398 mother-child pairs, followed from early pregnancy to age 1 year in Benin. Malaria was actively and passively screened using thick blood smear. We assessed the effect of SGA on risk of malaria infection and clinical malaria from birth to 12 months, after stratifying on the infant's age using a logistic mixed regression model.

RESULTS

After adjustment for potential confounding factors and infant's exposure to mosquitoes, SGA was associated with a 2-times higher risk of malaria infection (adjusted odds ratio [aOR] = 2.16; 95% confidence interval [CI], 1.04-4.51; P = .039) and clinical malaria (aOR = 2.33; 95% CI, 1.09-4.98; P = .030) after age 6 months.

CONCLUSION

Results suggest higher risk of malaria during the second semester of life in SGA infants, and argue for better follow-up of these infants after birth, as currently for preterm babies.

First genome-wide association study of non-severe malaria in two birth cohorts in Benin

Recent research efforts to identify genes involved in malaria susceptibility using genome-wide approaches have focused on severe malaria. Here, we present the first GWAS on non-severe malaria designed to identify genetic variants involved in innate immunity or innate resistance mechanisms. Our study was performed on two cohorts of infants from southern Benin (525 and 250 individuals used as discovery and replication cohorts, respectively) closely followed from birth to 18-24 months of age, with an assessment of a space- and time-dependent environmental risk of exposure. Both the recurrence of mild malaria attacks and the recurrence of malaria infections as a whole (symptomatic and asymptomatic) were considered. Post-GWAS functional analyses were performed using positional, eQTL, and chromatin interaction mapping to identify the genes underlying association signals. Our study highlights a role of PTPRT, a tyrosine phosphatase receptor involved in STAT3 pathway, in the protection against both mild malaria attacks and malaria infections (p = 9.70 × 10^-8 and p = 1.78 × 10^-7, respectively, in the discovery cohort). Strong statistical support was also found for a role of MYLK4 (meta-analysis, p = 5.29 × 10^-8 with malaria attacks), and for several other genes, whose biological functions are relevant in malaria infection. Results shows that GWAS on non-severe malaria can successfully identify new candidate genes and inform physiological mechanisms underlying natural protection against malaria.

Placental impression smears is a good indicator of placental malaria in sub-Saharan Africa

Introduction

Placental malaria (PM) is an important predictor of infant morbidity and mortality in sub-Saharan Africa. Although placental histology is the gold standard test to diagnose PM, the placenta impression smears remains widely used in epidemiological studies. This study is set to evaluate the performance of placental impression smears to detect PM in pregnant women in southern Benin.

Methods

A cross-sectional analysis was performed on data collected in the framework a multicenter randomized clinical trial (Malaria in Pregnancy Preventive and Alternative Drugs). Samples from 491 pregnant women were examined in the district of Allada, Southern Benin. Plasmodium falciparum infections have been assessed in placental blood and placental biopsy.

Results

Placental malaria detected by placenta impression smears and histology were prevalent in 11.4% and 10.8%, respectively. Sensitivity and specificity of placental impression smears were 90.6% and 98.4%. Among 55 pregnant women tested positive by placenta impression smears, 48 were positive by the histology, while 7 were negative (positive predictive value: 87.3%). Four hundred and twenty four (424) of the 429 tested negative by the placenta impression smears, were also negative according to histology whereas the rest (5 of 429) of the women were positive (negative predictive value: 98.8%).

Conclusion

Placenta impression smear is an accurate and easy method for the diagnosis of placental malaria.

Impact of Plasmodium falciparum malaria and intermittent preventive treatment of malaria in pregnancy on the risk of malaria in infants: a systematic review

Background

Studies of the association between malaria in pregnancy (MiP) and malaria during infancy have provided mixed results. A systematic review was conducted to evaluate available evidence on the impact of Plasmodium falciparum malaria infection during pregnancy, and intermittent preventive treatment of malaria during pregnancy (IPTp), on the risk of clinical malaria or parasitaemia during infancy.

Methods

MEDLINE, EMBASE, Global Health, and Malaria in Pregnancy Library databases were searched from inception to 22 May 2018 for articles published in English that reported on associations between MiP and malaria risk in infancy. Search terms included malaria, Plasmodium falciparum, pregnancy, placenta, maternal, prenatal, foetal, newborn, infant, child or offspring or preschool. Randomized controlled trials and prospective cohort studies, which followed infants for at least 6 months, were included if any of the following outcomes were reported: incidence of clinical malaria, prevalence of parasitaemia, and time to first episode of parasitaemia or clinical malaria. Substantial heterogeneity between studies precluded meta-analysis. Thus, a narrative synthesis of included studies was conducted.

Results

The search yielded 14 published studies, 10 prospective cohort studies and four randomized trials; all were conducted in sub-Saharan Africa. Infants born to mothers with parasitaemia during pregnancy were at higher risk of malaria in three of four studies that assessed this association. Placental malaria detected by microscopy or histology was associated with a higher risk of malaria during infancy in nine of 12 studies, but only one study adjusted for malaria transmission intensity. No statistically significant associations between the use of IPTp or different IPTp regimens and the risk of malaria during infancy were identified.

Conclusion

Evidence of an association between MiP and IPTp and risk of malaria in infancy is limited and of variable quality. Most studies did not adequately adjust for malaria transmission intensity shared by mothers and their infants. Further research is needed to confirm or exclude an association between MiP and malaria in infancy. Randomized trials evaluating highly effective interventions aimed at preventing MiP, such as IPTp with dihydroartemisinin–piperaquine, may help to establish a causal association between MiP and malaria in infancy.

HLA-G expression during hookworm infection in pregnant women

INTRODUCTION

HLA-G plays a key role on immune tolerance. Pathogens can induce soluble HLA-G (sHLA-G) production to down-regulate the host immune response, creating a tolerogenic environment favorable for their dissemination. To our knowledge, no study has yet been conducted to assess the relationship between sHLA-G and geohelminth infections.

METHODS

The study was conducted in Allada, Southeastern Benin, from 2011-2014. The study population encompassed 400 pregnant women, included before the end of the 28th week of gestation and followed-up until delivery. At two antenatal care visits and at delivery, stool and blood samples were collected. Helminths were diagnosed by means of the Kato-Katz concentration technique. We used quantile regression to analyze the association between helminth infections and sHLA-G levels during pregnancy.

RESULTS

sHLA-G levels gradually increased during pregnancy and reached maximal levels at delivery. Prevalence of helminth infections was low, with a majority of hookworm infections. We found significantly more hookworm-infected women above the 80th quantile (Q80) of the distribution of the mean sHLA-G level (p < 0.03, multivariate quantile regression). Considering only women above the Q80 percentile, the mean sHLA-G level was significantly higher in hookworm-infected compared to uninfected women (p = 0.04).

CONCLUSION

High levels of sHLA-G were associated with hookworm infection in pregnant women. This result is consistent with the potential involvement of sHLA-G in immune tolerance induced by helminths during pregnancy.

High level of soluble human leukocyte antigen (HLA)-G at beginning of pregnancy as predictor of risk of malaria during infancy

Placental malaria has been associated with an immune tolerance phenomenon and a higher susceptibility to malaria infection during infancy. HLA-G is involved in fetal maternal immune tolerance by inhibiting maternal immunity. During infections HLA-G can be involved in immune escape of pathogens by creating a tolerogenic environment. Recent studies have shown an association between the risk of malaria and HLA-G at both genetic and protein levels. Moreover, women with placental malaria have a higher probability of giving birth to children exhibiting high sHLA-G, independently of their own level during pregnancy. Our aim was to explore the association between the level of maternal soluble HLA-G and the risk of malaria infection in their newborns. Here, 400 pregnant women and their children were actively followed-up during 24 months. The results show a significant association between the level of sHLA-G at the first antenatal visit and the time to first malaria infection during infancy adjusted to the risk of exposure to vector bites (aHR = 1.02, 95%CI [1.01–1.03], p = 0.014). The level of sHLA-G is a significant predictor of the occurrence of malaria infection during infancy consistent with the hypothesis that mother sHLA-G could be a biomarker of malaria susceptibility in children.

Recurrent event survival analysis predicts future risk of hospitalization in patients with paroxysmal and persistent atrial fibrillation

Background

In patients with paroxysmal atrial fibrillation (PAF) or persistent atrial fibrillation (PeAF) symptom burden and fear of hospital readmission are major causes of reduced quality of life. We attempted to develop a prediction model for future atrial fibrillation hospitalization (AFH) risk in PAF and PeAF patients including all previously experienced AFHs in the analysis, as opposed to time to first event.

Methods

Recurrent event survival analysis was used to model the impact of past AFHs on the risk of future AFHs. A recurrent event was defined as a hospitalization due to a new episode of AF. Death or progression to permanent AF were included as competing risks.

Results

We enrolled 174 patients with PAF or PeAF, mean follow up duration was 1279 days, and 325 AFHs were observed. Median patient age was 63.0 (IQR 52.2–68.0), 29% had PAF, and 71% were male. Highly significant predictors of future AFH risk were PeAF (HR 3.20, CI 2.01–5.11) and number of past AFHs observed (HR for 1 event: 2.97, CI 2.04–4.32, HR for ≥2 events: 7.54, CI 5.47–10.40).

Conclusion

In PAF and PeAF patients, AF type and observed AFH frequency are highly significant predictors of future AFH risk. The developed model enables risk prediction in individual patients based on AFH history and baseline characteristics, utilizing all events experienced by the patient. This is the first time recurrent event survival analysis has been used in AF patients.