Higher platelet counts and platelet factors are associated with a reduction in Plasmodium falciparum parasite density in young Malian children

OBJECTIVES

The association between thrombocytopenia and parasite density or disease severity is described in numerous studies. In recent years, several studies described the protective role of platelets in directly killing Plasmodium parasites, mediated by platelet factor 4 (PF4) binding to Duffy antigen. This study aimed to evaluate the protective role of platelets in young children who are Duffy antigen-negative, such as those in sub-Saharan Africa.

METHODS

A zero-inflated negative binomial model was used to relate platelet count and parasite density data collected in a longitudinal birth cohort. Platelet factors were measured by enzyme-linked immunosorbent assay in samples collected from malaria-infected children who participated in a cross-sectional study.

RESULTS

We described that an increase of 10,000 platelets/μl was associated with a 2.76% reduction in parasite count. Increasing levels of PF4 and CXCL7 levels were also significantly associated with a reduction in parasite count.

CONCLUSIONS

Platelets play a protective role in reducing parasite burden in Duffy-negative children, possibly mediated through activation of the innate immune system.

Acquisition of antibodies that block Plasmodium falciparum adhesion to placental receptor chondroitin sulfate A with increasing gravidity in Malian women

In malaria-endemic areas, pregnant women are more susceptible to Plasmodium falciparum infection, especially primigravidae. During pregnancy, parasites sequester in the placenta and bind to the receptor chondroitin sulfate (CSA). This unique adhesion is mediated by the parasite protein VAR2CSA expressed on the surface of infected erythrocytes (IE). Placental malaria is associated with poor pregnancy outcomes including perinatal mortality, preterm delivery, small for gestational age (SGA) and low birthweight deliveries. Over successive pregnancies, women acquire functional antibodies that inhibit IE adhesion to CSA. Here, we examine the development of anti-adhesion activity and the breadth of anti-adhesion activity as a function of number of previous pregnancies, using samples collected from pregnant women living in an area with high seasonal malaria transmission. Women reached plateau levels of anti-adhesion activity and breadth of anti-adhesion activity after 5 pregnancies. We related the level of anti-adhesion activity and reactivity with surface IE to SGA 19/232 pregnancies resulted in SGA, and report that an increase of 10% in median anti-adhesion activity reduced the odds of SGA by 13% and this relationship approached significance. Further, at an anti-adhesion activity level of 43.7%, an increase of 10% in the breadth of activity significantly reduced the odds of SGA by 21.5%. Antibodies that recognize IE surface increased over successive pregnancies, but were not associated with a reduction in SGA. These results can serve as a guideline for assessing vaccine candidates aiming to reduce poor pregnancy outcomes associated with placental malaria.

Postprandial Triglyceride, Glucose and Insulin Levels 10 Years After Bariatric Surgery in Women With Severe Obesity - A Pilot Study: Part 1 - Laparoscopic Greater Curvature Plication

The long-term effects of bariatric surgery on postprandial profiles in patients with obesity and type 2 diabetes (T2D) have not yet been investigated. Therefore, this study examined postprandial profiles before laparoscopic greater curvature plication (LGCP), and then at 2 and 10 years after surgery.The studied cohort included 10 women (mean age= 54.4±5 years) with obesity (mean BMI= 42.5±7.8 kg/m?) and T2D who underwent LGCP. All subjects underwent a standardized liquid mixed-meal test. For statistical evaluation, ANOVA with Bonferroni multiple comparison was used. Mean postprandial levels were significantly decreased 2 years after surgery. Responses 10 years after the surgery also remained significantly lower than before surgery. Changes observed during the follow-up were significant: glucose: F=34.5, p<0.001; insulin: F=49.3, p<0.001; triglycerides F=9.2, p<0.001. The long-term favorable effects of bariatric surgery on cardiometabolic health may be partly mediated by reductions in postprandial glucose, insulin, and triglyceride levels.

Postprandial Triglyceride, Glucose and Insulin Levels 10 Years After Bariatric Surgery in Women With Severe Obesity - A Pilot Study: Part 2 - Biliopancreatic Diversion

Obesity significantly increases the risk of developing metabolic and cardiovascular diseases. The most effective management tool for both obesity and type 2 diabetes (T2D) is bariatric/metabolic surgery. Delayed postprandial plasma triglyceride clearance contributes to the development of atherosclerosis in patients with T2D. Biliopancreatic diversion (BPD) was shown to be the most effective procedure in long-term T2D remission. However, the effect of BPD on postprandial metabolic profile has not been studied so far. In this pilot study, we therefore examined the changes in postprandial glucose, insulin, and triglyceride in women with severe obesity and T2D before surgery and then two and ten years after BPD. The studied cohort included 7 women (mean age at baseline=49.3±8.2 years) with severe obesity (mean BMI= 45.7±2.9 kg/m?) and T2D. A standardized liquid mixed-meal test was carried out in all subjects and the mean postprandial levels of plasma glucose, insulin, and triglyceride were analyzed by standard laboratory procedures. For statistical evaluation, ANOVA with Bonferroni multiple comparisons was used. Ten years after BPD not only a significant reduction of an average BMI (F=32.9, p<0.001) but also significant declines in mean postprandial plasma levels of glucose (F=155.3, p<0.001), insulin (F=69.8, p<0.001), and triglyceride (F=139.9, p<0.001) were demonstrated. The observed changes in postprandial metabolic profile may contribute to improved cardiometabolic health after bariatric surgery.

Aotus nancymaae model predicts human immune response to the placental malaria vaccine candidate VAR2CSA

Placental malaria vaccines (PMVs) are being developed to prevent severe sequelae of placental malaria (PM) in pregnant women and their offspring. The leading candidate vaccine antigen VAR2CSA mediates parasite binding to placental receptor chondroitin sulfate A (CSA). Despite promising results in small animal studies, recent human trials of the first two PMV candidates (PAMVAC and PRIMVAC) generated limited cross-reactivity and cross-inhibitory activity to heterologous parasites. Here we immunized Aotus nancymaae monkeys with three PMV candidates (PAMVAC, PRIMVAC and ID1-ID2a_M1010) adjuvanted with Alhydrogel, and exploited the model to investigate boosting of functional vaccine responses during PM episodes as well as with nanoparticle antigens. PMV candidates induced high levels of antigen-specific IgG with significant cross-reactivity across PMV antigens by enzyme-linked immunosorbent assay. Conversely, PMV antibodies recognized native VAR2CSA and blocked CSA adhesion of only homologous parasites and not of heterologous parasites. PM episodes did not significantly boost VAR2CSA antibody levels or serum functional activity; nanoparticle and monomer antigens alike boosted serum reactivity but not functional activities. Overall, PMV candidates induced functional antibodies with limited heterologous activity in Aotus monkeys, similar to responses reported in humans. The Aotus model appears suitable for preclinical downselection of PMV candidates and assessment of antibody boosting by PM episodes.

Natural History of Malaria Infections During Early Childhood in Twins

BACKGROUND

The frequency and clinical presentation of malaria infections show marked heterogeneity in epidemiological studies. However, deeper understanding of this variability is hampered by the difficulty in quantifying all relevant factors. Here, we report the history of malaria infections in twins, who are exposed to the same in utero milieu, share genetic factors, and are similarly exposed to vectors.

METHODS

Data were obtained from a Malian longitudinal birth cohort. Samples from 25 twin pairs were examined for malaria infection and antibody responses. Bayesian models were developed for the number of infections during follow-up.

RESULTS

In 16 of 25 pairs, both children were infected and often developed symptoms. In 8 of 25 pairs, only 1 twin was infected, but usually only once or twice. Statistical models suggest that this pattern is not inconsistent with twin siblings having the same underlying infection rate. In a pair with discordant hemoglobin genotype, parasite densities were consistently lower in the child with hemoglobin AS, but antibody levels were similar.

CONCLUSIONS

By using a novel design, we describe residual variation in malaria phenotypes in naturally matched children and confirm the important role of environmental factors, as suggested by the between-twin pair heterogeneity in malaria history.

Pregnancy outcomes in a malaria-exposed Malian cohort of women of child-bearing age

In Sub-Saharan Africa, malaria continues to be associated with adverse pregnancy outcomes including stillbirth, early neonatal death, preterm delivery, and low birth weight. Current preventive measures are insufficient and new interventions are urgently needed. However, before such interventions can be tested in pregnant women, background information on pregnancy outcomes in this target population must be collected. We conducted an observational study in Ouélessébougou, Mali, a malaria-endemic area where first antenatal visit commonly occurs during the second trimester of pregnancy, hindering calculation of miscarriage rate in the population. To accurately determine the rate of miscarriage, 799 non-pregnant women of child-bearing age were enrolled and surveyed via monthly follow up visits that included pregnancy tests. Out of 505 women that completed the study, 364 became pregnant and 358 pregnancies were analyzed: 43 (12%) resulted in miscarriage, 28 (65.1%) occurred during the first trimester of pregnancy. We also determined rates of stillbirth, neonatal death, preterm delivery, and small for gestational age. The results showed high rate of miscarriage during the first trimester and established a basis to evaluate new interventions to prevent pregnancy malaria. This survey design enabled identification of first trimester miscarriages that are often missed by studies conducted in antenatal clinics.

Clinical trial registration

[https://clinicaltrials.gov/], identifier [NCT0297 4608].

Plasmodium falciparum in Aotus nancymaae: A New Model for Placental Malaria

Plasmodium falciparum-infected erythrocytes that display the variant surface antigen VAR2CSA bind chondroitin sulfate A (CSA) to sequester in placental intervillous spaces, causing severe sequelae for mother and offspring. Here, we establish a placental malaria (PM) monkey model. Pregnant Aotus infected with CSA-binding P. falciparum CS2 parasites during the third trimester developed pronounced sequestration of late-stage parasites in placental intervillous spaces that express VAR2CSA and bind specifically to CSA. Similar to immune multigravid women, a monkey infected with P. falciparum CS2 parasites over successive pregnancies acquired antibodies against VAR2CSA, with potent functional activity that was boosted upon subsequent pregnancy infections. Aotus also developed functional antibodies after multiple acute PM episodes and subsequent VAR2CSA immunization. In summary, P. falciparum infections in pregnant Aotus monkeys recapitulate all the prominent features of human PM infection and immunity, and this model can be useful for basic mechanistic studies and preclinical studies to qualify candidate PM vaccines. Clinical Trials Registration: NCT02471378.

Implications of conformational flexibility, lipid binding, and regulatory domains in cell traversal-protein CelTOS for apicomplexan migration

Malaria and other apicomplexan-caused diseases affect millions of humans, agricultural animals, and pets. Cell traversal is a common feature used by multiple apicomplexan parasites to migrate through host cells and can be exploited to develop therapeutics against these deadly parasites. Here, we provide insights into the mechanism of the Cell-traversal protein for ookinetes and sporozoites (CelTOS), a conserved cell-traversal protein in apicomplexan parasites and malaria vaccine candidate. CelTOS has previously been shown to form pores in cell membranes to enable traversal of parasites through cells. We establish roles for the distinct protein regions of Plasmodium vivax CelTOS and examine the mechanism of pore formation. We further demonstrate that CelTOS dimer dissociation is required for pore formation, as disulfide bridging between monomers inhibits pore formation, and this inhibition is rescued by disulfide-bridge reduction. We also show that a helix-destabilizing amino acid, Pro127, allows CelTOS to undergo significant conformational changes to assemble into pores. The flexible C terminus of CelTOS is a negative regulator that limits pore formation. Finally, we highlight that lipid binding is a prerequisite for pore assembly as mutation of a phospholipids-binding site in CelTOS resulted in loss of lipid binding and abrogated pore formation. These findings identify critical regions in CelTOS and will aid in understanding the egress mechanism of malaria and other apicomplexan parasites as well as have implications for studying the function of other essential pore-forming proteins.

Plasma biomarkers of hemoglobin loss in Plasmodium falciparum-infected children identified by quantitative proteomics

Anemia is common among young children infected with Plasmodium falciparum and severe malarial anemia (SMA) is a major cause of their mortality. Two major mechanisms cause malarial anemia: hemolysis of uninfected as well as infected erythrocytes and insufficient erythropoiesis. In a longitudinal birth cohort in Mali, we commonly observed marked hemoglobin reductions during P falciparum infections with a small proportion that progressed to SMA. We sought biomarkers of these processes using quantitative proteomic analysis on plasma samples from 9 P falciparum-infected children, comparing those with reduced hemoglobin (with or without SMA) vs those with stable hemoglobin. We identified higher plasma levels of circulating 20S proteasome and lower insulin-like growth factor-1 (IGF-1) levels in children with reduced hemoglobin. We confirmed these findings in independent enzyme-linked immunosorbent assay-based validation studies of subsets of children from the same cohort (20S proteasome, N = 71; IGF-1, N = 78). We speculate that circulating 20S proteasome plays a role in digesting erythrocyte membrane proteins modified by oxidative stress, resulting in hemolysis, whereas decreased IGF-1, a critical factor for erythroid maturation, might contribute to insufficient erythropoiesis. Quantitative plasma proteomics identified soluble mediators that may contribute to the major mechanisms underlying malarial anemia. This study was registered at www.clinicaltrials.gov as #NCT01168271.

Effect of three years' seasonal malaria chemoprevention on molecular markers of resistance of Plasmodium falciparum to sulfadoxine-pyrimethamine and amodiaquine in Ouelessebougou, Mali

Background

In 2012, seasonal malaria chemoprevention (SMC) was recommended as policy for malaria control by the World Health Organization (WHO) in areas of highly seasonal malaria transmission across the Sahel sub-region in Africa along with monitoring of drug resistance. We assessed the long-term impact of SMC on Plasmodium falciparum resistance to sulfadoxine-pyrimethamine (SP) and amodiaquine (AQ) over a 3-year period of SMC implementation in the health district of Ouelessebougou, Mali.

Methods

In 8 randomly selected sub-districts of Ouelessebougou, Mali, children aged 0–5 years were randomly selected during cross-sectional surveys at baseline (August 2014) and 1, 2 and 3 years post-SMC, at the beginning and end of the malaria transmission season. Blood smears and blood spots on filter paper were obtained and frequencies of mutation in P. falciparum genes related to resistance to SP and AQ (Pfdhfr, Pfdhps, Pfmdr1, and Pfcrt) were assessed by PCR amplification on individual samples and PCR amplification followed by deep sequencing on pooled (by site and year) samples.

Results

At each survey, approximately 50–100 individual samples were analysed by PCR amplification and a total of 1,164 samples were analysed by deep sequencing with an average read depth of 18,018–36,918 after pooling by site and year. Most molecular markers of resistance did not increase in frequency over the period of study (2014–2016). After 3 years of SMC, the frequencies of Pfdhps 540E, Pfdhps 437G and Pfcrt K76T remained similar compared to baseline (4.0 vs 1.4%, p = 0.41; 74.5 vs 64.6%, p = 0.22; 71.3 vs 67.4%, p = 0.69). Nearly all samples tested carried Pfdhfr 59R, and this proportion remained similar 3 years after SMC implementation (98.8 vs 100%, p = 1). The frequency of Pfmdr1 N86Y increased significantly over time from 5.6% at baseline to 18.6% after 3 years of SMC (p = 0.016). Results of pooled analysis using deep sequencing were consistent with those by individual analysis with standard PCR, but also indicated for the first time the presence of mutations at the Pfdhps A581G allele at a frequency of 11.7% after 2 years of SMC, as well as the Pfdhps I431V allele at frequencies of 1.6–9.3% following 1 and 2 years of SMC, respectively.

Conclusion

Two and 3 years of SMC implementation were associated with increased frequency of the Pfmdr1 N86Y mutation but not Pfdhps 540E, Pfdhps 437G and Pfcrt K76T. The first-time detection of the Pfdhps haplotype bearing the I431V and A581G mutations in Mali, even at low frequency, warrants further long-term surveillance.

A single full-length VAR2CSA ectodomain variant purifies broadly neutralizing antibodies against placental malaria isolates

Placental malaria (PM) is a deadly syndrome most frequent and severe in first pregnancies. PM results from accumulation of Plasmodium falciparum-infected erythrocytes (IE) that express the surface antigen VAR2CSA and bind to chondroitin sulfate A (CSA) in the placenta. Women become PM-resistant over successive pregnancies as they develop anti-adhesion and anti-VAR2CSA antibodies, supporting VAR2CSA as the leading PM-vaccine candidate. However, the first VAR2CSA subunit vaccines failed to induce broadly neutralizing antibody and it is known that naturally acquired antibodies target both variant-specific and conserved epitopes. It is crucial to determine whether effective vaccines will require incorporation of many or only a single VAR2CSA variants. Here, IgG from multigravidae was sequentially purified on five full-length VAR2CSA ectodomain variants, thereby depleting IgG reactivity to each. The five VAR2CSA variants purified ~0.7% of total IgG and yielded both strain-transcending and strain-specific reactivity to VAR2CSA and IE-surface antigen. In two independent antibody purification/depletion experiments with permutated order of VAR2CSA variants, IgG purified on the first VAR2CSA antigen displayed broad cross-reactivity to both recombinant and native VAR2CSA variants, and inhibited binding of all isolates to CSA. IgG remaining after depletion on all variants showed significantly reduced binding-inhibition activity compared to initial total IgG. These findings demonstrate that a single VAR2CSA ectodomain variant displays conserved epitopes that are targeted by neutralizing (or binding-inhibitory) antibodies shared by multiple parasite strains, including maternal isolates. This suggests that a broadly effective PM-vaccine can be achieved with a limited number of VAR2CSA variants.

Contracting malaria during pregnancy – especially a first pregnancy – can lead to a severe, placental form of the disease that is often fatal. Red blood cells infected with the malaria parasite Plasmodium falciparum display a protein, VAR2CSA, which can recognize and bind CSA molecules present on placental cells and in placental blood spaces. This leads to the infected blood cells accumulating in the placenta and inducing harmful inflammation.

Having been exposed to the parasite in prior pregnancies generates antibodies that target VAR2CSA, stopping the infected blood cells from latching onto placental CSA or tagging them for immune destruction. Overall, this makes placental malaria less severe in following pregnancies, and suggests that vaccines could be developed based on VAR2CSA.

However, this protein has regions that can vary in structure, meaning that P. falciparaum can generate many VAR2CSA variants. Individuals exposed to the parasite naturally generate antibodies that block a wide array of variants from attaching to CSA. In contrast, first-generation vaccines based on VAR2CSA fragments have only induced variant-specific antibodies, therefore offering limited protection against infection.

As a response, Doritchamou et al. set out to find VAR2CSA structures that could be recognized by antibodies targeting an array of variants. Blood was obtained from women who had had multiple pregnancies and were immune to malaria. Their plasma was passed over five different large VAR2CSA variants in order to isolate and purify antibodies that attached to these structures.

Doritchamou et al. found that antibodies binding to individual VAR2CSA structures could also recognise a wide array of VAR2CSA variants and blocked all tested parasites from sticking to CSA. While further research is needed, these findings highlight antibodies that cross-react to diverse VAR2CSA variants and could be used to design more effective vaccines targeting placental malaria.

Allelic variants of full-length VAR2CSA, the placental malaria vaccine candidate, differ in antigenicity and receptor binding affinity

Plasmodium falciparum-infected erythrocytes (IE) sequester in the placenta via surface protein VAR2CSA, which binds chondroitin sulfate A (CSA) expressed on the syncytiotrophoblast surface, causing placental malaria (PM) and severe adverse outcomes in mothers and their offspring. VAR2CSA belongs to the PfEMP1 variant surface antigen family; PfEMP1 proteins mediate IE adhesion and facilitate parasite immunoevasion through antigenic variation. Here we produced deglycosylated (native-like) and glycosylated versions of seven recombinant full-length VAR2CSA ectodomains and compared them for antigenicity and adhesiveness. All VAR2CSA recombinants bound CSA with nanomolar affinity, and plasma from Malian pregnant women demonstrated antigen-specific reactivity that increased with gravidity and trimester. However, allelic and glycosylation variants differed in their affinity to CSA and their serum reactivities. Deglycosylated proteins (native-like) showed higher CSA affinity than glycosylated proteins for all variants except NF54. Further, the gravidity-related increase in serum VAR2CSA reactivity (correlates with acquisition of protective immunity) was absent with the deglycosylated form of atypical M200101 VAR2CSA with an extended C-terminal region. Our findings indicate significant inter-allelic differences in adhesion and seroreactivity that may contribute to the heterogeneity of clinical presentations, which could have implications for vaccine design.

Full-length VAR2CSA is a potential placental malaria vaccine candidate and in this study, Renn et al. compare antigenicity and receptor binding affinity of different allelic variants in blood samples from pregnant women. Their data show that inter-allelic differences may contribute to the heterogeneity of clinical presentations, which could have implications for vaccine design.

An invariant protein that co-localizes with VAR2CSA on Plasmodium falciparum-infected red cells binds to chondroitin sulfate A

Plasmodium falciparum-infected red blood cells (iRBCs) bind and sequester in deep vascular beds, causing malaria-related disease and death. In pregnant women, VAR2CSA binds to chondroitin sulfate A (CSA) and mediates placental sequestration, making it the major placental malaria (PM) vaccine target. Here, we characterize an invariant protein associated with PM called Plasmodium falciparum chondroitin sulfate A ligand (PfCSA-L). Recombinant PfCSA-L binds both placental CSA and VAR2CSA with nanomolar affinity, and is coexpressed on the iRBC surface with VAR2CSA. Unlike VAR2CSA, which is anchored by a transmembrane domain, PfCSA-L is peripherally associated with the outer surface of knobs through high affinity protein-protein interactions with VAR2CSA. This suggests iRBC sequestration involves complexes of invariant and variant surface proteins, allowing parasites to maintain both diversity and function at the iRBC surface. PfCSA-L is a promising target for intervention because it is well conserved, exposed on infected cells, and expressed and localized with VAR2CSA.

A newly characterized malaria antigen on erythrocyte and merozoite surfaces induces parasite inhibitory antibodies

We previously identified a Plasmodium falciparum (Pf) protein of unknown function encoded by a single-copy gene, PF3D7_1134300, as a target of antibodies in plasma of Tanzanian children in a whole-proteome differential screen. Here we characterize this protein as a blood-stage antigen that localizes to the surface membranes of both parasitized erythrocytes and merozoites, hence its designation as Pf erythrocyte membrane and merozoite antigen 1 (PfEMMA1). Mouse anti-PfEMMA1 antisera and affinity-purified human anti-PfEMMA1 antibodies inhibited growth of P. falciparum strains by up to 68% in growth inhibition assays. Following challenge with uniformly fatal Plasmodium berghei (Pb) ANKA, up to 40% of mice immunized with recombinant PbEMMA1 self-cured, and median survival of lethally infected mice was up to 2.6-fold longer than controls (21 vs. 8 d, P = 0.005). Furthermore, high levels of naturally acquired human anti-PfEMMA1 antibodies were associated with a 46% decrease in parasitemia over 2.5 yr of follow-up of Tanzanian children. Together, these findings suggest that antibodies to PfEMMA1 mediate protection against malaria.

Fetal Cytokine Balance, Erythropoietin and Thalassemia but Not Placental Malaria Contribute to Fetal Anemia Risk in Tanzania

Fetal anemia is common in malaria-endemic areas and a risk factor for anemia as well as mortality during infancy. Placental malaria (PM) and red cell abnormalities have been proposed as possible etiologies, but the relationship between PM and fetal anemia has varied in earlier studies, and the role of red cell abnormalities has not been studied in malaria-endemic areas. In a Tanzanian birth cohort study designed to elucidate the pathogenesis of severe malaria in young infants, we performed a cross-sectional analysis of risk factors for fetal anemia. We determined PM status, newborn red cell abnormalities, and maternal and cord blood levels of iron regulatory proteins, erythropoietin (EPO), cytokines and cytokine receptors. We examined the relationship between these factors and fetal anemia. Fetal anemia was present in 46.2% of the neonates but was not related to PM. Maternal iron deficiency was common (81.6%), most frequent in multigravidae, and interacted with parity to modify risk of fetal anemia, but it was not directly related to risk. Among offspring of iron-deficient women, the odds of fetal anemia increased with fetal α⁺-thalassemia, as well as these patterns of cord blood cytokines: increased cord IL-6, decreased TNF-RI, and decreased sTfR. The EPO response to fetal anemia was low or absent and EPO levels were significantly decreased in newborns with the most severe anemia. This study from an area of high malaria transmission provides evidence that 1) fetal α⁺-thalassemia and cytokine balance, but not PM at delivery, are related to fetal anemia; 2) maternal iron deficiency increases the risk that other factors may cause fetal anemia; and 3) fetal anemia has a multifactorial etiology that may require a variety of interventions, although measures that reduce maternal iron deficiency may be generally beneficial.

Malaria infection is common and associated with perinatal mortality and preterm delivery despite widespread use of chemoprevention in Mali: an observational study 2010 to 2014

BACKGROUND

In malaria-endemic areas, pregnant women and especially first-time mothers are more susceptible to Plasmodium falciparum. Malaria diagnosis is often missed during pregnancy, since many women with placental malaria remain asymptomatic or have submicroscopic parasitemia, masking the association between malaria and pregnancy outcomes Severe maternal anemia and low birthweight deliveries are well-established sequelae, but few studies have confirmed the relationship between malaria infection and severe outcomes like perinatal mortality in high transmission zones.

METHODS

Pregnant women of any gestational age enrolled at antenatal clinic into a longitudinal cohort study in Ouelessebougou, Mali, an area of high seasonal malaria transmission. Follow-up visits included scheduled and unscheduled visits throughout pregnancy. Blood smear microscopy and PCR analysis were employed to detect both microscopic and submicroscopic infections, respectively. Intermittent preventative treatment in pregnancy with sulfadoxine-pyrimethamine (IPTp-SP) was documented and prompt treatment regardless of symptoms given upon malaria diagnosis.

RESULTS

Of the 1850 women followed through delivery, 72.6% of women received 2 or more IPTp-SP doses, 67.2% of women experienced at least one infection between enrollment up to and including delivery. Malaria infection increased the risks of stillbirth (adjusted-hazard ratio (aHR) 3.87, 95%CI 1.18-12.71) and preterm delivery (aHR 2.41, 95%CI 1.35-4.29) in primigravidae, and early neonatal death (death within 7 days) in secundigravidae and multigravidae (HR 6.30, 95%CI 1.41-28.15).

CONCLUSIONS

Malaria treatment after diagnosis, alongside IPTp-SP, is insufficient to prevent malaria-related stillbirth, early neonatal death and PTD. While IPTp-SP was beneficial in Mali during the study period, new tools are needed to improve pregnancy outcomes.

Malaria is a cause of iron deficiency in African children

Malaria and iron deficiency (ID) are common and interrelated public health problems in African children. Observational data suggest that interrupting malaria transmission reduces the prevalence of ID1. To test the hypothesis that malaria might cause ID, we used sickle cell trait (HbAS, rs334 ), a genetic variant that confers specific protection against malaria2, as an instrumental variable in Mendelian randomization analyses. HbAS was associated with a 30% reduction in ID among children living in malaria-endemic countries in Africa (n = 7,453), but not among individuals living in malaria-free areas (n = 3,818). Genetically predicted malaria risk was associated with an odds ratio of 2.65 for ID per unit increase in the log incidence rate of malaria. This suggests that an intervention that halves the risk of malaria episodes would reduce the prevalence of ID in African children by 49%.

Effect of 4 years of seasonal malaria chemoprevention on the acquisition of antibodies to Plasmodium falciparum antigens in Ouelessebougou, Mali

Background

More than 200 million people live in areas of highly seasonal malaria transmission where Seasonal Malaria Chemoprevention (SMC) with sulfadoxine-pyrimethamine (SP) and amodiaquine (AQ) was recommended in 2012 by WHO. This strategy is now implemented widely and protected more than 19 million children in 2018. It was previously reported that exposure to SMC reduced antibody levels to AMA1, MSP-1₄₂ and CSP, but the duration of exposure to SMC up to three 3 years, had no effect on antibody levels to MSP-1₄₂ and CSP.

Methods

In 2017, a cross-sectional survey was carried out 1 month after the last dose of SMC had been given to children aged 4–5 years randomly selected from areas where SMC had been given for 2 or 4 years during the malaria transmission season. A total of 461 children were enrolled, 242 children in areas where SMC had been implemented for 4 years and 219 children in areas where SMC had been implemented for 2 years. Antibody extracted from dry blood spots was used to measure IgG levels to the malaria antigens CSP, MSP-1₄₂ and AMA1 by ELISA.

Results

The prevalence of antibodies to MSP-1₄₂ was similar in children who had received SMC for 4 years compared to those who had received SMC for only 2 years (85.1 vs 86.0%, ajusted odd ratio (aOR) = 1.06, 95% confidence intervals (CI 0.62–1.80), p = 0.80). The prevalence of antibodies to AMA-1 and to CSP was not lower in children who received SMC for 4 years compared to those who had received SMC for only 2 years (95.3 vs 88.8%, aOR = 3.16, 95% CI 1.44–6.95, p = 0.004 for AMA-1; and 91.2 vs 81.9%, aOR = 3.14, 95% CI 1.70–5.76, p < 0.001 for CSP). Median antibody levels for anti-MSP-1₄₂ IgG were not significatively inferior in children who had received SMC for four rather than 2 years (0.88 (IQR: 0.64–1.15) and 0.95 ((0.68–1.15), respectively), anti-CSP (1.30 (1.00–1.56) and 1.17 (0.87–1.47)), and anti-AMA-1 (1.45 (1.24–1.68) and 1.41 (1.17–1.64)).

Conclusion

In an area of high seasonal malaria transmission, children who had received SMC for 4 years did not had lower seropositivity or antibody levels to AMA1, MSP-1₄₂ and CSP compared to children who had received SMC for only 2 years suggesting that children who have received SMC for 4 years may not be more at risk of malaria after the cessation of SMC than children who have received SMC for a shorter period.

Antimalarial antibody repertoire defined by plasma IG proteomics and single B cell IG sequencing

Plasma antimalarial Ab can mediate antiparasite immunity but has not previously been characterized at the molecular level. Here, we develop an innovative strategy to characterize humoral responses by integrating profiles of plasma immunoglobulins (IGs) or Abs with those expressed on B cells as part of the B cell receptor. We applied this strategy to define plasma IG and to determine variable (V) gene usage after vaccination with the Plasmodium falciparum zygote antigen Pfs25. Using proteomic tools coupled with bulk immunosequencing data, we determined human antigen-binding fragment [F(ab')2] peptide sequences from plasma IG of adults who received 4 doses of Pfs25-EPA/Alhydrogel. Specifically, Pfs25 antigen-specific F(ab')2 peptides (Pfs25-IG) were aligned to cDNA sequences of IG heavy (IGH) chain complementarity determining region 3 from a data set generated by total peripheral B cell immunosequencing of the entire vaccinated population. IGHV4 was the most commonly identified IGHV subgroup of Pfs25-IG, a pattern that was corroborated by V heavy/V light chain sequencing of Pfs25-specific single B cells from 5 vaccinees and by matching plasma Pfs25-IG peptides and V-(D)-J sequences of Pfs25-specific single B cells from the same donor. Among 13 recombinant human mAbs generated from IG sequences of Pfs25-specific single B cells, a single IGHV4 mAb displayed strong neutralizing activity, reducing the number of P. falciparum oocysts in infected mosquitoes by more than 80% at 100 μg/mL. Our approach characterizes the human plasma Ab repertoire in response to the Pfs25-EPA/Alhydrogel vaccine and will be useful for studying circulating Abs in response to other vaccines as well as those induced during infections or autoimmune disorders.

Metabolic changes following transcatheter bariatric embolotherapy for weight loss in obesity: secondary outcomes from a prospective RCT

Background/Introduction

Obesity and its comorbid conditions (i.e. type II diabetes mellitus, atrial fibrillation, coronary artery disease, hypertension, etc...) is a growing burden globally, however, the current treatments (i.e. bariatric surgery, intragasrtic balloons and/or pharmaceutical therapy) pose substantial risks or are contraindicated for various populations. Transcatheter bariatric embolotherapy of left gastric artery by reducing “hunger” hormones from the gastric fundus is a procedure for weight loss that has been growing in prominence over the last several years, however, to date no randomized-controlled trial has been conducted until our study. We studied TBE in a double-blind, sham procedure, first in human RCT of patients (pts) with obesity.

Purpose

The purpose of this study was to assess the safety and efficacy of TBE for weight loss in obese patients as well as to evaluate metabolic changes.

Methods

After IV propofol, eligible pts (age 21–60; BMI 35–50 kg/m2) were randomized 1:1 to Sham (skin nick & 1 hr wait) or TBE. All pts received Lifestyle Therapy (behavioral and diet education). Study staff following the pts were also blinded to treatment. Blood samples for gastrointestinal hormones were collected in EDTA tubes containing a protease inhibitor cocktail and frozen per local laboratory standards. All collected samples were assessed together in two batches at the end of the study. The hormones analyzed included ghrelin, GIP, GLP-1, Visfatin, resistin, PAI-1 (total), Leptin, and C-Peptide. An Oral Glucose Tolerance Test (OGTT) and a diabetes assay was performed at baseline and at 6- and 12-months post-intervention. Note, while diabetes was an exclusion criterion for this study, pre-diabetes was not.

Results

44 pts were enrolled, of which 40 pts were randomized equally to the groups, with no major complications in either group. TBE demonstrated superior weight loss over the control group at 6- and 12-months post-intervention in both intention-to-treat and per-protocol analyses. At 6 and 12 months, the TBE group demonstrated a clinically meaningful decrease in glucose 1-hour post-fasting by OGTT. GIP levels in the TBE group increased at a mean of 21%, indicative of an improvement in pre-diabetic milieu. Circulating plasma visfatin levels decreased 20% at 6 months and 26% at 12 months in the TBE group indicating a decrease in body fat. C-Peptide levels were noticeably increased in the TBE group at 6 months possibly indicating improvements in insulin sensitivity and beta-cell function.

Conclusion(s)

TBE is safe and results in clinically significant weight loss and demonstrated a positive effect on glucose homeostasis in pre-diabetic patients.

Funding Acknowledgement

Type of funding source: Private company. Main funding source(s): Endobar Solutions, LLC

Percutaneous transcatheter bariatric embolotherapy for weight loss in obesity: two year data from a prospective RCT

Background/Introduction

Obesity is an important risk factor associated with poor cardiovascular and metabolic outcomes. Dietary, medical, and surgical weight loss strategies are often unsuccessful, unsustainable or accompanied by risks. Pre-clinical and early case series reported that transcatheter bariatric embolotherapy (TBE) of the left gastric artery reduces weight, by reducing “hunger” hormones from the gastric fundus. We studied TBE in a double-blind, sham procedure, first in human RCT of patients (pts) with obesity, and following completion of the initial study we asked subjects to return after 2 years post-embolization for further evaluation.

Purpose

The purpose of this extension study was to assess the long-term weight loss and other outcomes in subjects who underwent TBE for weight loss.

Methods

In the initial RCT subjects were randomized 1:1 to either a Sham (skin nick & 1 hr wait) or TBE following IV Propofol sedation. All pts received Lifestyle Therapy (behavioral and diet education); these staff following the pts were also blinded to treatment. Subjects completed the initial study when reaching the 1 year-follow-up visit. Subjects were then invited to return to the weight loss clinic at 2 years post-embolization for further evaluation on weight loss, blood pressure, pre-diabetic clinical status, satiety, and quality of life.

Results

A total of 44 pts (age 45.5±9.8; 36/8 M/F; BMI 39.6±3.8) were enrolled, of which 40 pts were randomized equally to groups, with no major complications. Mild, transient epigastric pain was seen, but EGDs showed no major abnormalities. Weight loss was improved with TBE by 6 mo, and maintained over the full 12 mo by both intention-to-treat and per-protocol analyses. At 2 years post-embolization, subjects treated with TBE demonstrated a mean 9% TBWL and 25% EBWL.

Conclusion(s)

Bariatric embolization is safe and when used along with lifestyle therapy, results in clinically significant weight loss. Long-term data demonstrates evidence that subjects treated with TBE continue to maintain their weight loss up to 2 years post-treatment.

Funding Acknowledgement

Type of funding source: Private company. Main funding source(s): Endobar Solutions LLC

CXCR4 and MIF are required for neutrophil extracellular trap release triggered by Plasmodium-infected erythrocytes

Neutrophil extracellular traps (NETs) evolved as a unique effector mechanism contributing to resistance against infection that can also promote tissue damage in inflammatory conditions. Malaria infection can trigger NET release, but the mechanisms and consequences of NET formation in this context remain poorly characterized. Here we show that patients suffering from severe malaria had increased amounts of circulating DNA and increased neutrophil elastase (NE) levels in plasma. We used cultured erythrocytes and isolated human neutrophils to show that Plasmodium-infected red blood cells release macrophage migration inhibitory factor (MIF), which in turn caused NET formation by neutrophils in a mechanism dependent on the C-X-C chemokine receptor type 4 (CXCR4). NET production was dependent on histone citrullination by peptidyl arginine deiminase-4 (PAD4) and independent of reactive oxygen species (ROS), myeloperoxidase (MPO) or NE. In vitro, NETs functioned to restrain parasite dissemination in a mechanism dependent on MPO and NE activities. Finally, C57/B6 mice infected with P. berghei ANKA, a well-established model of cerebral malaria, presented high amounts of circulating DNA, while treatment with DNAse increased parasitemia and accelerated mortality, indicating a role for NETs in resistance against Plasmodium infection.

Effect of Seasonal Malaria Chemoprevention on Immune Markers of Exhaustion and Regulation

BACKGROUND

Seasonal malaria chemoprevention (SMC) is a novel strategy to reduce malaria infections in children. Infection with Plasmodium falciparum results in immune dysfunction characterized by elevated expression of markers associated with exhaustion, such as PD1 and LAG3, and regulatory CD4+FOXP3+ T cells.

METHODS

In the current study, the impact of seasonal malaria chemoprevention on malaria-induced immune dysfunction, as measured by markers associated with exhaustion and regulatory T cells, was explored by flow cytometry.

RESULTS

Children that received seasonal malaria chemoprevention had fewer malaria episodes and showed significantly lower fold changes in CD4+PD1+ and CD4+PD1+LAG3+ compared to those that did not receive SMC. Seasonal malaria chemoprevention had no observable effect on fold changes in CD8 T cells expressing PD1 or CD160. However, children receiving SMC showed greater increases in CD4+FOXP3+ T regulatory cells compared to children not receiving SMC.

CONCLUSIONS

These results provide important insights into the dynamics of malaria-induced changes in the CD4 T-cell compartment of the immune system and suggest that the reduction of infections due to seasonal malaria chemoprevention may also prevent immune dysfunction.

CLINICAL TRIALS REGISTRATION

NCT02504918.

Maternally-derived Antibodies to Schizont Egress Antigen-1 and Protection of Infants From Severe Malaria

BACKGROUND

In holoendemic areas, children suffer the most from Plasmodium falciparum malaria, yet newborns and young infants express a relative resistance to both infection and severe malarial disease (SM). This relative resistance has been ascribed to maternally-derived anti-parasite immunoglobulin G; however, the targets of these protective antibodies remain elusive.

METHODS

We enrolled 647 newborns at birth from a malaria-holoendemic region of Tanzania. We collected cord blood, measured antibodies to Plasmodium falciparum Schizont Egress Antigen-1 (PfSEA-1), and related these antibodies to the risk of severe malaria in the first year of life. In addition, we vaccinated female mice with PbSEA-1, mated them, and challenged their pups with P. berghei ANKA parasites to assess the impact of maternal PbSEA-1 vaccination on newborns' resistance to malaria.

RESULTS

Children with high cord-blood anti-PfSEA-1 antibody levels had 51.4% fewer cases of SM compared to individuals with lower anti-PfSEA-1 levels over 12 months of follow-up (P = .03). In 3 trials, pups born to PbSEA-1-vaccinated dams had significantly lower parasitemia and longer survival following a P. berghei challenge compared to pups born to control dams.

CONCLUSIONS

We demonstrate that maternally-derived, cord-blood anti-PfSEA-1 antibodies predict decreased risk of SM in infants and vaccination of mice with PbSEA-1 prior to pregnancy protects their offspring from lethal P. berghei challenge. These results identify, for the first time, a parasite-specific target of maternal antibodies that protect infants from SM and suggest that vaccination of pregnant women with PfSEA-1 may afford a survival advantage to their offspring.

Adverse pregnancy outcomes among women presenting at antenatal clinics in Ouélessébougou, Mali

Background

In sub-Saharan Africa, malaria continues to scourge the population and is the primary cause of morbidity and mortality in young children and pregnant women. As current preventative measures such as intermittent preventive treatment and use of insecticide-treated nets provide incomplete protection, several malaria vaccines are currently under development, including one to specifically prevent pregnancy malaria. Prior to conducting vaccine trials, it is important to obtain background information on poor pregnancy outcomes in the target population to establish a baseline.

Methods

Pregnant women presenting at community health care centers for antenatal care were recruited to the study. Gestational age was determined by ultrasound examination following recruitment. Antenatal care and pregnancy outcome information were collected during a visit 4–8 weeks post-delivery.

Results

One thousand eight hundred fifty women completed the study, and analysis included 1814 women after excluding multiple gestations (n = 26) and missing/incomplete data (n = 10). The percentage (95% CI) of adverse pregnancy outcomes is as follows: miscarriage, 0.28% (0.04–0.52); stillbirth, 1.93% (1.30–2.56); early neonatal death, 1.65% (1.03–2.24); late neonatal death, 0.39%, (0.10–0.68); and preterm delivery (PTD), 4.74% (3.76–5.73). The percentages of early and late neonatal deaths and PTD were significantly higher (p < 0.01) in primigravid compared to multigravid women. In primigravidae, 3.1, 1.1 and 7.1% of pregnancies resulted in early neonatal death, late neonatal death and PTD, respectively, while these outcomes in multigravidae were 1.0, 0.1 and 2.7%, respectively. Major malformations were identified in 4 newborns.

Conclusions

Low gravidity and young age predict perinatal death and PTD. The information collected here can be used as a baseline for adverse pregnancy outcomes in future vaccine trials in pregnant women.

Impact of seasonal malaria chemoprevention on hospital admissions and mortality in children under 5 years of age in Ouelessebougou, Mali

BACKGROUND

Seasonal malaria chemoprevention is widely implemented in Sahel and sub-Sahel countries in Africa. Few studies have assessed the impact of the SMC on hospital admission and death when it is implemented in the health system. This retrospective study assessed the impact of seasonal malaria chemoprevention (SMC) on hospitalizations and deaths of children under 5 years of age during the second year of implementation of SMC in the health district of Ouelessebougou in Mali.

METHODS

In February 2017, a survey was conducted to assess hospital admissions and deaths in children under 5 years of age in two health sub-districts where SMC was implemented in 2015 and two health sub-districts where SMC was not implemented. The survey reviewed deaths and hospitalizations of children under 5, in the four health sub-districts. The crude and specific incidence rates of hospitalizations and deaths were determined in both groups and expressed per 1000 children per year. A negative binomial regression model and a Cox model were used to estimate the relative risks of hospitalization and death after adjusting for confounders. The R software was used for data analysis.

RESULTS

A total of 6638 children under 5 years of age were surveyed, 2759 children in the SMC intervention areas and 3879 children in the control areas. All causes mortality rate per 1000 person-years was 8.29 in the control areas compared to 3.63 in the intervention areas; age and gender adjusted mortality rate ratio 0.44 (95% CI 0.22-0.91), p = 0.027. The incidence rate of all causes hospital admissions was 19.60 per 1000 person-years in the intervention group compared to 33.45 per 1000 person-years in the control group, giving an incidence rate ratio (IRR) adjusted for age and gender of 0.61 (95% CI 0.44-0.84), p = 0.003.

CONCLUSION

The implementation of SMC was associated with a substantial reduction in hospital admissions and all-cause mortality. Trial registration ClinicalTrials.gov NCT02646410.

Placental malaria vaccine candidate antigen VAR2CSA displays atypical domain architecture in some Plasmodium falciparum strains

Two vaccines based on Plasmodium falciparum protein VAR2CSA are currently in clinical evaluation to prevent placental malaria (PM), but a deeper understanding of var2csa variability could impact vaccine design. Here we identified atypical extended or truncated VAR2CSA extracellular structures and confirmed one extended structure in a Malian maternal isolate, using a novel protein fragment assembly method for RNA-seq and DNA-seq data. Extended structures included one or two additional DBL domains downstream of the conventional NTS-DBL1X-6ɛ domain structure, with closest similarity to DBLɛ in var2csa and non-var2csa genes. Overall, 4/82 isolates displayed atypical VAR2CSA structures. The maternal isolate expressing an extended VAR2CSA bound to CSA, but its recombinant VAR2CSA bound less well to CSA than VAR2CSANF54 and showed lower reactivity to naturally acquired parity-dependent antibody. Our protein fragment sequence assembly approach has revealed atypical VAR2CSA domain architectures that impact antigen reactivity and function, and should inform the design of VAR2CSA-based vaccines.

Proteomics Pipeline for Identifying Variant Proteins in Plasmodium falciparum Parasites Isolated from Children Presenting with Malaria

Plasmodium falciparum variant antigens named erythrocyte membrane protein 1 (PfEMP1) are important targets for developing a protective immunity to malaria caused by P. falciparum. One of the major challenges in P. falciparum proteomics studies is identifying PfEMP1s at the protein level due to antigenic variation. To identify these PfEMP1s using shotgun proteomics, we developed a pipeline that searches high-resolution mass spectrometry spectra against a custom protein sequence database. A local alignment algorithm, LAX, was developed as a part of the pipeline that matches peptide sequences to the most similar PfEMP1 and calculates a weight value based on peptide's uniqueness used for PfEMP1 protein inference. The pipeline was first validated in the analysis of a laboratory strain with a known PfEMP1, then it was implemented on the analysis of parasite isolates from malaria-infected pregnant women and finally on the analysis of parasite isolates from malaria-infected children where there was an increase of PfEMP1s identified in 27 out of 31 isolates using the expanded database.

Impact of maternally derived antibodies to Plasmodium falciparum Schizont Egress Antigen-1 on the endogenous production of anti-PfSEA-1 in offspring

Background

We evaluated whether maternally-derived antibodies to a malarial vaccine candidate, Plasmodium falciparum Schizont Egress Antigen-1 (PfSEA-1), in cord blood interfered with the development of infant anti-PfSEA-1 antibodies in response to natural exposure.

Methods

We followed 630 Tanzanian infants who were measured their antibodies against PfSEA-1 (aa 810-1023; PfSEA-1A) at birth and 6, 12, 18, and 24 months of age, and examined the changes in anti-PfSEA-1A antibody levels in response to parasitemia, and evaluated whether maternally-derived anti-PfSEA-1A antibodies in cord blood modified infant anti-PfSEA-1A immune responses.

Results

Infants who experienced parasitemia during the first 6 months of life had significantly higher anti-PfSEA-1A antibodies at 6 and 12 months of age compared to uninfected infants. Maternally-derived anti-PfSEA-1A antibodies in cord blood significantly modified this effect during the first 6 months. During this period, infant anti-PfSEA-1A antibody levels were significantly associated with their P. falciparum exposure when they were born with low, but not higher, maternally-derived anti-PfSEA-1A antibody levels in cord blood. Nevertheless, during the first 6 months of life, maternally-derived anti-PfSEA-1A antibodies in cord blood did not abrogate the parasitemia driven development of infant anti-PfSEA-1A: parasitemia were significantly correlated with anti-PfSEA-1A antibody levels at 6 months of age in the infants born with low maternally-derived anti-PfSEA-1A antibody levels in cord blood and borderline significantly correlated in those infants born with middle and high levels.

Conclusions

Maternal vaccination with PfSEA-1A is unlikely to interfere with the development of naturally acquired anti-PfSEA-1A immune responses following exposure during infancy.

Age-dependent increase in antibodies that inhibit Plasmodium falciparum adhesion to a subset of endothelial receptors

Background

Plasmodium falciparum-infected erythrocytes (IE) sequester in deep vascular beds where their adhesion is mediated by an array of endothelial surface receptors. Because parasite adhesion has been associated with disease, antibodies that block this activity may confer protective immunity. Here, levels of plasma anti-adhesion activity and surface reactivity against freshly collected IEs from malaria-infected children were measured in a Malian birth cohort and related to child age and malaria infection history.

Methods

Plasma samples from children enrolled at birth in a longitudinal cohort study of mother–infant pairs in Ouelessebougou, Mali were collected at multiple time points during follow-up visits. Anti-adhesion antibodies (i.e., inhibit IE binding to any of several endothelial receptors) and reactivity with surface IE proteins were measured using a binding inhibition assay and by flow cytometry, respectively.

Results

Levels of antibodies that inhibit the binding of children’s IE to the receptors ICAM-1, integrin α₃β₁ and laminin increased with age. The breadth of antibodies that inhibit ICAM-1 and laminin adhesion (defined as the proportion of IE isolates whose binding was reduced by ≥ 50%) also significantly increased with age. The number of malaria infections prior to plasma collection was associated with levels of plasma reactivity to IE surface proteins, but not levels of anti-adhesion activity.

Conclusions

Age is associated with increased levels of antibodies that reduce adhesion of children’s IE to three of the ten endothelial receptors evaluated here. These results suggest that anti-adhesion antibodies to some but not all endothelial receptors are acquired during the first few years of life.

Electronic supplementary material

The online version of this article (10.1186/s12936-019-2764-4) contains supplementary material, which is available to authorized users.

Malaria vaccine trials in pregnant women: An imperative without precedent

Pregnant women are highly susceptible to Plasmodium falciparum malaria, leading to substantial maternal, perinatal, and infant mortality. While malaria vaccine development has made significant progress in recent years, no trials of malaria vaccines have ever been conducted in pregnant women. In December 2016, an expert meeting was convened at NIAID, NIH, in Rockville, Maryland to deliberate on the rationale and design of malaria vaccine trials in pregnant women. The discussions highlighted the progress made over recent years in the field of maternal immunization for other infectious diseases, and the evolving regulatory and ethical environment, all of which support a new emphasis on testing malaria vaccines that offer direct benefits to pregnant women. Initial safety and immunogenicity studies of malaria vaccines will be conducted in non-pregnant adult volunteers. Subsequently, efficacy trials involving pregnant women will likely be conducted in malaria-endemic and often resource-poor environments where sufficiently high malaria incidence will allow vaccine activity to be measured. Such trials will need to meet all international standards to ensure the safety of mother and offspring, under oversight of appropriate ethical and regulatory bodies. The convened experts drafted a clinical development plan to test a malaria vaccine product during pregnancy, using as a case study PfSPZ Vaccine being developed by Sanaria Inc. that is currently in phase 2 testing. Following the expert recommendations, a pregnancy registry has been initiated in Ouelessebougou, Mali, to provide baseline information on maternal and fetal outcomes as a context for evaluating PfSPZ Vaccine safety in the future, and new regimens are being assessed that will be suitable for evaluation in pregnant women.

Unusual complications after bariatric surgery gastric plication

Laparoscopic gastric plication (LGCP) is a relatively new bariatric-metabolic operation. The greater gastric curvature is invaginated into the gastric lumen, resulting in a shape similar to that obtained after sleeve gastrectomy. In our paper, we report two interesting cases of patients with gastric plication who presented specific findings - food bezoar and gastric diverticulum. Case reports of bezoars after bariatric surgery are reported most commonly after gastric banding and gastric bypass surgery. Diverticulum of the gastric wall is a complication specific to LGCP when a part of the invaginated gastric wall is slipped between two sutures. A prompt endoscopic intervention is recommended to relieve the obstruction and, in case of diverticulum, to diagnose and manage it surgically.

Systemic Inflammatory Response to Malaria During Pregnancy Is Associated With Pregnancy Loss and Preterm Delivery

Background

Pregnancy malaria (PM) is associated with a proinflammatory immune response characterized by increased levels of cytokines and chemokines such as tumor necrosis factor-α, interferon-γ, interleukin 10 (IL-10), and CXCL9. These changes are associated with poor outcomes including low birthweight delivery and maternal anemia. However, it is unknown if inflammatory pathways during malaria are related to pregnancy loss and preterm delivery (PTD).

Methods

Cytokine and chemokine levels were measured in maternal peripheral blood at enrollment, gestational week 30-32, and delivery, and in placental blood, of 638 women during a longitudinal cohort study in Ouelessebougou, Mali. Plasmodium falciparum infection was assessed by blood smear microscopy at all visits.

Results

PM was associated with increased levels of cytokines and chemokines including IL-10 and CXCL9. In a competing risks model adjusted for known covariates, high CXCL9 levels measured in the peripheral blood during pregnancy were associated with increased risk of pregnancy loss and PTD. At delivery, high IL-10 levels in maternal blood were associated with an increase in pregnancy loss, and increased IL-1β levels in placental blood were associated with pregnancy loss and PTD.

Conclusions

PM is associated with increased proinflammatory cytokine and chemokine levels in placental and maternal peripheral blood. Systemic inflammatory responses to malaria during pregnancy predict increased risk of pregnancy loss and PTD.

Clinical Trials Registration

NCT01168271.

Five-Year Outcomes: Laparoscopic Greater Curvature Plication for Treatment of Morbid Obesity

BACKGROUND

Laparoscopic greater curvature plication (LGCP) is a newer metabolic/bariatric surgical procedure that requires no resection, bypass, or implantable device. We report outcomes in a cohort of LGCP patients at 5-year follow-up.

METHODS

Body mass index (BMI, kg/m²) evolution, excess weight loss (%EWL), excess BMI loss (%EBMIL), and total weight loss (%TWL) were recorded. Repeated measures analysis of variance (ANOVA) was used to assess BMI change over 5 years. Two-step cluster analysis was used to profile LGCP patients according to significant characteristics relative to successful 5-year weight loss.

RESULTS

Of patients entering the study between 2010 and 2011 with complete weight data through 5-year follow-up (86.9%, 212/244), mean age was 45.8 ± 10.9 years; mean baseline BMI, 41.4 ± 5.5 (81.6% women); 58 patients (27.4%) had type 2 diabetes. Mean operative time was 69.0 min; mean hospitalization, 38 h (24-72). ANOVA indicated a significant BMI reduction out to 2 years (p < 0.001), a plateau at 3 and 4 years, and a moderate but significant BMI increase at 5 years (p < 0.01). EBMIL at 1, 2, 3, 4, and 5 years was as follows: 50.7 ± 9.1%, 61.5 ± 8.1%, 60.2 ± 7.0%, 58.5 ± 7.0%, and 56.8 ± 6.3%. At 5 years, 79.2% (168/212) of patients were successful; 20.8% (44/212) experienced a suboptimal weight outcome; mean weight regain, 9.2%. Cluster analysis identified four distinct LGCP patient profiles. Diabetes improvement rate was 65.5%. There were 12 reoperations (4.9%): 4 emergency (1.6%) and 8 (3.3%) elective. There was no mortality.

CONCLUSIONS

At 5-year follow-up, LGCP proved to be safe and effective, with 56.8% EBMIL and a low rate of complications.

Antibody levels to recombinant VAR2CSA domains vary with Plasmodium falciparum parasitaemia, gestational age, and gravidity, but do not predict pregnancy outcomes

Background

Maternal malaria is a tropical scourge associated with poor pregnancy outcomes. Women become resistant to Plasmodium falciparum pregnancy malaria as they acquire antibodies to the variant surface antigen VAR2CSA, a leading vaccine candidate. Because malaria infection may increase VAR2CSA antibody levels and thereby confound analyses of immune protection, gravidity-dependent changes in antibody levels during and after infection, and the effect of VAR2CSA antibodies on pregnancy outcomes were evaluated.

Methods

Pregnant women enrolled in a longitudinal cohort study of mother-infant pairs in Ouelessebougou, Mali provided plasma samples at enrollment, gestational week 30–32, and delivery. Antibody levels to VAR2CSA domains were measured using a multiplex bead-based assay.

Results

Antibody levels to VAR2CSA were higher in multigravidae than primigravidae. Malaria infection was associated with increased antibody levels to VAR2CSA domains. In primigravidae but not in secundigravidae or multigravidae, antibodies levels sharply declined after an infection. A relationship between any VAR2CSA antibody specificity and protection from adverse pregnancy outcomes was not detected.

Conclusions

During malaria infection, primigravidae acquire short-lived antibodies. The lack of an association between VAR2CSA domain antibody reactivity and improved pregnancy outcomes suggests that the recombinant proteins may not present native epitopes targeted by protective antibodies.

Electronic supplementary material

The online version of this article (10.1186/s12936-018-2258-9) contains supplementary material, which is available to authorized users.

Malaria in pregnancy: the relevance of animal models for vaccine development

Malaria during pregnancy due to Plasmodium falciparum or P. vivax is a major public health problem in endemic areas, with P. falciparum causing the greatest burden of disease. Increasing resistance of parasites and mosquitoes to existing tools, such as preventive antimalarial treatments and insecticide-treated bed nets respectively, is eroding the partial protection that they offer to pregnant women. Thus, development of effective vaccines against malaria during pregnancy is an urgent priority. Relevant animal models that recapitulate key features of the pathophysiology and immunology of malaria in pregnant women could be used to accelerate vaccine development. This review summarizes available rodent and nonhuman primate models of malaria in pregnancy, and discusses their suitability for studies of biologics intended to prevent or treat malaria in this vulnerable population.

Diagnostic use of endoscopic full-thickness wall resection (eFTR)-a novel minimally invasive technique for colonic tissue sampling in patients with severe gastrointestinal motility disorders

BACKGROUND

Complex gastrointestinal (GI) motility disorders such as chronic intestinal pseudo-obstruction (CIPO) or Hirschsprung's disease (HD) are challenging to diagnose and treat appropriately. Thorough assessment of patient history, radiographic exams, endoscopy, and motility measurements aid in diagnostic workup, yet underlying histology is the cornerstone to enable a more distinct diagnosis of neuromuscular GI disorders. Traditionally, surgical procedures have been performed to obtain specimen suitable for accurate histologic analysis.

METHODS

We performed endoscopic full-thickness resection (eFTR) using a full-thickness-resection device (FTRD) under moderate propofol sedation in four patients with suspected severe neuromuscular gut disorders including CIPO.

KEY RESULTS

The mean age of the four patients was 43 y (range 19-56 y). Technical and histological success providing large colonic full-thickness tissue samples of excellent quality was achieved in all four patients (success rate 100%). The mean procedure time was 12 min (range 5-20 min). The mean diameter of the resected specimen was 21 mm (range 20-22 mm). No adverse events connected to the procedure itself occurred. Histology ranged from aganglionosis such as Hirschsprung's disease (HD) to hypoganglionosis and eosinophilic leiomyositis combined with lymphocytic ganglionitis in a third patient. Histology was unspecific in one patient.

CONCLUSION AND INFERENCES

EFTR allows safe and minimal invasive harvesting of ample full-thickness tissue samples for accurate histological analysis in patients with suspicion of neuromuscular gut disorders.

Maternal Microchimerism Predicts Increased Infection but Decreased Disease due to Plasmodium falciparum During Early Childhood

Background

A mother's infection with placental malaria (PM) can affect her child's susceptibility to malaria, although the mechanism remains unclear. The fetus acquires a small amount of maternal cells and DNA known as maternal microchimerism (MMc), and we hypothesized that PM increases MMc and that MMc alters risk of Plasmodium falciparum malaria during infancy.

Methods

In a nested cohort from Muheza, Tanzania, we evaluated the presence and level of cord blood MMc in offspring of women with and without PM. A maternal-specific polymorphism was identified for each maternal-infant pair, and MMc was assayed by quantitative polymerase chain reaction. The ability of MMc to predict malaria outcomes during early childhood was evaluated in longitudinal models.

Results

Inflammatory PM increased the detection rate of MMc among offspring of primigravidae and secundigravidae, and both noninflammatory and inflammatory PM increased the level of MMc. Detectable MMc predicted increased risk of positive blood smear but, interestingly, decreased risk of symptomatic malaria and malaria hospitalization.

Conclusions

The acquisition of MMc may result in increased malaria infection but protection from malaria disease. Future studies should be directed at the cellular component of MMc, with attention to its ability to directly or indirectly coordinate anti-malarial immune responses in the offspring.

A Malaria-Resistant Phenotype with Immunological Correlates in a Tanzanian Birth Cohort Exposed to Intense Malaria Transmission

AbstractMalaria incidence is highly heterogeneous even in areas of high transmission, although no conclusive evidence exists that innate or naturally acquired resistance can prevent infection over an extended period of time. This longitudinal study examined immunoparasitological evidence for a malaria-resistant phenotype in which children do not develop malaria despite an extended period of exposure to parasites. Within a birth cohort followed from 2002 to 2006 in Muheza, Tanzania, an area of intense transmission, children (N = 687) provided blood smears biweekly during infancy and monthly thereafter. Maternal and childhood characteristics were obtained, cord-blood cytokines were measured, and antibody responses were assayed as measures of stage-specific exposure. Sixty-three (9.2%) children had no blood smear-positive slides over 2 years of follow-up (range: 1-3.5 years) and were identified as malaria resistant. Malaria-resistant children were similar to other children with respect to completeness of follow-up and all maternal and childhood characteristics except residence area. Antibody seroprevalence was similar for two sporozoite antigens, but malaria-resistant children had a lower antibody seroprevalence to merozoite antigens merozoite surface protein 1 (5.4% versus 30.2%; P < 0.0001) and apical membrane antigen 1 (7.2% versus 33.3%; P < 0.0001). Malaria-resistant children had higher cytokine levels in cord blood, particularly interleukin-1β. In summary, a subset of children living in an area of intense transmission was exposed to malaria parasites, but never developed patent parasitemia; this phenotype was associated with a distinct cytokine profile at birth and antibody profile during infancy. Further research with malaria-resistant children may identify mechanisms for naturally acquired immunity.

Effect of seasonal malaria chemoprevention on the acquisition of antibodies to Plasmodium falciparum antigens in Ouelessebougou, Mali

BACKGROUND

Seasonal malaria chemoprevention (SMC) is a new strategy to reduce malaria burden in young children in Sahelian countries. It consists of the administration of full treatment courses of sulfadoxine-pyrimethamine plus amodiaquine to children at monthly intervals during the malaria season. However, it is not clear if there is a cumulative effect of SMC over time on acquisition of antibodies to malaria antigens.

METHODS

A cross-sectional serosurvey was carried out 1 month after the last dose of SMC in 2016. Children aged 3-4 years were randomly selected from areas where SMC was given for 1, 2 or 3 years during the malaria season. Children in the areas where SMC had been implemented for 1 year but who failed to receive SMC were used as comparison group. Antibody extracted from dry blood spots was used to measure IgG levels to CSP, MSP-1₄₂ and AMA1.

RESULTS

The prevalence of antibodies to AMA-1 were high and similar in children who received SMC for 1, 2 or 3 years and also when compared to those who never received SMC (96.3 vs 97.5%, adjusted OR = 0.99, 95% CI 0.33-2.97, p = 0.99). The prevalence of antibodies to MSP-1₄₂ and to CSP were similar in children that received SMC for 1, 2 or 3 years, but were lower in these children compared to those who did not receive SMC (87.1 vs 91.2%, adjusted OR = 0.55, 95% CI 0.29-1.01, p = 0.05 for MSP-1₄₂; 79.8 vs 89.2%, adjusted OR = 0.52, 95% CI 0.30-0.90, p = 0.019 for CSP).

CONCLUSIONS

SMC reduced seropositivity to MSP-1₄₂ and CSP, but the duration of SMC did not further reduce seropositivity. Exposure to SMC did not reduce the seropositivity to AMA1.

Malaria during Pregnancy

One hundred and twenty-five million women in malaria-endemic areas become pregnant each year (see Dellicour et al. PLoS Med7: e1000221 [2010]) and require protection from infection to avoid disease and death for themselves and their offspring. Chloroquine prophylaxis was once a safe approach to prevention but has been abandoned because of drug-resistant parasites, and intermittent presumptive treatment with sulfadoxine-pyrimethamine, which is currently used to protect pregnant women throughout Africa, is rapidly losing its benefits for the same reason. No other drugs have yet been shown to be safe, tolerable, and effective as prevention for pregnant women, although monthly dihydroartemisinin-piperaquine has shown promise for reducing poor pregnancy outcomes. Insecticide-treated nets provide some benefits, such as reducing placental malaria and low birth weight. However, this leaves a heavy burden of maternal, fetal, and infant morbidity and mortality that could be avoided. Women naturally acquire resistance to Plasmodium falciparum over successive pregnancies as they acquire antibodies against parasitized red cells that bind chondroitin sulfate A in the placenta, suggesting that a vaccine is feasible. Pregnant women are an important reservoir of parasites in the community, and women of reproductive age must be included in any elimination effort, but several features of malaria during pregnancy will require special consideration during the implementation of elimination programs.

Prevalence and risk factors for functional bowel disorders in South China: a population based study using the Rome III criteria

BACKGROUND

Functional bowel disorders (FBDs) such as irritable bowel syndrome (IBS) impact on quality of life and health care resources. It is uncertain whether patients with functional digestive symptoms have similar characteristics in different populations. This population-based study assessed the prevalence and identified risk factors for these disorders in South-East China.

METHODS

Five communities were selected at random and invitations distributed to a representative sample (block randomization). Questionnaires were completely supervised by investigators. Demographic and medical data with FBD symptoms (Rome III criteria), psychological condition, life event stress, and quality of life were collected.

KEY RESULTS

Functional bowel disorder prevalence was 41.6% in 1999/2115 (94.5%) completed questionnaires: 9.9% functional constipation (FC), 6.8% bloating (FB), 6.5% diarrhea (FD), 5.9% IBS (IBS-D 47.1%, IBS-M 23.9%, IBS-C 12.8%, IBS-U 16.2%), and 12.6% unspecified. Similar numbers of men and women had FBDs or IBS (overall; 51.3% male vs 48.7% female, P=.796); however, there was female predominance in FC (62.1%, P<.001) and FB (58.5%, P=.038). FBDs were associated with greater anxiety, depression, life event stress, and a lower quality of life compared with those without symptoms (all, P<.0001). Logistic regression identified medical co-morbidity, anxiety/depression, and life event stress as independent risk factors for these disorders.

CONCLUSIONS & INFERENCES

Functional bowel disorders are as common in South China as in western populations. A similar number of men and women report FBDs and IBS. Only FC and FB are more prevalent in females. Independent risk factors associated with FBDs included physical and psychosocial stressors.

Cord Blood Hepcidin: Cross-Sectional Correlates and Associations with Anemia, Malaria, and Mortality in a Tanzanian Birth Cohort Study

Hepcidin, the master regulator of bioavailable iron, is a key mediator of anemia and also plays a central role in host defense against infection. We hypothesized that measuring hepcidin levels in cord blood could provide an early indication of interindividual differences in iron regulation with quantifiable implications for anemia, malaria, and mortality-related risk. Hepcidin concentrations were measured in cord plasma from a birth cohort (N = 710), which was followed for up to 4 years in a region of perennial malaria transmission in Muheza, Tanzania (2002-2006). At the time of delivery, cord hepcidin levels were correlated with inflammatory mediators, iron markers, and maternal health conditions. Hepcidin levels were 30% (95% confidence interval [CI]: 12%, 44%) lower in children born to anemic mothers and 48% (95% CI: 11%, 97%) higher in placental malaria-exposed children. Relative to children in the lowest third, children in the highest third of cord hepcidin had on average 2.5 g/L (95% CI: 0.1, 4.8) lower hemoglobin levels over the duration of follow-up, increased risk of anemia and severe anemia (adjusted hazard ratio [HR] [95% CI]: 1.18 [1.03, 1.36] and 1.34 [1.08, 1.66], respectively), and decreased risk of malaria and all-cause mortality (adjusted HR [95% CI]: 0.78 [0.67, 0.91] and 0.34 [0.14, 0.84], respectively). Although longitudinal measurements of hepcidin and iron stores are required to strengthen causal inference, these results suggest that hepcidin may have utility as a biomarker indicating children's susceptibility to anemia and infection in early life.

VAR2CSA Domain-Specific Analysis of Naturally Acquired Functional Antibodies to Plasmodium falciparum Placental Malaria

BACKGROUND

Placental malaria is caused by Plasmodium falciparum-infected erythrocytes (IEs) that surface-express VAR2CSA and bind chondroitin sulfate A. The inflammatory response to placenta-sequestered parasites is associated with poor pregnancy outcomes, and protection may be mediated in part by VAR2CSA antibodies that block placental IE adhesion.

METHODS

In this study, we used a new approach to assess VAR2CSA domains for functional epitopes recognized by naturally acquired antibodies. Antigen-specific immunoglobulin (Ig) G targeting Duffy binding-like (DBL) domains from different alleles were sequentially purified from plasma pooled from multigravid women and then characterized using enzyme-linked immunosorbent assay, flow cytometry, and antiadhesion assays.

RESULTS

Different DBL domain-specific IgGs could react to homologous as well as heterologous antigens and parasites, suggesting that conserved epitopes are shared between allelic variants. Homologous blocking of IE binding was observed with ID1-DBL2-ID2a-, DBL4-, and DBL5-specific IgG (range, 42%-75%), whereas partial cross-inhibition activity was observed with purified IgG specific to ID1-DBL2-ID2a and DBL4 antigens. Plasma retained broadly neutralizing activity after complete depletion of these VAR2CSA specificities.

CONCLUSIONS

Broadly neutralizing antibodies of multigravidae are not depleted on VAR2CSA recombinant antigens, and hence development of VAR2CSA vaccines based on a single construct and variant might induce antibodies with limited broadly neutralizing activity.

Preparing for future efficacy trials of severe malaria vaccines

Severe malaria is a major cause of mortality in children, but comprises only a small proportion of Plasmodium falciparum infections in naturally exposed populations. The evaluation of vaccines that prevent severe falciparum disease will require clinical trials whose primary efficacy endpoint will be severe malaria risk during follow-up. Here, we show that such trials are feasible with fewer than 1000 participants in areas with intense malaria transmission during the age interval when severe malaria incidence peaks.

[10 years of sleeve gastrectomy in the Czech Republic in terms of the surgical procedure]

INTRODUCTION

Sleeve gastrectomy (SG) as a single bariatric/metabolic procedure has been performed since 2003 in the world, and since 2006 in the Czech Republic. We report 10 years experience with SG in the Czech Republic from 2006 to 2015.

METHOD

Prospectively collected data from 14 surgical departments was evaluated retrospectively using descriptive statistics for every year from 2006 to 2015 and subsequently evaluated and compared for the entire period. The number of the patients, mean age, mean weight and BMI at the time of surgery, the number of patients with T2DM after SG, mean follow-up, mean %BMIL (% Body Mass Index Loss), distance of the starting point of the resection line from the pylorus, the size of the calibration bougie, the rate of complications, and the number and type of conversion procedures were evaluated.

RESULTS

4134 sleeve gastrectomies were done in the Czech Republic from 2006 to 2015 with the mean follow-up of 32.9 months (range 2145 months) from the procedure. The mean weight at the time of surgery fluctuated between 114.2 kg and 128.9 kg; mean BMI fluctuated between 42.3 and 46.7. Mean %BMIL was 63.2% for the entire evaluated period. The distance of the starting point of the resection line from the pylorus changed from the mean 6.1 cm (range 67 cm) to mean 4.2 cm (range 36 cm) and the size of the calibration bougie changed from the mean 39.2 F (range 3642 F) to mean 37.1 F (range 3542 F). As regards early postoperative complications, bleeding from the resection line occurred in 1.4% and a leak from the staple line occurred in 1.1%. The gastroesophageal reflux disease and hiatal hernia occurred in 17.3% as the most frequent late complications. Conversion to another bariatric procedure was approached in 3.8% in the event of an unsatisfactory effect of the SG.

CONCLUSION

Bariatric or metabolic surgery, respectively, is a safe and effective surgical method for the treatment of severe obesity and T2DM in morbidly obese patients. Currently, SG is the most widely used bariatric/metabolic procedure in the Czech Republic as well as in most other countries and the long-time results are similar in comparison with other authors.Key words: bariatric surgery - sleeve gastrectomy - resection line - complications.

Designing a VAR2CSA-based vaccine to prevent placental malaria

Placental malaria (PM) due to Plasmodium falciparum is a major cause of maternal, fetal and infant mortality, but the mechanisms of pathogenesis and protective immunity are relatively well-understood for this condition, providing a path for vaccine development. P. falciparum parasites bind to chondroitin sulfate A (CSA) to sequester in the placenta, and women become resistant over 1–2 pregnancies as they acquire antibodies that block adhesion to CSA. The protein VAR2CSA, a member of the PfEMP1 variant surface antigen family, mediates parasite adhesion to CSA, and is the leading target for a vaccine to prevent PM. Obstacles to PM vaccine development include the large size (~350 kD), high cysteine content, and sequence variation of VAR2CSA. A number of approaches have been taken to identify the combination of VAR2CSA domains and alleles that can induce broadly active antibodies that block adhesion of heterologous parasite isolates to CSA. This review summarizes these approaches, which have examined VAR2CSA fragments for binding activity, antigenicity with naturally acquired antibodies, and immunogenicity in animals for inducing anti-adhesion or surface-reactive antibodies. Two products are expected to enter human clinical studies in the near future based on N-terminal VAR2CSA fragments that have high binding affinity for CSA, and additional proteins preferentially expressed by placental parasites are also being examined for their potential contribution to a PM vaccine.