Anti-PfGARP activates programmed cell death of parasites and reduces severe malaria.

Malaria caused by Plasmodium falciparum remains the leading single-agent cause of mortality in children1, yet the promise of an effective vaccine has not been fulfilled. Here, using our previously described differential screening method to analyse the proteome of blood-stage P. falciparum parasites2, we identify P. falciparum glutamic-acid-rich protein (PfGARP) as a parasite antigen that is recognized by antibodies in the plasma of children who are relatively resistant-but not those who are susceptible-to malaria caused by P. falciparum. PfGARP is a parasite antigen of 80 kDa that is expressed on the exofacial surface of erythrocytes infected by early-to-late-trophozoite-stage parasites. We demonstrate that antibodies against PfGARP kill trophozoite-infected erythrocytes in culture by inducing programmed cell death in the parasites, and that vaccinating non-human primates with PfGARP partially protects against a challenge with P. falciparum. Furthermore, our longitudinal cohort studies showed that, compared to individuals who had naturally occurring anti-PfGARP antibodies, Tanzanian children without anti-PfGARP antibodies had a 2.5-fold-higher risk of severe malaria and Kenyan adolescents and adults without these antibodies had a twofold-higher parasite density. By killing trophozoite-infected erythrocytes, PfGARP could synergize with other vaccines that target parasite invasion of hepatocytes or the invasion of and egress from erythrocytes.

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.

Parasite burden and severity of malaria in Tanzanian children.

BACKGROUND: Severe Plasmodium falciparum malaria is a major cause of death in children. The contribution of the parasite burden to the pathogenesis of severe malaria has been controversial. METHODS: We documented P. falciparum infection and disease in Tanzanian children followed from birth for an average of 2 years and for as long as 4 years. RESULTS: Of the 882 children in our study, 102 had severe malaria, but only 3 had more than two episodes. More than half of first episodes of severe malaria occurred after a second infection. Although parasite levels were higher on average when children had severe rather than mild disease, most children (67 of 102) had high-density infection (>2500 parasites per 200 white cells) with only mild symptoms before severe malaria, after severe malaria, or both. The incidence of severe malaria decreased considerably after infancy, whereas the incidence of high-density infection was similar among all age groups. Infections before and after episodes of severe malaria were associated with similar parasite densities. Nonuse of bed nets, placental malaria at the time of a woman's second or subsequent delivery, high-transmission season, and absence of the sickle cell trait increased severe-malaria risk and parasite density during infections. CONCLUSIONS: Resistance to severe malaria was not acquired after one or two mild infections. Although the parasite burden was higher on average during episodes of severe malaria, a high parasite burden was often insufficient to cause severe malaria even in children who later were susceptible. The diverging rates of severe disease and high-density infection after infancy, as well as the similar parasite burdens before and after severe malaria, indicate that naturally acquired resistance to severe malaria is not explained by improved control of parasite density. (Funded by the National Institute of Allergy and Infectious Diseases and others.).

Fetal origins of malarial disease: cord blood cytokines as risk markers for pediatric severe malarial anemia.

BACKGROUND: Severe malarial anemia (SMA) remains a major cause of pediatric illness and mortality in Sub-Saharan Africa. Here we test the hypothesis that prenatal exposures, reflected by soluble inflammatory mediators in cord blood, can condition an individual's susceptibility to SMA. METHODS: In a Tanzanian birth cohort (n = 743), we measured cord blood concentrations of tumor necrosis factor (TNF), TNF receptors I and II (TNF-RI and TNF-RII), interleukin (IL)-1ß, IL-4, IL-5, IL-6, IL-10, and interferon gamma (IFN-γ). After adjusting for conventional covariates, we calculated the hazard ratios (HR) for time to first SMA event with log(e) cytokine concentrations dichotomized at the median, by quartile, and per standard deviation (SD) increase. RESULTS: Low levels of TNF, TNF-RI, IL-1ß, and IL-5 and high levels of TNF-RII were associated statistically significantly and respectively with approximately 3-fold, 2-fold, 8-fold, 4-fold, and 3-fold increased risks of SMA (Hb < 50 g/L). TNF, TNF-RI, and IL-1ß concentrations were inversely and log-linearly associated with SMA risk; the HR (95% confidence interval [CI]) per 1-SD increase were respectively 0.81 (.65, 1.02), 0.76 (.62, .92), and 0.50 (.40, .62). CONCLUSIONS: These data suggest that proinflammatory cytokine levels at birth are inversely associated with SMA risk and support the hypothesis that pediatric malarial disease has fetal origins.

Prevalence of Plasmodium falciparum anti-malarial resistance-associated polymorphisms in pfcrt, pfmdr1 and pfnhe1 in Muheza, Tanzania, prior to introduction of artemisinin combination therapy.

BACKGROUND: A report of the chloroquine and amodiaquine resistance pfcrt-SVMNT haplotype in Tanzania raises concern about high-level resistance to the artesunate-amodiaquine combination treatment widely employed in Africa. Mutations in the pfmdr1 multi-drug resistance gene may also be associated with resistance, and a highly polymorphic microsatellite (ms-4760) of the pfnhe1 gene involved in quinine susceptibility has not been surveyed in Tanzania. METHODS: A total of 234 samples collected between 2003 - 2006 from an observational birth cohort of young children in Muheza, Tanzania were analysed. In these children, 141 cases of P. falciparum infections were treated with AQ and 93 episodes were treated with QN. Haplotypes of pfcrt and pfmdr1 were determined by a Taqman assay, and ms-4760 repeats in pfnhe1 were assessed by nested PCR amplification and direct sequencing. Parasite population diversity was evaluated using microsatellite markers on five different chromosomes. RESULTS: The pfcrt-CVIET haplotype was present alone in 93.6% (219/234) of the samples over the study period; the wild-type chloroquine- and amodiaquine-sensitive haplotype pfcrt-CVMNK was present in 4.3% (10/234) of the samples; and both haplotypes were present in 2.1% (5/234) of the samples. No significant change in wild-type pfcrt-CVMNK prevalence was evident over the 4-year period of the study. The pfcrt-SVMNT haplotype associated with high-level amodiaquine resistance was not detected in this study. The pfmdr1 locus was genotyped in 178 of these samples. The pfmdr1-YYNY haplotype predominated in 67.4% (120/178) of infections and was significantly associated with the pfcrt-CVIET haplotype. All samples carried the wild-type pfmdr1-N1042 codon. The ms-4760 repeat on pfnhe1 locus displayed 12 distinct haplotypes with ms-4760-1 predominating in the population. Analysis of these haplotypes showed no association of a particular haplotype with quinine treatment outcome. CONCLUSION: The pfcrt-CVIET chloroquine resistance haplotype dominated in the collection of P. falciparum samples from Muheza. The pfcrt-SVMNT haplotype, which threatens the efficacy of amodiaquine and was reported in the same time period from Korogwe, Tanzania, 40 Km from Muheza, was not detected. Relative low prevalence of pfcrt-SVMNT in Africa may result from genetic or other factors rendering P. falciparum less supportive of this haplotype than in South America or other regions. TRIAL REGISTRATION: Trial Protocol Number: 08-I-N064.

Independent lineages of highly sulfadoxine-resistant Plasmodium falciparum haplotypes, eastern Africa.

Sulfadoxine-resistant Plasmodium falciparum undermines malaria prevention with sulfadoxine/pyrimethamine. Parasites with a highly resistant mutant dihydropteroate synthase (dhps) haplotype have recently emerged in eastern Africa; they negated preventive benefits of sulfadoxine/pyrimethamine, and might exacerbate placental malaria. We explored emerging lineages of dhps mutant haplotypes in Malawi, the Democratic Republic of the Congo, and Tanzania by using analyses of genetic microsatellites flanking the dhps locus. In Malawi, a triple-mutant dhps SGEG (mutant amino acids are underlined) haplotype emerged in 2010 that was closely related to pre-existing double-mutant SGEA haplotypes, suggesting local origination in Malawi. When we compared mutant strains with parasites from the Democratic Republic of the Congo and Tanzania by multiple independent analyses, we found that SGEG parasites were partitioned into separate lineages by country. These findings support a model of local origination of SGEG dhps haplotypes, rather than geographic diffusion, and have implications for investigations of emergence and effects of parasite drug resistance.

Immunization with PfGBP130 generates antibodies that inhibit RBC invasion by P. falciparum parasites.

Background: Despite decades of effort, Plasmodium falciparum malaria remains a leading killer of children. The absence of a highly effective vaccine and the emergence of parasites resistant to both diagnosis as well as treatment hamper effective public health interventions. Methods and results: To discover new vaccine candidates, we used our whole proteome differential screening method and identified PfGBP130 as a parasite protein uniquely recognized by antibodies from children who had developed resistance to P. falciparum infection but not from those who remained susceptible. We formulated PfGBP130 as lipid encapsulated mRNA, DNA plasmid, and recombinant protein-based immunogens and evaluated the efficacy of murine polyclonal anti-PfGBP130 antisera to inhibit parasite growth in vitro. Immunization of mice with PfGBP130-A (aa 111-374), the region identified in our differential screen, formulated as a DNA plasmid or lipid encapsulated mRNA, but not as a recombinant protein, induced antibodies that inhibited RBC invasion in vitro. mRNA encoding the full ectodomain of PfGBP130 (aa 89-824) also generated parasite growth-inhibitory antibodies. Conclusion: We are currently advancing PfGBP130-A formulated as a lipid-encapsulated mRNA for efficacy evaluation in non-human primates.

CXC ligand 9 response to malaria during pregnancy is associated with low-birth-weight deliveries.

Placental infection with Plasmodium falciparum is associated with increased levels of proinflammatory cytokines, including tumor necrosis factor alpha (TNF-α) and gamma interferon (IFN-γ), and previous studies have associated increased levels of these cytokines with low birth weight (LBW), especially for malaria-infected primigravidae. To define the contribution of TNF-α and IFN-γ networks to placental-malaria-associated LBW, we measured chemokines induced by TNF-α and IFN-γ and related them to birth weight in a birth cohort of 782 mother-infant pairs residing in an area of P. falciparum holoendemicity in Tanzania. Among primigravidae, levels of CCL2, CXC ligand 9 (CXCL9), and CXCL13 were significantly higher during malaria infection in both the placenta and peripheral blood. Placental CXCL9 and CXCL13 levels were also higher in placental blood from secundigravidae and multigravidae. In multivariate analyses adjusted for known predictors of birth weight, malaria-infected primigravidae with placental CXCL9 levels in the lowest tertile gave birth to babies who weighed 610 g more than babies born to mothers with high CXCL9 levels. CXCL9 expression is induced by IFN-γ, and the strong association between birth weight and placental CXCL9 is consistent with previous observations relating IFN-γ to poor pregnancy outcomes.

Intermittent treatment to prevent pregnancy malaria does not confer benefit in an area of widespread drug resistance.

BACKGROUND: Millions of African women receive sulfadoxine-pyrimethamine (SP) as intermittent preventive treatment during pregnancy (IPTp) to avoid poor outcomes that result from malaria. However, parasites resistant to SP are widespread in parts of Africa, and IPTp may perversely exacerbate placental infections that contain SP-resistant parasites. METHODS: The study used a cross-sectional design. We determined IPTp use in a delivery cohort of 880 pregnant women in Muheza, Tanzania, by report and by plasma sulfa measurements, and we examined its effects on maternal and fetal delivery outcomes. RESULTS: In the overall cohort, IPTp was not associated with decreased odds of placental malaria or with increased mean maternal hemoglobin or mean birth weight. Unexpectedly, IPTp was associated with decreased cord hemoglobin level and increased risk of fetal anemia, which may be related to in utero SP exposure. CONCLUSIONS: IPTp does not improve overall pregnancy outcomes in Muheza, Tanzania, where SP-resistant parasites predominate and may increase the odds of fetal anemia. As parasite resistance increases in a community, the overall effect of IPTp may transition from net benefit to neutral or net harm.

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.

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.

Fetal responses during placental malaria modify the risk of low birth weight.

Inflammation during placental malaria (PM) is associated with low birth weight (LBW), especially during the first pregnancy, but the relative contribution of maternal or fetal factors that mediate this effect remains unclear and the role of gamma interferon (IFN-gamma) has been controversial. We examined the relationship of maternal and cord plasma levels of IFN-gamma, tumor necrosis factor alpha, interleukin-10, ferritin, and leptin to birth weight for Tanzanian women delivering in an area where there is a high rate of malaria transmission. The placental levels of inflammatory cytokines, including IFN-gamma, increased significantly during PM in primigravid and multigravid women but not in secundigravid women. PM also increased maternal peripheral levels of all inflammatory markers except IFN-gamma but had strikingly little effect on cord levels of these proteins. In a multivariate analysis, placental IFN-gamma was negatively associated (P = 0.01) and cord ferritin was positively associated (P < 0.0001) with birth weight in infected (PM-positive [PM+]) first-time mothers. This relationship was not observed in other mothers, consistent with the epidemiology of PM and disease. Cord leptin had a strong positive relationship with birth weight in offspring of PM-negative women (P = 0.02 to P < 0.0001) but not in offspring of PM+ women (all differences were not significant) in the three gravidity groups. The results confirmed that placental IFN-gamma is related to LBW due to PM during first pregnancies and suggest that fetal ferritin plays a protective role. Because fetal cells are a source of placental IFN-gamma and cord ferritin, the fetal response to PM may modify the risk of LBW.

Maternal peripheral blood level of IL-10 as a marker for inflammatory placental malaria.

BACKGROUND: Placental malaria (PM) is an important cause of maternal and foetal mortality in tropical areas, and severe sequelae and mortality are related to inflammation in the placenta. Diagnosis is difficult because PM is often asymptomatic, peripheral blood smear examination detects parasitemia as few as half of PM cases, and no peripheral markers have been validated for placental inflammation. METHODS: In a cohort of Tanzanian parturients, PM was determined by placental blood smears and placental inflammation was assessed by histology and TNF mRNA levels. Maternal peripheral blood levels of several immune mediators previously implicated in PM pathogenesis, as well as ferritin and leptin were measured. The relationship between the levels of these soluble factors to PM and placental inflammation was examined. RESULTS: Peripheral levels of TNF, TNF-RI, TNF-RII, IL-1, IL-10, and ferritin were elevated during PM, whereas levels of IFN-gamma, IL-4, IL-5 and IL-6 were unchanged and levels of leptin were decreased. In receiver operating characteristic curve analysis, IL-10 had the greatest area under the curve, and would provide a sensitivity of 60% with a false positive rate of 10%. At a cut off level of 15 pg/mL, IL-10 would detect PM with a sensitivity of 79.5% and a specificity of 84.3%. IL-10 levels correlated with placental inflammatory cells and placental TNF mRNA levels in first time mothers. CONCLUSION: These data suggest that IL-10 may have utility as a biomarker for inflammatory PM in research studies, but that additional biomarkers may be required to improve clinical diagnosis and management of malaria during pregnancy.

Seroepidemiology of helminths and the association with severe malaria among infants and young children in Tanzania.

The disease burden of Wuchereria bancrofti and Plasmodium falciparum malaria is high, particularly in Africa, and co-infection is common. However, the effects of filarial infection on the risk of severe malaria are unknown. We used the remaining serum samples from a large cohort study in Muheza, Tanzania to describe vector-borne filarial sero-reactivity among young children and to identify associations between exposure to filarial parasites and subsequent severe malaria infections. We identified positive filarial antibody responses (as well as positive antibody responses to Strongyloides stercoralis) among infants as young as six months. In addition, we found a significant association between filarial seropositivity at six months of age and subsequent severe malaria. Specifically, infants who developed severe malaria by one year of age were 3.9 times more likely (OR = 3.9, 95% CI: 1.2, 13.0) to have been seropositive for filarial antigen at six months of age compared with infants who did not develop severe malaria.

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-1ß. 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.

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.

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.

Cytokine profiles at birth predict malaria severity during infancy.

BACKGROUND: Severe malaria risk varies between individuals, and most of this variation remains unexplained. Here, we examined the hypothesis that cytokine profiles at birth reflect inter-individual differences that persist and influence malaria parasite density and disease severity throughout early childhood. METHODS AND FINDINGS: Cytokine levels (TNF-α, IFN-γ, IL-1ß, IL-4, IL-5, IL-6 and IL-10) were measured at birth (cord blood; N=783) and during subsequent routine follow-up visits (peripheral blood) for children enrolled between 2002 and 2006 into a birth cohort in Muheza, Tanzania. Children underwent blood smear and clinical assessments every 2-4 weeks, and at the time of any illness. Cord blood levels of all cytokines were positively correlated with each other (Spearman's rank correlation). Cord levels of IL-1ß and TNF-α (but not other cytokines) correlated with levels of the same cytokine measured at routine visits during early life (P < 0.05). Higher cord levels of IL-1ß but not TNF-α were associated with lower parasite densities during infancy (P=0.003; Generalized Estimating Equation (GEE) method), with an average ~40% reduction versus children with low cord IL-1ß levels, and with decreased risk of severe malaria during follow-up (Cox regression): adjusted hazard ratio (95% CI) 0.60 (0.39-0.92), P = 0.02. CONCLUSION: IL-1ß levels at birth are related to future IL-1ß levels as well as the risk of severe malaria in early life. The effect on severe malaria risk may be due in part to the effect of inflammatory cytokines to control parasite density.

Plasma levels of apolipoprotein A1 in malaria-exposed primigravidae are associated with severe anemia.

BACKGROUND: Plasmodium falciparum placental malaria (PM) contributes to 10,000 maternal deaths due to severe anemia (SA) each year in Africa, primarily among primigravid women who are most susceptible. Increased levels of proinflammatory cytokines like TNF-alpha are associated with maternal anemia in first time mothers but not in other women. Here we aimed to identify additional changes in the plasma proteome associated with pregnancy malaria that may contribute to the development of malaria-related maternal anemia. PRINCIPAL FINDINGS: A semi-quantitative mass spectrometry approach was used to compare the relative abundance of plasma proteins in anemic versus non-anemic women with PM. Levels of 24 proteins differed significantly between anemic and non-anemic primigravidae, including several lipid metabolism proteins and molecular transport proteins involved in the acute phase response signaling network. These differences were not observed in multigravid women who enjoy specific immunity that protect them from PM. In a confirmatory study of a larger cohort of primigravid women, levels of the lipid metabolism protein Apolipoprotein (Apo)-AI were significantly lower in PM+ women with SA. CONCLUSIONS: Apo-AI levels are significantly lower in severely anemic primigravidae with PM, and ApoA1 levels positively correlate with hemoglobin levels in primigravid but not multigravid women. Apo-AI is known to have anti-inflammatory effects, and thus Apo-AI reductions may contribute to the inflammatory processes that result in SA.

The iron trap: iron, malaria and anemia at the mother-child interface.

Iron deficiency causes anemia, but prevents malaria for unknown reasons, thus hindering iron supplementation programs for mothers and children. Iron homeostasis is tightly regulated, including at the mother-fetus interface where iron-malaria relationships are complex. Improved iron status assays, and understanding of malaria protection mechanisms, are needed to manage these disorders.