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Meta-analysis of Plasmodium falciparum var Signatures Contributing to Severe Malaria in African Children and Indian Adults.

ABSTRACT: The clinical presentation of severe Plasmodium falciparum malaria differs between children and adults, but the mechanistic basis for this remains unclear. Contributing factors to disease severity include total parasite biomass and the diverse cytoadhesive properties mediated by the polymorphic var gene parasite ligand family displayed on infected erythrocytes. To explore these factors, we performed a multicohort analysis of the contribution of var expression and parasite biomass to severe malaria in two previously published pediatric cohorts in Tanzania and Malawi and an adult cohort in India. Machine learning analysis revealed independent and complementary roles for var adhesion types and parasite biomass in adult and pediatric severe malaria and showed that similar var profiles, including upregulation of group A and DC8 var, predict severe malaria in adults and children. Among adults, patients with multiorgan complications presented infections with significantly higher parasite biomass without significant differences in var adhesion types. Conversely, pediatric patients with specific complications showed distinct var signatures. Cerebral malaria patients showed broadly increased expression of var genes, in particular group A and DC8 var, while children with severe malaria anemia were classified based on high transcription of DC8 var only. This study represents the first large multisite meta-analysis of var expression, and it demonstrates the presence of common var profiles in severe malaria patients of different ages across distant geographical sites, as well as syndrome-specific disease signatures. The complex associations between parasite biomass, var adhesion type, and clinical presentation revealed here represent the most comprehensive picture so far of the relationship between cytoadhesion, parasite load, and clinical syndrome.IMPORTANCE P. falciparum malaria can cause multiple disease complications that differ by patient age. Previous studies have attempted to address the roles of parasite adhesion and biomass in disease severity; however, these studies have been limited to single geographical sites, and there is limited understanding of how parasite adhesion and biomass interact to influence disease manifestations. In this meta-analysis, we compared parasite disease determinants in African children and Indian adults. This study demonstrates that parasite biomass and specific subsets of var genes are independently associated with detrimental outcomes in both childhood and adult malaria. We also explored how parasite var adhesion types and biomass play different roles in the development of specific severe malaria pathologies, including childhood cerebral malaria and multiorgan complications in adults. This work represents the largest study to date of the role of both var adhesion types and biomass in severe malaria.

SUBMITTER: Duffy F

PROVIDER: S-EPMC6495371 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature

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Meta-analysis of Plasmodium falciparum var Signatures Contributing to Severe Malaria in African Children and Indian Adults.

Duffy Fergal F Bernabeu Maria M Babar Prasad H PH Kessler Anne A Wang Christian W CW Vaz Marina M Chery Laura L Mandala Wilson L WL Rogerson Stephen J SJ Taylor Terrie E TE Seydel Karl B KB Lavstsen Thomas T Gomes Edwin E Kim Kami K Lusingu John J Rathod Pradipsinh K PK Aitchison John D JD Smith Joseph D JD

mBio 20190430 2

The clinical presentation of severe Plasmodium falciparum malaria differs between children and adults, but the mechanistic basis for this remains unclear. Contributing factors to disease severity include total parasite biomass and the diverse cytoadhesive properties mediated by the polymorphic var gene parasite ligand family displayed on infected erythrocytes. To explore these factors, we performed a multicohort analysis of the contribution of var expression and parasite bio ...[more]

PMID: 31040236

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Project description:The primary target of the human immune response to the malaria parasite Plasmodium falciparum, P. falciparum erythrocyte membrane protein 1 (PfEMP1), is encoded by the members of the hyper-diverse var gene family. The parasite exhibits antigenic variation via mutually exclusive expression (switching) of the ~60 var genes within its genome. It is thought that different variants exhibit different host endothelial binding preferences that in turn result in different manifestations of disease.Var sequences comprise ancient sequence fragments, termed homology blocks (HBs), that recombine at exceedingly high rates. We use HBs to define distinct var types within a local population. We then reanalyze a dataset that contains clinical and var expression data to investigate whether the HBs allow for a description of sequence diversity corresponding to biological function, such that it improves our ability to predict disease phenotype from parasite genetics. We find that even a generic set of HBs, which are defined for a small number of non-local parasites: capture the majority of local sequence diversity; improve our ability to predict disease severity from parasite genetics; and reveal a previously hypothesized yet previously unobserved parasite genetic basis for two forms of severe disease. We find that the expression rates of some HBs correlate more strongly with severe disease phenotypes than the expression rates of classic var DBL? tag types, and principal components of HB expression rate profiles further improve genotype-phenotype models. More specifically, within the large Kenyan dataset that is the focus of this study, we observe that HB expression differs significantly for severe versus mild disease, and for rosetting versus impaired consciousness associated severe disease. The analysis of a second much smaller dataset from Mali suggests that these HB-phenotype associations are consistent across geographically distant populations, since we find evidence suggesting that the same HB-phenotype associations characterize this population as well.The distinction between rosetting versus impaired consciousness associated var genes has not been described previously, and it could have important implications for monitoring, intervention and diagnosis. Moreover, our results have the potential to illuminate the molecular mechanisms underlying the complex spectrum of severe disease phenotypes associated with malaria--an important objective given that only about 1% of P. falciparum infections result in severe disease.

Project description:OBJECTIVES:Perturbed hemodynamic function complicates severe malaria. The Fluid Expansion as Supportive Therapy trial demonstrated that fluid resuscitation, involving children with severe malaria, was associated with increased mortality, primarily due to cardiovascular collapse, suggesting that myocardial dysfunction may have a role. The aim of this study was to characterize cardiac function in children with severe malaria. DESIGN:A prospective observational study with clinical, laboratory, and echocardiographic data collected at presentation (T0) and 24 hours (T1) in children with severe malaria. Cardiac index and ejection fraction were calculated at T0 and T1. Cardiac troponin I and brain natriuretic peptide were measured at T0. We compared clinical and echocardiographic variables in children with and without severe malarial anemia (hemoglobin < 5?mg/dL) at T0 and T1. SETTING:Mbale Regional Referral Hospital. PATIENTS:Children 3 months to 12 years old with severe falciparum malaria. INTERVENTIONS:Usual care. MEASUREMENTS AND MAIN RESULTS:We enrolled 104 children, median age 23.3 months, including 61 children with severe malarial anemia. Cardiac troponin I levels were elevated (> 0.1?ng/mL) in n equals to 50, (48%), and median brain natriuretic peptide was within normal range (69.1 pg/mL; interquartile range, 48.4-90.8). At T0, median Cardiac index was significantly higher in the severe malarial anemia versus nonsevere malarial anemia group (6.89 vs 5.28?L/min/m) (p = 0.001), which normalized in both groups at T1 (5.60 vs 5.13?L/min/m) (p = 0.452). Cardiac index negatively correlated with hemoglobin, r equals to -0.380 (p < 0.001). Four patients (3.8%) had evidence of depressed cardiac systolic function (ejection fraction < 45%). Overall, six children died, none developed pulmonary edema, biventricular failure, or required diuretic treatment. CONCLUSIONS:Elevation of cardiac index, due to increased stroke volume, in severe malaria is a physiologic response to circulatory compromise and correlates with anemia. Following whole blood transfusion and antimalarial therapy, cardiac index in severe malarial anemia returns to normal. The majority (> 96%) of children with severe malaria have preserved myocardial systolic function. Although there is evidence for myocardial injury (elevated cardiac troponin I), this does not correlate with cardiac dysfunction.

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Meta-analysis of Plasmodium falciparum var Signatures Contributing to Severe Malaria in African Children and Indian Adults.

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Meta-analysis of Plasmodium falciparum <i>var</i> Signatures Contributing to Severe Malaria in African Children and Indian Adults.

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