Cytoadherence phenotype of Plasmodium falciparum-

Background: Cytoadherence of Plasmodium falciparum-infected erythrocytes (IEs) in deep microvasculature endothelia plays a major role in the pathogenesis of cerebral malaria (CM). This biological process is thought to be mediated by P. falciparum erythrocyte membrane protein-1 (PfEMP-1) and human receptors such as CD36 and ICAM-1. The relationship between the expression of PfEMP-1 variants and cytoadherence phenotype in the pathology of malaria is not well established. Methods: Cytoadherence phenotypes of IEs to CD36, ICAM-1, CSPG and the transcription patterns of A, B, var2csa, var3, var gene groups and domain cassettes DC8 and DC13 were assessed in parasites from children with CM and uncomplicated malaria (UM) to determine if cytoadherence is related to a specific transcription profile of pfemp-1 variants. Results: Parasites from CM patients bind significantly more to CD36 than those from UM patients, but no difference was observed in their binding ability to ICAM-1 and CSPG. CM isolates highly transcribed groups A, B, var2csa, var3, DC8 and DC13 compared to UM parasites. The high transcription levels of var genes belonging to group B positively correlated with increased binding level to CD36. Conclusion: CM isolates bind significantly more to CD36 than to ICAM-1, which was correlated with high transcription level of group B var genes, supporting their implication in malaria pathogenesis

Expression of the Domain Cassette 8 <i>Plasmodium falciparum</i> Erythrocyte Membrane Protein 1 Is Associated with Cerebral Malaria in Benin

<div><p>Background</p><p><i>Plasmodium falciparum</i> erythrocyte membrane protein-1 (<i>Pf</i>EMP-1) is a highly polymorphic adherence receptor expressed on the surface of infected erythrocytes. Based on sequence homology <i>Pf</i>EMP-1 variants have been grouped into three major groups A-C, the highly conserved VAR2CSA variants, and semi-conserved types defined by tandem runs of specific domains (“domain cassettes” (DC)). The <i>Pf</i>EMP-1 type expressed determines the adherence phenotype, and is associated with clinical outcome of infection.</p><p>Methods</p><p>Parasite isolates from Beninese children or women presenting with, respectively, CM or PAM were collected along with samples from patients with uncomplicated malaria (UM). We assessed the transcript level of <i>var</i> genes by RT-qPCR and the expression of PfEMP-1 proteins by LC-MS/MS.</p><p>Results</p><p><i>Var</i> genes encoding DC8 and Group A <i>Pf</i>EMP-1 were transcribed more often and at higher levels in cerebral malaria <i>vs.</i> uncomplicated malaria patients. LC-MS/MS identified peptides from group A, DC8 <i>Pf</i>EMP-1 more frequently in cerebral malaria than in uncomplicated malaria and pregnancy-associated malaria samples.</p><p>Conclusion</p><p>This is the first study to show association between <i>Pf</i>EMP-1 subtype and disease outcome by direct analysis of parasites proteome. The results corroborate that group A and specifically the <i>Pf</i>EMP-1 types DC8 are universally associated with cerebral malaria. This is a crucial observation for promoting studies on malaria pathogenesis.</p></div

<i>Var</i> gene transcript levels and <i>Pf</i>EMP-1 proteins identified in the samples collected from patients with cerebral malaria.

<p>Each line corresponds to one sample, the right axis shows <i>var</i> genes transcription levels for each sample and the left axis shows the proteins identified by LC-MS/MS.</p

List of primers used for RT-qPCR [20].

<p>The primers targeted the indicated domain subclasses. Some domains occur in domain cassettes and all can be associated to a <i>Pf</i>EMP-1 UPS grouping.</p

Proportion of proteins identified by LC-MS/MS in parasite samples in Benin, by clinical group.

<p>Cerebral malaria (CM, circle), pregnancy-associated malaria (PAM, triangle), and uncomplicated malaria (UM, diamond). Each data point represents the proportion of proteins associated to each UPS group among all <i>Pf</i>EMP-1 proteins, for one patient. Bars indicate median with interquartile range. (*) shows a difference between CM vs PAM <i>P</i> = 0.017. (**) shows a difference between PAM vs CM and vs UM <i>P</i> = 0.0085, <i>P</i> = 0.0190 respectively.</p

<i>Var</i> type transcription in samples from patients with cerebral and uncomplicated malaria in Benin.

<p>White boxes show transcript units (Tu) <2; light-grey box: 250. Statically significant higher transcript levels in patients with cerebral malaria than in patients with uncomplicated malaria is indicated by (*) p≤0,05; (**) p≤0,01; (***) p≤10⁻³. Statistically significant higher transcript level among patients with uncomplicated malaria compared to patients with malaria cerebral is indicated as (+) p≤10⁻³.</p

Clinical and biological characteristics of patients presenting with malaria in Benin.

<p>Cerebral malaria (CM), uncomplicated malaria (UM), or pregnancy-associated malaria (PAM).</p