PfEMP1 A-Type ICAM-1-Binding Domains Are Not Associated with Cerebral Malaria in Beninese Children

Abstract

PfEMP1 is the major antigen involved in Plasmodium falciparum-infected erythrocyte sequestration in cerebrovascular endothelium. While some PfEMP1 domains have been associated with clinical phenotypes of malaria, formal associations between the expression of a specific domain and the adhesion properties of clinical isolates are limited. In this context, 73 cerebral malaria (CM) and 98 uncomplicated malaria (UM) Beninese children were recruited. We attempted to correlate the cytoadherence phenotype of Plasmodium falciparum isolates with the clinical presentation and the expression of specific PfEMP1 domains. Cytoadherence level on Hbec-5i and CHO-ICAM-1 cell lines and var genes expression were measured. We also investigated the prevalence of the ICAM-1-binding amino acid motif and dual receptor-binding domains, described as a potential determinant of cerebral malaria pathophysiology. We finally evaluated IgG levels against PfEMP1 recombinant domains (CIDRα1.4, DBLβ3, and CIDRα1.4-DBLβ3). CM isolates displayed higher cytoadherence levels on both cell lines, and we found a correlation between CIDRα1.4-DBLβ1/3 domain expression and CHO-ICAM-1 cytoadherence level. Endothelial protein C receptor (EPCR)-binding domains were overexpressed in CM isolates compared to UM whereas no difference was found in ICAM-1-binding DBLβ1/3 domain expression. Surprisingly, both CM and UM isolates expressed ICAM-1-binding motif and dual receptor-binding domains. There was no difference in IgG response against DBLβ3 between CM and UM isolates expressing ICAM-1-binding DBLβ1/3 domain. It raises questions about the role of this motif in CM pathophysiology, and further studies are needed, especially on the role of DBLβ1/3 without the ICAM-1-binding motif. IMPORTANCE Cerebral malaria pathophysiology remains unknown despite extensive research. PfEMP1 proteins have been identified as the main Plasmodium antigen involved in cerebrovascular endothelium sequestration, but it is unclear which var gene domain is involved in Plasmodium cytoadhesion. EPCR binding is a major determinant of cerebral malaria whereas the ICAM-1-binding role is still questioned. Our study confirmed the EPCR-binding role in CM pathophysiology with a major overexpression of EPCR-binding domains in CM isolates. In contrast, ICAM-1-binding involvement appears less obvious with A-type ICAM-1-binding and dual receptor-binding domain expression in both CM and UM isolates. We did not find any variations in ICAM-1-binding motif sequences in CM compared to UM isolates. UM and CM patients infected with isolates expressing the ICAM-1-binding motif displayed similar IgG levels against DBLβ3 recombinant protein. Our study raises interrogations about the role of these domains in CM physiopathology and questions their use in vaccine strategies against cerebral malaria.

Transcriptome analysis of Plasmodium falciparum isolates from Benin reveals specific gene expression associated with cerebral malaria

“…In these isolates, sixteen full length PfEMP1 sequences were obtained (8 CM and 2 UM). A search for the ICAM-1 binding motif showed the pattern in 12/15 CM and 5/8 UM isolates, confirmed by previous RT-qPCR assay (17). The pattern was concordantly not found by the two techniques in 2 CM and 3 UM and for 1 CM, the motif was found by RT-qPCR and not by RNA-seq.…”

“…For this purpose, children presenting with CM and uncomplicated malaria (UM) were recruited in Benin in 2018, during the malaria transmission season (16). A first comparative study (17) highlighted that CM isolates display a greater adherence to Hbec-5i and CHO-ICAM-1 cell lines than UM. The overexpression of EPCR binding CIDRα1 domains was confirmed in CM isolates by RT-qPCR (17).…”

“…A first comparative study (17) highlighted that CM isolates display a greater adherence to Hbec-5i and CHO-ICAM-1 cell lines than UM. The overexpression of EPCR binding CIDRα1 domains was confirmed in CM isolates by RT-qPCR (17). However, DBLβ1/3 domains containing ICAM-1 binding motif were found in both groups and were not overexpressed in CM isolates compared to UM, questioning its role in CM pathophysiology.…”

“…While the var genes domains expression associated with CM has been extensively studied (13,17,18), the others parasitic factors causing CM are not yet fully understood. Previous studies focusing on severe malaria (SM) parasite transcriptome have shown that parasites had a specific gene expression compared to those infecting patients presenting UM (5,6).…”

G6pd-Deficient Mice Are Protected From Experimental Cerebral Malaria and Liver Injury by Suppressing Proinflammatory Response in the Early Stage of Plasmodium berghei Infection

“…The current theory holds that the overactivation of the immune system, coupled with the secretion of proinflammatory cytokines, such as TNF-α, IFN-γ, IL-1β, IL-6 and IL-12, correlates with CM pathogenesis ( 11 ). These proinflammatory cytokines induce brain vascular endothelial cells to express some chemokines and adhesion molecules, like CD36 ( 12 ) and ICAM-1 ( 13 , 14 ). The interaction between the brain vascular endothelium and immune cells via specific adhesion molecules leads to the sequestration of blood cells in brain microvessels and induces blood-brain barrier(BBB) injury ( 10 ).…”