Severe malaria is associated with parasite binding to endothelial protein C receptor

Abstract

Sequestration of Plasmodium falciparum-infected erythrocytes in host blood vessels is a key triggering event in the pathogenesis of severe childhood malaria, which is responsible for about one million deaths every year 1 . Sequestration is mediated by specific interactions between members of the P. falciparum erythrocyte membrane protein 1 (PfEMP1) family and receptors on the endothelial lining 2 . Severe malaria is associated with expression of specific PfEMP1 subtypes containing domain cassettes (DC) 8 and 13 3 , but the endothelial receptor for parasites expressing these proteins was unknown 4,5 . Here, we identify endothelial protein C receptor (EPCR), which mediates cytoprotective effects of activated protein C 6 , as the endothelial receptor for DC8 and DC13 PfEMP1. We show that EPCR binding is mediated through the N-terminal cysteine-rich interdomain region (CIDRα1) of DC8 and group A PfEMP1 subfamilies and that CIDRα1 interferes with protein C binding to EPCR. This PfEMP1 adhesive property links P. falciparum Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:http://www.nature.com/authors/editorial_policies/license.html#terms † Correspondence to: thomasl@sund.ku.dk and lturner@sund.ku.dk. * These authors contributed equally to the work.Supplementary Information is linked to the online version of the paper at www.nature.com/nature.Author Contributions: LT, TL, JDS and AJB produced recombinant proteins; JF performed the protein array experiments; SSB, CWW, JEVP, MAN, MA, JSJ and JDS performed the work with malaria parasites; PM, JL and TGT organized clinical work and processed clinical samples; MKK performed the surface plasmon resonance studies; LT performed the ELISA studies. The study was conceived and planned by LT, TL and TGT. The manuscript was written by TL, TGT, LT, JDS, and MH. All authors read and commented on the manuscript. LT and TL contributed equally to the work.Author Informaton: Reprints and permissions information is available at www.nature.com/reprints.The authors have no competing financial interests. To identify the DC8-PfEMP1 receptor, we produced a full-length DC8-containing PfEMP1 using the var gene IT4var20 from the FCR3/IT4 parasite. This 288 kDa His-tagged recombinant protein (rIT4VAR20) was screened against an array of 2505 full-length human plasma membrane proteins expressed on HEK293 cells (Table S1) S3) and all found to bind brain-derived endothelial cells via EPCR (Table S3). Previous work has shown that DC8-and DC13-variants selected on brain endothelial cells also bind to non-brain microvascular endothelial cells from heart and lung 4,5 . Binding of the FCR3 IT4VAR19b parasite line (described in 4 ) to brain, heart, lung and bone marrow endothelial cells was evaluated and found to be mediated by EPCR (Table S3). Altogether, these results demonstrate cytoadhesion of DC8 PfEMP1 expressing parasites via EPCR on endothelial cells of diverse tissu...

Sequence variation and structural conservation allows development of novel function and immune evasion in parasite surface protein families

“…In contrast, affinities of the entire IT4var13 and IT4var20 PfEMP1 ectodomains for ICAM‐151 and EPCR,35 respectively, are extremely similar to those of individual domains (CIDRα to ECPR and DBLβ to ICAM‐1), suggesting that these PfEMP1s are modular in nature. SAXS analysis of one such ectodomain [Fig.…”

Malaria Parasites in the Asymptomatic: Looking for the Hay in the Haystack

“…PfEMP1s bind to several host receptors to mediate the sequestration of infected erythrocytes in vital organs [11] and drive inflammation by blocking the cytoprotective function of the endothelial protein C receptor [22]. PfEMP1s are encoded by approximately 60 var genes per parasite genome, which are expressed in a mutually exclusive manner to avoid simultaneous recognition by the immune system [11].…”

Towards an anti-disease malaria vaccine

“…Each PfEMP1 is formed from multiple copies of two parasite-specific domain types, the CIDR and DBL domains, which are most often spatially arranged in a linear array (Figure 1) [15]. Different individual domains are capable of interacting with specific human endothelial surface proteins, including endothelial protein C receptor, EPCR [16], intracellular adhesion molecule 1, ICAM-1 [17] and cluster of differentiation 36, CD36 [18].…”

“…Expression of a subset of PfEMP1s, which contain a specific set of domains, known as CIDRα1 domains, was associated with severe malaria or brain endothelial cell binding [32][33][34][35]. Later, CIDRα1 domains were found to bind to human EPCR [16], thereby preventing EPCR from interacting with its natural ligand, activated protein C [16,36] (Figure 1). The blockage of EPCR-mediated signalling, through PfEMP1 binding, is proposed to lead to localized inflammation and to symptoms of severe disease [12,16,36,37].…”

“…Later, CIDRα1 domains were found to bind to human EPCR [16], thereby preventing EPCR from interacting with its natural ligand, activated protein C [16,36] (Figure 1). The blockage of EPCR-mediated signalling, through PfEMP1 binding, is proposed to lead to localized inflammation and to symptoms of severe disease [12,16,36,37].…”