Structure of the DBL3X-DBL4ε region of the VAR2CSA placental malaria vaccine candidate: insight into DBL domain interactions

Abstract

The human malaria parasite, Plasmodium falciparum, is able to evade spleen-mediated clearing from blood stream by sequestering in peripheral organs. This is due to the adhesive properties conferred by the P. falciparum Erythrocyte Membrane Protein 1 (PfEMP1) family exported by the parasite to the surface of infected erythrocytes. Expression of the VAR2CSA variant of PfEMP1 leads to pregnancy-associated malaria, which occurs when infected erythrocytes massively sequester in the placenta by binding to low-sulfated Chondroitin Sulfate A (CSA) present in the intervillous spaces. VAR2CSA is a 350 kDa protein that carries six Duffy-Binding Like (DBL) domains, one Cysteine-rich Inter-Domain Regions (CIDR) and several inter-domain regions. In the present paper, we report for the first time the crystal structure at 2.9 Å of a VAR2CSA double domain, DBL3X-DBL4ε, from the FCR3 strain. DBL3X and DBL4ε share a large contact interface formed by residues that are invariant or highly conserved in VAR2CSA variants, which suggests that these two central DBL domains (DBL3X-DBL4ε) contribute significantly to the structuring of the functional VAR2CSA extracellular region. We have also examined the antigenicity of peptides corresponding to exposed loop regions of the DBL4ε structure.

Plasmodium falciparum PfEMP1 Modulates Monocyte/Macrophage Transcription Factor Activation and Cytokine and Chemokine Responses

“…In this study, we established a novel aspect of PfEMP1 immunosuppression through modulations of TF activation and subsequent VAR2CSA-specific reductions of cytokine and chemokine responses from monocytes/macrophages. As there is currently a malaria vaccine strategy targeting PfEMP1 ( 59 , 60 ), it is important that the various functions of this protein are thoroughly and adequately investigated. Therefore, further efforts to reveal the diverse roles of PfEMP1 during malaria immune responses are warranted.…”

Malaria Parasites: The Great Escape

“…In the recent years, it has become clear that some members of these multigene family has a particular role and may be involved in certain pathology. As example, var2 CSA mediated the specific cytoadherence of iRBC to placenta (142) and is associated with placental pathology, such as still birth and fetus growth retardation Vaccination using immunogens based on var2 CSA will thus induce inhibitory antibodies, preventing cytoadherence (157, 158) and placental sequestration. Thus defining the role of members of these multigene families may lead to tailored immune intervention.…”

Molecular architecture and domain arrangement of the placental malaria protein VAR2CSA suggests a model for receptor binding

“…DBL1x and DBL2x fit into the base, although the arrangement of these two domains is speculative because the folds of ID1 and ID2 are not known. DBL3x and DBL4ε can be accommodated in an arrangement similar to the structure of the DBL3x-DBL4ε tandem domains (44). Fitted in this way, the two large pores, P1 and P2, observed in NTS-DBL6ε, are created by DBL1x, ID1, DBL2x and DBL4ε, and DBL2x, DBL3x and DBL4ε, respectively.…”

“…The expression and purification of proteins is based on Srivatsava et al (44) pre-equilibrated with SEC Buffer A (10 mM NaKHPO4, pH 6.8, 150 mM NaCl). The protein was eluted with the same buffer and protein-containing fractions were analyzed by SDS-PAGE and Coomassie and/or silver staining.…”