Modifications in the CD36 binding domain of the Plasmodium falciparum variant antigen are responsible for the inability of chondroitin sulfate A adherent parasites to bind CD36

Abstract

Adhesion of mature Plasmodium falciparum parasitized erythrocytes to microvascular endothelial cells or to placenta contributes directly to the virulence and severe pathology of P falciparum malaria. Whereas CD36 is the major endothelial receptor for microvasculature sequestration, infected erythrocytes adhering in the placenta bind chondroitin sulfate A (CSA) but not CD36. Binding to both receptors is mediated by different members of the large and diverse protein family P falciparum erythrocyte membrane protein-1 (PfEMP-1) and involves different regions of the molecule. The PfEMP-1-binding domain for CD36 resides in the cysteine-rich interdomain region 1 (CIDR-1). To explore why CSA-binding parasites do not bind CD36, CIDR-1 domains from CD36-or CSA-binding parasites were expressed in mammalian cells and tested for adhesion. Although CIDR-1 domains from CD36-adherent strains strongly bound CD36, those from CSAadherent parasites did not. The CIDR-1 domain has also been reported to bind CSA. However, none of the CIDR-1 domains tested bound CSA. Chimeric proteins between CIDR-1 domains that bind or do not bind CD36 and mutagenesis experiments revealed that modifications in the minimal CD36-binding region (M2 region) are responsible for the inability of CSA-selected parasites to bind CD36. One of these modifications, mapped to a 3-amino acid substitution in the M2 region, ablated binding in one variant and largely reduced binding of another. These findings provide a molecular explanation for the inability of placental sequestered parasites to bind CD36 and provide additional insight into critical residues for the CIDR-1/CD36 interaction. (Blood. 2001;97:3268-3274)

Recombinant PfEMP1 peptide inhibits and reverses cytoadherence of clinical Plasmodium falciparum isolates in vivo

“…This interaction is mediated by the M2 region of the CIDR1 domain of PfEMP1. 36 In this study, we show that a 179-amino acid peptide from the CIDR domain of MCvar1 PfEMP1 inhibited and reversed the adhesion of IRBCs from multiple clinical parasite isolates to HDMECs under flow conditions in vitro and to human microvessels in skin grafts on SCID mice in vivo. This is the first demonstration that cytoadherence of diverse wild-type parasite strains on a physiologic substratum can be inhibited by a single parasite protein under shear stress.…”

“…This protein is the homologous region to MC-179 in the CIDR1 domain from the FCR3-CSA strain of P falciparum. This CIDR1 domain is known not to bind to CD36 25 and served to demonstrate the specificity of the assay to detect proteins that specifically bind to CD36. Furthermore, PpMC-179 inhibited the binding of IRBCs from the FMG strain to recombinant CD36 in a static binding assay, whereas an unrelated yeast recombinant protein yPyCSP had no effect ( Table 1).…”

DNA Immunization with the Cysteine-Rich Interdomain Region 1 of the Plasmodium falciparum Variant Antigen Elicits Limited Cross-Reactive Antibody Responses

“…These parasites are known to express antigenically variant PfEMP1s (22) (MCvar1 1273-1714 ; accession no. AAB60251) were cloned and grown in culture as described previously (23).…”

“…The majority of the antibody response is directed to the M2 region in MC CIDR1. The CIDR1 domain can be divided to three parts, the M1, M2, and M3 regions, where M2 represents the minimal CD36 binding domain (23). We examined whether DNA immunization with the full-length CIDR1 directed most of the antibody response to the M2 region or to the M1 and M3 regions.…”

The C-Terminal Segment of the Cysteine-Rich Interdomain of Plasmodium falciparum Erythrocyte Membrane Protein 1 Determines CD36 Binding and Elicits Antibodies That Inhibit Adhesion of Parasite-Infected Erythrocytes

“…The region within PfEMP-1 responsible for CD36 binding was initially mapped in the Malayan Camp (MC) line of P. falciparum to a 179-amino-acid fragment (MC-r179) within the central M2 region of the CIDR␣ domain (4) and confirmed using other parasite lines (15,31). Comparison of various CIDR domains from several strains of P. falciparum showed that this cysteine-rich "minimal" binding domain had a conserved sequence, including the presence of five cysteine residues forming the motif CX 8 CX 3 CX 3 CXC (Fig.…”