Recombinant Plasmodium falciparum reticulocyte homology protein 4 binds to erythrocytes and blocks invasion

Abstract

Plasmodium falciparum invasion of human erythrocytes involves several parasite and erythrocyte receptors that enable parasite invasion by multiple redundant pathways. A key challenge to the development of effective vaccines that block parasite infection of erythrocytes is identifying the players in these pathways and determining their function. Invasion by the parasite clone, Dd2, requires sialic acid on the erythrocyte surface; Dd2/NM is a variant selected for its ability to invade neuraminidase-treated erythrocytes that lack sialic acid. The P. falciparum protein, reticulocyte homology 4 (PfRH4), is uniquely up-regulated in Dd2/NM compared with Dd2, suggesting that it may be a parasite receptor involved in invasion. The aim of the present study was to determine the role of PfRH4 in invasion of erythrocytes and to determine whether it is a target of antibody-mediated blockade and thus a vaccine candidate. We show that both native PfRH4 and a recombinant 30-kDa protein to a conserved region of PfRH4 (rRH430) bind strongly to neuraminidase-treated erythrocytes. rRH430 blocks both the erythrocyte binding of the native PfRH4 and invasion of neuraminidase-treated erythrocytes by Dd2/NM. Taken together, these results indicate that PfRH4 is a parasite receptor involved in sialic acid-independent invasion of erythrocytes. Although antibodies to rRH430 block binding of the native protein to erythrocytes, these antibodies failed to block invasion. These findings suggest that, although PfRH4 is required for invasion of neuraminidase-treated erythrocytes by Dd2/NM, it is inaccessible for antibody-mediated inhibition of the invasion process.erythrocyte invasion ͉ red cell invasion ͉ invasion pathways ͉ erythrocyte binding ͉ sialic acids U nlike Plasmodium vivax, which depends completely on the single interaction of the parasite's Duffy binding protein with the Duffy blood group antigen on erythrocytes (1, 2), Plasmodium falciparum exploits multiple parasite receptors to invade erythrocytes. The redundancy in molecular interactions allows P. falciparum to use alternate pathways for invasion of human erythrocytes. The full repertoire of parasite receptors is not yet identified, and the role in alternate invasion pathways of those identified still remains to be fully defined (3-5).Most of the parasite receptors that are known to play a role in erythrocyte binding and invasion of Plasmodium can be classified into two families. First, the Duffy binding-like (DBL) family that includes the P. vivax/Plasmodium knowlesi Duffy binding proteins and the P. falciparum erythrocyte binding-like proteins (EBA-175, BAEBL, JESEBL, EBL-1, and PEBL). Second, the reticulocyte binding-like (RBL) family that includes the Plasmodium yoelii 235-kDa rhoptry proteins, the P. vivax reticulocyte binding proteins (PvRBP-1 and -2), and the P. falciparum reticulocyte homology (PfRH) proteins (PfRH1, PfRH2a, PfRH2b, PfRH3, PfRH4, and PfRH5) (3-5).Here, we focus on one member of the PfRH family of parasite receptors, P. falciparum reticulocyte homology 4, P...

Complement receptor 1 is the host erythrocyte receptor for Plasmodium falciparum PfRh4 invasion ligand

“…Because PfRh4 is a key player in phenotypic variation of invasion and sialic acid-independent pathway, we sought to identify its host erythrocyte receptor. We observed that erythroid CR1 is susceptible to trypsin and chymotrypsin treatment, an enzyme profile consistent with that obtained for the abolishment of PfRh4 erythrocyte binding (13,14). Here we show that PfRh4 binds to CR1 on the erythrocyte surface, and that this interaction mediates a functional sialic acid-independent pathway for P. falciparum invasion of human erythrocytes.…”

Multiprotein complex between the GPI-anchored CyRPA with PfRH5 and PfRipr is crucial for Plasmodium falciparum erythrocyte invasion

“…falciparum culture (33), BN-PAGE (34), erythrocyte binding assay (35), isolation of viable merozoites (18), immunofluorescence microscopy (36), tritium labeling (22,23), animal immunization, and invasion inhibition assay (37) experiments were done as described previously.…”

Evidence That the Erythrocyte Invasion Ligand PfRh2 is a Target of Protective Immunity against Plasmodium falciparum Malaria

“…experimental animals to PfRh1, PfRh2, PfRh4, and PfRh5 can inhibit invasion (22,(24)(25)(26)(27). Furthermore, genetic disruption of specific members alters the erythrocyte receptor preference of merozoites during invasion (6,13).…”