A Novel Erythrocyte Binding Protein of Plasmodium vivax Suggests an Alternate Invasion Pathway into Duffy-Positive Reticulocytes

Abstract

Erythrocyte invasion by malaria parasites is essential for blood-stage development and an important determinant of host range. In Plasmodium vivax, the interaction between the Duffy binding protein (DBP) and its cognate receptor, the Duffy antigen receptor for chemokines (DARC), on human erythrocytes is central to blood-stage infection. Contrary to this established pathway of invasion, there is growing evidence of P. vivax infections occurring in Duffy blood group-negative individuals, suggesting that the parasite might have gained an alternative pathway to infect this group of individuals. Supporting this concept, a second distinct erythrocyte binding protein (EBP2), representing a new member of the DBP family, was discovered in P. vivax and may be the ligand in an alternate invasion pathway. Our study characterizes this novel ligand and determines its potential role in reticulocyte invasion by P. vivax merozoites. EBP2 binds preferentially to young (CD71high) Duffy-positive (Fy+) reticulocytes and has minimal binding capacity for Duffy-negative reticulocytes. Importantly, EBP2 is antigenically distinct from DBP and cannot be functionally inhibited by anti-DBP antibodies. Consequently, our results do not support EBP2 as a ligand for invasion of Duffy-negative blood cells, but instead, EBP2 may represent a novel ligand for an alternate invasion pathway of Duffy-positive reticulocytes.

Receptor-ligand and parasite protein-protein interactions inPlasmodium vivax: Analysing rhoptry neck proteins 2 and 4

“…When Pv RON4 binding to RBC ( m = 34 ± 2.7) was compared with binding to normocytes ( m = 11 ± 1.4), it was observed that the amount of rosettes compared with normocytes became significantly reduced, t test: t (10) = 18.68, p = .001 (Figure b,c). This suggested that Pv RON4 binding to RBC depends on a more immature RBC population, similar to that reported for other P. vivax antigens, such as Pv AMA1 (Arevalo‐Pinzon, Bermudez, Hernandez, Curtidor, & Patarroyo, ), Pv GAMA (Baquero et al, ), and EBP2 (Ntumngia et al, ), whereas Pv DBPRII bound to both RBC and normocytes (Figure c).…”

“…All Rosetting assays were performed three times in triplicate PvRON4 binding to RBC (m = 34 ± 2.7) was compared with binding to normocytes (m = 11 ± 1.4), it was observed that the amount of rosettes compared with normocytes became significantly reduced, t test: t(10) = 18.68, p = .001 (Figure 1b,c). This suggested that PvRON4 binding to RBC depends on a more immature RBC population, similar to that reported for other P. vivax antigens, such as PvAMA1 (Arevalo-Pinzon, Bermudez, Hernandez, Curtidor, & Patarroyo, 2017), PvGAMA , and EBP2 (Ntumngia et al, 2016), whereas PvDBPRII bound to both RBC and normocytes (Figure 1c). Several reports have shown that different P. falciparum strains differ regarding their ability to invade RBC treated with different enzymes, such as trypsin, chymotrypsin, and neuraminidase, removing different receptors from RBC surface DeSimone et al, 2009).…”

A new Plasmodium vivax reference sequence with improved assembly of the subtelomeres reveals an abundance of pir genes

“…Although the majority of newly identified genes belong to subtelomeric gene families, we confirmed the recently identified EBP2 (erythrocyte binding protein 2, PVP01_0102300) and RBP2e (reticulocyte binding protein 2e, PVP01_0700500) genes 11 . These genes are members of families encoding proteins implicated in host cell recognition during red blood cell (RBC) invasion, and present potential vaccine targets 48–51 .…”

Malaria Parasites: The Great Escape

“…This serves as a strong argument for the existence of only one invasion pathway for P. vivax . However, in the recent years, many studies have reported P. vivax infections in Duffy-negative patients (220, 222–228), suggesting that P. vivax merozoites may use another pathway to invade reticulocytes (229). This may limit the efficacy of vaccine based on the Duffy-binding protein, the ligand of the Duffy antigen (230), by selecting for parasites that are able to invade via this alternative pathway.…”