A novel ligand from Plasmodium falciparum that binds to a sialic acid-containing receptor on the surface of human erythrocytes

Invasion of the merozoite form of Plasmodium falciparum into human erythroc ytes involves multiple receptor-ligand interactions. The EBA175 protein of P. falciparum has been shown to be the ligand that binds to a sialic acid-d ependent site on glycophorin A. We have identified a novel P. falciparum li gand, termed erythrocyte-binding antigen 140 (EBA740), that shares structur al features and homology with EBA175, Subcellular localization of EBA140 su ggests that it is located in the micronemes, the same localization as EBA17 5, EBA140 binds to a sialic acid-dependent receptor on the surface of human erythrocytes, Binding of EBA140 to this erythrocyte receptor is sensitive to neuraminidase and resistant to trypsin, proteinase K and pronase. The pr otease-resistant properties of the erythrocyte receptor suggests that it is not glycophorin A or C. Additionally, analysis of mutant erythrocytes from humans has shown that EBA140 does not bind glycophorin B. Interestingly, w e have identified a parasite line that lacks the eba140 gene, suggesting th at this protein is not essential for in vitro invasion. These results sugge st that EBA140 may be involved in merozoite invasion using a sialic acid-de pendent receptor on human erythrocytes.