A novel erythrocyte binding antigen-175 paralogue from Plasmodium falciparum defines a new trypsin-resistant receptor on human erythrocytes

Abstract

The recognition and invasion of human erythrocytes by the most lethal malaria parasite Plasmodium falciparum is dependent on multiple ligand-receptor interactions. Members of the erythrocyte binding-like (ebl) family, including the erythrocyte binding antigen-175 (EBA-175), are responsible for high affinity binding to glycoproteins on the surface of the erythrocyte. Here we describe a paralogue of EBA-175 and show that this protein (EBA-181/JESEBL) binds in a sialic acid-dependent manner to erythrocytes. EBA-181 is expressed at the same time as EBA-175 and co-localizes with this protein in the microneme organelles of asexual stage parasites. The receptor binding specificity of EBA-181 to erythrocytes differs from other members of the ebl family and is trypsin-resistant and chymotrypsin-sensitive. Furthermore, using glycophorin B-deficient erythrocytes we show that binding of EBA-181 is not dependent on this sialoglycoprotein. The level of expression of EBA-181 differs among parasite lines, and the importance of this ligand for invasion appears to be strain-dependent as the EBA-181 gene can be disrupted in W2mef parasites, without affecting the invasion phenotype, but cannot be targeted in 3D7 parasites.