Identification of Plasmodium falciparum reticulocyte binding protein RBP-2 homologue a and b (PfRBP-2-Ha and -Hb) sequences that specifically bind to erythrocytes

Plasmodium falciparum reticulocyte binding protein RBP-2 homologues a and b (PfRBP-2-Ha and -Hb) have been described as being high molecular weight proteins, expressed at the P. falciparum merozoite apical extreme, belonging to a family of proteins found in other Plasmodium involved in the search for erythrocyte populations before being invaded by merozoites. 185, 20-mer-long non-overlapping peptides, spanning the entire PfRBP-2-Ha and -Hb sequences, were synthesised, radiolabelled and tested in erythrocyte binding assays. Fifteen PfRBP-2-Ha and -Hb high binding activity peptides (HBAPs) specifically binding to erythrocytes with high affinity were identified. Dissociation constants were between 70 and 300 nM and Hill coefficients were 1 approximately. HBAPs residues critical for binding to erythrocytes were determined. Cross-linking was performed allowing possible receptors for PfRBP-2-Ha and -Hb to be identified on the surface of the erythrocytes. Some of the HABPs showed merozoite invasion inhibition greater than 90% in in vitro assays.