A recombinant baculovirus-expressed Plasmodium falciparum receptor-bindingdomain of erythrocyte binding protein EBA-175 biologically mimics native protein

EBA-175 of Plasmodium falciparum is a merozoite ligand that binds its recep tor glycophorin A on erythrocytes during invasion, The ligand-receptor inte raction is dependent on sialic acids as well as the protein backbone of gly cophorin A Region II (RII) of EBA-175 has been defined as the receptor-bind ing domain. RII is divided into regions F1 and F2, which contain duplicated cysteine motifs. We expressed RII in a baculovirus and show that RII binds erythrocytes,vith a specificity identical to that of the native protein. W e found that, consistent with the binding of erythrocytes to COS cells expr essing F2 recombinant baculovirus expressed F2 bound erythrocytes. About 20 % of all baculovirus-expressed RII is N-glycosylated, unlike native P, falc iparum proteins that remain essentially unglycosylated, However, glycosylat ion of recombinant RII did not affect its immunogenicity, Antibodies raised against both glycosylated and unglycosylated baculovirus-expressed RII rec ognized P. falciparum schizonts in immunofluorescence assays and also gave similar enzyme-linked immunosorbent assay titers, Furthermore, these antibo dies have similar abilities to block native EBA-175 binding to erythrocytes . These results allow the development of RII as a vaccine candidate for pre clinical assessment.