A recombinant baculovirus-expressed Plasmodium falciparum receptor-binding domain of erythrocyte binding protein EBA-175 biologically mimics native protein.
EBA-175 of Plasmodium falciparum is a merozoite ligand that binds its receptor glycophorin A on erythrocytes during invasion. The ligand-receptor interaction is dependent on sialic acids as well as the protein backbone of glycophorin A. Region II (RII) of EBA-175 has been defined as the receptor-binding 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 with a specificity identical to that of the native protein. We found that, consistent with the binding of erythrocytes to COS cells expressing F2, recombinant baculovirus-expressed F2 bound erythrocytes. About 20% of all baculovirus-expressed RII is N-glycosylated, unlike native P. falciparum proteins that remain essentially unglycosylated. However, glycosylation of recombinant RII did not affect its immunogenicity. Antibodies raised against both glycosylated and unglycosylated baculovirus-expressed RII recognized P. falciparum schizonts in immunofluorescence assays and also gave similar enzyme-linked immunosorbent assay titers. Furthermore, these antibodies have similar abilities to block native EBA-175 binding to erythrocytes. These results allow the development of RII as a vaccine candidate for preclinical assessment.
Liang
H
H
EntreMed, Inc., Rockville, Maryland 20850, USA.
Narum
D L
DL
Fuhrmann
S R
SR
Luu
T
T
Sim
B K
BK
D000818:Animals; D000913:Antibodies, Protozoan / Q000276:immunology; D000953:Antigens, Protozoan; D016367:Baculoviridae / Q000235:genetics; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology; D004912:Erythrocytes / Q000378:metabolism; D006021:Glycophorins / Q000378:metabolism; D006023:Glycoproteins / Q000276:immunology; D006801:Humans; D017780:Malaria Vaccines / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D010446:Peptide Fragments / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D010963:Plasmodium falciparum / Q000145:classification / Q000235:genetics / Q000276:immunology; D015800:Protozoan Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology; D011994:Recombinant Proteins / Q000096:biosynthesis*
D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D002352:Carrier Proteins; D006021:Glycophorins; D006023:Glycoproteins; D017780:Malaria Vaccines; D010446:Peptide Fragments; D015800:Protozoan Proteins; D011994:Recombinant Proteins; C065668:erythrocyte-binding antigen 175, Plasmodium