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

Infect Immun. 2000 Jun;68(6):3564-8. doi: 10.1128/IAI.68.6.3564-3568.2000.

Abstract

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.

MeSH terms

  • Animals
  • Antibodies, Protozoan / immunology
  • Antigens, Protozoan*
  • Baculoviridae / genetics
  • Carrier Proteins / biosynthesis*
  • Carrier Proteins / genetics
  • Carrier Proteins / immunology
  • Erythrocytes / metabolism
  • Glycophorins / metabolism
  • Glycoproteins / immunology
  • Humans
  • Malaria Vaccines / biosynthesis*
  • Malaria Vaccines / genetics
  • Malaria Vaccines / immunology
  • Mice
  • Mice, Inbred BALB C
  • Peptide Fragments / genetics
  • Peptide Fragments / immunology
  • Peptide Fragments / metabolism
  • Plasmodium falciparum* / classification
  • Plasmodium falciparum* / genetics
  • Plasmodium falciparum* / immunology
  • Protozoan Proteins / biosynthesis*
  • Protozoan Proteins / genetics
  • Protozoan Proteins / immunology
  • Recombinant Proteins / biosynthesis*

Substances

  • Antibodies, Protozoan
  • Antigens, Protozoan
  • Carrier Proteins
  • Glycophorins
  • Glycoproteins
  • Malaria Vaccines
  • Peptide Fragments
  • Protozoan Proteins
  • Recombinant Proteins
  • erythrocyte-binding antigen 175, Plasmodium