Characterization of the 175-kilodalton erythrocyte binding antigen of Plasmodium falciparum.
EBA-175 is a soluble 175-kDa Plasmodium falciparum antigen that is released into culture supernatants during rupture of schizont-infected erythrocytes. EBA-175 binds to erythrocytes and binding is sialic acid-dependent. A clone expressing the gene encoding EBA-175 was obtained previously by screening a genomic DNA expression library with antibodies that had been affinity-purified from EBA-175. Antibodies were raised against a 43-amino-acid peptide (EBA-peptide 4) synthesized according to the deduced amino acid sequence. Antibodies to peptide 4 and affinity-purified antibodies specific for EBA-175 were used to characterize further EBA-175 giving the following results: (1) EBA-175 differs biochemically and immunologically from other reported malarial antigens; (2) the EBA-175s from six geographical isolates of P. falciparum are antigenically conserved; (3) EBA-175 is expressed during schizogony as a 190-kDa protein which is larger than the culture supernatant form of the antigen. The 190-kDa form of the protein is recovered from the cell pellet in schizont-infected erythrocytes and partitions to the soluble fraction when extracted with detergent; (4) release of soluble EBA-175 into the culture supernatant coincides with schizont rupture; (5) there was no observable change in pI (pI = 6.86) by isoelectric focusing between the cellular and supernatant species of the protein; and (6) release of EBA-175 into the culture supernatant is inhibited by the addition of chymostatin and leupeptin. The continued research into the role of EBA-175 during erythrocyte invasion may aid in vaccine development for malaria.
Department of Immunology, Walter Reed Army Institute of Research, Washington, DC 20307-5100.
P A
PA
Orlandi
B K
BK
Sim
J D
JD
Chulay
J D
JD
Haynes
D000818:Animals; D000913:Antibodies, Protozoan / Q000276:immunology; D000953:Antigens, Protozoan / Q000276:immunology*; D002478:Cells, Cultured; D004912:Erythrocytes / Q000276:immunology*; D006801:Humans; D008288:Malaria / Q000276:immunology; D008970:Molecular Weight; D010963:Plasmodium falciparum / Q000276:immunology*; D015800:Protozoan Proteins / Q000276:immunology*
D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D015800:Protozoan Proteins