title: Comparative analysis of the Plasmodium falciparum histidine-rich proteins HRP-I, HRP-II and HRP-III in malaria parasites of diverse origin.
abstract: Plasmodium falciparum-infected erythrocytes (IRBC) synthesize 3 histidine-rich proteins: HRP-I or the knob-associated HRP, HRP-II and HRP-III or SHARP. In order to distinguish these proteins immunochemically we prepared monoclonal antibodies which react with HRP-I, HRP-II and HRP-III, and rabbit antisera against synthetic peptides derived from the HRP-II and HRP-III sequences. A comparative analysis of diverse P. falciparum parasites was made using these antibodies and immunoprecipitation or Western blotting. HRP-I (Mr 80,000-115,000) was identified in all knob-positive P. falciparum parasites including isolates examined directly from Gambian patients. However, this protein was of lower abundance in these isolates and in 6 knob-positive, culture-adapted parasites compared to Aotus monkey-adapted parasites or culture-adapted parasites studied previously. HRP-II (Mr 60,000-105,000) was identified in all P. falciparum parasites regardless of knob-phenotype, and was recovered from culture supernatants as a secreted water-soluble protein. Within IRBC, HRP-II was found as a complex of several closely spaced bands. Cell surface radio-iodination of IRBC from several isolates and immunoprecipitation with a rabbit antiserum against the HRP-II repeat sequence identified HRP-II as a surface-exposed protein. Like HRP-I, the abundance of HRP-II was lower in the Gambian isolates than with Aotus monkey-adapted parasites studied earlier. Neither HRP-I nor HRP-II were identified in a knob-positive isolate of P. malariae collected from a Gambian patient. Analogues of these HRP were also absent from asexual parasites of diverse primate and murine malaria species screened with this panel of antibodies. HRP-III (Mr 40,000-55,000) was distinguished by its lower apparent size and by specific reaction with rabbit antibody against its 5-mer repeat sequence. HRP-III was of lowest abundance compared with the other two HRP. These antibody reagents and distinguishing properties should prove useful in studies on the separate functions of the 3 P. falciparum HRP.
authors.affiliation: Howard Hughes Medical Institute, Bethesda, Maryland 20814.
authors.forename: E P
authors.initials: EP
authors.lastname: Rock
authors.forename: K
authors.initials: K
authors.lastname: Marsh
authors.forename: A J
authors.initials: AJ
authors.lastname: Saul
authors.forename: T E
authors.initials: TE
authors.lastname: Wellems
authors.forename: D W
authors.initials: DW
authors.lastname: Taylor
authors.forename: W L
authors.initials: WL
authors.lastname: Maloy
authors.forename: R J
authors.initials: RJ
authors.lastname: Howard
mesh_terms: D000328:Adult; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D004591:Electrophoresis, Polyacrylamide Gel; D004912:Erythrocytes / Q000469:parasitology; D005260:Female; D005455:Fluorescent Antibody Technique; D006023:Glycoproteins / Q000032:analysis* / Q000276:immunology; D006801:Humans; D007106:Immune Sera / Q000276:immunology; D007118:Immunoassay; D010963:Plasmodium falciparum / Q000032:analysis* / Q000276:immunology; D010965:Plasmodium malariae / Q000032:analysis / Q000276:immunology; D011506:Proteins / Q000032:analysis* / Q000276:immunology; D000099053:Histidine-Rich Glycoprotein
chemical_list: D000911:Antibodies, Monoclonal; D006023:Glycoproteins; D007106:Immune Sera; D011506:Proteins; D000099053:Histidine-Rich Glycoprotein