Localization of Plasmodium falciparum histidine-rich protein 1 in the erythrocyte skeleton under knobs.
Plasmodium falciparum parasites that induce knobs in the host erythrocyte membrane (K+ phenotype) synthesize a 90 kDa histidine-rich protein (PfHRP-1), whereas knobless variants do not. A monoclonal antibody (mAb 89) to PfHRP-1, in combination with cryo-thin section immunoelectron microscopy, localized the antigen in the parasitophorous vacuolar space and vesicles within the erythrocyte cytosol. Additional immunoelectron microscopic studies showed that PfHRP-1 was also associated with submembranous electron-dense material under knobs and with microfilaments of the host erythrocyte skeletal network. Immunofluorescence and immunoelectron microscopy of intact, non-fixed K+ infected erythrocytes using mAb 89 and a rabbit antiserum raised against purified PfHRP-1, failed to identify any surface exposed epitopes. These antibodies also failed to block cytoadherence of infected erythrocytes to C32 melanoma cells or to affect macrophage phagocytosis of infected erythrocytes.
D000818:Animals; D000911:Antibodies, Monoclonal; D000953:Antigens, Protozoan / Q000032:analysis* / Q000276:immunology; D001029:Aotus trivirgatus; D003599:Cytoskeleton / Q000032:analysis / Q000648:ultrastructure; D000939:Epitopes / Q000032:analysis; D004912:Erythrocytes / Q000032:analysis / Q000469:parasitology* / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D007150:Immunohistochemistry; D008264:Macrophages / Q000276:immunology; D008854:Microscopy, Electron; D010587:Phagocytosis; D010963:Plasmodium falciparum / Q000276:immunology* / Q000378:metabolism
D000911:Antibodies, Monoclonal; D000953:Antigens, Protozoan; D000939:Epitopes