CD36-DEPENDENT ADHESION AND KNOB EXPRESSION OF THE TRANSMISSION STAGES OF PLASMODIUM-FALCIPARUM IS STAGE-SPECIFIC

Plasmodium falciparum trophozoites sequester from the peripheral circu lation by adherence to host endothelium. Gametocytes, also sequester d uring maturation. Analysis of the adhesion phenotype of stage I to V g ametocytes of several isolates/clones was assessed by binding of infec ted cells to C32 melanoma cells (C32MC) and the purified adhesion prot eins, leucocyte differentiation antigen (CD36) and intercellular adhes ion molecule-1 (ICAM-1). These cells and proteins, have previously bee n shown to be receptors for adherence of trophozoites. Early gametocyt es (stages I-IIA) were found to bind to C32MC as well as the purified receptor CD36 but not to ICAM-1. Early gametocytes bound to C32MC via CD36 and the parasite ligand involved in this binding was trypsin sens itive. Stage IIB to V gametocytes did not adhere to C32MC, CD36 nor IC AM-1. Electron-dense protruberances known as knobs and histidine rich protein 1 (HRP 1) expression have been associated with trophozite adhe sion to CD36. Knobs were present at the surface of early but not late gametocyte infected cells. Stage-specific patterns of HRP 1 expression , consistent with a role for this molecule in CD36 adhesion of early g ametocytes, were also observed. The adhesion phenotype of these young gametocytes was indistinguishable from that of the trophozoites by all criteria examined. These data support the hypothesis that other host receptors mediate the binding of late gametocytes. (C) 1998 Elsevier S cience B.V. All rights reserved.