MULTIPLE LIGANDS FOR CYTOADHERENCE CAN BE PRESENT SIMULTANEOUSLY ON THE SURFACE OF PLASMODIUM-FALCIPARUM-INFECTED ERYTHROCYTES

A major virulence factor of Plasmodium falciparum is the adherence of parasitized erythrocytes to the wall of postcapillary venules via a sp ecific interaction between parasite-derived erythrocyte surface ligand s and receptors on endothelial cells. To study this phenomenon in vitr o, we selected a parasite population that expressed at least two diffe rent ligands and demonstrated that parasitized cells may coexpress lig ands with specificity for multiple receptors. This selected parasite l ine had several antigenic and cytoadherence characteristics that were different from those of the parent line. Single parasitized erythrocyt es were able to adhere to three distinct receptors via at least two se parate ligands; a trypsin-sensitive molecule mediated cytoadherence to CD36 and intercellular adhesion molecule 1 and a trypsin-insensitive molecule(s) was responsible for adherence to a third receptor on the s urface of melanoma cells. We present evidence that this newly discover ed receptor for cytoadherence is an N-linked glycosaminoglycan, as tre atment of melanoma cells with endoglycosidase H abolished cytoadherenc e. These observations emphasize the adaptability of P. falciparum and the complexity of the cytoadherence phenomenon.