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Hyaluronic acid (HA) and chondroitin sulfate A (CSA) have been identified as receptors for adhesion of Plasmodium falciparum-infected erythrocytes (IEs) and appear to be involved in mediating parasite accumulation in the placenta.
We demonstrate here that some, but not all, parasite populations can adhere to both receptors, and we identify distinguishing features of adhesion.
Adhesion to HA and CSA was greatest among pigmented trophozoite-infected erythrocytes and at physiologic pH and was associated with a lack of rosette formation and little adhesion to CD36 and intercellular adhesion molecule-1.
Adhesion to HA was sensitive to trypsin cleavage of the IE surface, whereas trypsin-resistant and trypsin-sensitive CSA adhesion were both observed. Soluble HA, but not CSA, could cause aggregation or clumping of IEs.
Different HA types varied in adhesion-inhibitory activity, which was altered by physical treatment, suggesting that structural features of HA influence IE interactions.
These findings have important implications for understanding the pathogenesis of malaria, particularly in pregnancy.