The effects of chemical modification on the adhesion of Plasmodium falciparum-infected and uninfected erythrocytes

Abstract

Binding of Plasmodium falciparum-infected erythrocytes (PE) to endothelial cells is mediated by the erythrocyte-membrane protein, band 3-related adhesin. To determine its role, the binding of infected cells treated with various chemical modifiers was investigated. Binding was inhibited by a lysine modifier (4,4′-diisothiocyanostilbene-2,2′-di-sulfonate (DIDS)) known to specifically bind to band 3, another lysine modifier (trinitrobenzene sulfonic acid), a tyrosine modifier (sodium iodide in conjunction with lactoperoxidase, hydrogen peroxide) and oxidants (diamide, sodium periodate and ADP-chelated ferric ion), but binding was unaffected by the histidine modifier (diethylpyrocarbonate) and the arginine modifier (phenyl glyoxyl monohydrate). To artificially expose the band 3-related adhesin, uninfected erythrocytes were treated with acridine orange or loaded with calcium. These cells bound to C32 amelanotic melanoma cells, were immunostained with a monoclonal antibody that specifically binds to the band 3-related adhesin on PE, and the binding was inhibited by this monoclonal antibody. The binding of acridine orange-treated and calcium-loaded uninfected erythrocytes, could also be blocked by DIDS. In the case of acridine orange-treated erythrocytes, the patterns of the effects of the chemical modification on binding were consistent with that of PE except for tyrosine modification. These results demonstrate that the band 3-related adhesin, even in the absence of parasite-encoded proteins, contributes to PE adhesion.