Neoglycoproteins as tools for the detection of carbohydrate-specific receptors on the cell surface of Leishmania.

Abstract

Promastigote and amastigote forms of human pathogenic Leishmania from the Old and New World, including promastigotes of L. enrietti, were tested with neoglycoproteins to ascertain the existence of endogenous lectins. These tools expose the chemically coupled sugar that is attached to the inert carrier as a potential ligand for the binding reaction. Agglutination tests demonstrated that the promastigotes of human Leishmania reacted only with the neoglycoproteins N-acetyl-D-galactosamine-para-aminophenyl-bovine serum albumin (gal-NAc-BSA) and N-acetyl-D-glucosamine-para-amino-phenyl-bovine serum albumin (glcNAc-BSA), whereas the amastigote forms failed to react with the neoglycoproteins. In contrast, the promastigotes of L. enriettii were agglutinated by the neoglycoprotein D-mannose-bovine serum albumin (man-BSA). The agglutination reactions could be inhibited by the homologous sugars N-acetyl-beta-D-glucosamine, N-acetyl-beta-D-galactosamine, and alpha-D-mannose. Fluorescence tests yielded the same results. The incubation of the promastigotes with ethylenedinitrolotetraacetic acid (EDTA) prevented their reaction with the neoglycoproteins, whereas the addition of calcium restored it. This result demonstrates that Leishmania express calcium-dependent lectins that are accessible on their surface.