Neoglycosylated liposomes as efficient ligands for the evaluation of specific sugar receptors on macrophages in health and in experimental leishmaniasis.

Abstract

Receptors interacting with terminal sugars as ligands are involved in the binding of Leishmania donovani promastigotes to the macrophage surface and their subsequent internalization. Mannose and glucose are specifically involved in the binding process. Decreased binding occurs to macrophages already infected with L. donovani either in vivo or in vitro. When mannose- or glucose-bearing liposomes are used as ligands the binding shows similar trends and the percentage inhibition of binding with mannose-bearing liposomes increases when compared to that for the glucose-bearing ones. The decreased binding of the ligand seems to be due to a decrease in the number of receptors after infection. The affinity of the ligands for the binding sites either on the normal macrophages or on the infected macrophages apparently remains the same. The results based on the incorporation of [3H]phenyl alanine and supported by the binding of glycosylated liposomes to both infected and non-infected macrophages suggest that protein synthesis, in general, is suppressed in L. donovani-infected macrophages thus affecting also mannose/glucose receptor protein synthesis, resulting in fewer receptors on the macrophage surface.