Structural Studies on Surface Glycoproteins of Leishmania Promastigotes: Isolation, Amino Acid Composition and Amino Terminal Sequence Studies

Abstract

Successful initiation and maintenance of the parasitic state for Leishmania species of protozoan parasites, requires identification and specific adhesion to host cells followed by internalization and establishment of an intracellular existence. Clearly any strategy to block initial promastigote binding or subsequent spread of amastigotes will require knowledge about the molecular nature of host parasite cellular interactions. A number of laboratories have made good progress in this area demonstrating some of the characteristics of the macrophage receptors and promastigote ligands. At this time, evidence exists for a complicated interaction with a number of receptors including the iC3b complement receptor CR3 and the mannosyl/fucosyl receptor (Blackwell et al., 1985; Channon et al., 1984). Particular emphasis has been placed on those which bind a major surface glycolipid (Handman and Goding, 1985) and glycoproteins (Chang and Chang, 1986; Russell and Wilhelm, 1986) as well as covalently linked complement fragments (Blackwell et al., 1985). Very little attention has been placed on the other components of the parasite surface to assess whether the former ligands are singularly important or whether an array of glycosylated molecular species can interact with macrophage receptors via a redundant set of oligosaccharides. It is frequently observed for example, that monoclonal antibodies developed against cell surface antigens cross-react with many molecules of varying molecular weights - a phenomenon readily explained by a restricted set of oligosaccharides held in common by varying protein and lipid species.