Leishmanial excreted factors and their possible biological role.

In the study of interactions between parasites of Leishmania species and their environment the release of a variety of materials has been detected. Some of these exo-metabolites are species-specific and may be exploited to characterize different leishmanial isolates. As the plasma membrane is the site of interaction between parasite and host it appears that the presence of metabolic products on, and their subsequent release from, the leishmanial cell surface bears a strong relationship to the biological performance of the parasite. The presence of a shedding mechanism in addition to other means of secretion has been shown in Leishmania braziliensis (NR strain). The products shed from the cell surface include glycoproteins and polysaccharide-like complexes. One of these glycoproteins has been purified, and it appears to affect macrophage activity. Because the recognition of these leishmanial metabolic products by antibody is mediated by the glycosylated portion of the secreted macromolecules, a limited repertoire of sugar residues may be common to these types of surface and extra-surface immunogens. Minor changes in the branching or sequence of sugars might constitute a code related to both serotype and biological activity of a given Leishmania strain.