The role of surface glycoconjugates in Leishmania midgut attachment examined by competitive binding assays and experimental development in sand flies.

Binding of promastigotes to the sand fly midgut epithelium is regarded as an essential part of the Leishmania life cycle in the vector. Among Leishmania surface molecules putatively involved in attachment to the sand fly midgut, two GPI-anchored molecules are the most prominent: lipophosphoglycan (LPG) and promastigote surface protease gp63. In this work, we examined midgut attachment of Leishmania lines mutated in GPI-anchored molecules and compared results from 2 different techniques: in vivo development in sand flies and in vitro competitive binding assays using fluorescently labelled parasites.

Stage-specific adhesion of Leishmania promastigotes to sand fly midguts assessed using an improved comparative binding assay.

Background: The binding of Leishmania promastigotes to the midgut epithelium is regarded as an essential part of the life-cycle in the sand fly vector, enabling the parasites to persist beyond the initial blood meal phase and establish the infection. However, the precise nature of the promastigote stage(s) that mediate binding is not fully understood.

Methodology/principal Findings: To address this issue we have developed an in vitro gut binding assay in which two promastigote populations are labelled with different fluorescent dyes and compete for binding to dissected sand fly midguts.

Leishmania major glycosylation mutants require phosphoglycans (lpg2-) but not lipophosphoglycan (lpg1-) for survival in permissive sand fly vectors.

Background: Sand fly species able to support the survival of the protozoan parasite Leishmania have been classified as permissive or specific, based upon their ability to support a wide or limited range of strains and/or species. Studies of a limited number of fly/parasite species combinations have implicated parasite surface molecules in this process and here we provide further evidence in support of this proposal. We investigated the role of lipophosphoglycan (LPG) and other phosphoglycans (PGs) in sand fly survival, using Leishmania major mutants deficient in LPG (lpg1(-)), and the phosphoglycan (PG)-deficient mutant lpg2(-).

Inhibitor of cysteine peptidase does not influence the development of Leishmania mexicana in Lutzomyia longipalpis.

It has been proposed that the natural cysteine peptidase inhibitor ICP of Leishmania mexicana protects the protozoan parasite from insect host proteolytic enzymes, thereby promoting survival. To test this hypothesis, L. mexicana mutants deficient in ICP were evaluated for their ability to develop in the sand fly Lutzomyia longipalpis.