Monday 29 October 2012, 1.15PM
Speaker: Dr Matthew E Rogers, London School of Hygiene and Tropical Medicine
Host: Debbie Smith
The protozoan parasite, Leishmania, faces numerous challenges within their sand fly vector to achieve transmission. Not least, they must resist being defecated from the sand fly midgut and anchor themselves in the anterior midgut and foregut. When infectious sand flies bite they deliver a highly enriched population of infective, metacyclic promastigotes. Metacyclogenesis is accompanied by the accumulation of a viscous glycan gel secreted by the parasites. The promastigote secretory gel (PSG) blocks the sand fly gut and embeds the parasites in the gut lumen. PSG is formed of a dense 3D matrix of filamentous proteophosphoglycan which impairs the bloodfeeding behaviour of the sand fly and promotes transmission by regurgitation.
Here we extend the ‘blocked fly hypothesis’ of Leishmania transmission by showing that the non-infective promastigote forms of Leishmania mexicana bind to PSG in vitro and are immobilised within the gel-like plug. In contrast, the infective metacyclic forms cannot bind to PSG and is freely motile with it. This feature of PSG allows metacyclics to accumulate in high proportions in the anterior midgut, foregut and proboscis of the sand fly and ‘sieves’ non-infective forms from the infectious bite.
Our results identify a new example of stage-specific binding during the life cycle of Leishmania which directly influences the vectorial capacity of the infected sand fly. I will discuss this result, and others, in the wider context of the Leishmania-sand fly interaction.
Location: Biology Lecture Theatre (K018)
Telephone: 01904 328875