Molecular aspects of parasite-vector and vector-host interactions in Leishmaniasis

Leishmania-sand fly interactions are reviewed in the context of the potenti al barriers to the complete development of the parasite that exist within t he midgut environment of phlebotomine flies and the molecular adaptations t hat the parasite has evolved that permit the development of transmissible i nfections to proceed. Cell surface and secreted phosphoglycans protect the parasite from the proteolytic activities of the blood-fed midgut, mediate a ttachment to the gut wall in order to maintain infection during excretion o f the bloodmeal, and contribute to the formation of a biological plug in th e anterior gut that may promote transmission by bite. The importance of vec tor saliva in modulating the host response to transmitted parasites is also reviewed.