Manipulação da fisiologia digestiva de Lutzomyia longipalpis (Diptera: Psychodidae): efeito da Galactosamina na atividade tripsinolítica intestinal do principal vetor de Leishmania infantum nas Américas.

Abstract

Leishmaniasis is a complex of diseases caused by protozoan parasites belonging to the genus Leishmania, being transmitted to their vertebrate hosts by small insects called sandflies. The causative agent of visceral leishmaniasis, Leishmania infantum, in Brazil is mainly transmitted to their vertebrate hosts by the sand fly species Lutzomyia longipalpis (Diptera, Psychodidae). Female sand flies feed primarily on sugar solutions but need to bloodfeed to maturate their ovaries and perform oviposition. Leishmania develop exclusively within the gut of the female sand fly and this means that Leishmania will be exposed to other microorganisms that are either resident or passing through the gut. Adult sand flies acquire their microbiota from several sources: during blood feeding on their animal hosts or from plants on which the adults feed. These microorganisms is acquired during their feed may interfere with sand fly vectorial capacity. Trypsins are one of the key enzymes in the sand fly gut, having the function to digest blood. During their life cycle inside their insect vector, Leishmania is more susceptible to trypsin activity during the transition from the amastigote form present in newly digested macrophages to promastigotes, which are the parasite form responsible for their development within the insect vector. This study aimed to manipulate the digestive physiology of the sand fly species L. longipalpis in order to increase their susceptibility to Leishmania infection and try to understand some of the mechanisms undelying trypsin production during sand fly blood digestion. The results showed that it is possible to reduce the cultivable bacterial flora using abroad spectrum antibiotic solution. The supplementation of 15 mM Galactosamine during bloodfeed was sufficient to reduce trypsin activity in the sand fly gut. The administration of a 30 mM mixture of all amino acids during bloodfeed supplemented with Galactosamine was able to partially reverse this effect produced by this amino sugar. However, the ingestion of galactose and glucosamine at 15mM did not reduce the trypsin activity in the L. longipalpis gut. Bloodmeal supplementation with Galactose increased the trypsinolytic activity in the sand fly gut 48 hours after feeding. This work has generated results that will allow us to manipulate the digestive physiology of L. longipalpis in order to obtain sand flies massively infected with Leishmania. The new sand fly infection protocol we intend to develop involves the manipulation of sand fly digestion and their innate immune system associated with the removal of bacterial and fungal infections by the use of antibiotics. This new treatment would generate massively infected sand flies with their anterior midgut and stomodeal valve blocked by the accumulation of PSG. With 16 these infected insects, it would be possible to create a sand fly facility producing insects to be used in vaccine challenges that aim to test new immunogenic antigens against L. infantum.