The principal vectors of leishmania parasites are phlebotomine sand flies (Diptera: Phlebotominae). In the vector, leishmania undergo a complex development through several morphologically and functionally distinct forms. However, of the almost 900 described phlebotomine species, only about 10% are listed as proven or suspected vectors of leishmania. Some of these species display strict specificity for a particular leishmania species – they are so called specific vectors, e.g. Phlebotomus papatasi supports late-stage development of L. major)and L. turanica only. On the other hand, the majority of Phlebotomus and Lutzomyia species support late-stage development of multiple leishmania species and are thus called “permissive vectors”. The research of our team is concerned on the key moments of leishmania – sand fly interactions and molecular background of factors controlling leishmania development in vectors and their transmission to mammalian hosts.
- The first crucial moment of the leishmania development in the vector is a survival of the blood digestion in the sand fly midgut. We study factors influencing blood digestion and early leishmania development in sand flies - both extrinsic factors (effect of the external temperature, effect of different blood sources) and intrinsic factors (activity of midgut proteases, development and breakdown of the peritrophic matrix, microbiota in sand flies, viral co-infections). The peritrophic matrix (PM) is an acellular chitinous envelope which surrounds the blood in engorged females. It is important for compartmentalization of the blood digestion and protection of the midgut epithelium and constitutes the first mechanical barrier which must leishmania overcome during their development in sand flies. Using histology and fluorescent and electron microscopy we gained new information about the interactions of leishmania with the PM. After escape from the PM, leishmania must avoid defecation of blood remnants and therefore attach to the midgut epithelium. Our team has described a lipophosphoglycan-independent mechanism of the attachment in permissive vectors. This alternative binding modality has important implications for parasite transmission and evolution.
- The final step in leishmania development in sand flies is a colonization of the anterior part of the midgut and transmission to the next host. We showed that leishmania chitinases play important role in damage of the chitin lining of the stomodeal valve, the sphincter separating foregut and midgut. Damage of the stomodeal valve facilitates the regurgitation of parasites into the vertebrate host.
- We study vector competence of particular sand fly species (e.g. Sergentomyia schwetzi) for leishmania parasites and clarify mechanism of their resistance.
- We are concerned also on leishmania genetic exchange. For many years leishmania have been considered to replicate asexually. Recently, genetic exchange in the vector has been demonstrated which is potentially of profound epidemiological significance. Hybrid offspring might show a strong selective advantage and spread relative to the parental strains. Co-infection of sand flies with transgenic L. donovani strains carrying fluorescent markers enabled us to detect genetic exchange in the sand fly gut, localize the origin of hybrids and describe their morphological forms.
- We collaborate with the University of Ostrava (Prof. Yurchenko's laboratory) and major research teams abroad to test the ability of leishmania isolates differing in drug resistance to develop in sand flies. Similarly, mutant lines with targeted gene deletion are being tested (CRISPR/Cas 9 method).
- We study the vector competence of different sand fly species (e.g. Sergentomyia schwetzi) for leishmania parasites and clarify their resistance mechanisms.
- We also study alternative vectors of leishmania, mainly biting midges (Diptera: Ceratopogonidae). We confirmed their role in the transmission of leishmania of the subgenus Mundinia.