Abstract
Phlebotomus papatasi is the vector of Leishmania major, causing cutaneous leishmaniasis in the Old World. We investigated whether P. papatasi immunity genes were expressed toward L. major, commensal gut microbes, or a combination of both. We focused on sand fly transcription factors dorsal and relish and antimicrobial peptides (AMPs) attacin and defensin and assessed their relative gene expression by qPCR. Sand fly larvae were fed food with different bacterial loads. Relish and AMPs gene expressions were higher in L3 and early L4 larval instars, while bacteria 16S rRNA increased in late L4 larval instar, all fed rich-microbe food compared to the control group fed autoclaved food. Sand fly females were treated with an antibiotic cocktail to deplete gut bacteria and were experimentally infected by Leishmania. Compared to non-infected females, dorsal and defensin were upregulated at early and late infection stages, respectively. An earlier increase of defensin was observed in infected females when bacteria recolonized the gut after the removal of antibiotics. Interestingly, this defensin gene expression occurred specifically in midguts but not in other tissues of females and larvae. A gut-specific defensin gene upregulated by L. major infection, in combination with gut-bacteria, is a promising molecular target for parasite control strategies.
Highlights
Introduction and Rasa BernotienėPhlebotomine sand flies (Diptera: Psychodidae) belonging to Lutzomyia and Phlebotomus genera are proven vectors of Leishmania parasites, causing 700,000 to one million new cases of leishmaniasis every year [2]
We selected two transcription factors genes belonging to Toll and immune deficiency (IMD) pathways and two antimicrobial peptides (AMPs) to tackle the questions we raised regarding the P. papatasi immune response toward the changes in gut bacteria and L. major
Sub-family sequences that lack the ankyrin-repeat domain [39,40,41]. Both P. papatasi dorsal and relish sequences are similar to those previously identified in L. longipalpis [21]
Summary
Phlebotomine sand flies (Diptera: Psychodidae) belonging to Lutzomyia and Phlebotomus genera are proven vectors of Leishmania parasites (reviewed by [1]), causing 700,000 to one million new cases of leishmaniasis every year [2]. Phlebotomus papatasi is dispersed across Mediterranean European countries, North Africa, the Middle East, and Central. It transmits Leishmania major, one of the etiological agents of cutaneous leishmaniasis (reviewed by [3]). During the cycle in the sand fly vector (reviewed by [4,5]), Leishmania parasites coexist with a diverse microbial community that may interfere with the parasite establishment in. The sand fly immune response is adjusted to the presence of commensal and other possible harmful microbes (reviewed by [14])
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