Phlebotomus papatasi Antimicrobial Peptides in Larvae and Females and a Gut-Specific Defensin Upregulated by Leishmania major Infection

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.

RNAi-mediated gene silencing of Phlebotomus papatasi defensins favors Leishmania major infection

“…The bacteria depleted sand flies were used to access the immune response caused mainly by L. major . The efficiency of our choice of AtbC and a possible interference with parasite development in the vector was previously addressed in this parasite-vector pair by our team, and no negative correlation between parasite development and AtbC was detected ( Kykalová et al, 2021 ).…”

“…Phlebotomus papatasi relish (PpRel) (PPAI012820), attacin (PpAtt) (PPAI003791), and PpDef1 (PPAI004256) gene sequences were previously identified ( Louradour et al, 2019 ; Kykalová et al, 2021 ; Sloan et al, 2021 ) and are available from the Vector Base website ( Amos et al, 2022 ). A second P. papatasi defensin sequence (PpDef2) was identified by similarity using the L. longipalpis defensin sequences ( Telleria et al, 2021b ) as a query to search on the P. papatasi RNAseq database publicly available from the Vector Base using blast search tools.…”

“…The choice of injecting dsRNA in 3-day infected females was based on two factors. First, to match the period of efficient gene silencing with the time when PpDef1 is differentially expressed in the sand fly gut (72 h or 144 h post infection) ( Kykalová et al, 2021 ). Second, to match with the crucial moment in Leishmania cycle in P. papatasi when blood digestion ends, and the parasites migrate to the anterior part of the sand fly gut (between 72°h and 96 h.post infection) ( Dillon and Lane, 1993 ; Pruzinova et al, 2015 ).…”

Genomic analysis of two phlebotomine sand fly vectors of Leishmania from the New and Old World

“…Despite the potential importance for influencing Leishmania development and survival in the gut the sand fly immune response is poorly studied. To date, work has been largely restricted to the study of defensins [41][42][43][44]. However, gene depletion via RNAi of the negative regulator of the Immune Deficiency (IMD) pathway caspar [45] led to a reduction in Leishmania population in the gut of Lu.…”

Genomic Analysis of Two Phlebotomine Sand Fly Vectors ofLeishmaniafrom the New and Old World

“…Despite the potential importance of the sand fly immune system for influencing Leishmania development and survival in the sand fly gut the immune response is poorly studied. To date, this work has been largely restricted to defensins [30][31][32][33]. However, gene depletion via RNAi of the negative regulator of the IMD pathway caspar [34] led to a reduction in Leishmania population in the gut of Lu.…”