Single cell sequencing and functional genetic analyses of ROS-induced Leishmania hybridization during sand fly infection – SFLeishHyb

Phlebotomine sand flies are responsible for the transmission of Leishmania parasites, causing Leishmaniasis, a disease whose wide spectrum of symptoms range from cutaneous lesions to visceral damages. Aside clonal reproduction that causes massive parasite burden in infected individuals, Leishmania engages inside the sand fly in a cryptic sexual cycle resulting in hybrid progeny. Sexual mating is a major source of Leishmania genetic diversity, which drives changes in tissue tropism, pathology and drug resistance. Experimental generation of hybrids was until recently confined to parasites growing in the sand fly gut, a major limitation in the investigation of the mechanisms involved. I developed a protocol lifting this roadblock by allowing the generation of hybrids from axenic cultures. However, the frequency of hybrids generated in vivo is much higher than in vitro, showing that the vector gut environment is particularly adapted for Leishmania sexual mating. In vitro hybrid production opens unique possibilities of investigating the mechanisms of Leishmania sexual reproduction and the parameters rendering the vector’s gut favorable to this process, currently unknown. I recently established that pre-exposing parental parasite cultures to Reactive Oxygen Species (ROS) leads to an increased hybrid production in vitro, which led me to hypothesize a role for DNA damage repair mechanisms and for ROS, present in large amount in the sand fly gut, in the control of hybrid production. Using a dual genetic approach applied on both the parasite and the vector, and a combination of in vitro and in vivo experimentation, I aim to decipher the impact of the ROS produced by the sand fly gut cells on the engagement of Leishmania parasites in a sexual reproduction path. This project will generate important knowledge on the Leishmania/sand fly interaction and will set the stage for my future research group on this exciting yet understudied subject.