Project description:Transmission of Trypanosoma brucei by tsetse flies involves the deposition of the infective quiescent metacyclic stage into the mammalian skin at the site of the fly’s bite. In the skin, the metacyclic parasites reactivate and differentiate into proliferative trypanosomes before colonizing the host's blood and tissues. We have generated an advanced human skin equivalent and used tsetse flies to naturally infect the artificial skin with trypanosomes. We have detailed the chronological order of the parasites' development in the skin and found a rapid activation and differentiation of the tsetse-transmitted cell cycle‑arrested metacyclic trypanosomes to proliferative parasites. Single-parasite transcriptomics documented the biological events during differentiation and host invasion at five different time points. After the establishment of a proliferative trypanosome population in the skin, the parasites entered a reversible quiescence program characterized by slow replication and a strongly reduced metabolism. We termed these quiescent trypanosomes skin tissue forms (STF), which may play an important role in maintaining the trypanosome infection in aparasitemic, asymptomatic individuals.
Project description:Mitochondrial metabolic remodeling is a hallmark of the Trypanosoma brucei digenetic life cycle since the insect stage utilizes the cost-effective oxidative phosphorylation to generate ATP, while bloodstream cells switch to less energetically efficient aerobic glycolysis. Due to difficulties in acquiring enough parasites from the tsetse fly vector for biochemical analysis, the dynamics of the parasite´s mitochondrial metabolic rewiring in the vector have remained obscure. Here, we took advantage of in vitro-induced differentiation to follow changes at the RNA levels.
Project description:Tsetse flies are the sole vectors of Trypanosoma brucei parasites that cause sleeping sickness. Our knowledge on the early interface between the infective metacyclic forms and the mammalian host skin is currently highly limited. Glossina morsitans flies infected with fluorescently tagged T. brucei parasites were used in this study to initiate natural infections in mice. Metacyclic trypanosomes were found to be highly infectious through the intradermal route in sharp contrast with blood stream form trypanosomes. Parasite emigration from the dermal inoculation site resulted in detectable parasite levels in the draining lymph nodes within 18 hours and in the peripheral blood within 42 h. A subset of parasites remained and actively proliferated in the dermis. By initiating mixed infections with differentially labeled parasites, dermal parasites were unequivocally shown to arise from the initial inoculum and not from a re-invasion from the blood circulation. Scanning electron microscopy demonstrated intricate interactions of these skin-residing parasites with adipocytes in the connective tissue, entanglement by reticular fibers of the periadipocytic baskets and embedment between collagen bundles. Experimental transmission experiments combined with molecular parasite detection in blood fed flies provided evidence that dermal trypanosomes can be acquired from the inoculation site immediately after the initial transmission. High resolution thermographic imaging also revealed that intradermal parasite expansion induces elevated skin surface temperatures. Collectively, the dermis represents a delivery site of the highly infective metacyclic trypanosomes from which the host is systemically colonized and where a proliferative subpopulation remains that is physically constrained by intricate interactions with adipocytes and collagen fibrous structures.
Project description:Tsetse flies (Glossina spp.) are major vectors of African trypanosomes, causing either Human or Animal African Trypanosomiasis (HAT or AAT). Several approaches are developed to control the disease among which the anti-vector Sterile Insect Technique. Another approach in the frame of anti-vector strategies could consist in controlling the fly’s vector competence which needs identifying factors (genes, proteins, biological pathways, …) involved in this process. The present work aims to verify whether protein candidates identified under experimental controlled conditions on insectary-reared tsetse flies have their counterpart in field-collected flies. Glossina palpalis palpalis flies naturally infected with Trypanosoma congolense were sampled in two HAT/AAT foci in Southern Cameroon. After dissection, the proteome from guts of parasite-infected flies were compared to that from uninfected flies in order to identify quantitative and/or qualitative changes associated to infection. A total of 3291 proteins were identified of which 1818 could be quantified. The comparative analysis allowed identifying 175 proteins with significant decreased abundance in infected as compared to uninfected flies, while 61 proteins displayed increased abundance. Among the former are RNA binding proteins, kinases, actin, ribosomal proteins, endocytosis proteins, oxido-reductases, as well as proteins that are unusually found such as tsetse salivary proteins (Tsal) or Yolk proteins. Among the proteins with increased abundance are fructose-1,6-biphosphatase, serine proteases, membrane trafficking proteins, death proteins (or apoptosis proteins), and SERPINs (inhibitor of serine proteases, enzymes considered as trypanosome virulence factors) that displayed highest increased abundance. Sodalis, Wiggleswothia and Wolbachia proteins are strongly under-represented, particularly when compared to data from similar experimentation conducted under controlled conditions on T. brucei gambiense infected (or uninfected) G. palpalis gambiensis insectary reared flies. Comparing the overall recorded data, 364 proteins identified in gut extracts from field flies were shown to have a homologue in insectary flies. Discrepancies between the two studies may arise from differences in the species of studied flies and trypanosomes as well as in differences in environmental conditions in which the two experiments were carried out. Finally, the present study together with former proteomic and transcriptomic studies on the secretome of trypanosomes, on the gut extracts from insectary reared and on field collected tsetse flies, provide a pool of data and information on which to draw in order to perform further investigations on, for example, mammal host immunization or on fly vector competence modification via para-transgenic approaches.