Trypanosoma brucei gambiensegroup 2 experimentalin vivolife cycle: from procyclic to bloodstream form

Abstract

AbstractTrypanosoma brucei gambiense(Tbg) group 2 is a subgroup of trypanosomes able to infect humans in West and Central Africa. Unlike other agents causing sleeping sickness such asTbggroup 1 andTrypanosoma brucei rhodesiense, Tbg2 lacks the typical molecular markers associated with resistance to human serum. Only thirty-six strains ofTbg2 have been documented, and therefore, very limited research has been conducted despite its zoonotic nature. Some of these strains are only available in their procyclic form which hinders human serum resistance assays and mechanistic studies. Furthermore, the understanding ofTbg2’s potential to infect tsetse flies and mammalian hosts is limited. In this study, 165Glossina palpalis gambiensisflies were experimentally infected with procyclicTbg2 parasites. 35 days post-infection, 43 flies out of the 80 still alive flies were foundTbg2PCR-positive in the saliva. These flies were able to infect 3 out of the 4 mice used for blood-feeding. Dissection revealed that only six flies really carried mature infections in their midguts and salivary glands. Importantly, a single fly with a mature infection was sufficient to infect a mammalian host. ThisTbg2transmission success confirms thatTbg2 strains can establish in tsetse flies and infect mammalian hosts. The study describes an effectivein vivoprotocol for transformingTbg2 from procyclic to bloodstream form, reproducing the completeTbg2 cycle fromG. p. gambiensisto mice. These findings provide valuable insights intoTbg2’s host infectivity, and will facilitate further research on mechanisms of human serum resistance.