Discussion

Chagas disease is caused by the protozoan parasite Trypanosoma cruzi and is a major source of morbidity in Central and South America. The nitroheterocyclic compounds benznidazole and nifurtimox are the current front-line drugs. Recently, we generated a T. cruzi strain expressing a bioluminescent/fluorescent fusion protein. When used to infect mice, this reporter strain enables in vivo bioluminescent imaging and tracking of the parasite burden in whole animals, and in organs and tissues, and facilitates detection of individual fluorescent parasites in tissue sections at a cellular level.  This model was used to assess the recrudescence of T. cruzi infections following sub-optimal treatment with benznidazole, in both the acute and chronic stages.  The results reveal that no specific tissue or organ acts as a reservoir of infection, acting as a site where parasites are able to survive drug treatment. Morphologically unusual forms of the parasite were identified in multiple tissue types. TUNEL assays, which provide a read-out of kDNA replication, identified surviving parasites that had both replicative and non-replicative status following benznidazole treatment. These experiments demonstrate that the technology outlined here can be used to provide new insights into drug activity in an in vivo context, as well as being a valuable tool for exploring the pathogenesis of T. cruzi infections.