Detection of rare, non-proliferating Trypanosoma cruzi amastigotes in vivo and in vitro

WANG, WEI; SÁNCHEZ VALDÉZ FERNANDO JAVIER; TARLETON, RICK L; PADILLA ÁNGEL; ORR, DYLAN

Athens Georgia

Simposio; 27th The Molecular Parasitology/Vector Biology Symposium; 2017

Center for Tropical and emerging global diseases Univ of Georgia

Microbial dormancy,defined as a state of reduced metabolic activity, is well-recognized inbacterial systems as a mechanism of transient resistance to environmentalstresses, including antibiotic treatment. The ability of T. cruzi toresist long-term in vivo exposure to highly cytotoxic compounds, prompted us toexplore the potential for parasite dormancy and its contribution to failed drugtreatments in T. cruzi infection.  Using both the incorporation of thenucleotide analogue EdU and the cell proliferation tracking dyes CSFE andCellTrace Violet, we detected non-proliferating amastigotes in vivo in mice andin vitro in cultured host cells. T. cruziamastigotes became dormant early after host cell invasion and in the absence ofstressors such as drug selection and were present in host cells that contained substantialnumbers of other actively dividing amastigotes. Importantly, non-proliferative amastigotes ultimately converted totrypomastigotes and excited host cells and then established productive infectionsin new host cells, thus demonstrating their ability to propagateinfection.  Most significantly, wedetermined that these dormant amastigotes were uniquely resistant tobenznidazole treatment both in vivo and in vitro and could re-establish a flourishinginfection after >8 days of drug treatment. These results suggest the existence of a perhaps programed cessation ofreplication in T. cruzi that occursfrequently and is at least in part responsible for the common failure of highlycytotoxic compounds to completely resolve T.cruzi infection.  The ability of T. cruzi to establish dormant forms throws into question current efforts toidentify better anti-T. cruzicompounds but also suggests alternative screening approaches to identify suchcompounds and how current compounds are being used to treat infected subjects.