Authors

Discussion

An estimated 6 to 7 million people are infected with the protozoan parasite Trypanosoma cruzi (T. cruzi), the causative agent of Chagas’ disease, mostly in endemic regions of Latin America. Chagas’ disease has recently also been reported in the US and Europe resulting from increased immigration and tourism. Chagas’ disease can progress into a chronic phase causing irreversible damage to the heart, nervous and/or digestive systems. The current drugs, benznidazole and nifurtimox, have adverse side-effects and limited efficacy in the chronic phase. There is thus an urgent need for new drugs. High-content phenotypic screening of intracellular amastigotes has proven to be a successful tool to identify new small-molecules with anti-trypanosomal activity. Our original intracellular phenotypic screening assay could not distinguish between cytostatic and cytocidal compounds due to low numbers of parasite per cell at the start of the assay. This assay has a high hit-rate but a low confirmation rate in secondary assays which do differentiate cytostatic from cytocidal compounds. To address this and increase the efficiency of our screening cascade we have developed a “cidal” screening assay by increasing the initial level of infection by 10-fold. This now allows distinction of compounds that kill parasites versus compounds that merely arrest their growth. While our current suite of screening assays is able to prioritise compounds that are cytocida