Methodological advances in drug discovery for Chagas disease

Abstract

INTRODUCTION: Chagas disease is the highest impact human infectious disease in Latin America, and the leading worldwide cause of myocarditis. Despite the availability of several compounds that have demonstrated efficacy in limiting the effects of T. cruzi, these compounds are rarely used due to their variable efficacy, substantial side effects and the lack of methodologies for confirming their effectiveness. Furthermore, the development of more efficacious compounds is challenged by limitations of systems for assessing drug efficacy in vitro and in vivo. AREAS COVERED: Herein, the authors review the development of Chagas disease drug discovery methodology, focusing on recent developments in high throughput screening, in vivo testing methods and assessments of efficacy in humans. Particularly, this review documents the significant progress that has taken place over the last 5 years that have paved the way for both target-focused and high-throughput screens of compound libraries. EXPERT OPINION: The tools for in vitro and in vivo screening of anti-T. cruzi compounds have improved dramatically in the last few years and there are now a number of excellent in vivo testing models available; this somewhat alleviates the bottleneck issue of quickly and definitively demonstrating in vivo efficacy in a relevant host animal system. These advances emphasize the potential for additional progress resulting in new treatments for Chagas disease in the coming years. That being said, national and international agencies must improve the coordination of research and development efforts in addition to cultivating the funding sources for the development of these new treatments.

Figure 1

Image of tdTomato-expressing amastigotes of T. cruzi replicating in vitro within host cells.

Figure 2

Monitoring effect of benznidazole on growth of the indicated strains of T. cruzi amastigotes in Vero cells by the expression of the tdTomato protein. IC50 were calculated at 3 days of treatment.

Figure 3

(A) Schematic of the short in vivo assay used to screen anti-T. cruzi compounds in 1 week. Mice are infected in the hind foot pads with 2.5 × 10⁵ T. cruzi-tdTomato trypomastigotes of the CL strain, and the specific treatment (Benznidazole) was given at days 2 and 3 postinfection. B) Parasites are imaged at day 2 and 6 post-infection. C) Quantification of the fluorescent signal from the individual mice at day 2 and 6 post infection. The efficiency factor (EF) was calculated using the following formula: [Fluorescence of Treated mice day 6 - Fluorescence of Treated mice day 2)/(Fluorescence of Untreated mice day 6 - Fluorescence of Untreated mice day 2)] X 100.