Date Published: January 8, 2015
Publisher: Public Library of Science
Author(s): Fernanda Fortes de Araujo, Rana Nagarkatti, Charu Gupta, Ana Paula Marino, Alain Debrabant, Michael P. Pollastri. http://doi.org/10.1371/journal.pntd.0003451
Abstract: Drug discovery initiatives, aimed at Chagas treatment, have been hampered by the lack of standardized drug screening protocols and the absence of simple pre-clinical assays to evaluate treatment efficacy in animal models. In this study, we used a simple Enzyme Linked Aptamer (ELA) assay to detect T. cruzi biomarker in blood and validate murine drug discovery models of Chagas disease. In two mice models, Apt-29 ELA assay demonstrated that biomarker levels were significantly higher in the infected group compared to the control group, and upon Benznidazole treatment, their levels reduced. However, biomarker levels in the infected treated group did not reduce to those seen in the non-infected treated group, with 100% of the mice above the assay cutoff, suggesting that parasitemia was reduced but cure was not achieved. The ELA assay was capable of detecting circulating biomarkers in mice infected with various strains of T. cruzi parasites. Our results showed that the ELA assay could detect residual parasitemia in treated mice by providing an overall picture of the infection in the host. They suggest that the ELA assay can be used in drug discovery applications to assess treatment efficacy in-vivo.
Partial Text: Chagas disease (CD) is prevalent across various countries in Central and South America, with 28 million people at risk of getting infected , . The etiological agent of CD, Trypanosoma cruzi, has two life cycle stages in the infected host, an extracellular trypomastigote form that circulates in blood of infected individuals, and an intracellular amastigote form that is present in the infected tissues and organs, such as the heart , . Parasite infection and disease progression typically presents an acute phase characterized by blood parasitemia followed by a lifelong chronic phase, when circulating parasites can no longer be detected by direct blood examination .
One of the primary reasons for failure to develop new drugs for CD has been the lack of standardized end-point assays in animal models . The lack of universally accepted reliable tests to assess parasite burden and clearance and the hindrance this places on the development and evaluation of potential new drugs, both in experimental animal models and humans is well documented , . In this study we describe a biomarker-based detection assay to assess treatment efficacy in murine drug discovery models for the screening of anti-T. cruzi drugs. The fact that aptamers bound to purified trypomastigote extract and that T. cruzi infected drug treated mice showed reduced levels of biomarkers, compared to the infected group alone, indicates that the targets of the aptamers were of parasite origin.