Aptamer-Based Detection of Disease Biomarkers in Mouse Models for Chagas Drug Discovery

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.

Author Summary

A marked decrease in incidence of Chagas Disease has been observed in the last decade achieved by vector control strategies; however, there are still geographical areas where the disease reaches endemic proportions. Due to high morbidity and disease burden, other avenues of Chagas control, such as vaccines and therapeutic agents need to be employed for comprehensive disease control and mitigation. As there are no vaccines available currently, two drugs (Benznidazole and Nifurtimox) have been the mainstay of treatment. However, these drugs produce multiple side effects and frequently lead to early termination of the treatment. In this study, we have successfully developed a new method to evaluate the presence of Chagas biomarkers in the plasma of infected drug treated mice. Our study shows that high biomarker levels in T. cruzi infected mice, after drug treatment, can indicate treatment failure. Our assay provides a global picture of parasitemia in the host and a positive result would thus suggest that the treated animals continue to harbor T. cruzi parasites somewhere in the body. This study provides a new method to test for T. cruzi infection and for assessing the effectiveness of treatment.