Genetic Characterization of Trypanosoma cruzi I Populations from an Oral Chagas Disease Outbreak in Venezuela: Natural Resistance to Nitroheterocyclic Drugs

Abstract

The oral transmission of Chagas disease (oCD) in Venezuela announced its appearance in 2007. Different from other populations affected by oCD and despite close supervision during treatment with nitroheterocyclic drugs, the result was treatment failure. We studied genetic features of natural bloodstream parasite populations and populations after treatment of nine patients of this outbreak. In total, we studied six hemoculture isolates, eight Pre-Tx blood samples, and 17 samples collected at two or three Post-Tx time-points between 2007 and 2015. Parasitic loads were determined by quantitative polymerase chain reaction (qPCR), and discrete typing units (DTU), minicircle signatures, and Tcntr-1 gene sequences were searched from blood samples and hemocultures. Half-maximal inhibitory concentration (IC 50 ) values were measured from the hemocultures. All patients were infected by TcI. Significant decrease in parasitic loads was observed between Pre-Tx and Post-Tx samples, suggesting the evolution from acute to chronic phase of Chagas disease. 60% of intra-DTU-I variability was observed between Pre-Tx and Post-Tx minicircle signatures in the general population, and 43 single-nucleotide polymorphisms (SNPs) were detected in a total of 12 Tcntr-1 gene sequences, indicative of a polyclonal source of infection. SNPs in three post-Tx samples produced stop codons giving rise to putative truncated proteins or displaced open reading frames, which would render resistance genes. IC 50 values varied from 5.301 ± 1.973 to 104.731 ± 4.556 μM, demonstrating a wide range of susceptibility. The poor drug response in the Pre-Tx parasite populations may be associated with the presence of naturally resistant parasite clones. Therefore, any information that can be obtained on drug susceptibility from in vitro assays, in vivo assays, or molecular characterization of natural populations of Trypanosoma cruzi becomes essential when therapeutic guidelines are designed in a given geographical area.

Treatment options for Chagas Disease: a systematic review and meta-analysis applied to the preclinical studies using animal models

“…Heightening this issue is the pharmaceutical industry’s limited interest in the subject, exacerbated by the meager financial prospects of medicines targeting illnesses primarily affecting low-income regions (57,58). The emergence of drug-resistant strains underscores the urgent need for alternative therapeutics, while regulatory hurdles associated with approving novel treatments for neglected diseases further compound the delays in progress (53,59–61). Collectively, these factors converge to create a daunting and intricate landscape that significantly hampers the development of novel CD treatments.…”

“…Compounding this issue, the pharmaceutical industry shows limited interest due to the low commercial potential of medications targeting diseases prevalent in low-income regions (57,58). Furthermore, the emergence of drug-resistant strains emphasizes the urgency of finding alternative treatments, yet regulatory hurdles associated with approving novel therapeutics for neglected diseases further contribute to delays (53,59–61). Collectively, these factors create a complex and discouraging landscape that severely hinders the development of new CD treatments.…”

Unveiling challenges in real-time PCR strategies for detecting treatment failure: observations from clinical trials on chronic Chagas disease

“…Parasite genotyping can aid in understanding the differences in outcomes observed across different trials conducted in various geographical regions, as well as in detecting naturally resistant populations (Parrado et al, 2019;Muñoz-Calderoń et al, 2023). Biorepositories containing well-conserved blood samples and extracted DNAs can be valuable for typing parasite populations from previous trials.…”