Benznidazole-Resistance in Trypanosoma cruzi Is a Readily Acquired Trait That Can Arise Independently in a Single Population

Abstract

Benznidazole is the frontline drug used against Trypanosoma cruzi, the causative agent of Chagas disease. However, treatment failures are often reported. Here, we demonstrate that independently acquired mutations in the gene encoding a mitochondrial nitroreductase (TcNTR) can give rise to distinct drug-resistant clones within a single population. Following selection of benznidazole-resistant parasites, all clones examined had lost one of the chromosomes containing the TcNTR gene. Sequence analysis of the remaining TcNTR allele revealed 3 distinct mutant genes in different resistant clones. Expression studies showed that these mutant proteins were unable to activate benznidazole. This correlated with loss of flavin mononucleotide binding. The drug-resistant phenotype could be reversed by transfection with wild-type TcNTR. These results identify TcNTR as a central player in acquired resistance to benznidazole. They also demonstrate that T. cruzi has a propensity to undergo genetic changes that can lead to drug resistance, a finding that has implications for future therapeutic strategies.

Benznidazole-resistance in Trypanosoma cruzi: Evidence that distinct mechanisms can act in concert

“…For example, instances where resistance to nifurtimox occurs independently of benznidazole-resistance have been reported [10]. Likewise, wide natural variations in benznidazole-sensitivity have been identified in Colombian isolates (EC 50 4–30 μM), which are not associated with changes in the TcNTR sequence [8].…”

Natural sesquiterpene lactones induce programmed cell death in Trypanosoma cruzi: A new therapeutic target?

“…Current treatment of Chagas disease relies on two drugs, Bz and Nx, discovered empirically more than three decades ago (Boiani et al 2010;Cerecetto and Gonzalez 2002;Mejia et al 2012). The aims for treatment of Chagas disease are (1) to cure the infection in the acute phase; (2) to prevent organ damage in chronic asymptomatic infection, and (3) to limit incapacity and prevent morbidity and mortality once the disease is already clinically manifested (Rassi et al 2012).…”

“…Bz and Nx are effective for treating acute infections but both cause undesirable side effects, frequently leading to abandonment of the treatment. Their efficacy during the chronic phase is still controversial with a lack of consensus about the methods for evaluating parasitological cure (Cerecetto and Gonzalez 2002;Mejia et al 2012;Menna-Barreto et al 2009). Moreover, treatment failure due to drug inefficacy is known to occur even during acute infection, the stage in which anti-parasitic drug therapy is most effective (Machado et al 2010).…”

Assessing the Essentiality of Leishmania donovani Nitroreductase and Its Role in Nitro Drug Activation

“…This pressure may have the added advantage of limiting the maximum levels of fexinidazole resistance achievable, with SKO promastigotes less than 2-fold more resistant to the drug. In recent studies with T. cruzi, laboratory-generated benznidazoleresistant parasites were found to have lost a single copy of the NTR gene, and mutations arising in the remaining copy of the gene abolished enzyme activity (18). However, these "functional null" parasites demonstrated such reduced levels of virulence that the capacity for such highly drug resistant T. cruzi parasites to spread within the population would be severely compromised.…”