Induction of Resistance to Azole Drugs in Trypanosoma cruzi

Abstract

Trypanosoma cruzi is the protozoan parasite that causes Chagas’ disease, a frequently fatal illness affecting the heart and gastrointestinal systems. An estimated 16 million to 18 million people in Latin America and 50,000 to 100,000 people in the United States are infected with this pathogen. Treatment options for T. cruziinfections are suboptimal due to the toxicities and limited effectiveness of the available drugs. Azole antimicrobial agents have been discovered to have antitrypanosomal activity by inhibition of ergosterol synthesis. The triazole itraconazole was recently shown to produce a parasitologic cure rate of 53% in chronically infected patients (W. Apt et al., Am. J. Trop. Med. Hyg. 59:133–138, 1998), a result which may lead to more use of this family of drugs for the treatment of T. cruzi infections. In the experiments reported on here, resistance to azoles was induced in vitro by serial passage of mammalian-stage parasites in the presence of fluconazole for 4 months. These parasites were cross resistant to the other azoles, ketoconazole, miconazole, and itraconazole. They remained susceptible to benznidazole and amphotericin B. The azole-resistant phenotype was stable for more than 2 months of in vitro serial passage without fluconazole. In addition, the parasites resisted treatment in mice receiving ketoconazole. The rapid development of azole resistance inT. cruzi in vitro suggests that resistance to azole drugs has the potential to occur in patients and may pose an impediment to the progress being made in the treatment of T. cruziinfection.

Gene expression study using real-time PCR identifies an NTR gene as a major marker of resistance to benznidazole in Trypanosoma cruzi

“…On the other hand, we found that BZ-resistance parasites presented cross-resistance to NFX (Figure 1B), based upon previous experimental evidence where it was confirmed that resistance could be shared among similar nitroheterocyclic compounds of induced and natural resistance parasites [15,54-56]. However, G418 susceptibility did not show differences within all the phenotypes (Figure 1C).…”

“…The stability of the resistant phenotype has been confirmed in many in vitro and in vivo models through different parasite species [19,54]. This condition is the result of many cases of stable genetic alterations such as mutations, amplifications and deletions [16,18,58].…”

Nitroheterocyclic compounds are more efficacious than CYP51 inhibitors against Trypanosoma cruzi: implications for Chagas disease drug discovery and development

“…Variation in susceptibility to nitroheterocyclics can also be due to emergence of resistance within a population; indeed, it is well known that drug-resistant T. cruzi can be easily generated in the laboratory405455, and a recent study proposed that T. cruzi genome plasticity underlies quick selection of phenotypes resistant to benznidazole56. However, the most important point may be the way resistance is defined: if one considers EC 50s – defined as the compound concentration that reduces infection by 50% – as a parameter to measure resistance, our study confirms findings that there are differences in susceptibility to benznidazole, nifurtimox, and fexinidazole sulfone (Table 1 and Fig.…”

Rational Development of 4-Aminopyridyl-Based Inhibitors Targeting Trypanosoma cruzi CYP51 as Anti-Chagas Agents

“…10–11 However, all of these lead compounds are azoles, and there is an emerging issue of the rapid appearance of laboratory-induced resistance to azoles in T. cruzi cell culture. 12 Thus, the development of therapeutics with different scaffolds targeting Tc CYP51 is an important undertaking.…”