Tissue-Specific Parasite Persistence Following Chemotherapy in a Drug-Resistant Trypanosoma cruzi Preclinical Model

Abstract Therapeutic failure in Chagas disease remains a major unmet medical challenge, often associated with intrinsic variability in drug susceptibility among Trypanosoma cruzi strains. However, the biological basis of incomplete parasite clearance after treatment remains poorly understood. Here, we investigated the tissue distribution of an intrinsically drug-resistant T. cruzi strain in a murine model of acute infection and evaluated the effects of short-term treatment with benznidazole or E1224 on parasite burden and host immune responses. Parasite loads were quantified by qPCR in multiple tissues before and after cyclophosphamide-induced immunosuppression, and plasma cytokines were measured to assess systemic immune responses. The heart, skeletal muscle, and white adipose tissue harbored the highest parasite burdens. Although both drugs significantly reduced parasite loads, incomplete clearance and tissue-specific recrudescence were observed following immunosuppression. Benznidazole-treated mice showed parasite rebound in the heart, adipose tissue, and large intestine, whereas E1224-treated animals exhibited recrudescence in the heart, skeletal muscle, and liver. Acute infection induced a robust pro-inflammatory response, and parasite reduction was accompanied by decreased Th1 cytokine levels. These findings demonstrate parasite persistence within defined tissue reservoirs despite chemotherapy, suggesting tissue-specific survival as a potential biological basis for therapeutic failure.