Serological Evaluation of a Cohort of Patients with Chronic Chagas Disease Treated with Benznidazole in a Low Endemic Area of Central Brazil

Background: The most widely accepted criterion for assessing the cure of chronic Chagas disease after etiological therapy is the negativization of anti-Trypanosoma cruzi antibodies long after the completion of treatment.

Materials and Methods: We employed various serological antibody detection techniques to ascertain whether benznidazole treatment successfully cured chronic Chagas disease in a retrospective cohort of patients in a low-endemic area in central Brazil. Antibodies were assessed using indirect immunofluorescence (IIF) and enzyme immunoassay (ELISA) before treatment and 1-18 years post-treatment. A reevaluation of 89 patients was conducted in 2018, which included indirect hemagglutination (IHA), chemiluminescence (CL), and polymerase chain reaction (PCR) analyses.

Results: Seventeen patients were monitored for 15 years or more, seven for 10-15 years, 50 for 6-10 years, and 17 for 1-5 years. Only two patients who received treatment tested PCR-positive at reevaluation, indicating treatment failure. Both patients discontinued treatment early due to benznidazole's side effects. The incidence of serological test negativization was 10.1%. However, antibody levels determined by ELISA decreased with the increased duration of follow-up (p=0.002). Similarly, antibody titers of IIF-positive sera were lower in post-treatment reevaluations than those in pre-treatment titers, indicating reduced levels of anti-T. cruzi antibodies. These levels decreased in a duration-dependent manner during follow-up.

Conclusion: The results reveal a low cure rate based on antibody negativization, but antibody titers significantly decreased in all conventional serological tests. These findings suggest that decreased antibody levels may be associated with parasitological cure in patients with chronic Chagas disease after etiological treatment with benznidazole. Further prospective studies should be conducted to confirm and validate these findings.