Desempenho da pesquisa de anticorpos antiTrypanosoma cruzi, por citometria de fluxo, na monitoração precoce de cura pósterapêuticaetiológica da doença de Chagas

Abstract

Specific therapy of chronic Chagas disease aims mainly to reduce parasitemia, besides preventing and reducing symptoms. However, monitoring treatment efficacy still remains unclear due to the lack of laboratorial methods that could certify a complete parasitologicalcure. Currently, the cure criteria used by various researchers is based on repeated serological and parasitological negative tests. Several studies have shown that serology can remain positive for decades after specific therapeutics. The introduction of highly sensitive techniques such as specific antibodies detection by flow citometry brought new perspectivesin Chagas disease cure monitoring. Herein, we developed two studies aiming to evaluate the performance of FC-AFEA and FC-ALTA techniques on post therapeutic evaluation. Our results showed that in a retrospective study using a population with 10 to 15 years of followup after specific therapeutics (n=60), FC-AFEA was capable to segregate cured chagasicpatients from non cured ones. Since the method presents a very high sensitivity, some modifications on the original technique, like the utilization of higher dilutions and higher cutoffs, were shown to be necessary. In a prospective study along five years of post therapeuticfollow-up (n=44), none of the serological methods used (FC-AFEA, FC-ALTA, IIF, IHA, ELISA, PaGIA) evidenced seronegativity. Nevertheless, we observed that the etiological treatment induced a decrease on FC-AFEA and FC-ALTA reactivity intensity. In addition, in patients presenting post therapy negative hemocultures (TEA), we could identify two subgroups of patients based on their magnitude of reactivity decrease. It is possible that patients with therapeutic success are included in the subgroup presenting higher reactivity decrease. Among the conventional serological tests applied in this study, IHA showed moretiter variations, creating difficulties for its use on cure monitoring. IIF was capable to identify reactivity decrease in more than 2 titers in some patients of TEA group. ELISA and PaGIA, in the way they are standardized for diagnostic proposal, were not able to segregate treated andnon-treated patients, indicating that modifications on the criterion have to be made for cure monitoring. Therefore, we conclude serology presents important limitations on early cure definition after etiological treatment of chronic Chagas disease. Seroreversion seems to be an inadequate approach for this purpose. Studies should be supported in order to investigate other markers associated to the presence of active infection other than searching for anti-T. cruzi antibodies.