Trypanosoma cruzi reinfections provoke synergistic effect and cardiac beta-adrenergic receptors' dysfunction in the acute phase of experimental Chagas' disease.

Cardiac beta-adrenergic receptors' function was studied in the acute phase of Chagas' disease in mice reinfected with Trypanosoma cruzi Tulahuen strain (Tul) and with parasites isolated from an infected patient (SGO-Z12). Genetic characterization of SGO-Z12 isolates demonstrated that it belongs to the zimodeme Z12, one of the prevalent ones in humans in Argentina. Electrocardiography, heart histopathology, parasitemias, and survival in infected and reinfected mice were also analyzed. Reinfected mice reached higher parasitemias, 14% of the infected with SGO-Z12 and 76% of the reinfected groups showed electrocardiographic abnormalities. Similar results were found in mice that were infected and reinfected with Tul. SGO-Z12-Reinfected and Tul-Infected groups exhibited cardiac beta-adrenergic receptors' affinity significantly diminished (p<0.001) and its density significantly increased (p<0.001) than in infected and non-infected groups. Histopathologic alterations in hearts from Tul and SGO-Z12-Reinfected mice were detected. Reinfections with T. cruzi, Tulahuen strain or SGO-Z12 isolate provoked cardiac dysfunctions of different degrees, from the acute phase on.