Background: Although patients with chronic chagasic cardiopathy do have a strong immune response against Trypanosoma cruzi, they have transient and low parasitemia as well as tissue amastigote nests. When conventional studies were carried out, demonstration of such abnormalities is minimally achieved. Molecular biology may provide the best tools to demonstrate parasite persistence, which could be pathogenic in this progressive disease.
Methods: We studied 16 patients with chronic chagasic cardiopathy (CCC) at the Instituto Nacional de Cardiología Ignacio Chávez in Mexico City. Patients had undergone a complete clinical evaluation, and had antibodies against Trypanosoma cruzi. They came from different rural areas in Mexico. Blood samples were obtained and processed for hemoculture and PCR technique. A CCC necropsy case was also sought for the presence of parasite antigen or DNA, using immunohistochemistry and PCR methods in archival tissues.
Results: Five of 16 (31%) hemocultures demonstrated circulating T. cruzi; 60% occurred in persons between 25 and 40 years old. In contrast, we found a positive PCR amplification in 81%; therefore, molecular biology tools appear to be more sensitive for demonstrating parasite persistence. There were no correlations between parasitemic state and clinical findings or specific antibody titer. The autopsy case had parasite antigens and DNA in heart tissues.
Conclusions: Chronic chagasic cardiopathy patients do have persistence of parasite even when parasitemia is low or absent. The continuous presence of a parasite load could maintain immune stimulus and perhaps enhance a pathogenic immune or autoimmune tissue damage in susceptible hosts.