Immunoglobulin A antibodies to Trypanosoma cruzi antigens in digestive forms of Chagas' disease.

In an attempt to find a serological marker for the diagnosis of chronic digestive forms of Chagas' disease, we compared amastigote and trypomastigote antigens obtained from immunosuppressed mice infected with Trypanosoma cruzi (Y strain) with conventional epimastigote antigens to search for immunoglobulin A (IgA) antibodies. A total of 255 serum samples from patients with acute and chronic (indeterminate, digestive, and cardiac) forms of Chagas' disease and with nonchagasic diseases and from healthy individuals were studied. Amastigote antigens proved to be the most adequate for our purpose, since IgA antibodies could be detected in 23 of 25 serum samples from patients with digestive forms, with relative indices of sensitivity, specificity, and efficiency of 0.

The direct agglutination test for chronic Chagas's disease. The effect of pre-treatment of test samples with 2-mercaptoethanol.

The relative sensitivity and relative specificity of the direct agglutination (DA) test for the diagnosis of human Trypanosoma cruzi infection were studied in human serum samples, with and without previous treatment with 2-mercaptoethanol (2-ME), which were obtained from different areas of Brazil. Results obtained with these tests were related to those obtained with the indirect immunofluorescence (IIF) and indirect haemagglutination (IHA) tests. The DA test results from the sample not previously treated with 2-ME did not agree with those from the IIF and IHA tests.