Antibodies to an epitope from the Cha human autoantigen are markers of Chagas' disease

Chagas' disease is a prevalent disease in South America that is thought to have an autoimmune etiology. We previously identified human Cha as a new au toantigen recognized by chagasic sera. Those sera recognized an epitope spa nning amino acids 120 to 129 of Cha, named R3. In the present study we have used the synthetic R3 peptide for the detection of serum immunoglobulin G antibodies from patients at different stages of Chagas' disease, including a therapeutically treated group. The immunoreactivity with R3 by enzyme-lin ked immunosorbent assay (ELISA) showed 92.4% sensitivity and 100% specifici ty for Chagas' disease sera. This sensitivity and specificity were higher t han for, any other autoantigen described to date. No anti-R3 antibodies wer e detected in sera from Leishmania-infected or idiopathic dilated cardiomyo pathy patients or healthy controls from the same areas. Moreover, anti-R3 a ntibody reactivity detected by ELISA correlated with conventional serologic al tests as indirect immunofluorescence and ELISA assays with Trypanosoma c ruzi extracts and other diagnostic tests as indirect hemagglutination. The levels of anti-R3 antibodies increased with progression and symptomatology of Chagas' disease. More interestingly, a statistically significant fall in anti-R3 antibody titer was observed in patients treated with antiparasitic drugs. Those results suggest that the presence of anti-R3 antibodies is a highly specific marker of Chagas' disease and that R3 ELISA could be helpfu l in the diagnosis and monitoring of this disease.