Dominant T- and B-cell epitopes in an autoantigen linked to Chagas' disease.

In Chagas' disease caused by Trypanosoma cruzi, a paradigm of autoimmune disease, both autoantibodies and autoreactive T cells have been described. We have identified a novel dominant autoantigen, named Cha, recognized by the majority of sera from T. cruzi-infected humans and mice. We noted significant homologies between amino acids 120-129 of Cha, where the B-cell epitope maps, and an expressed sequence tag from T. cruzi, and also between amino acids 254-273 of Cha and a repeated amino acid sequence from the shed acute-phase antigen (SAPA) of T. cruzi. Moreover, T. cruzi-infected mice contain autoreactive T cells that can cross-react with Cha and the SAPA homologous peptides. Transfer of T cells from infected mice triggered anti-Cha (120-129) Ab production in naive recipients. Interestingly, heart tissue sections from those adoptive transferred mice showed cardiac pathology similar to T. cruzi-infected mice. Our results demonstrate the presence of both T- and B-cell cross-reactive epitopes in the Cha antigen. This dual mimicry may lead to T/B cell cooperation and give rise to a pathological immunodominant response against Cha in T. cruzi infected animals.