Trypanosoma cruzi: recognition of a 43-kDa muscle glycoprotein by autoantibodies present during murine infection.

The production of autoimmune antibodies during infection with the hemoflagellate parasite Trypanosoma cruzi has been previously reported by this and other laboratories. The present investigation indicates a potential target in normal heart tissue that may be the binding site for the autoimmune antibodies. Using Western blot analysis, sera obtained from chronically infected C57 B1/6 mice was examined for its ability to recognize normal tissue antigens from uninfected syngeneic animals. Antibodies from chronic sera recognized an antigen in normal mouse heart and skeletal muscle tissue at a molecular weight between 43 and 45 kilodaltons (kDa). This proposed target antigen was found in cytoplasmic extracts from normal heart antigen preparations. The autoantibody recognition of the normal tissue in Western blots was inhibited by periodate oxidation of the antigen sample. This suggests that the binding of the autoantibodies may be dependent upon a glycosylation present on the antigen targets. Isotype analysis indicated that the autoreactive antibodies are of the IgM and IgG2b isotypes. These results suggest that a target for autoantibodies in Chagas' disease may be a 43- to 45-kDa glycoprotein found in normal heart and skeletal muscle tissue. Exposure of the immune system to this antigen may follow the damaging effects of the parasite itself, or of the immune response toward the parasite. In either scenario the identification of a target in the ongoing autoimmunity may help to define the autoimmune process in American Trypanosomiasis.