[Pathogenesis of human chronic chagasic myocarditis]. / Patogenia de la miocarditis chagásica crónica humana.

Studies carried out during the last decades provided evidence in support of an autoimmune pathogenesis for chronic chagasic myocarditis. This opinion was based on 1) the demonstration of molecular mimicry between parasite and host antigens, 2) the appearance of autoantibodies recognizing heart epitopes during the chronic phase of infection, 3) the induction of myocarditis and electrocardiographic alterations in animals immunized with whole parasites, parasite fragments or with biochemically-defined antigens, 4) the isolation from the heart of inflammatory infiltrates of B cells elaborating antibodies against myocardial antigens and 5) or of T cell clones reacting with heart epitopes and 6) induction of heart and nervous tissue alterations by transfer of lymphocytes from infected animals into naive syngeneic hosts. However, the characteristics of the inflammatory infiltrate in human myocarditis, displaying a wide variety of cells, many of them not involved in autoreactivity, such as the presence of giant cell granulomas and abundant eosinophils, as well as its focality and asynchrony, and the frequent association with pericarditis, casts doubts about the possibility of autoimmunity being responsible for the perpetuation of the myocarditis. This is supported by the recent observation that treatment of asymptomatic patients with trypanocidal drugs prevents the development of cardiopathy and that parasite components, either antigens or genomic fragments, are present at the site of the inflammatory lesions. On the basis of this new evidence, other alternative pathogenetic mechanisms should be sought to explain the appearance of a polymorphic long-lasting myocarditis that needs the presence of tiny fragments of parasites to develop. In addition to the well known immunological pathogenesis, the link between such a small amount of parasite components, below the level of microscopic detection, and the induction of such an extensive inflammatory infiltrate, represents interesting avenues for research in the near future.

Presence of antiheart and antiskeletal muscle glycolipid autoantibodies in the sera of patients with chagasic cardiopathy.

OBJECTIVE: To characterize biochemically and isolate the skeletal and heart muscle cell epitope recognized by the autoantibodies present in the serum of chronically infected Trypanosoma cruzi patients. Secondly, to use that epitope in an immunoenzymatic assay for determining differences in antibody titre among Chagas' and other protozoan and heart diseases and between asymptomatic and cardiopathic chagasic patients. DESIGN: Isolated human skeletal and heart muscle cells were treated with organic solvents, pronase, neuraminidase and sodium metaperiodate before immunofluorescence assay. Glycolipids were extracted from human skeletal muscle for ELISA. PATIENTS: Sera were collected from 155 patients with positive serology for T cruzi infection; 44 healthy blood bank donors; and from patients after heart transplantation (16 patients), during the first month after cardiac infarction (eight) or cardiotomy (10), dilated myocardiopathy (21), leishmaniasis (12), acute toxoplasmosis (four) and hyperthyroid ophthalmopathy (five). MAIN RESULTS: Immunofluorescence assay revealed that the chagasic sera recognized epitopes that appeared to be glycolipid in nature. ELISA showed that the chagasic sera contained a higher titre of antiskeletal muscle glycolipid antibodies than the control sera and that, in the chagasic population, antibody titre was significantly higher in patients with heart failure than in asymptomatic subjects or in those presenting only electrocardiographic abnormalities. CONCLUSIONS: The skeletal and heart muscle epitope recognized by antibodies present in the sera of chagasic patients has the characteristics of a glycolipid. ELISA with glycolipids extracted from human skeletal muscle indicated that chagasic patients presented a higher antibody titre and that patients with heart failure showed a titre significantly higher than those who were asymptomatic or with electrocardiographic abnormalities, suggesting that those antibodies could be immunological markers and even predictors of heart failure in Chagas' disease.

Presence of cells producing antiheart autoantibodies in the inflammatory infiltrate of chronic chagasic myocarditis.

Chagasic myocarditis is associated with the appearance of circulating antiheart autoantibodies. In order to find out if there was local synthesis of those antibodies we investigated, by means of a solid immunoenzymatic technique, the presence of cells secreting antibody (ASC) against syngeneic soluble heart antigens in the mononuclear cell (MNC) population isolated from the hearts of mice chronically infected with Trypanosoma cruzi. In seven animals the number of ASC ranged between 300 and 2080 per 10(6) MNC. A similar number of cells was observed when the assay was carried out with T. cruzi-soluble antigens. When the ASC were enumerated in an assay simultaneously with both antigens, their number doubled that found in the single antigen assay, suggesting that there was no cross-reactivity between the heart and the parasite antigens. These results indicate that some of the cells in the inflammatory infiltrate of chronic chagasic myocarditis synthesize IgG autoantibodies against heart antigens, a phenomenon which may lead to a local concentration of antibody large enough to induce tissue damage.

Antibody-dependent Cytotoxicity of Human Platelets Against Trypanosoma Cruzi.

Human platelets in the presence of sera from humans with chronic Chagas' disease display cytotoxic activity against Trypanosoma cruzi (T. cruzi) trypomastigotes. Adsorption of IgE from those sera decrease the cytotoxic effect and IgG purified from the same sera revealed a cytotoxic action similar to the whole sera. Morphological studies suggest that chagasic serum promotes adhesion between parasites and platelets. On the basis of these results it is postulated that platelets may represent a defensive mechanism in South American trypanosomiasis by killing circulating forms of the parasite and that both IgG and IgE are relevant for that action.

Presence of anti-Trypanosoma cruzi antibodies in the sera of mice with experimental autoimmune myocarditis.

The existence of antigens shared in common by T. cruzi and heart muscle cells is suggested by the presence of antibodies binding to the parasite surface in the serum of mice with autoimmune myocarditis induced by immunization with syngenic heart antigens.

[Immunologic studies on a murine model of Chagas disease]. / Estudios inmunológicos en un modelo murino de enfermedad de Chagas.

In an experimental model, T. cruzi infected mice develop a chronic myocarditis with mononuclear infiltrates rich in CD4 lymphocytes and macrophages with scarce B and CD8 lymphocytes. The infected mice present in the spleen lymphocytes cytotoxic for adult syngeneic cardiocytes and in their sera antibodies able to induce antibody-dependent cytotoxicity (ADCC) against adult cardiocytes in a syngeneic system with spleen lymphocytes as effector cells. Myocarditis with electrocardiographic alterations was induced in naive recipients by transfer of lymphocytes from chagasic syngeneic mice. Immunization with subcellular fractions of T. cruzi led to a chronic myocarditis similar to that observed in infected animals; mice with autoimmune myocarditis induced by immunization with heart antigens developed antibodies which bind to T. cruzi epitopes. Glucocorticoids administered with trypanocidal drugs dramatically reduce the electrocardiographic alterations and to a lesser extent the myocarditis. Parasitological "cure" by treatment with trypanocidal drugs led to loss of the premunition state associated with the disappearance of antibodies able to induce complement-mediated lysis or ADCC against circulating forms of T. cruzi. However, both resistance against a challenge with a small number of parasites and cell-mediated anti T. cruzi immunity persisted. Our studies suggest that more than a single immunopathological mechanism is involved since anti-heart T cell cytotoxicity delayed type hypersensitivity and antiheart ADCC have been observed in chronically infected mice; this could be due to the existence of epitopes shared by the heart and the parasite.

Estudios inmunológicos en un modelo murino de enfermedad de Chagas. / [Immunologic studies on a murine model of Chagas disease]

In an experimental model, T. cruzi infected mice develop a chronic myocarditis with mononuclear infiltrates rich in CD4 lymphocytes and macrophages with scarce B and CD8 lymphocytes. The infected mice present in the spleen lymphocytes cytotoxic for adult syngeneic cardiocytes and in their sera antibodies able to induce antibody-dependent cytotoxicity (ADCC) against adult cardiocytes in a syngeneic system with spleen lymphocytes as effector cells. Myocarditis with electrocardiographic alterations was induced in naive recipients by transfer of lymphocytes from chagasic syngeneic mice. Immunization with subcellular fractions of T. cruzi led to a chronic myocarditis similar to that observed in infected animals; mice with autoimmune myocarditis induced by immunization with heart antigens developed antibodies which bind to T. cruzi epitopes. Glucocorticoids administered with trypanocidal drugs dramatically reduce the electrocardiographic alterations and to a lesser extent the myocarditis. Parasitological [quot ]cure[quot ] by treatment with trypanocidal drugs led to loss of the premunition state associated with the disappearance of antibodies able to induce complement-mediated lysis or ADCC against circulating forms of T. cruzi. However, both resistance against a challenge with a small number of parasites and cell-mediated anti T. cruzi immunity persisted. Our studies suggest that more than a single immunopathological mechanism is involved since anti-heart T cell cytotoxicity delayed type hypersensitivity and antiheart ADCC have been observed in chronically infected mice; this could be due to the existence of epitopes shared by the heart and the parasite.

Induction of heart alterations by immunization with subcellular fractions from Crithidia fasciculata.

Immunization of mice with subcellular fractions of C. fasciculata led to myocarditis and electrocardiographic alterations similar to those induced by immunization with T. cruzi, the etiological agent of Chagas' disease, suggesting the presence of similar cardiotoxic antigens in both trypanosomatid flagellates.