Trypanosoma cruzi: location of a specific antigen on the surface of bloodstream trypomastigote and culture epimastigote forms

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 autoantigen recognized by chagasic sera. Those sera recognized an epitope spanning 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-linked immunosorbent assay (ELISA) showed 92.4% sensitivity and 100% specificity for Chagas' disease sera. This sensitivity and specificity were higher than for any other autoantigen described to date. No anti-R3 antibodies were detected in sera from Leishmania-infected or idiopathic dilated cardiomyopathy patients or healthy controls from the same areas. Moreover, anti-R3 antibody reactivity detected by ELISA correlated with conventional serological tests as indirect immunofluorescence and ELISA assays with Trypanosoma cruzi 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 helpful in the diagnosis and monitoring of this disease.

Trypanosoma cruzi exoantigens: can those recognized by sera from chagasic patients trigger a protective immune response in mice?

Exoantigens (Ea) of Trypanosoma cruzi released in blood during the acute phase of experimental murine infection and recognized as antigens by sera from chagasic patients were grouped into two zones: one zone of pI 4-5 (Ea4-5), which had components of 35 kDa, 50 kDa and slightly higher than 100 kDa, MW, and another zone, of pI 6-7 (Ea 6-7), with Ea of 50 kDa, 66-80 kDa and higher than 100 kDa. Immunization of mice with Ea4-5 or Ea6-7 prior to infection induced a protective immune response, as judged by levels of parasitaemia which were significantly lower than those of controls. Analysis of the immune response by skin test revealed that both groups of Ea induced immediate type hypersensitivity, the values of which were higher in animals immunized with Ea4-5. These antigens also induced specific cellular immunity (delayed-type hypersensitivity). There was a direct correlation between intensity of reactivity and the drop in the number of blood forms of parasites in these animals. Antibodies able to fix the epimastigote surface were also detected by ELISA and the immunofluorescence test in mice immunized with Ea4-5 or Ea6-7. There were no qualitative or quantitative differences in the antibody induced by the two groups of Ea; the main isotypes of these antibodies which recognized Ea expressed on the parasite surface were IgG1 and IgG2.

Trypanosoma cruzi: expression of antigenic component 5 among 35 laboratory clones obtained from 18 different isozymic variants

Two monoclonal antibodies anti-component 5 of Trypanosoma cruzi (I-35/115 and II-190/30) were tested in IFA and ELISA respectively against 35 T. cruzi laboratory clones. Among the 35 clones tested, 18 different isozyme patterns were detected. All clones were recognized by both monoclonal antibodies except one clone which did not react with II-190/30. These results support the universal expression of specific component 5 within the taxon T. cruzi.

Effects of extracts of Trypanosoma cruzi on immune responses: induction of a nonspecific suppressor factor

Extracts of epimastigotes of Trypanosoma cruzi were examined for the ability to augment or suppress in vivo and in vitro responses of mouse spleen cells. When administered to mice 4 days before immunization with sheep erythrocytes, the 12,000 X g pellet and the 104,000 X g pellet and supernatant fractions of extracts of T. cruzi had no effect on the subsequent plaque-forming cell responses. Testing of the two 104,000 X g fraction in vitro resulted in a slight dose-dependent modification of anti-sheep erythrocyte responses. Also, these two fractions had a moderate dose-dependent blastogenic effect on normal spleen cells. Most significantly, the 104,000 X g supernatant fraction elicited the production of a suppressor factor when incubated with spleen cells from infected mice. This suppressor factor was also apparent when spleen cells from infected mice were incubated with intact epimastigotes or trypomastigotes. Production of the suppressor factor was insensitive to indomethacin and, therefore, presumably was not a prostaglandin.

Cross-reactivity of vector-borne metacyclic forms of Trypanosoma cruzi with mammalian and culture stages

Metacyclic forms of Trypanosoma cruzi isolated from the hindgut of infected insect vectors (Rhodnius prolixus) were found to be immunologically cross-reactive with cultured epimastigote, amastigote, and metacyclic stages of the parasite as well as with bloodstream trypomastigote forms by direct agglutination and indirect immunofluorescence techniques. Sera specific for each of these forms of the parasite systematically yielded maximal antibody titers when measured against the homologous antigen, indicating that antigenic determinants are shared by all of the developmental forms used in this work. Supporting this conclusion were the significant reductions in anti-insect-derived metacyclic antibody titer caused by absorption with any of the other life stages of T. cruzi. These results are relevant to the potential use of laboratory-grown forms of T. cruzi in vaccination against a natural infection with this parasite.