Strain Trypomastigotes Research Articles

Susceptibility to acute Trypanosoma cruzi infection in autoimmune strains of mice.

We previously observed that mice bearing the autoimmune associated lpr gene exhibit increased susceptibility to challenge with Trypanosoma cruzi, the causative agent of Chagas' disease. We have now tested two other autoimmune prone strains of mice, BXSB and NZB, and found that these animals also show increased sensitivity to acute T. cruzi infection. When challenged with a standard dose (10(2)) of Y strain trypomastigotes, BXSB males (BXSB-YSB), which develop early onset autoimmune disease, suffered high mortality, while late onset autoimmune BXSB females and minimally autoimmune male BXSB mice whose Y chromosome was derived from C57BL/6J mice (BXSB-YB/6) also recover. NZB mice were found to be highly susceptible to challenge while NZW and NZB/W were resistant. A finding common to all groups of susceptible autoimmune mice was increased plasma levels of T. cruzi specific antibody, especially IgM. The data indicate that in two of the three autoimmune prone strains examined, increased T. cruzi susceptibility appears to be linked to restricted genetic elements (i.e. lpr gene and the YSB associated factor) which also influence the rapidity of onset of autoimmunity.

Resistance of mice immunized with killed culture trypomastigotes against infection by insect-derived trypomastigotes of Trypanosoma cruzi.

Mice immunized with heat or merthiolate-killed culture trypomastigotes of the non-virulent G strain were resistant to the challenge by insect-derived trypomastigotes of the CL strain of Trypanosoma cruzi. No parasitemia was detected, by direct microscopic examination of blood samples, in 90% of immunized mice while all control animals developed a high parasitemia. Trypsinization before heat-inactivation, or fixation with paraformaldehyde, apparently reduced the immunogenicity of the G strain trypomastigotes. Mice immunized with trypomastigotes treated by either of these procedures were not protected against infection by virulent T. cruzi. Analysis of the 13I-labeled surface proteins of G strain trypomastigotes inactivated by the various methods suggests that these components are involved in eliciting protective immunity against T. cruzi infection.

Bone Marrow Eosinophil Levels in Trypanosoma cruzi Infected Mice

Eosinophilic granulocytes have been implicated as possible effector cells in host resistance to Trypanosoma cruzi infection. Eosinophils have been found in the parasite-containing lesions of hosts with acute Chagas' disease (Koberle, 1968, Adv. Parasit. (B. Dawes, ed.) 6: 63-110) and are thought to function as the cellular component of an antibody dependent cellular cytotoxicity (ADCC) response against the parasite. Indeed, eosinophils from man (Kierszenbaum, 1979, Am. J. trop. Med. Hyg. 28: 965-968) and rodents (Sanderson et al., 1977, Nature, Lond. 268: 340341; Kipnis et al., 1981, Am. J. trop. Med. Hyg. 30: 47-53) have been shown capable of destroying trypanosomes by ADCC in the presence of immune serum. If eosinophils play a role in host protection against T. cruzi, the dynamics of this cell type during infection becomes an important consideration. To evaluate eosinophil levels through T. cruzi infection, the bone marrows of 8 wk old C3H(He) (Dominion Labs, Dublin, VA) and C57B1/6 (Jackson Labs, Bar Harbor, ME) female mice infected intraperitoneally with 1 x 103 Brazil strain trypomastigotes were assayed by 2 methods. One technique involved removal of the left femur from mice asphyxiated with CO2 and flushing the marrow with 1.0 ml of Alsever's solution (femoral bone marrow wash; FBMW). The resulting cell suspension was examined microscopically by standard hemocytometer methods for the total nucleated cell count by Turk's stain and the number of eosinophils using Discombe's stain (Discombe, 1946, Lancet 1, pp. 195-196). Discombe's stain (8 parts dH2O, 1 part 3% eosin Y and 1 part acetone) was incubated for 5 min at a 1 part cell suspension to 10 parts stain ratio prior to counting. The level of eosinophils for each animal was estimated as follows: % eosinophils = (# eosinophils per ml FBMW/# of nucleated cells per ml FBMW) x 100. Eosinophil percent data were normalized by the arcsin transformation before statistical analysis using ANOVA and Duncan's statistical tests (Zar, 1974. Biostatistical analysis. PrenticeHall, Inc., Englewood Cliffs, NJ). Parasitemia determination was done by microscopic examination of 4 ul of tail vein blood under an 18 mm circular coverslip (Kuhn et al., 1975, Int. J. Parasit. 5: 557-560). C3H(He) mice, on days 7, 14, 21, and 28 of acute infection, and C57B1/6 mice, on days 14, 28, and 42 of acute infection and day 90 representing post-acute infection, were sacrificed and

Strain Specific Protective Immunity against Trypanosoma cruzi

Swiss albino, C57BL/10J, and B10.A mice previously inoculated with an LD50 dose of T. cruzi Y strain were protected against subsequent challenge with the homologous strain, but had a parasitemia comparable to that of control mice when challenged with F strain trypomastigotes, although they were protected against mortality. In contrast, animals previously inoculated with an LD50 of T. cruzi F strain were protected both against a subsequent challenge with the homologous strain and the Y strain.

Development of cell mediated immunity to flagellar antigens and acquired resistance to infection by Trypanosoma cruzi in mice.

Modulation by BCG and/or cyclophosphamide of sensitization of mice with flagellar fraction (a tubulin-enriched fraction) prevented death of mice challenged with T. cruzi CL strain trypomastigotes recovered from Vero cells. A methodology was ceveloped to assay specific antigens and to determine optimal doses for sensitization and elicitation of DTH in mice. CL strain is predominantly myotropic strain which does not produce important parasitism of mononuclear phagocyte cells; these cells appear to control infection when activated in vivo. Maximum protection was seen in this study when BCG and cyclophosphamide were associated, but protection was observed also when cyclophosphamide, that prevents supressor T cells, was applied 2 days before flagellar fraction sensitization in normal mice. These experiments suggested that the macrophage may have an important role in the early phases of infection particularly when nonspecific stimulation is associated with specific sensitization. A correlation betwen delayed hypersensitivity to parasite antigens and protection was observed.

Trypanosoma cruzi: Ability of T-cell-enriched and -depleted lymphocyte populations to passively protect mice

T-Cells and a T-cell-depleted population were prepared from the spleens of C3H mice immunized with epimastigotes of the Brazil strain of Trypanosoma cruzi. Both populations of cells, as well as unfractionated spleen cells, were capable of reducing parasitemias and protecting against death when transferred to susceptible C3H mice 24 hr before challenge with 10 4 Brazil strain trypomastigotes. The immune T-cell-depleted subpopulation was, on an equal cell basis, more effective in engendering resistance than the immune T-cell subpopulation. Protection could also be transferred with unfractionated immune spleen cells if the cells were given within 8 days following challenge of recipient mice. Transfer after 8 days led to significantly reduced parasitemias but all mice died.

Protective Effects of Specific Antibodies in Trypanosoma Cruzi Infections

The action of immune sera from animals with chronic Chagas disease on Trypanosoma cruzi bloodstream forms (Y and CL strains) was investigated. Y strain trypomastigotes were agglutinated by anti-CL or anti-Y immune sera and their infectivity was decreased when inoculated into normal mice. CL strain trypomastigotes, however, remained apparently unchanged, with neither agglutination nor decline of infectivity being observed after incubation with both immune sera. Sera from three patients with chronic Chagas disease clearly agglutinated and two of them decreased the infectivity of Y strain trypomastigotes. Passive transfer of immunity was achieved in mice that recieved anti-CL or anti-Y immune sera and that were challenged with Y strain parasites. These results suggest that humoral immunity participates in the protective immune response against T. cruzi and that bloodstream trypomastigotes represent a more suitable model for studies of antigenic variation in these infections.