Leiomyosarcoma of the esophagus in a patient with chagasic megaesophagus: case report and literature review.
(17/1819)
Leiomyosarcoma constitutes approximately 0.5% of the malignant neoplasias of the esophagus and its association with megaesophagus has not been described. We report on a case of a woman with dysphagia that was slowly progressive from the age of 19 due to chagasic megaesophagus. The woman was subjected to cardiomyotomy at the age of 49. She presented a rapid worsening of the dysphagia due to leiomyosarcoma at the age of 61, and was subjected to subtotal esophagectomy with cervical esophagogastroplasty. She developed pulmonary and hepatic metastases 14 months after surgery and died six months later. (+info)
Suppression of humoral responses during Trypanosoma cruzi infections in mice.
(18/1819)
C57BL/6 mice exhibit low parasitemias and often survive Trypanosoma cruzi infections, whereas C3H(He) mice die during the acute phase with relatively high parasitemias. The present study showed that both strains of mice develop nonspecific immunosuppression to challenge with sheep erythrocytes during the course of infection. Several major differences in immunosuppression-related phenomena between the two strains of mice were determined, yet there is no apparent relationship between immunosuppression and resistance to T. cruzi. Both the number of direct plaque-forming cells and the titer of 2-mercaptoethanol-sensitive agglutinating antibody were significantly lower on day 11 for C57BL/6 mice and day 9 for C3H(He) mice. The number of indirect plaque-forming cells and the titer of mercaptoethanol-resistant agglutinating antibody were reduced by day 36 of infection in C57BL/6 mice and 13 days postinfection in C3H(He) mice. In both strains the degree of humoral response suppression of mice increased concomitant with the period of infection, but was not correlated with the changes in spleen cell numbers. Preliminary experiments designed to explore the mechanism underlying the induction and maintenance of immunosuppression in this hostparasite model disclosed the presence of suppressor substance in the serum of T. cruzi-infected mice. The passive transfer of serum from infected mice to syngeneic recipients elicited a state of immunosuppression to sheep erythrocytes, but did not diminish anti-erythrocyte activity in allogeneic recipients. The induction of immunosuppression in normal mice was further found to be dependent on the interval between serum transfer and challenge with antigen. No quantitative differences existed between the magnitude of suppressed humoral responses in mice infected for varying lengths of time and recipients of serum collected from similarly infected mice. (+info)
Contact sensitivity responses in mice infected with Trypanosoma cruzi.
(19/1819)
Mechanisms of depression of contact sensitivity responses in C57BL/10 mice infected with Trypanosoma cruzi were studied. Cellular involvement during sensitization with oxazolone was investigated in mice acutely infected with T. cruzi. Contact sensitivity was not expressed in mice during the latter stages of the acute infection. Spleen cells from sensitized, infected mice which were unable to respond to oxazolone could confer contact sensitivity upon normal syngenic mice as effectively as spleen cells from uninfected, sensitized donors. The ability of mice infected with T. cruzi to respond to an eliciting dose of oxazolone was significantly improved when macrophages from normal syngenic donors were administered to them at the time of skin test. When either normal or infected mice were used as recipients of lymphocytes from sensitized donors, the normal mice responded significantly better than did infected mice after administration of an eliciting dose of oxazolone. An increase in pyroninophilic cells was observed in draining lymph nodes after application of a sensitizing dose of oxaxolone to the ears of either normal or acutely infected mice. These results indicate that suppression of contact sensitivity during acute T. cruzi infection is directed toward the efferent arm rather than the afferent arm of the response. (+info)
Parasite persistence correlates with disease severity and localization in chronic Chagas' disease.
(20/1819)
The protozoan parasite Trypanosoma cruzi infects up to 20 million people in Latin America, and the resulting disease (Chagas' disease) is a leading cause of heart disease and death in young adults in areas endemic for the parasite. The clinical symptoms of Chagas' disease have been attributed to autoimmune reactivity to antigens shared by the parasite and host muscle or neuronal tissue. In the present study, in situ polymerase chain reaction analysis was used in murine models of Chagas' disease to demonstrate an absolute correlation between the persistence of parasites and the presence of disease in muscle tissue. Clearance of parasites from tissues, presumably by immunologic mechanisms, correlated with the abatement of inflammatory responses and the resolution of disease. These data provide strong evidence for parasite persistence as a primary cause of Chagas' disease and argue for efforts to eliminate T. cruzi from the host as a means for prevention and treatment of Chagas' disease. (+info)
Gamma interferon modulates CD95 (Fas) and CD95 ligand (Fas-L) expression and nitric oxide-induced apoptosis during the acute phase of Trypanosoma cruzi infection: a possible role in immune response control.
(21/1819)
We have previously shown that splenocytes from mice acutely infected with Trypanosoma cruzi exhibit high levels of nitric oxide (NO)-mediated apoptosis. In the present study, we used the gamma interferon (IFN-gamma)-knockout (IFN-gamma(-/-)) mice to investigate the role of IFN-gamma in modulating apoptosis induction and host protection during T. cruzi infection in mice. IFN-gamma(-/-) mice were highly susceptible to infection and exhibited significant reduction of NO production and apoptosis levels in splenocytes but normal lymphoproliferative response compared to the infected wild-type (WT) mice. Furthermore, IFN-gamma modulates an enhancement of Fas and Fas-L expression after infection, since the infected IFN-gamma(-/-) mice showed significantly lower levels of Fas and Fas-L expression. The addition of recombinant murine IFN-gamma to spleen cells cultures from infected IFN-gamma(-/-) mice increased apoptosis levels, Fas expression, and NO production. In the presence of IFN-gamma and absence of NO, although Fas expression was maintained, apoptosis levels were significantly reduced but still higher than those found in splenocytes from uninfected mice, suggesting that Fas-Fas-L interaction could also play a role in apoptosis induction in T. cruzi-infected mice. Moreover, in vivo, the treatment of infected WT mice with the inducible nitric oxide synthase inhibitor aminoguanidine also led to decreased NO and apoptosis levels but not Fas expression, suggesting that IFN-gamma modulates apoptosis induction by two independent and distinct mechanisms: induction of NO production and of Fas and Fas-L expression. We suggest that besides being of crucial importance in mediating resistance to experimental T. cruzi infection, IFN-gamma could participate in the immune response control through apoptosis modulation. (+info)
Ecogenetics of Triatoma sordida and Triatoma guasayana (Hemiptera: reduviidae) in the Bolivian chaco.
(22/1819)
Triatoma guasayana and two putative cryptic species pertaining to T. sordida complex (named groups 1 and 2) occur in sympatry in the Bolivian Chaco. Using multilocus enzyme electrophoresis and subsequent genetic analysis, our work assesses their population distribution and dispersal capacity in domestic, peridomestic, and silvatic environments. Our collections by light trap in the silvatic environment indicated a predominance of T. guasayana and T. sordida group 2 and a lesser abundance of T. sordida group 1 ( pound 10% of the total of captures). Their similar distribution in two silvatic areas 80 km apart supports the hypothesis of their homogeneous dispersal through the Bolivian Chaco. The distribution of T. guasayana and T. sordida groups 1 and 2 was similar between silvatic environment and peridomestic ecotopes where 25% of positive places was occupied by two or three species. Bromeliads were confirmed as favorable shelter for T. guasayana but were free of T. sordida. T. sordida group 1 and to a lesser extent T. guasayana would be more invasive vectors for houses than T. sordida group 2. The spatial partition in the three species sampled in two distant sites suggested a reduced dispersive capacity. (+info)
Prevalence of antibody to Trypanosoma cruzi in pregnant Hispanic women in Houston.
(23/1819)
We assessed the seroprevalence of antibodies to Trypanosoma cruzi among pregnant Hispanic women in Houston. Sera from 2,107 Hispanic and 1,658 non-Hispanic subjects were tested by ELISA for the presence of antibodies to T. cruzi. Twenty-two (0.6%) of 3,765 subjects had sera that were reactive. Seroreactivity was confirmed by hemagglutination assay. Eleven subjects had reactive sera, giving a confirmed seroprevalence of 0.3% (95% CI, 0-1%). Nine sera from Hispanic and two from non-Hispanic women were positive by hemagglutination assay, for a prevalence of 0.4% and 0.1%, respectively, during pregnancy. On the basis of these seroreactivity data, transplacental transmission of T. cruzi could occur in the continental United States. Screening for antibodies to T. cruzi during pregnancy would provide the potential for early intervention in congenital Chagas' disease. (+info)
Immunization of mice with a TolA-like surface protein of Trypanosoma cruzi generates CD4(+) T-cell-dependent parasiticidal activity.
(24/1819)
The gene family encoding a trypomastigote-specific protein restricted to the part of the flagellum in contact with the cell body of the trypomastigote form of Trypanosoma cruzi has been isolated, characterized, and expressed in a baculovirus expression system. The gene family contains three tandemly repeated members that have 97 to 100% sequence identity. The predicted protein encoded by the gene family has both significant amino acid sequence identity and other physical and biological features in common with the TolA proteins of Escherichia coli and Pseudomonas aeruginosa. Based on these similarities, we have designated this gene family tolT. Immunization of mice with recombinant TolT generates a population of CD4(+) T lymphocytes that recognize T. cruzi-infected macrophages, resulting in the production of gamma interferon (IFN-gamma), which leads to NO production and a 50 to 60% reduction in parasite numbers compared to that seen with infected macrophages incubated with naive T cells. This population of T cells also produces both IFN-gamma and interleukin 2 (IL-2) but not IL-4 or IL-5 when incubated with spleen cells stimulated with TolT antigen, indicating that they are of the T-helper 1 type. T cells from mice chronically infected with T. cruzi also produce significant levels of IFN-gamma when cocultured with macrophages and either TolT protein or paraflagellar rod protein, indicating that both of these flagellar proteins produce positive T-cell responses in mice chronically infected with T. cruzi. (+info)