Immunoregulatory mechanisms and Chagas' disease. (73/382)

During the course of experimental Chagas' disease, several immune disorders occur. In the acute phase, T and B cell polyclonal activation is associated to immunosuppression. At the chronic stage, T cells--of the TH2 subset--participate to the pathology characteristic of Chagas' disease. Data obtained after infection of BALB/Xid mice suggest that polyclonal activation may be dependent on B1 (CD5) cell-activation. Moreover, these mice fail to develop the pathological features of the chronic infection. Control of lymphokine secretion might play a key role in the clinical status of Chagas' disease.  (+info)

Macrophage activation and histopathological findings in Calomys callosus and Swiss mice infected with several strains of Trypanosoma cruzi. (74/382)

Peritoneal macrophage activation as measured by H2O2 release and histopathology was compared between Swiss mice and Calomys callosus, a wild rodent, reservoir of Trypanosoma cruzi, during the course of infection with four strains of this parasite. In mice F and Y strain infections result in high parasitemia and mortality while with silvatic strains Costalimai and M226 parasitemia is sub-patent, with very low mortality. H2O2 release peaked at 33.6 and 59 nM/2 x 10(6) cells for strains Y and F, respectively, 48 and 50 nM/2 x 10(6) for strains Costalimai and M226, at different days after infection. Histopathological findings of myositis, myocarditis, necrotizing arteritis and absence of macrophage parasitism were found for strains F and Costalimai. Y strain infection presented moderate myocarditis and myositis, with parasites multiplying within macrophages. In C. callosus all four strains resulted in patent parasitemia which was eventually overcome, with scarce mortality. H2O2 release for strains Y and F was comparable to that of mice-peaks of 27 and 53 nM/2 x 10(6) cells, with lower values for strains Costalimai and M226-16.5 and 4.6 nM/2 x 10(6) cells, respectively. Histopathological lesions with Y and F strain injected animals were comparable to those of mice at the onset of infections; they subsided completely at the later stages with Y strain and partially with F strain infected C. callosus. In Costalimai infected C. callosus practically no histopathological alterations were observed.  (+info)

Chagas' disease. (75/382)

Chagas' disease, caused by Trypanosoma cruzi, is an important cause of morbidity in many countries in Latin America. The important modes of transmission are by the bite of the reduviid bug and blood transfusion. The organism exists in three morphological forms: trypomastigotes, amastigotes, and epimastigotes. The mechanism of transformation and differentiation is currently being explored, and signal transduction pathways of the parasites may be involved in this process. Parasite adherence to and invasion of host cells is a complex process involving complement, phospholipase, penetrin, neuraminidase, and hemolysin. Two clinical forms of the disease are recognized, acute and chronic. During the acute stage pathological damage is related to the presence of the parasite, whereas in the chronic stage few parasites are found. In recent years the roles of tumor necrosis factor, gamma interferon, and the interleukins in the pathogenesis of this infection have been reported. The common manifestations of chronic cardiomyopathy are arrhythmias and thromboembolic events. Autoimmune, neurogenic, and microvascular factors may be important in the pathogenesis of the cardiomyopathy. The gastrointestinal tract is another important target, and "mega syndromes" are common manifestations. The diagnosis and treatment of this infection are active areas of investigation. New serological and molecular biological techniques have improved the diagnosis of chronic infection. Exacerbations of T. cruzi infection have been reported for patients receiving immuno-suppressive therapy and for those with AIDS.  (+info)

Pathophysiology of the heart in Chagas' disease: current status and new developments. (76/382)

In the present review we have summarized remarkable historical data on Chagas' disease studies putting special emphasis on histopathological findings and pathogenetic theories as well as recent discoveries based on the use of advanced modern technologies in pathology and immunology. A unified theory that links almost all of these findings is proposed. Chronic cardiac Chagas' disease represents the result of a close interaction between the host and the parasite, causing different clinical pictures: patients with an efficient immune response may adequately circumvent the parasitic infection and the individual will develop the indeterminate form. Deficient immune response of the host and/or a high initial parasitemia favor an immune imbalance that might lead to development of a permanent inadequate immunological response against the parasite. The inflammatory response, which is probably recurrent, undergoing periods of more accentuated exacerbation, is most likely responsible for progressive neuronal damage, microcirculatory alterations, heart matrix deformations and consequent organ failure.  (+info)

Chagas' disease and the involvement of the autonomic nervous system. (77/382)

Chagas' disease is a major endemic disease in Latin America and a great cause for concern due to its high incidence: it afflicts 16 to 18 million individuals and places over 90 million people at risk of infection. At present, five mechanisms can be proposed to explain the pathogenesis of chronic Chagas cardiopathy: 1. direct lesion of the tissue by Trypanosoma cruzi; 2. dysfunction of the autonomic nervous system (neurogenic concept); 3. microvascular disease; 4. immunologic reaction; 5. alterations in the extracellular matrix. The neurogenic concept is the most attractive explanation for the pathogenesis of chronic Chagas cardiopathy through the involvement of the autonomic nervous system, an issue that has been prominent ever since Chagas first initiated research in the field. Koberle, in his pioneering studies on the role of the autonomic nervous system in Chagas patients in the 1950s, adopted the technique of neuron counts, whereby he registered a reduction in parasympathetic nerve cells, and thus considered Chagas cardiopathy a "parasympathetic reduction" with predominance of the sympathetic. In the 1960s, systematic studies on autonomic function, organized by Professor Dalmo Amorim, were initiated in the School of Medicine in Ribeirao Preto. Several aspects of cardiac autonomic control were later described independently by teams in Brazil (Ribeirao Preto and Brasilia), Argentina (Cordoba) and Venezuela (Merida). In general, the studies performed in Ribeirao Preto by Amorim and Marin Neto and in Brasilia by Junqueira Jr. reflected the functional involvement of the parasympathetic system, while the studies performed in Cordoba were linked with the view of cardiovascular sympathetic dysfunction. In Brazil, the involvement of the sympathetic system, with relation to the functional aspect of sympathetic denervation, is well characterized by Marin Neto through the assessment of heart rate using the tilt test in both Chagas and control groups. Further evidence of autonomic nervous system dysfunction in Chagas' disease as a factor modulating complex ventricular arrhythmias was demonstrated by Pedrosa (RJ), who reported on a specific group of chronic Chagas patients with complex ventricular arrhythmias and dilated cardiopathy. In this study, when serum from chronic Chagas patients showing neither complex ventricular arrhythmias nor ventricular dilation was inoculated in isolated rabbit hearts, it produced no harmful effect in the conduction system, in contrast to what was observed in the conduction system of rabbits inoculated with serum from the Chagas patients group with complex ventricular arrhythmias and ventricular dilatation. These facts confirm Carlos Chagas as the pioneer in postulating involvement of the autonomic nervous system in Chagas' disease, and provide an important opportunity to understand ventricular involvement in chronic Chagas cardiopathy.  (+info)

Myosin autoimmunity is not essential for cardiac inflammation in acute Chagas' disease. (78/382)

Infection with the protozoan parasite Trypanosoma cruzi leads to acute myocarditis that is accompanied by autoimmunity to cardiac myosin in susceptible strains of mice. It has been difficult to determine the contribution of autoimmunity to tissue inflammation, because other inflammatory mechanisms, such as parasite-mediated myocytolysis and parasite-specific immunity, are coincident during active infection. To begin to investigate the contribution of myosin autoimmunity to myocarditis, we selectively inhibited myosin autoimmunity by restoring myosin tolerance via injection of myosin-coupled splenocytes. This tolerization regimen suppressed the strong myosin-specific delayed-type hypersensitivity (DTH) that normally develops in infected mice, although it did not affect myosin-specific Ab production. Suppression of myosin autoimmunity had no effect on myocarditis or cardiac parasitosis. In contrast, myosin tolerization completely abrogated myocarditis in mice immunized with purified myosin, which normally causes severe autoimmune myocarditis. In this case, myosin-specific DTH and Ab production were significantly reduced. We also examined the contribution of T. cruzi-specific immunity to inflammation by injection of T. cruzi-coupled splenocytes before infection. This treatment reduced T. cruzi DTH, although there was no effect on parasite-specific Ab production. Interestingly, cardiac inflammation was decreased, cardiac parasitosis was significantly increased, and mortality occurred earlier in the parasite-tolerized animals. These results indicate that myosin-specific autoimmunity, while a potentially important inflammatory mechanism in acute and chronic T. cruzi infection, is not essential for inflammation in acute disease. They also confirm previous studies showing that parasite-specific cell-mediated immunity is important for myocarditis and survival of T. cruzi infection.  (+info)

Cardiovascular function in elderly patients with chronic chagasic cardiopathy. (79/382)

The objective of this work was to verify the degree and type of heart damage of elderly chagasic patients seen at an outpatient referral center and to compare them with the changes found in young chagasic patients with a similar degree of heart damage. Elderly and young patients without advanced cardiopathy presented good functional behavior. Elderly patients with advanced cardiopathy had more ventricular premature beats (VPB) in 24 h and less functional capacity in the exercise test than young patients of the same subgroup. There was a higher occurrence of effort-induced VPB and a lower prevalence of severe forms in elderly men, suggesting that Chagas' disease may have a worse evolution in males. The association of cardiac damage characteristic of aging with the secondary damage due to Chagas' disease could explain the greater functional damage found in elderly chagasic patients. Thus, it appears that the physiopathological components of Chagas' disease do have an influence on the clinical course of cardiopathy in the elderly population.  (+info)

Cerebral infarction in autopsies of chagasic patients with heart failure. (80/382)

OBJECTIVE: To determine the frequency of encephalic infarction and its contribution to lethality in patients with Chagas' disease and heart failure. METHODS: Medical records and autopsy reports of patients with Chagas' disease complicated by heart failure, who died at the Professor Edgar Santos Hospital of the Federal University of Bahia in the past 45 years were retrospectively analyzed. Data comprised information regarding the clinical history on hospital admission, complementary and anatomicopathological examinations, including the presence of encephalic infarction, the impaired region, and the cause of death. RESULTS: Of the 5,447 autopsies performed, 524 were in patients with heart failure due to Chagas' disease. The mean age was 45.7 years, and 51 (63%) patients were of the male sex. The frequency of encephalic infarction was 17.5%, corresponding to 92 events in 92 individuals, 82 (15.8%) of which involved the brain, 8 (1.5%) involved the cerebellum, and 2 (0.4%) involved the hypophysis. CONCLUSION: Cerebral infarction has been a frequent finding in autopsies of chagasic patients with heart failure, and it has been an important cause of death in our region. The presence of cerebral infarction and its complications have been associated with death in 52% of the cases studied.  (+info)