Abstract

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.

1. Introduction

Chagas’ disease, caused by the hemoflagellate protozoan Trypanosoma cruzi, is a widespread disease that affects millions of people in South and Central America. The incidence of the disease varies from country to country, basically related to the implantation of national control programs to exterminate the domestic vector of Trypanosoma cruzi. Even though, according to the Word Health Organization, 16–18 million people are infected by the parasite in South America, and another 90 million are at risk of becoming infected. In Brazil, the prevalence is around 4%, corresponding to 6 million people [1]. Chronic chagasic cardiopathy (CCC) is the most devastating manifestation of Chagas’ disease, affecting about a third of the infected people. Despite this obvious clinical importance the pathogenesis of CCC is still poorly understood. Chronic Chagas’ disease is still an incurable disease, but only some of the infected patients exhibit late clinical manifestations. Most of the contaminated people remain asymptomatic (indeterminate form) and around 30% of them present cardiac and digestive complications, in a late phase of the disease. Patients presenting cardiopathy usually show progressive heart failure, cardiac arrhythmias or both. The pathogenesis of chronic Chagas’ heart disease involves many interrelated factors that will be summarized in this review.

2. Outstanding historical facts

The first descriptions of the etiopathology and clinical characteristics of Chagas’ disease were provided at the beginning of the last century by Chagas [2] and Vianna [3]. According to these authors, the acute phase of the disease is characterized by high numbers of T. cruzi parasites in the blood or lymphatic vessels, parasitism of almost all cell types, preferentially muscle fibers and inflammation. Carlos Chagas [4] pointed out differences between the acute and chronic forms of the disease, emphasizing the high degree of cardiac involvement with severe myocardial parasitism during the acute phase and low number of parasites associated with the myocarditis in the chronic form. Several early studies on Chagas’ disease [5–7] have already emphasized the scarcity of parasites in histological sections during the chronic form as well as the presence of severe myocardial fibrosis.

In 1929 [8] and 1941 [9], Torres argued that chronic chagasic myocarditis was a result of an active and progressive myocarditis due to a continued action of the parasite associated with an ‘allergic’ state of the host. Some authors failed to demonstrate such an ‘allergic’ state by cutaneous tests [10,11] but Muniz and Penna in 1947 [12] provoked myocarditis and granulomas in the pleura by inoculating T. cruzi antigens in monkeys previously treated with endovenous injections of T. cruzi lysates. Mazza [13] and Mazza and Miyara [14] reported human cases of chronic Chagas' disease with allergic cutaneous manifestations while Mazza and Jorg [15] induced a Schwartzman phenomenon in dogs by injecting T. cruzi products. Andrade and Andrade [16] and Torres [9] postulated that chronic chagasic patients would react hyperergically to the presence of parasites.

The papers by Köberle and co-workers [17,18] had an outstanding influence on future strategies in Chagas research, by proposing an original and attractive idea: CCC should be considered as a neuronal cardiopathy that primarily affects the parasympathetic autonomous system. According to this hypothesis, megaesophagus, megacolon and cardiac dilation in Chagas' disease are consequences of the denervation of the parasympathetic autonomous system, whereas the myocardial inflammation should not be considered as an important element for cardiac failure [19–21]. Several authors have demonstrated [17,22–25] a diminished number of parasympathetic cardiac ganglion cells in chagasic hearts. Koberle [26] proposed that exacerbation of the sympathetic action would cause myocardial hypertrophy and dilation of the ventricles. In rats, high doses of catecholamines induced a dilated cardiopathy with an apical lesion [27]. A proposed T. cruzi neurotoxin has never been confirmed and a lack of correlation between parasympathetic ganglia lesions and cardiac alterations in chagasic patients has kept such theory in check [28–30]. Auto-immunity against neurons has also been suggested [31]. Recent studies did not identify neuronal depletion in the heart, only slight neuronal damage. The authors concluded that such neuronal lesions occur as an epiphenomenon in a heart presenting several pathological alterations, mainly inflammation and fibrosis [32,33]. Favoring such a point of view, degenerative lesions of neurons in CCC have been found to be dependent on the inflammatory infiltrate [30,34].

3. Knowledge obtained from endomyocardial biopsies

Endomyocardial biopsies from patients in different clinical stages of Chagas' disease have provided new insights on some important questions, in particular on the inflammatory process and the development of heart failure. An early autopsy study had suggested that inflammatory infiltrate was also present in patients presenting the indeterminate form of Chagas' disease [35]. However, more recent biopsy studies have outlined that patients with heart failure presented higher percentages of severe myocarditis, fibrosis and myocardial hypertrophy compared to patients in indeterminate and cardiac arrhythmic forms. According to these observations, CCC may be considered a progressive, fibrotic disease in which myocardial inflammation plays a fundamental role [36–38]. The microscopic characteristics of the myocardium in chronic chagasic hearts are shown in Fig. 1. Comparison of endomyocardial biopsies in acute and chronic phases demonstrated that patients in acute phase present 100% of myocarditis and 58% of T. cruzi antigens, whereas in patients in the chronic phase these values were reduced to 45% of myocarditis and 0% of T. cruzi antigens [39]. Another finding of this study was that the number of CD4+ T cells increased in parallel to the number of CD8+ T cells (r = 0.91) in the acute phase but not in the chronic phase (r = 0.42), suggesting an immunologic imbalance response in the late phase of the disease. In the chronic phase, patients with heart failure present a predominance of CD8+ T cells, with a CD4+/CD8+ T cell ratio of 0.8. The lack of parasite antigens in biopsy material from patients in the chronic phase is expected as, according with which we will describe latter, it seems necessary to examine several different sections of the heart to detect the parasite in this phase of the disease.

Fig. 1

Microscopic images demonstrating the main histopathological characteristics of chronic chagasic cardiopathy. (A) Severe myocarditis with many lymphocytes aggressing non-infected hypertrophic myocytes (H&E staining, objective magnification: 40 ×). (B) Diffuse myocardial fibrosis, involving each myocardial fiber and focal dense fibrosis associated with thickened arterioles, suggestive of ischemic injury (Masson trichrome staining, objective magnification: 20 ×). (C) A whole myocardial fiber containing a large pseudocyst of T. cruzi (arrow), that did not elicit inflammatory reaction (Masson trichrome staining, objective magnification: 100 ×). (D) Macrophages containing antigens of T. cruzi (arrow) in the middle of a granulomatous arrangement (immunoperoxidase technique, objective magnification: 40 ×).

Fig. 1

Microscopic images demonstrating the main histopathological characteristics of chronic chagasic cardiopathy. (A) Severe myocarditis with many lymphocytes aggressing non-infected hypertrophic myocytes (H&E staining, objective magnification: 40 ×). (B) Diffuse myocardial fibrosis, involving each myocardial fiber and focal dense fibrosis associated with thickened arterioles, suggestive of ischemic injury (Masson trichrome staining, objective magnification: 20 ×). (C) A whole myocardial fiber containing a large pseudocyst of T. cruzi (arrow), that did not elicit inflammatory reaction (Masson trichrome staining, objective magnification: 100 ×). (D) Macrophages containing antigens of T. cruzi (arrow) in the middle of a granulomatous arrangement (immunoperoxidase technique, objective magnification: 40 ×).

4. The parasite versus autoimmunity

The relative lack of parasites in the myocardium during the chronic phase originated many autoimmune theories, of both humoral and cellular origin. Cossio et al. [40] described a serum antibody in chagasic patients that reacted against myocardial and skeletal muscle, endocardium, vessels, and interstitium. This antibody was called EVI factor and was found in almost 100% of patients with CCC, whereas it was absent in normal individuals or in patients with other diseases [41]. However, immunoglobulins were not detected in myocardial biopsies from patients presenting CCC, indicating that the EVI factor probably does not participate directly in the genesis of myocarditis [42,43]. On the other hand, there is evidence for the participation of antibodies in some lesions. A necrotizing arteritis has been observed in humans and in experimental chagasic disease, probably related to the humoral response of the host to parasitic antigens [44,45]. A growing number of reports have suggested a pathogenic role of antibodies present in the serum of chagasic patients that reacts against muscarinic and adrenergic receptors of cardiomyocytes [46,47]. The production of autoantibodies against β-adrenoreceptors and other receptors may interfere with cardiac and mechanical activities of myocardial cells [48–50].

Teixeira and co-workers [51–53] demonstrated that chronic T. cruzi infection induces the appearance of lymphocytes with specific cytotoxicity against myocardial fibers. Myocarditis was obtained by injecting several doses of subcellular antigens of T. cruzi in rabbits, suggesting cellular autoimmunity and delayed hypersensitivity to T. cruzi antigens. Common antigens between T. cruzi and human myocardial fibers, auto-reactive T cells specific to heart or nerve tissue antigens have been demonstrated in experimental animals and patients [54–59]. These autoimmune theories suggest that the myocarditis perpetuates independently of the presence of the parasite [60,61]. An interesting finding in favor of such a theory was obtained by Ribeiro-dos-Santos et al. [62] using a heterotopic heart transplant model. They transplanted syngeneic hearts of normal mice in ears of T. cruzi infected mice, resulting in rejection of the transplanted hearts by CD4+ T cells. However, a similar experiment performed by others did not result in graft rejection except when parasites could be found in the heart graft [63].

In our view, only autoimmunity is not sufficient to explain the multifocal nature of the myocarditis and the preferential location of fibrosis in certain regions such as the apical or the posterior left ventricular wall in CCC. Moreover, frequent positive xenodiagnosis during the chronic phase of Chagas' disease and during episodes of reactivation in immunocompromised patients (by AIDS, neoplasia or cardiac transplant) has provided evidence that the parasite is present under active control of the immunological system of the host in the chronic phase [64,65].

Knowledge of the exact role of the parasite in the pathogenesis of CCC appears extremely important to guide potential therapeutic strategies. If chronic chagasic myocarditis is an autoimmune process independent of the presence of the parasite, administration of a vaccine may also induce myocarditis. On the other hand, if the persistence of the parasite is the principal cause of the late cardiac manifestations of the disease, the control of a possible autoimmune disease through immunodepressive drugs, may lead to reactivation of the infectious agent. In this hypothesis, the elimination of the parasite should be the primary focus of any therapeutic intervention.

The presence of Trypanosoma cruzi in the chronic phase of the disease has been already observed in early descriptions [3] and has been emphasized later by other authors [66,67]. Nevertheless, the number of parasites is disproportionately low in relation to the intensity of the myocarditis and whole myocardial fibers containing parasites do not elicit inflammation (Fig. 1C). Recent studies using modern techniques such as immunohistochemistry and polymerase chain reaction (PCR) have demonstrated higher frequencies of T. cruzi antigens (Ags) in CCC, providing evidence that the presence of T. cruzi Ags are indeed associated with myocardial inflammation (Fig. 1D). T. cruzi Ags were detected in 100% of hearts from chronic chagasic patients that died due to heart failure when several samples of the myocardium were analyzed [68,69]. In these studies, we observed no direct correlation between the amount of T. cruzi Ags and the intensity of the inflammatory infiltrate but a significant association between the presence of T. cruzi Ags and severe or moderate inflammation. Parasite Ags probably work as a trigger for the hypersensitive response against the myocardial fibers. Experimental studies in mice [70] and guinea pigs [71] have provided similar results. Jones et al. [72] have described a high incidence of T. cruzi DNA using the PCR technique in myocardial fragments exhibiting significant inflammation. T. cruzi antigens were also detected in myocardial biopsies [73].

Thus, in agreement with others [74], we believe that the pathogenesis of chronic myocarditis in Chagas' disease is directly related to the presence of the parasite, although additional immunological mechanisms are probably involved. De Brito [75] proposed that T. cruzi might function as an adjuvant for an immunological cross-reaction between common parasitic and myocardial fiber antigens, resulting in severe lymphocytic myocarditis.

5. Immunosuppression, cytokines, adhesion molecules and MHC antigens

Acute experimental studies [76] and reports in humans [77] have provided convincing evidence that T. cruzi, like other parasitic infective agents, induces alterations in the immunological system of the hosts to circumvent their defense mechanisms before, during and after entry into their cells. T. cruzi decreases the expression of the lymphocyte surface molecules CD3+, CD4+ and CD8+ [78] favoring its own survival. Studies on myocardial biopsy fragments from patients with chronic chagasic myocarditis have demonstrated that the inflammatory infiltrate was mainly composed of T cells, with a predominance of CD8+ T cells [79,80]. CD4+ T cells were present in lower numbers and were only mildly stained compared to CD8+ T cells. The number of CD8+ T cells increased in the presence of scarce or abundant T. cruzi antigens, while the number of CD4+ T cells remained unchanged [81]. These findings reinforce the hypothesis that T. cruzi Ags play a fundamental role in the development of chronic myocarditis, and that a certain degree of immunosuppression is present during this phase of the disease.

Administration of IL-2 [82] restores the immune response in experimental T. cruzi infection. In situ quantitative analysis of cytokines present in the myocardium of chronic chagasic patients by immunohistochemical techniques also revealed a severe, immune depressed helper T cell response: Very few lymphocytes stained positively for IL-2+ and IL4+; however the number of IL4+ cells increased in cases with abundant pseudocysts of T. cruzi amastigotes, suggesting that this cytokine, as in other infectious diseases, is related to the dissemination of the parasite. On the other hand, IFNγ+ lymphocytes were present in higher numbers mainly in those groups of patients, in which T. cruzi Ags were absent or scarce, suggesting that this cytokine is related to the control of the infection [83]. It seems that Th2 response favors the permanence of the parasite in the myocardium in human chronic chagasic disease. In contrast, experimental data in mice [84] showed that CD4+ T cells and the TH2 subset are responsible for the control of parasitic infection and that both may be involved in the autoimmune response.

Macrophages are active cells for the control and killing of parasites by oxidative and non-oxidative mechanisms. On the other hand, macrophages may also serve as host cells that facilitate the replication and survival of pathogens. IL-10 is a cytokine that presents immunosuppressive functions by down-regulating the macrophage production of IFN-γ, NO and by decreasing expression of class II MHC antigens. Neutralization of IL-10 increases the resistance to infection with certain pathogens, including T. cruzi. Despite an early resistance, IL-10-deficient mice died within the third week of infection, whereas all control mice survived acute infection with a toxic-like syndrome, possibly mediated by systemic TNF-α overproduction [85,86]. This represents a highly interesting new field in research that deserves future studies. Some interesting gender differences have been observed in patients with CCC. Usually, women seem to present a better clinical outcome than men [87]. In an autopsy study of chagasic patients that died due to severe heart failure, we found a significant difference between men and women regarding the composition of the myocardial inflammatory cells [88].

Adhesion molecules are very important for the development of inflammation. Although the normal myocardium presents ICAM-1 on endothelial cells, we detected an up-regulation of this molecule and induction of VCAM-1 expression on capillaries and venules in patients with CCC. Besides the endothelium, some cases also presented induction of ICAM-1 expression on the sarcolemma of myocytes [89]. Adhesion molecules seem to be over-expressed not only in the myocardium, but also in the blood of patients with Chagas' disease. Laucella et al. [90] described reduced serum levels of some adhesion molecules after specific chemotherapy with benznidazole in children with the indeterminate phase of Chagas' disease, suggesting that measurement of these molecules could be a valuable tool to evaluate the parasitological clearance.

MHC antigens are also up-regulated in the myocardium of patients with CCC. We detected an up-regulation of class I MHC in the sarcolemma of myocytes (Fig. 2C), and there is also evidence for an over-expression of class II MHC in endothelial cells of patients with CCC [89,91]. However, it is important to realize that up-regulation of adhesion molecules and MHC antigens in CCC appear to be related to the presence of myocarditis. We did not detect over-expression of these molecules in the myocardium of patients with idiopathic dilated cardiomyopathy [89] that did not present myocardial inflammation (Fig. 2D). Since inflammatory cytokines have been demonstrated in inflammatory foci in hearts of patients with chagasic cardiomyopathy, they are probably responsible for the up-regulation of adhesion molecules and MHC antigens [92]. However, over-expression of adhesion molecules on the endothelium is probably very important to perpetuate inflammation and the up-regulation of class I MHC antigens on myocytes could represent a target for CD8+ T lymphocyte adhesion, promoting direct cytotoxicity.

Fig. 2

Microscopic features comparing chagasic cardiopathy (left side) and idiopathic dilated cardiomyopathy (right side). (A) Staining of the extracellular matrix in chagasic myocardium by the Del Rio Hortega technique, emphasizing increased collagen fibers surrounding the myocytes (struts, coins and weaves) (objective magnification: 16 ×). (B) Dilated cardiomyopathy presents attenuated and ruptured collagen fibers (objective magnification: 40 ×). (C) Class I HLA antigens are present on the membranes of myocytes in chagasic hearts. (D) Dilated cardiomyopathy presents class I HLA antigens on endothelial cells of capillaries, whereas no staining of myocytes becomes obvious (immunoperoxidase technique, objective magnification: 40 ×). (E) Membrane attack complex of the complement (C5b-9) is expressed on the membranes of myocytes in chagasic myocardium. (F) Dilated cardiomyopathy shows positivity only in the subendothelial layer of arterioles and venules, as seen in the right lower corner (immunoperoxidase technique, objective magnification: 40 ×). (G) TUNEL-staining in chagasic myocardium is restricted to apoptotic interstitial cells (green fluorescence). At least one of the apoptotic interstitial cells is double-stained with the human macrophage marker CD68 (red fluorescence) (objective magnification: 40 ×). (H) In contrast, many TUNEL-stained apoptotic cardiomyocytes (yellow fluorescence) are present in dilated cardiomyopathy. Red fluorescence indicates muscular elements as stained with Phalloidin (objective magnification: 40 ×).

Fig. 2

Microscopic features comparing chagasic cardiopathy (left side) and idiopathic dilated cardiomyopathy (right side). (A) Staining of the extracellular matrix in chagasic myocardium by the Del Rio Hortega technique, emphasizing increased collagen fibers surrounding the myocytes (struts, coins and weaves) (objective magnification: 16 ×). (B) Dilated cardiomyopathy presents attenuated and ruptured collagen fibers (objective magnification: 40 ×). (C) Class I HLA antigens are present on the membranes of myocytes in chagasic hearts. (D) Dilated cardiomyopathy presents class I HLA antigens on endothelial cells of capillaries, whereas no staining of myocytes becomes obvious (immunoperoxidase technique, objective magnification: 40 ×). (E) Membrane attack complex of the complement (C5b-9) is expressed on the membranes of myocytes in chagasic myocardium. (F) Dilated cardiomyopathy shows positivity only in the subendothelial layer of arterioles and venules, as seen in the right lower corner (immunoperoxidase technique, objective magnification: 40 ×). (G) TUNEL-staining in chagasic myocardium is restricted to apoptotic interstitial cells (green fluorescence). At least one of the apoptotic interstitial cells is double-stained with the human macrophage marker CD68 (red fluorescence) (objective magnification: 40 ×). (H) In contrast, many TUNEL-stained apoptotic cardiomyocytes (yellow fluorescence) are present in dilated cardiomyopathy. Red fluorescence indicates muscular elements as stained with Phalloidin (objective magnification: 40 ×).

6. Heart failure and natriuretic peptides

Atrial and brain natriuretic peptides (ANP and BNP, respectively) are elevated in the blood and ventricular tissues in several cardiac diseases evolving with cardiac hypertrophy and heart failure. The main stimulus for a ventricular production of these peptides is elevation of the wall stress of the ventricular chambers. In these settings, the ventricular production of ANP and BNP can be increased dramatically, approaching the levels in the atria, where these peptides are normally produced.

With regard to Chagas' disease, there is evidence for elevated blood levels and ventricular up-regulation of ANP and BNP in both acute experimental and chronic human chagasic cardiomyopathy [93–95]. It is interesting to note that myocarditis itself does not appear to influence the expression of ANP in ventricular myocytes. In CCC, the expression of ANP was restricted to the subendocardial region, where wall stress is higher, and the peptide was not found around inflammatory foci located away from the subendocardial region [94]. As in other cardiac diseases, the measurement of BNP in the blood of patients with Chagas' disease is considered to be a very sensitive and specific method to detect asymptomatic heart dysfunction [95]. Since the detection of BNP in the blood is easy to perform, this can lead to reevaluation of the concept of the indeterminate phase of the disease.

In summary, ANP and BNP are elevated in the blood and ventricular tissues of patients with chagasic cardiomyopathy and ventricular dysfunction. However, the increased synthesis of the peptides seems not to be directly related to inflammation, but is probably due to the altered hemodynamic conditions and the elevation of the wall stress in the cardiac chambers.

7. Dilated chagasic cardiopathy versus idiopathic dilated cardiomyopathy

In this section, idiopathic dilated cardiomyopathy (IDC) is defined as a poorly functioning dilated heart without evidence of coronary artery disease, valve disease, congenital heart malformation or uncompensated hypertensive heart disease. CCC is frequently used as a model of a dilated cardiomyopathy with a defined etiology, in the concept that both probably have a similar structural disarrangement that leads to ventricular dilatation. Experimental works with T. cruzi have been performed with the aim to achieve a better understanding of dilated cardiomyopathy and its treatment [96–98]. However, we like to point out some important histopathological differences that have been observed between IDC and CCC that alert for different therapeutic approaches. In contrast to CCC, IDC is usually characterized by absent or only mild myocarditis and less fibrosis that does not surround each myocardial fiber [39]. A network of fibrillar collagen enveloping the myocardial fibers and tethering each other is important for the maintenance of normal shape and efficient contraction of the heart [99,100]. In IDC, attenuation and rupture of extracellular matrix connections occur that might favor the slippage of those myocardial fibers, which are thin and stretched. In Chagas' disease, the most important feature is a dense extracellular collagen accumulation enclosing each fiber or group of myocardial fibers, which probably prevents their normal distension and contraction (Fig. 2A,B). The lateral connections are preserved within the groups of cardiac fibers, which usually are severely hypertrophic [101]. The presence of parasitic antigens may induce fibrogenesis.

Myocardial lymphocytes and macrophages may favor the development of fibrosis by production of cytokines and growth factors [83,102]. Regarding some growth factors, we have observed a strong correlation between numbers of PDGF-A+ and PDGF-B+ cells. In contrast, there was a lack of correlation between PDGF-A and TGF-β1; PDGF-A and GM-CSF; and between PDGF-B and TGF-β1. GM-CSF and TGF-β1, which are considered important elements for the immune response against T. cruzi parasites, were present in very scarce amounts [103,104]. In contrast, IL-15 seems to be involved in survival and proliferation of CD8+ T cells and IL-2 [105,106]. Recent studies have indicated that IL-15 may also play an important role in chronic chagasic myocarditis. Addition of IL-15 induced growth of CD8+ T cell cultures, obtained from chagasic endomyocardial biopsies [107] and IL-15+ T cells were found to be abundant in chronic chagasic myocardial sections [108].

It has been shown that endothelial cells infected with T. cruzi display higher platelet adherence and aggregation [97]. The neuraminidase produced by the parasite removes sialic acid components from the endothelial surface and may favor linkage with thrombin. Large amounts of C3 and C5b-9 products were present on the surface of T. cruzi amastigotes and could explain the resistance of amastigotes to destruction by complement action, as well as the presence of trypomastigote decay-accelerating factor [109]. These products may also favor thrombosis [110]. In chronic human chagasic disease, the mechanism of release of growth factors has not been completely clarified and a possible role of sub-lytical amounts of MAC (C5b-9—membrane attack complex of the complement cascade) inducing such release was studied, comparing IDC and CCC. C5b-9 was detected on the sarcolemma of myocytes in hearts with CCC but not in hearts from patients with IDC (Fig. 2E,F). These findings suggest that C5b-9 may be involved in the pathogenesis of the fibrosis that surrounds each myocardial fiber in chagasic specimens [111]. This type of fibrosis has also been demonstrated by confocal microscopy [101] and scanning electron microscopy [112]. The presence of the parasite in the extracellular matrix may induce fibrogenesis although the pathogenesis is not very well understood [113]. On the other hand, T. cruzi has collagenolytic and proteolytic properties [114], which may contribute to the destruction of the extracellular matrix, favoring cardiac remodeling and heart failure.

Cardiomyocyte apoptosis as well as proliferation have been described in congestive heart failure, but their clinical relevance remains unclear. Interestingly, we have observed different amounts of myocardial cell apoptosis between IDC and chagasic hearts. In a recent study, apoptosis of myocardial fibers correlated with bad long-term outcome after a surgical treatment of IDC [115]. In an ongoing study, we are analyzing whether apoptosis of myocardial cells occurs in chagasic patients with severe heart failure. Apoptosis was detected by a fluorescent TUNEL assay (Roche) and by caspase-3 immunohistochemistry in myocardial fragments from chagasic hearts. By both methods, apoptotic cells were detected in high numbers in all fragments examined. However, all TUNEL- or caspase-3 positive cells were interstitial cells and no apoptotic cardiomyocyte at all could be detected [116]. The majority of the TUNEL- and caspase-3 stained interstitial cells showed morphological characteristics of inflammatory mononuclear cells. A double-labeling approach indicated that a great percentage of apoptotic interstitial cells stained positively for the human macrophage marker CD68 (Fig. 2G) and also demonstrated that apoptosis of CD4 T-cells seems not to be an important event in human chronic Chagas' disease. Negative TUNEL-staining of cardiomyocytes was also obtained by Rossi et al. [117], leading to the conclusion that the absence of apoptosis in cardiomyocytes suggests that necrosis rather than apoptosis should be considered as the mechanism of myocardial cell loss in CCC. In an in vitro study, the transialidase produced by T. cruzi inhibited the apoptosis of Schwann cells [118]. The role of T. cruzi in such phenomenon needs further investigation. In contrast, experimental T. cruzi infection was accompanied by the occurrence of severe apoptosis of lymphocytes [119]. Furthermore, in vitro, CD4+ T cells apoptosis exacerbated parasite replication in co-cultured macrophage infected with T. cruzi[120]. The mechanisms of such a replication have been suggested to be related to prostaglandins E2/TGF-β in macrophages and it was shown that cyclooxygenase inhibitors almost completely ablate it [121].

8. Microcirculation, fibrosis and ischemic lesions in chagasic hearts

Severe myocardial fibrosis associated with microvascular alterations has been described long time ago [16,122]. Recent experimental studies on acute Chagas' disease have demonstrated microvascular alterations characterized by microspasms [123], microthrombi [124], dysfunction of endothelial cells and increased platelet activity [125,126]. All of these phenomena may play an important role in the further development of myocytolysis and fibrosis. In our previous work analyzing the interstitial alteration versus microvascular status in chagasic and non-chagasic dilated hearts, a severe microvascular dilatation was only observed in chagasic hearts [101]. We hypothesize that the lack of arteriolar contraction might be due to the presence of vasodilator substances induced by the inflammation and/or by the parasite. This may cause impaired myocardial irrigation in distal areas of the coronary branches. Such a low blood pressure perfusion should be present mainly at the watershed zones between two main coronary artery branches. The resulting ischemia would explain fibrotic lesions at the following loci: (1) the apex (Fig. 3A,B), a watershed zone between the anterior descending and the posterior descending arteries; (2) the posterior lateral wall of the left ventricle (Fig. 3C), a borderzone between the right coronary and circumflex arteries, and (3) fibrotic segmental lesions in the conduction system [127,128] (Fig. 3D) which is doubled irrigated. In addition, the epicardial coronary artery cross-sectional luminal areas are diminished in left ventricular wall dysfunctional segments where they frequently exhibit the appearance of fibrotic thinning of the myocardium that sometimes was substituted by adipose tissue [112,129]. These regions are generally related to the origin of sustained ventricular tachychardia in chronic chagasic patients and they exhibit a similar histopathological pattern as a healed myocardial infarction. Similar as in ventricular sustained tachycardia of myocardial infarction scars, the radiofrequency by catheter ablation may block such malignant arrhythmia [130]. Fig. 4 demonstrates schematically such possible ischemic focal lesions.

Fig. 4

Schematic representation of cardiac blood perfusion in a chagasic heart: Autopsy hearts from chagasic patients with heart failure present a typical microvascular dilatation that may cause impaired blood perfusion in borderzones. This scheme would explain focal fibrotic lesions in the following heart regions: (1) between anterior descending and posterior descending branches causing apex aneurism; (2) between circumflex and distal right coronary arteries causing posterior wall fibrotic lesion; and (3) between first septal perforating artery and atrioventricular nodal artery originating from dominant coronary artery at the crux cordis leading to segmental fibrosis of the His bundle and its branches (LA, left atrium; RA, right atrium; RV, right ventricle; LV, left ventricle; SA, sinoatrial node; AV, atrioventricular node).

Fig. 4

Schematic representation of cardiac blood perfusion in a chagasic heart: Autopsy hearts from chagasic patients with heart failure present a typical microvascular dilatation that may cause impaired blood perfusion in borderzones. This scheme would explain focal fibrotic lesions in the following heart regions: (1) between anterior descending and posterior descending branches causing apex aneurism; (2) between circumflex and distal right coronary arteries causing posterior wall fibrotic lesion; and (3) between first septal perforating artery and atrioventricular nodal artery originating from dominant coronary artery at the crux cordis leading to segmental fibrosis of the His bundle and its branches (LA, left atrium; RA, right atrium; RV, right ventricle; LV, left ventricle; SA, sinoatrial node; AV, atrioventricular node).

Fig. 3

Macroscopic and microscopic chagasic features, emphasizing the segmental myocardial fibrosis. (A) A chronic chagasic heart exhibits severe dilation of left and right ventricles plus thinning, fibrosis and thrombosis of the left ventricular apex (arrow). (B) A moderately dilated and hypertrophic left ventricle showing segmental fibrosis on the apex (arrow), considered to be a pathognomonic lesion of Chagas heart disease. (C) Fibrotic thinning of the myocardium adjacent to the mitral valve at the posterior wall of the left ventricle (arrow). (D) Microscopic view of the bifurcation of the His bundle showing segmental fibrosis (asterisk) at the origin of the right bundle branch (Masson trichrome, objective magnification: 2.5 ×).

Fig. 3

Macroscopic and microscopic chagasic features, emphasizing the segmental myocardial fibrosis. (A) A chronic chagasic heart exhibits severe dilation of left and right ventricles plus thinning, fibrosis and thrombosis of the left ventricular apex (arrow). (B) A moderately dilated and hypertrophic left ventricle showing segmental fibrosis on the apex (arrow), considered to be a pathognomonic lesion of Chagas heart disease. (C) Fibrotic thinning of the myocardium adjacent to the mitral valve at the posterior wall of the left ventricle (arrow). (D) Microscopic view of the bifurcation of the His bundle showing segmental fibrosis (asterisk) at the origin of the right bundle branch (Masson trichrome, objective magnification: 2.5 ×).

9. Conclusions

In conclusion, in our view chronic cardiac Chagas' disease represents the result of a close interaction between the host and the parasite, causing different clinical pictures. A scheme of the main factors involved in chronic chagasic cardiopathy and their hypothetical interactions that might lead to different cardiac lesions is provided in Fig. 5. Patients with a good 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 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.

Fig. 5

Hypothetical scheme of the main factors involved in chronic chagasic cardiopathy and their hypothetical interactions that might lead to different cardiac lesions (MAC, membrane attack complex of the complement cascade).

Fig. 5

Hypothetical scheme of the main factors involved in chronic chagasic cardiopathy and their hypothetical interactions that might lead to different cardiac lesions (MAC, membrane attack complex of the complement cascade).

Acknowledgements

Studies from our lab were supported by FAPESP (Proc 99/00322-9) and CAPES-DADD.

References

[1]
Dias
J.C.P.
A doença de Chagas e seu controle na América Latina. Uma análise de possibilidades
Cad Saúde Públ (RJ)
 
1993
9
201
209
[2]
Chagas
C.
Nova tripanosomíase humana
Mem Inst Oswaldo Cruz
 
1909
1
159
218
[3]
Vianna
G.
Contribuição para o estudo da anatomia patológica da ‘Moléstia de Carlos Chagas’
Mem Inst Oswaldo Cruz
 
1911
3
276
293
[4]
Chagas
C.
Processos patogênicos da tripanosomíase americana
Mem Inst Oswaldo Cruz
 
1916
8
5
37
[5]
Andrade
Z.A.
Andrade
S.G.
The pathology of Chagas' disease (cardiac chronic form)
Bol Fund G Moniz
 
1955
6
1
53
[6]
Laranja
F.S.
Dias
E.
Nobrega
G.
Miranda
A.
Chagas' disease. A clinical, epidemiologic, and pathologic study
Circulation
 
1956
14
1035
1060
[7]
Mazza
S.
La enfermedad de Chagas en la Rep. Argentina
Mem Inst Oswaldo Cruz
 
1949
47
273
288
[8]
Torres
C.M.
Patogenia de la miocarditis cronica en la ‘enfermedad de Chagas’
Reunión Soc Argent Patol Region Norte
 
1929
2
902
916
[9]
Torres
C.M.
Sobre a anatomia patológica da doença de Chagas
Mem Inst Oswaldo Cruz
 
1941
36
391
404
[10]
Muniz
J.
Freitas
G.
Contribuição para o diagnóstico da doença de Chagas pelas reações de imunidade
Rev Bras Biol
 
1944
4
421
438
[11]
Pessoa
S.B.
Cardoso
F.A.
Sobre a imunidade cruzada na leishmaniose tegumentar e na moléstia de Chagas
Hospital (RJ)
 
1942
21
187
193
[12]
Muniz
J.
Penna
A.
Novo conceito da patogenia da doença de Chagas
Hospital (RJ)
 
1947
32
51
73
[13]
Mazza
S.
Esquizotripanides. Manifestaciones eruptivas agudas en la Enfermedad de Chagas
Publ Mis Estud Pat Reg Argent (MEPRA)
 
1941
51
3
74
[14]
Mazza
S.
Miyara
S.
Esquizotripanides (3a. nota). Esquizotripanides eritematosas polimorfas
Publ Mis Estud Pat Reg Argent (MEPRA)
 
1941
53
3
22
[15]
Mazza
S.
Jorg
M.E.
Reproducción experimental de nódulos de histiocitosis del granuloma chagásico mediante el fenomeno de Schwartzman
Publ Mis Estud Pat Reg Argent (MEPRA)
 
1940
47
3
18
[16]
Andrade
Z.A.
Andrade
S.G.
A patogenia da miocardite crônica chagásica: a importância das lesões isquêmicas
Arq Bras Med
 
1955
45
279
288
[17]
Köberle
F.
Cardiopatia chagásica
Hospital (RJ)
 
1958
53
311
346
[18]
Köberle
F.
Patologia y anatomia patológica de la enfermedad de Chagas
Bol Ofic Sanit Panamer
 
1961
51
404
428
[19]
Hurst
A.F.
Rake
G.W.
Achalasia of the cardia (so-called cardiospasm)
Q J Med
 
1930
23
491
508
[20]
Köberle
F.
Nador
E.
Etiologia e patogenia do megaesôfago no Brasil
Rev Paul Med
 
1955
47
643
661
[21]
Köberle
F.
Patogenia do megaesôfago brasileiro e europeu
Rev Goiana Med
 
1963
9
79
116
[22]
Andrade
Z.A.
Andrade
S.G.
O coração nos ‘megas’ do aparelho digestivo
Hospital (RJ)
 
1967
71
719
726
[23]
Oria
J.S.
Ramos
J.
Alterações do metassimpático do coração nos portadores de megaesôfago (cardiospasm)
Arq Bras Cardiol
 
1949
2
311
326
[24]
Oliveira
J.S.M.
A natural model of intrinsic heart nervous system denervation: Chagas' cardiopathy
Am Heart J
 
1985
110
1092
1098
[25]
Iosa
D.
De Quattro
V.
De-Ping
L.
Elkayam
U.
Palmero
H.A.
Plasma norepinephrine in Chagas' cardioneuropathy: a marker of progressive dysautonomia
Am Heart J
 
1989
117
882
891
[26]
Köberle
F.
Cardiopatia parasympativopriva
Münch Med Wschr
 
1959
101
1308
1310
[27]

Oliveira JSM. Cardiopatia ‘chagásica’ experimental. Thesis, Ribeirão Preto: University of São Paulo, 1968.

[28]
Almeida
H.O.
Brandão
M.C.
Reis
M.A.
Gobbi
H.
Teixeira
V.P.
Denervação e cardiopatia no chagásico crônico
Arq Bras Cardiol.
 
1987
48
43
47
[29]
Lopes
E.R.
Tafuri
W.L.
Involvement of the autonomic nervous system in Chagas' heart disease
Rev Soc Bras Med Trop
 
1983
16
206
212
[30]
Suarez JA. Los ganglios neurovegetativos intracardiacos en la miocarditis chagasica (Estudo histopatologico humano y experimental). Thesis, Caracas: University of Caracas, 1967.
[31]
Ribeiro-dos-Santos
R.
Marquez
J.O.
Von Gal Furtado
C.C.
et al
Antibodies against neurons in chronic Chagas' disease
Tropenmed Parasitol
 
1979
30
19
23
[32]
Davila
D.F.
Rossell
R.O.
Donis
J.H.
Cardiac parasympathetic abnormalities: cause or consequence of Chagas' heart disease?
Parasitol Today
 
1989
5
327
329
[33]
Rossi
L.
Neuropathology of chronic chagasic cardiopathy: A diagnostic reassessment
Cardiovasc Pathol
 
1996
5
233
239
[34]
Andrade
S.G.
Andrade
Z.A.
Estudo histopatológico comparativo das lesões produzidas por duas cepas do Trypanosoma cruzi
Hospital (RJ)
 
1966
70
1268
1278
[35]
Lopes
E.R.
Chapadeiro
E.
Almeida
H.O.
Rocha
A.
Contribuição ao estudo da anatomia patológica dos corações de chagásicos falecidos subitamente
Rev Soc Bras Med Trop
 
1975
9
269
282
[36]
Higuchi
M.L.
de Morais
C.F.
Pereira-Barreto
A.C.
et al
The role of active myocarditis in the development of heart failure in chronic Chagas' disease: a study based on endomyocardial biopsies
Clin Cardiol
 
1987
10
665
670
[37]
Barreto
A.C.P.
Mady
C.
Arteaga-Fernandez
E.
et al
Right ventricular endomyocardial biopsy in chronic Chagas' disease
Am Heart J
 
1986
111
307
318
[38]
Carrasco Guerra
H.A.
Palacios-Pru
E.
Dagert de Scorza
C.
et al
Clinical histochemical and ultrastructural correlation in septal endomyocardial biopsies from chronic chagasic patients
Am Heart J
 
1987
113
716
724
[39]
Fuenmayor-Meza CE. Quantitative analysis of histopathological alterations in endomyocardial biopsies from patients in different clinical forms of Chagas' disease or with dilated cardiomyopathy, regarding myocardial structure, T. cruzi antigens and subsets of T lymphocytes. Thesis, São Paulo: University of São Paulo, 2000.
[40]
Cossio
P.M.
Diez
C.
Szarfman
A.
Chagasic cardiopathy. Demonstration of a serum gamma globulin factor which reacts with endocardium and vascular structures
Circulation
 
1974
49
13
21
[41]
Cossio
P.M.
Laguens
R.P.
Kreutzer
E.
et al
Chagasic cardiopathy. Immunopathologic and morphologic studies in myocardial biopsies
Am J Pathol
 
1977
86
533
544
[42]
Milei
J.
Alonso
G.F.
Vanzulli
S.
et al
Myocardial inflammatory infiltrate in human chronic chagasic cardiomyopathy: immunohistochemical findings
Cardiovasc Pathol
 
1996
5
209
219
[43]
Higuchi
M.L.
Lopes
E.A.
Saldanha
L.B.
et al
Immunopathologic studies in myocardial biopsies of patients with Chagas' disease and idiopathic cardiomyopathy
Rev Inst Med Trop S Paulo
 
1986
28
87
90
[44]
Adad
S.J.
Andrade
D.C.S.
Lopes
E.R.
Chapadeiro
E.
Contribuição ao estudo da anatomia patológica do megaesôfago chagásico
Rev Inst Med Trop S Paulo
 
1991
33
443
450
[45]
De Brito
T.
Vasconcelos
E.
Necrotizing arteritis in megaesophagus: histopathology of ninety-one biopsies taken from the cardia
Rev. Inst. Med. Trop S Paulo
 
1959
1
195
206
[46]
Borda
E.P.
Cossio
P.
Veja
M.V.
Arana
R.
Sterin-Borda
L.
A circulating IgG in Chagas disease which binds to β-adrenoreceptors of myocardium and modulates their activity
Clin Exp Immunol
 
1984
57
679
686
[47]
Sterin-Borda
L.
Gorelik
G.
Borda
E.S.
Chagasic IgG binding with cardiac muscarinic cholinergic receptors modifies cholinergic-mediated cellular transmembrane signals
Clin Immunol Immunopathol
 
1991
61
387
397
[48]
Costa
P.C.
Fortes
F.S.
Machado
A.B.
et al
Sera from chronic chagasic patients depress cardiac electrogenesis and conduction
Braz J Med Biol Res
 
2000
33
439
446
[49]
Chiale
P.A.
Rosenbaum
M.B.
Elizari
M.V.
et al
High prevalence of antibodies against beta1 and beta2-adrenoreceptors in patients with primary electrical cardiac abnormalities
J Am Coll Cardiol
 
1995
26
864
869
[50]
Kaplan
D.
Ferrari
I.
Bergami
P.L.
et al
Antibodies to ribosomal P proteins of Trypanosoma cruzi in Chagas' disease possess funtional autoreactivity with heart tissue and differ from anti-P autoantibodies in lupus
Proc Natl Acad Sci USA
 
1997
94
10301
10306
[51]
Santos-Buch
C.A.
Teixeira
A.R.
The immunology of experimental Chagas' disease. III. Rejection of allogeneic heart cells in vitro
J Exp Med
 
1974
140
38
53
[52]
Teixeira
A.R.L.
Santos-Buch
C.A.
The immunology of experimental Chagas' disease. II. Delayed hypersensitivity to Trypanosoma cruzi antigens
Immunology
 
1975
28
401
410
[53]
Teixeira
A.R.L.
Teixeira
M.L.
Santos-Buch
C.A.
The immunology of experimental Chagas' disease. IV. Production of lesions in rabbits similar to those of chronic Chagas' disease in man
Am J Pathol
 
1975
80
163
180
[54]
Rizzo
L.V.
Cunha-Neto
E.
Teixeira
A.R.
Autoimmunity in Chagas' disease: specific inhibition of reactivity of CD4+ T cells against myosin in mice chronically infected with T. cruzi
Infect Immun
 
1989
57
2640
2644
[55]
Cunha-Neto
E.
Duranti
M.
Gruber
A.
et al
Autoimmunity in Chagas' disease cardiopathy: biological relevance of a cardiac myosin-specific epitope crossreactive to an immunodominant Trypanosoma cruzi antigen
Proc Nat Acad Sci USA
 
1995
92
3541
3545
[56]
Levin
M.J.
Mesri
E.
Benarous
R.
et al
Identification of major Trypanosoma cruzi antigenic determinants in chronic Chagas' heart disease
Am J Trop Med Hyg
 
1989
4
530
538
[57]
Sadigursky
M.
Acosta
A.M.
Santos-Buch
C.A.
Muscle sarcoplasmic reticulum antigen shared by a Trypanosoma cruzi clone
Am J Trop Med Hyg
 
1982
31
934
941
[58]
Sadigursky
M.
Von Kreuter
B.F.
Santos-Buch
C.A.
Development of chagasic autoimmune myocarditis associated with anti-idiotype reaction
Mem Inst Oswaldo Cruz
 
1988
83
363
368
[59]
Hontebeyrie-Joskowicz
M.
Sid
G.
Milon
G.
Marchal
G.
Eisen
H.
L3T4+ cells able to mediate parasite-specific delayed-type hypersensitivity play a role in the pathology of experimental Chagas' disease
Eur J Immunol
 
1987
17
1027
1033
[60]
Acosta
A.M.
Santos-Buch
C.A.
Autoimmune myocarditis induced by Trypanosoma cruzi
Lab Invest
 
1985
71
1255
1261
[61]
Ribeiro-dos-Santos
R.
Rossi
M.A.
Imunopatologia
Cançado
J.R.
Chuster
M.
Cardiopatia chagásica
1985
Belo Horizonte
Fundação Carlos Chagas
10
22
[62]
Ribeiro-dos-Santos
R.
Rossi
M.A.
Laus
J.L.
et al
Anti-CD4 abrogates rejection and reestablishes long-term tolerance to syngeneic newborn hearts grafted in mice chronically infected with Trypanosoma cruzi
J Exp Med
 
1992
175
29
39
[63]
Tarleton
R.L.
Zhang
L.
Downs
M.O.
Autoimmune rejection of neonatal heart transplants in experimental Chagas' disease is a parasite-specific response to infected host tissue
Proc Natl Acad Sci USA
 
1997
94
3932
3937
[64]
Stolf
N.A.
Higuchi
L.
Bocchi
E.
et al
Heart transplantation in patients with Chagas' disease cardiomyopathy
J Heart Transplant
 
1987
6
5
307
312
[65]
Bocchi
E.A.
Bellotti
G.
Uip
D.
et al
Long-term follow-up after heart transplantation in Chagas' disease
Transplant Proc
 
1993
25
1329
1330
[66]
Almeida
H.O.
Teixeira
V.P.A.
Gobbi
H.
Rocha
A.
Brandão
M.C.
Inflamação associada a células musculares cardíacas parasitadas pelo T. cruzi em chagásicos crônicos
Arq Bras Cardiol
 
1984
42
183
186
[67]
Teixeira
V.P.
Araujo
M.B.
dos Reis
M.A.
et al
Possible role of an adrenal parasite resevoir in the pathogenesis of chronic Trypanosoma cruzi myocarditis
Trans R Soc Trop Med Hyg
 
1993
87
552
554
[68]
Higuchi
M.L.
Brito
T.
Reis
M.
et al
Correlation between T. cruzi parasitism and myocardial inflammation in human chronic chagasic myocarditis. Light microscopy and immunohistochemical findings
Cardiovasc Pathol
 
1993
2
101
106
[69]
Palomino
A.S.
Aiello
V.D.
Higuchi
M.L.
Systematic mapping of hearts from chronic chagasic patients: the association between the occurrence of histopathological lesions and Trypanosoma cruzi antigens
Ann Trop Med Parasitol
 
2000
94
6
571
579
[70]
Ben Younes-Chennoufi
A.
Hontebeyrie-Joskowicz
M.
Tricottet
V.
et al
Persistence of Trypanosoma cruzi antigens in the inflammatory lesions of chronically infected mice
Trans R Soc Trop Med Hyg
 
1988
82
77
83
[71]
Franco
M.F.
Experimental carditis induced by Trypanosoma cruzi (y strain) in guinea pigs: Correlation between histopathology and the presence of T. cruzi antigens identified by indirect immunofluorescence
Rev Soc Bras Med Trop
 
1990
23
187
189
[72]
Jones
E.M.
Colley
D.G.
Tostes
S.
et al
Amplification of Trypanosoma cruzi DNA sequence from inflammatory lesions in human chagasic cardiomyopathy
Am Trop Med Hyg
 
1993
48
348
357
[73]
Bellotti
G.
Bocchi
E.
de Moraes
A.V.
et al
In vivo detection of T. cruzi antigens in hearts of patients with chronic Chagas' heart disease
Am Heart J
 
1996
131
301
307
[74]
Tarleton
R.L.
Parasite persistence in the aetiology of Chagas' disease
Int J Parasitol
 
2001
31
550
554
[75]
De Brito T. Miocardite alérgica do cobaio e sua possível relação com a cardite chagásica experimental. Thesis, São Paulo: University of São Paulo, 1962.
[76]
Tarleton
R.L.
Trypanosoma cruzi-induced suppression of IL-2 production. I. Evidence for the presence of IL-2 producing cells
J Immunol
 
1988
140
2763
2768
[77]
Cunningham
D.S.
Grogl
M.
Kuhn
R.E.
Suppression of antibody responses in humans infected with Trypanosoma cruzi
Infect Immun
 
1980
30
496
499
[78]
Sztein
M.
Washington
R.C.
Kierszenbaum
F.
Trypanosoma cruzi inhibits the expression of CD3, CD4, CD8 and IL-2R by mitogen-activated helper and cytotoxic human lymphocytes
J Immunol
 
1990
144
3558
3562
[79]
Higuchi
M.L.
Gutierrez
P.S.
Aiello
V.D.
Immunohistochemical characterization of infiltrating cells in human chronic chagasic myocarditis: comparison with myocardial rejection process
Virchow's Arch A Pathol Anat
 
1993
423
157
160
[80]
Reis
D.D.
Jones
E.M.
Tostes
S.
et al
Characterisation of inflammatory infiltrate in chronic myocardial lesions: presence of tumor necrosis factor+ cells and dominance of granzime A+ CD8+ lymphocytes
Am J Trop Med Hyg
 
1993
48
637
644
[81]
Higuchi
M.L.
Reis
M.
Aiello
V.D.
et al
Association of an increase in CD8+ T cells with the presence of Trypanosoma cruzi antigens in chronic, human, chagasic myocarditis
Am J Trop Med Hyg
 
1997
56
485
489
[82]
Reed
S.G.
Inverso
J.A.
Roters
S.B.
Heterologous antibody responses in mice with chronic Trypanosoma cruzi infection: depressed T helper function restored with supernatants containing interleukin 2
J Immunol
 
1984
133
1558
1563
[83]
Reis
M.M.
Higuchi
M.L.
Benvenuti
L.A.
et al
An in situ quantitative immunohistochemical study of cytokines and IL-2R+ in chronic human chagasic myocarditis: Correlation with the presence of myocardial Trypanosoma cruzi antigens
Clin Immunol Immunopathol.
 
1997
83
165
172
[84]
Spinella
S.
Milon
G.
Hontebeyrie-Joskowicz
M.
A CD4+ TH2 cell line isolated from mice chronically infected with Trypanosoma cruzi induces IgG2 polyclonal response in vivo
Eur J Immunol
 
1990
20
1045
1051
[85]
Albert
J.C.S.
Soub
J.T.
Marino
A.P.M.P.
et al
Modulation of chemokine production and inflammatory responses in interferon-gamma and tumor necrosis factor-R-1-deficient mice during Trypanosoma cruzi infection
Am J Pathol
 
2001
158
1433
1440
[86]
Hölscher
C.
Mohrs
M.
Dai
W.J.
et al
Tumor necrosis factor alpha-mediated toxic shock in Trypanosoma cruzi-infected interleukin 10-deficient mice
Infect Immun
 
2000
68
4075
4083
[87]
Pereira-Barreto
A.C.
Arteaga
E.
Mady
C.
et al
Sexo Masculino. Fator prognóstico na doença de Chagas
Arq Bras Cardiol
 
1993
60
225
227
[88]
Reis MM. Growth factors in the myocardium of patients with chronic chagasic cardiomyopathy. Differences between men and women. Thesis, São Paulo: University of São Paulo, 2000.
[89]
Benvenuti
L.A.
Higuchi
M.L.
Reis
M.M.
Upregulation of adhesion molecules and class I HLA in the myocardium of chronic chagasic cardiomyopathy and heart allograft rejection, but not in dilated cardiomyopathy
Cardiovasc Pathol
 
2000
9
111
117
[90]
Laucella
A.S.
Segura
E.L.
Riarte
A.
Sosa
E.S.
Soluble platelet selectin (sP-selectin) and soluble vascular cell adhesion molecule-1 (sVCAM-1) decrease during therapy with benznidazole in children with indeterminate form of Chagas' disease
Clin Exp Immunol
 
1999
118
423
427
[91]
Reis
D.D.
Jones
E.M.
Tostes
S.
et al
Expression of major histocompatibility complex antigens and adhesion molecules in hearts of patients with chronic Chagas' disease
Am J Trop Med Hyg
 
1993
49
192
200
[92]
Zhang
L.
Tarleton
R.L.
Persistent production of inflammatory and anti-inflammatory cytokines and associated MHC and adhesion molecule expression at the site of infection and disease in experimental Trypanosoma cruzi infections
Exp Parasitol
 
1996
84
203
213
[93]
Piazza
L.A.
de Bold
A.J.
Santamarina
N.
Hliba
E.
Rubiolo
E.R.
Atrial natriuretic factor in experimental acute Chagas' disease
Parasitol Res
 
1994
80
78
80
[94]
Benvenuti
L.A.
Aiello
V.D.
Palomino
S.A.P.
Higuchi
M.L.
Ventricular expression of atrial natriuretic peptide in chronic chagasic cardiomyopathy is not induced by myocarditis
Int J Cardiol
 
2003
88
57
61
[95]
Ribeiro
A.L.P.
Reis
A.M.
Barros
M.V.L.
et al
Brain natriuretic peptide and left ventricular dysfunction in Chagas' disease
Lancet
 
2002
360
461
462
[96]
Morris
S.A.
Weiss
L.M.
Factor
S.
et al
Verapamil ameliorates clinical, pathologic and biochemical manifestations of experimental chagasic cardiomyopathy in mice
J Am Coll Cardiol
 
1989
14
782
789
[97]
Tanowitz
H.B.
Burns
E.R.
Sinha
A.K.
et al
Enhanced platelet adherence and aggregation in Chagas' disease: a potential pathogenic mechanism for cardiomyopathy
Am J Trop Med Hyg
 
1990
43
274
281
[98]
Factor
S.M.
Wittner
M.
Tanowitz
H.B.
Chagas' disease: microvascular and interstitial matrix abnormalities characteristic of congestive cardiomyopathy of diverse etiology
Cardiovasc Pathol
 
1996
5
203
207
[99]
Robinson
T.F.
Cohen-Gould
L.
Factor
S.M.
Skeletal framework of mammalian heart muscle Arrangements of inter- and pericellular connective tissue structures
Lab Invest
 
1983
49
482
498
[100]
Weber
K.T.
Janicki
J.S.
Shroff
S.G.
et al
Collagen remodeling of the pressure overloaded, hypertrophied nonhuman primate myocardium
Circ Res
 
1988
62
757
765
[101]
Higuchi
M.L.
Fukasawa
S.
De Brito
T.
et al
Different microcirculatory and interstitial matrix patterns in idiopathic dilated cardiomyopathy and Chagas' disease: a three-dimensional confocal microscopy study
Heart
 
1999
82
3
279
285
[102]
Cunha-Neto
E.
Rizzo
L.V.
Albuquerque
F.
et al
Cytokine production profile of heart-infiltrating T cells in Chagas' disease cardiomyopathy
Braz J Med Biol Res
 
1998
31
133
137
[103]
Reed
S.G.
Grabtein
H.K.
Pihl
D.L.
Morrissey
P.J.
Recombinant granulocyte/macrophage colony-stimulating factor restores deficient immune response in mice with chronic Trypanosoma cruzi infections
J Immunol
 
1990
145
1564
1570
[104]
Reis
M.M.
Higuchi
M.L.
Aiello
V.D.
Benvenuti
L.A.
Growth factors in the myocardium of patients with chronic chagasic cardiomyopathy
Rev Soc Bras Med Trop.
 
2000
33
509
518
[105]
Ku
C.C.
Murakami
M.
Sakamoto
A.
Kappler
J.
Marrack
P.
Control of homeostasis of CD8+ memory T cells by opposing cytokines
Science
 
2000
288
675
678
[106]
Zhang
X.
Sun
S.
Hwang
I.
Tough
D.F.
Sprent
J.
Potent and selective stimulation of memory-phenotype CD8+ T cells in vivo by IL-15
Immunity
 
1998
8
591
599
[107]
Fonseca SG. Estudo funcional dos linfócitos T CD8+ na cardiopatia chagásica crônica humana. Thesis, São Paulo: University of São Paulo, 2002.
[108]
Reis
M.M.
Fonseca
S.G.
Sambiase
N.V.
et al
Is heart-derived IL-15 involved in the predominance of CD8+ IL-2R alpha-T cells at heart lesions of human Chagas' disease cardiomyopathy?
Histopathology
 
2002
41
199A
[109]
Tambourgi
D.V.
Kipnis
T.L.
da Silva
W.D.
et al
A partial cDNA clone of trypomastigote decay-accelerating factor (T-DAF), a developmentally regulated complement inhibitor of Trypanosoma cruzi, has genetic and funtional similarities to the human complement inhibitor DAF
Infect Immun
 
1993
61
9
3656
3663
[110]
Iida
K.
Whitlow
M.B.
Nussenzweig
V.
Amastigotes of T. cruzi escape destruction by the terminal complement components
J Exp Med
 
1989
169
881
891
[111]
Aiello
V.D.
Reis
M.M.
Benvenuti
L.A.
et al
A possible role for complement in the pathogenesis of chronic chagasic cardiomyopathy
J Pathol
 
2002
197
224
229
[112]
Rossi
M.A.
Fibrosis and inflammatory cells in human chronic chagasic myocarditis: scanning electron microscopy and immunohistochemical observations
Int J Cardiol
 
1998
66
183
194
[113]
Wyler
D.J.
Libby
P.
Prakash
S.
Prioli
R.P.
Pereira
M.E.
Elaboration by mammalian mesenchymal cells infected with Trypanosoma cruzi of a fibroblast-stimulating factor that may contribute to chagasic cardiomyopathy
Infect Immun
 
1987
55
3188
3191
[114]
Factor
S.M.
Tanowitz
H.
Wittner
M.
Ventura
M.C.
Interstitial connective tissue matrix alterations in acute murine Chagas' disease
Clin Immun Immunopathol
 
1993
68
147
152
[115]
Metzger
M.
Higuchi
M.L.
Moreira
L.F.
et al
Apoptosis and cell proliferation relevance for survival of patients with dilated cardiomyopathy undergoing partial left ventriculectomy
Eur J Clin Invest
 
2002
32
394
399
[116]
Metzger
M.
Higuchi
M.L.
Brito
T.
Lack of apoptosis of cardiomyocytes in chronic chagasic myocarditis
Virchow's Arch
 
2001
439
352
[117]
Rossi
M.A.
Souza
A.C.
Is apoptosis a mechanism of cell death of cardiomyocytes in chronic chagasic myocarditis?
Int J Cardiol
 
1999
68
325
331
[118]
Chuenkova
M.V.
Furnari
F.B.
Cavenee
W.K.
Pereira
M.A.
Trypanosoma cruzi trans-sialidase: a potent and specific survival factor for human Schwann cells by means of phosphatidylinositol 3-kinase/Akt signaling
Proc Natl Acad Sci USA
 
2001
98
9936
9941
[119]
Lopes
M.F.
Veiga
V.F.
Santos
A.R.
Fonseca
M.E.F.
Dos Reis
G.A.
Activation-induced CD4+T cell death by apoptosis in experimental Chagas' disease
J Immunol
 
1995
154
744
752
[120]
Nunes
M.P.
Andrade
R.M.
Lopes
M.F.
Dos Reis
G.A.
Activation-induced T cell death exacerbates T. cruzi replication in macrophages co-cultured with CD4+ T lymphocytes from infected hosts
J Immunol
 
1998
160
1313
1319
[121]
Freire-de-Lima
C.G.
Nascimento
D.O.
Soares
M.B.P.
et al
Uptake of apoptotic cells drives the growth of a pathogenic trypanosome in macrophages
Nature
 
2000
403
199
203
[122]
Jorg
M.E.
Destruction of capillary vessels, myocytolysis and apical aneurism in the chagasic cardiopathy
Pren Med Argent
 
1980
67
490
494
[123]
Factor
S.M.
Cho
S.
Wittner
M.
Tanowitz
H.
Abnormalities of the coronary circulation in acute murine Chagas' disease
Am J Trop Med Hyg
 
1985
34
246
253
[124]
Rossi
M.A.
Gonçalves
S.
Ribeiro-dos-Santos
R.
Experimental Trypanosoma cruzi cardiomyopathy in BALB/c mice. The potential role of intravascular platelet aggregation in its genesis
Am J Pathol
 
1984
114
209
216
[125]
Morris
S.A.
Tanowitz
H.B.
Wittner
M.
Bilezikian
J.P.
Pathophysiological insights into the cardiomyopathy of Chagas' disease
Circulation
 
1990
82
1900
1909
[126]
Rossi
M.A.
Peres
L.C.
Effects of captopril on the prevention and regression of myocardial cell hypertrophy and interstitial fibrosis in pressure overload cardiac hypertrophy
Am Heart J
 
1992
124
700
709
[127]
Andrade
Z.A.
Andrade
S.G.
Oliveira
G.B.
Alonso
D.R.
Histopathology of the conducting tissue of the heart in Chagas' myocarditis
Am Heart J
 
1978
95
316
324
[128]
Higuchi
M.L.
Human chronic chagasic cardiopathy: participation of parasite antigens, subsets of lymphocytes, cytokines and microvascular abnormalities
Mem Inst Oswaldo Cruz
 
1999
94
Suppl 1
263
267
[129]
Sambiase
N.V.
D'Ávila
A.
Benvenutti
L.A.
Higuchi
M.L.
Segmental left ventricular wall abnormalities associated with the site of origin of ventricular tachycardia are caused by ischemic injury in patients with Chagas' disease
PACE
 
2001
24
693A
[130]
Scanavacca
M.
Sosa
E.
D'Ávila
A.
Higuchi
M.L.
Radiofrequency ablation of sustained ventricular tachycardia related to the mitral isthmus in Chagas' disease
PACE
 
2002
25
368
371

Author notes

Time for primary review 20 days.