Physical activity, opportunity for reinfection, and sibling history of heart disease as risk factors for Chagas' cardiopathy

Cardiac involvement in Chagas disease and African trypanosomiasis

Trypanosomiases are diseases caused by various species of protozoan parasite in the genus Trypanosoma, each presenting with distinct clinical manifestations and prognoses. Infections can affect multiple organs, with Trypanosoma cruzi predominantly affecting the heart and digestive system, leading to American trypanosomiasis or Chagas disease, and Trypanosoma brucei primarily causing a disease of the central nervous system known as human African trypanosomiasis or sleeping sickness. In this Review, we discuss the effects of these infections on the heart, with particular emphasis on Chagas disease, which continues to be a leading cause of cardiomyopathy in Latin America. The epidemiology of Chagas disease has changed substantially since 1990 owing to the emigration of over 30 million Latin American citizens, primarily to Europe and the USA. This movement of people has led to the global dissemination of individuals infected with T. cruzi. Therefore, cardiologists worldwide must familiarize themselves with Chagas disease and the severe, chronic manifestation - Chagas cardiomyopathy - because of the expanded prevalence of this disease beyond traditional endemic regions.

Exploring the latency period in Chagas disease: duration and determinants in a cohort from Colombia

BACKGROUND

Chagas disease has a varying latency period, the time between infection and onset of cardiac symptoms, due to multiple factors. This study seeks to identify and understand these factors to enhance our knowledge of the disease.

METHODS

A retrospective follow-up study was conducted in Colombia on patients with indeterminate chronic Chagas disease. Medical files were examined to evaluate the disease latency time using time ratios (TRs) and the AFT Weibull model.

RESULTS

The study followed 578 patients, of whom 309 (53.5%) developed cardiac disease, with a median latency period of 18.5 (95% CI 16 to 20) y for the cohort. Those with the TcISyl genotype (TR 0.72; 95% CI 0.61 to 0.80), individuals who lived 5-15 y (TR 0.80; 95% CI 0.67 to 0.95), 15-30 y (TR 0.63; 95% CI 0.53 to 0.74) or >30 y (vs 5 y) in areas with high disease prevalence had shorter latency periods. On the other hand, undergoing treatment increased the latency period (TR: 1.74; 95% CI 1.52 to 1.87).

CONCLUSIONS

The latency period of Chagas disease was found to be independently related to male gender, receipt of etiological treatment, length of time spent in an endemic area and the TcISyl genotype. The implications of these findings are discussed.

Chagas Disease Megaesophagus Patients Carrying Variant MRPS18B P260A Display Nitro-Oxidative Stress and Mitochondrial Dysfunction in Response to IFN-γ Stimulus

Chagas disease (CD), caused by the protozoan parasite Trypanosoma cruzi, affects 8 million people, and around 1/3 develop chronic cardiac (CCC) or digestive disease (megaesophagus/megacolon), while the majority remain asymptomatic, in the indeterminate form of Chagas disease (ASY). Most CCC cases in families with multiple Chagas disease patients carry damaging mutations in mitochondrial genes. We searched for exonic mutations associated to chagasic megaesophagus (CME) in genes essential to mitochondrial processes. We performed whole exome sequencing of 13 CME and 45 ASY patients. We found the damaging variant MRPS18B 688C > G P230A, in five out of the 13 CME patients (one of them being homozygous; 38.4%), while the variant appeared in one out of 45 ASY patients (2.2%). We analyzed the interferon (IFN)-γ-induced nitro-oxidative stress and mitochondrial function of EBV-transformed lymphoblastoid cell lines. We found the CME carriers of the mutation displayed increased levels of nitrite and nitrated proteins; in addition, the homozygous (G/G) CME patient also showed increased mitochondrial superoxide and reduced levels of ATP production. The results suggest that pathogenic mitochondrial mutations may contribute to cytokine-induced nitro-oxidative stress and mitochondrial dysfunction. We hypothesize that, in mutation carriers, IFN-γ produced in the esophageal myenteric plexus might cause nitro-oxidative stress and mitochondrial dysfunction in neurons, contributing to megaesophagus.

CD8+ T Cell Response Quality Is Related to Parasite Control in an Animal Model of Single and Mixed Chronic Trypanosoma cruzi Infections

Chagas disease (ChD) is a chronic infection caused by Trypanosoma cruzi. This highly diverse intracellular parasite is classified into seven genotypes or discrete typing units (DTUs) and they overlap in geographic ranges, vectors, and clinical characteristics. Although studies have suggested that ChD progression is due to a decline in the immune response quality, a direct relationship between T cell responses and disease outcome is still unclear. To investigate the relationship between parasite control and immune T cell responses, we used two distinct infection approaches in an animal model to explore the histological and parasitological outcomes and dissect the T cell responses in T. cruzi-infected mice. First, we performed single infection experiments with DA (TcI) or Y (TcII) T. cruzi strains to compare the infection outcomes and evaluate its relationship with the T cell response. Second, because infections with diverse T. cruzi genotypes can occur in naturally infected individuals, mice were infected with the Y or DA strain and subsequently reinfected with the Y strain. We found different infection outcomes in the two infection approaches used. The single chronic infection showed differences in the inflammatory infiltrate level, while mixed chronic infection by different T. cruzi DTUs showed dissimilarities in the parasite loads. Chronically infected mice with a low inflammatory infiltrate (DA-infected mice) or low parasitemia and parasitism (Y/Y-infected mice) showed increases in early-differentiated CD8⁺ T cells, a multifunctional T cell response and lower expression of inhibitory receptors on CD8⁺ T cells. In contrast, infected mice with a high inflammatory infiltrate (Y-infected mice) or high parasitemia and parasitism (DA/Y-infected mice) showed a CD8⁺ T cell response distinguished by an increase in late-differentiated cells, a monofunctional response, and enhanced expression of inhibitory receptors. Overall, our results demonstrated that the infection outcomes caused by single or mixed T. cruzi infection with different genotypes induce a differential immune CD8⁺ T cell response quality. These findings suggest that the CD8⁺ T cell response might dictate differences in the infection outcomes at the chronic T. cruzi stage. This study shows that the T cell response quality is related to parasite control during chronic T. cruzi infection.

Polymorphisms in Genes Affecting Interferon-γ Production and Th1 T Cell Differentiation Are Associated With Progression to Chagas Disease Cardiomyopathy

Background: Chagas disease, caused by the protozoan Trypanosoma cruzi, is endemic in Latin America. Thirty percent of infected individuals develop chronic Chagas cardiomyopathy (CCC), an inflammatory dilated cardiomyopathy that is the most important clinical consequence of T. cruzi infection, while the others remain asymptomatic (ASY). IFN-γ and IFN-γ-producing Th1-type T cells are increased in peripheral blood and CCC myocardium as compared to ASY patients, while the Th1-antagonizing cytokine IL-10 is more expressed in ASY patients. Importantly IFN-γ-producing Th1-type T cells are the most frequent cytokine-producing T cell subset in CCC myocardium, while expression of Th1-antagonizing cytokines IL-10 and IL-4 is unaltered. The control of IFN-γ production by Th1-type T cells may be a key event for progression toward CCC. A genetic component to disease progression was suggested by the familial aggregation of cases and the association of gene polymorphisms with CCC development. We here investigate the role of gene polymorphisms (SNPs) in several genes involved in the control of IFN-γ production and Th1 T cell differentiation in CCC development. Methods: We studied a Brazilian population including 315 CCC cases and 118 ASY subjects. We assessed 35 Tag SNPs designed to represent all the genetic information contained in the IL12B, IL10, IFNG, and IL4 genes. Results: We found 2 IL12 SNPs (rs2546893, rs919766) and a trend of association for a IL10 SNP (rs3024496) to be significantly associated with the ASY group. these associations were confirmed by multivariate analysis and allele tests. The rs919766C, 12rs2546893G, and rs3024496C alleles were associated to an increase risk to CCC development. Conclusions: Our data show that novel polymorphisms affecting IL12B and IL10, but not IFNG or IL4 genes play a role in genetic susceptibility to CCC development. This might indicate that the increased Th1 differentiation and IFN-γ production associated with CCC is genetically controlled.

Whole-Genome Cardiac DNA Methylation Fingerprint and Gene Expression Analysis Provide New Insights in the Pathogenesis of Chronic Chagas Disease Cardiomyopathy

Background

Chagas disease, caused by the protozoan Trypanosoma cruzi, is endemic in Latin America and affects 10 million people worldwide. Approximately 12000 deaths attributable to Chagas disease occur annually due to chronic Chagas disease cardiomyopathy (CCC), an inflammatory cardiomyopathy presenting with heart failure and arrythmia; 30% of infected subjects develop CCC years after infection. Genetic mechanisms play a role in differential progression to CCC, but little is known about the role of epigenetic modifications in pathological gene expression patterns in CCC patients’ myocardium. DNA methylation is the most common modification in the mammalian genome.

Methods

We investigated the impact of genome-wide cardiac DNA methylation on global gene expression in myocardial samples from end-stage CCC patients, compared to control samples from organ donors.

Results

In total, 4720 genes were differentially methylated between CCC patients and controls, of which 399 were also differentially expressed. Several of them were related to heart function or to the immune response and had methylation sites in their promoter region. Reporter gene and in silico transcription factor binding analyses indicated promoter methylation modified expression of key genes. Among those, we found potassium channel genes KCNA4 and KCNIP4, involved in electrical conduction and arrythmia, SMOC2, involved in matrix remodeling, as well as enkephalin and RUNX3, potentially involved in the increased T-helper 1 cytokine-mediated inflammatory damage in heart.

Conclusions

Results support that DNA methylation plays a role in the regulation of expression of pathogenically relevant genes in CCC myocardium, and identify novel potential disease pathways and therapeutic targets in CCC.

A retrospective study on the influence of siblings' relatedness in Bolivian patients with chronic Chagas disease

BACKGROUND

Chagas disease is a protozoan infection caused by Trypanosoma cruzi. The disease has a chronic course in which 20-30% of the patients would develop progressive damage to the cardiovascular system and the gastrointestinal tube. We are still unable to predict who will develop end-organ damage but there are some acquired and genetic risk factors already known.

RESULTS

We reviewed data from 833 patients with serologically confirmed Chagas disease in this retrospective study. Patients were classified as siblings or non-siblings (controls) and the results of pre-treatment blood PCR assay, end-organ damage (cardiac and/or gastrointestinal), and the presence of delayed type hypersensitivity (DTH) skin involvement in patients treated with benznidazole were analyzed. Siblings were grouped by family and we randomly generated groups of 2 or 3 persons with the remaining controls. We classified the results of each variable as concordant or discordant and compared the concordance in these results among the sibling groups with that among control groups. We identified 71 groups of siblings and randomly generated 299 groups of non-related patients. Pre-treatment blood PCR concordance was significantly higher (19%) among siblings compared to controls (P = 0.02), probably due to a higher frequency in pre-treatment positive results. No other statistically significant differences were found.

CONCLUSIONS

A significant difference was found in the concordance of pre-treatment blood PCR for T. cruzi among siblings compared to non-related controls.

Disease Tolerance and Pathogen Resistance Genes May Underlie Trypanosoma cruzi Persistence and Differential Progression to Chagas Disease Cardiomyopathy

Chagas disease is caused by infection with the protozoan Trypanosoma cruzi and affects over 8 million people worldwide. In spite of a powerful innate and adaptive immune response in acute infection, the parasite evades eradication, leading to a chronic persistent infection with low parasitism. Chronically infected subjects display differential patterns of disease progression. While 30% develop chronic Chagas disease cardiomyopathy (CCC)-a severe inflammatory dilated cardiomyopathy-decades after infection, 60% of the patients remain disease-free, in the asymptomatic/indeterminate (ASY) form, and 10% develop gastrointestinal disease. Infection of genetically deficient mice provided a map of genes relevant for resistance to T. cruzi infection, leading to the identification of multiple genes linked to survival to infection. These include pathogen resistance genes (PRG) needed for intracellular parasite destruction, and genes involved in disease tolerance (protection against tissue damage and acute phase death-DTG). All identified DTGs were found to directly or indirectly inhibit IFN-γ production or Th1 differentiation. We hypothesize that the absolute need for DTG to control potentially lethal IFN-γ PRG activity leads to T. cruzi persistence and establishment of chronic infection. IFN-γ production is higher in CCC than ASY patients, and is the most highly expressed cytokine in CCC hearts. Key DTGs that downmodulate IFN-γ, like IL-10, and Ebi3/IL27p28, are higher in ASY patients. Polymorphisms in PRG and DTG are associated with differential disease progression. We thus hypothesize that ASY patients are disease tolerant, while an imbalance of DTG and IFN-γ PRG activity leads to the inflammatory heart damage of CCC.

Inherited Cardiomyopathies and the Role of Mutations in Non-coding Regions of the Genome

Cardiomyopathies (CMs) are a group of cardiac pathologies caused by an intrinsic defect within the myocardium. The relative contribution of genetic mutations in the pathogenesis of certain CMs, such as hypertrophic cardiomyopathy (HCM), arrythmogenic right/left ventricular cardiomyopathy (ARVC) and left ventricular non-compacted cardiomyopathy (LVNC) has been established in comparison to dilated cardiomyopathy (DCM) and restrictive cardiomyopathy (RCM). The aim of this article is to review mutations in the non-coding parts of the genome, namely, microRNA, promoter elements, enhancer/silencer elements, 3′/5′UTRs and introns, that are involved in the pathogenesis CMs. Additionally, we will explore the role of some long non-coding RNAs in the pathogenesis of CMs.

Chagas disease: morbidity profile in an endemic area of Northeastern Brazil

INTRODUCTION

This study evaluated the clinical forms and manifestation severities of Chagas disease among serologically reactive individuals from Western Rio Grande do Norte (Northeastern Brazil).

METHODS

This cross-sectional study included 186 adults who were evaluated using electrocardiography, echocardiography, chest radiography, and contrast radiography of the esophagus and colon. A clinical-epidemiological questionnaire was also used.

RESULTS

The indeterminate, cardiac, digestive, and cardiodigestive clinical forms of Chagas disease were diagnosed in 51.6% (96/186), 32.2% (60/186), 8.1% (15/186) and 8.1% (15/186) of the participants, respectively. Heart failure (functional classes I-IV) was detected in 7.5% (14/186) of the participants, and 36.4% (24/66), 30.3% (20/66), 15.2% (10/66), 13.6% (9/66), and 4.5% (3/66) of the patients were at stage A, B1, B2, C, and D, respectively. Dilated cardiomyopathy and electrocardiographic changes were detected in 10.2% (19/186) and 48.1% (91/186) of the participants, respectively. Apical aneurysm was diagnosed in 10.8% (20/186) of the participants, and other changes in the segmental myocardial contractility of the left ventricle were diagnosed in 33.9% (63/186) of the participants. Megaesophagus (groups I-IV) was observed in 7% (13/186) of the participants, megacolon (grades 1-3) was detected in 12.9% (24/186) of the participants, and both organs were affected in 29.2% (7/24) of the megacolon cases.

CONCLUSIONS

We detected various clinical forms of Chagas disease (including the digestive form). Our findings indicate that clinical symptoms alone may not be sufficient to exclude or confirm cardiac and/or digestive damage, and the number of patients with symptomatic clinical forms may be underestimated.

Tolerance to Trypanosomatids: A Threat, or a Key for Disease Elimination?

So far, research on trypanosomatid infections has been driven by 'disease by disease' approaches, leading to different concepts and control strategies. It is, however, increasingly clear that they share common features such as the ability to generate long-lasting asymptomatic infections in their mammalian hosts. Trypanotolerance, long integrated in animal African trypanosomiasis control, historically refers to the ability of cattle breeds to limit Trypanosoma infection and pathology, but has only recently been recognized in humans. Whilst trypanotolerance is absent from the vocabulary on leishmaniasis and Chagas disease, asymptomatic infections also occur. We review the concept of trypanotolerance across the trypanosomatids and discuss the importance of asymptomatic carriage in the current context of elimination.

Chagas disease cardiomyopathy: immunopathology and genetics

Chagas disease, caused by the protozoan Trypanosoma cruzi, is endemic in Latin America and affects ca. 10 million people worldwide. About 30% of Chagas disease patients develop chronic Chagas disease cardiomyopathy (CCC), a particularly lethal inflammatory cardiomyopathy that occurs decades after the initial infection, while most patients remain asymptomatic. Mortality rate is higher than that of noninflammatory cardiomyopathy. CCC heart lesions present a Th1 T-cell-rich myocarditis, with cardiomyocyte hypertrophy and prominent fibrosis. Data suggest that the myocarditis plays a major pathogenetic role in disease progression. Major unmet goals include the thorough understanding of disease pathogenesis and therapeutic targets and identification of prognostic genetic factors. Chagas disease thus remains a neglected disease, with no vaccines or antiparasitic drugs proven efficient in chronically infected adults, when most patients are diagnosed. Both familial aggregation of CCC cases and the fact that only 30% of infected patients develop CCC suggest there might be a genetic component to disease susceptibility. Moreover, previous case-control studies have identified some genes associated to human susceptibility to CCC. In this paper, we will review the immunopathogenesis and genetics of Chagas disease, highlighting studies that shed light on the differential progression of Chagas disease patients to CCC.

Chagas cardiomyopathy and ischemic stroke

American trypanosomiasis, known as Chagas disease is a major cause of cardiomyopathy in South America. Irreversible damage to the heart can appear 10-20 years after chagasic infection. The relationship between Chagas cardiomyopathy and ischemic stroke has been reviewed. Significant variables that predict ischemic stroke in chagasic patients have been identified: apical aneurysm, cardiac insufficiency, electrocardiogram arrhythmia and female gender. Chagasic cardiomyopathy should be included in the differential diagnosis of the etiology of stroke, being a potential source of cardioembolic stroke.

Polymorphism in the alpha cardiac muscle actin 1 gene is associated to susceptibility to chronic inflammatory cardiomyopathy

Aims

Chagas disease, caused by the protozoan Trypanosoma cruzi is endemic in Latin America, and may lead to a life-threatening inflammatory dilated, chronic Chagas cardiomyopathy (CCC). One third of T. cruzi-infected individuals progress to CCC while the others remain asymptomatic (ASY). A possible genetic component to disease progression was suggested by familial aggregation of cases and the association of markers of innate and adaptive immunity genes with CCC development. Since mutations in multiple sarcomeric genes, including alpha-cardiac actin (ACTC1) have been involved in hereditary dilated cardiomyopathy, we investigated the involvement of the ACTC1 gene in CCC pathogenesis.

Methods and Results

We conducted a proteomic and genetic study on a Brazilian study population. The genetic study was done on a main cohort including 118 seropositive asymptomatic subjects and 315 cases and the replication was done on 36 asymptomatic and 102 CCC cases. ACTC1 protein and mRNA levels were lower in myocardial tissue from patients with end-stage CCC than those found in hearts from organ donors. Genotyping a case-control cohort of CCC and ASY subjects for all informative single nucleotide polymorphism (SNP) in the ACTC1 gene identified rs640249 SNP, located at the 5’ region, as associated to CCC. Associations are borderline after correction for multiple testing. Correlation and haplotype analysis led to the identification of a susceptibility haplotype. Functional assays have shown that the rs640249A/C polymorphism affects the binding of transcriptional factors in the promoter regions of the ACTC1 gene. Confirmation of the detected association on a larger independent replication cohort will be useful.

Conclusions

Genetic variations at the ACTC1 gene may contribute to progression to chronic Chagas Cardiomyopathy among T. cruzi-infected patients, possibly by modulating transcription factor binding to ACTC1 promoter regions.

Genetic susceptibility to Chagas disease cardiomyopathy: involvement of several genes of the innate immunity and chemokine-dependent migration pathways

BACKGROUND

Chagas disease, caused by the protozoan Trypanosoma cruzi is endemic in Latin America. Thirty percent of infected individuals develop chronic Chagas cardiomyopathy (CCC), an inflammatory dilated cardiomyopathy that is, by far, the most important clinical consequence of T. cruzi infection. The others remain asymptomatic (ASY). A possible genetic component to disease progression was suggested by familial aggregation of cases and the association of markers of innate and adaptive immunity genes with CCC development. Migration of Th1-type T cells play a major role in myocardial damage.

METHODS

Our genetic analysis focused on CCR5, CCL2 and MAL/TIRAP genes. We used the Tag SNPs based approach, defined to catch all the genetic information from each gene. The study was conducted on a large Brazilian population including 315 CCC cases and 118 ASY subjects.

RESULTS

The CCL2rs2530797A/A and TIRAPrs8177376A/A were associated to an increase susceptibility whereas the CCR5rs3176763C/C genotype is associated to protection to CCC. These associations were confirmed when we restricted the analysis to severe CCC, characterized by a left ventricular ejection fraction under 40%.

CONCLUSIONS

Our data show that polymorphisms affecting key molecules involved in several immune parameters (innate immunity signal transduction and T cell/monocyte migration) play a role in genetic susceptibility to CCC development. This also points out to the multigenic character of CCC, each polymorphism imparting a small contribution. The identification of genetic markers for CCC will provide information for pathogenesis as well as therapeutic targets.

Genetic epidemiology of Chagas disease

Genetic epidemiological approaches hold great promise for improving the understanding of the determinants of susceptibility to infection with Trypanosoma cruzi and the causes of differential disease outcome in T. cruzi-infected individuals. To date, a variety of approaches have been used to understand the role of genetic factors in Chagas disease. Quantitative genetic techniques have been used to estimate the heritabilities for seropositivity for T. cruzi infection and traits that are associated with disease progression in chronic T. cruzi infection. These studies have demonstrated that a significant proportion of the variation in seropositivity and a number of traits related to Chagas disease progression is attributable to genetic factors. Candidate gene studies have provided intriguing evidence for the roles of numerous individual genes in determining cardiac outcomes in chronically infected individuals. Recent results from a long-term study of Chagas disease in a rural area of Brazil have documented that over 60% of the variation in seropositivity status is attributable to genetic factors in that population. Additionally, there are significant genetic effects on a number of electrocardiographic measures and other Chagas disease-related traits. The application of genome-wide approaches will yield new evidence for the roles of specific genes in Chagas disease.

Autoimmunity

The scarcity of Trypanosoma cruzi in inflammatory lesions of chronic Chagas disease led early investigators to suggest that tissue damage had an autoimmune nature. In spite of parasite persistence in chronic Chagas disease, several reports indicate that inflammatory tissue damage may not be correlated to the local presence of T. cruzi. A significant number of reports have described autoantibodies and self-reactive T cells, often cross-reactive with T. cruzi antigens, both in patients and in animal models. Evidence for a direct pathogenetic role of autoimmunity was suggested by the development of lesions after immunization with T. cruzi antigens or passive transfer of lymphocytes from infected animals, and the amelioration of chronic myocarditis in animals made tolerant to myocardial antigens. Autoimmune and T. cruzi-specific innate or adaptative responses are not incompatible or mutually exclusive, and it is likely that a combination of both is involved in the pathogenesis of chronic Chagas disease cardiomyopathy. The association between persistent infection and autoimmune diseases-such as multiple sclerosis or diabetes mellitus-suggests that post-infectious autoimmunity may be a frequent finding. Here, we critically review evidence for autoimmune phenomena and their possible pathogenetic role in human Chagas disease and animal models, with a focus on chronic Chagas disease cardiomyopathy.

Immunological and non-immunological effects of cytokines and chemokines in the pathogenesis of chronic Chagas disease cardiomyopathy

The pathogenesis of Chagas disease cardiomyopathy (CCC) is not well understood. Since studies show that myocarditis is more frequent during the advanced stages of the disease, and the prognosis of CCC is worse than that of other dilated cardiomyopathies of non-inflammatory aetiology, which suggest that the inflammatory infiltrate plays a major role in myocardial damage. In the last decade, increasing evidence has shown that inflammatory cytokines and chemokines play a role in the generation of the inflammatory infiltrate and tissue damage. CCC patients have an increased peripheral production of the inflammatory Th1 cytokines IFN-gamma and TNF-alpha when compared to patients with the asymptomatic/indeterminate form. Moreover, Th1-T cells are the main producers of IFN-gamma and TNF-alpha and are frequently found in CCC myocardial inflammatory infiltrate. Over the past several years, our group has collected evidence that shows several cytokines and chemokines produced in the CCC myocardium may also have a non-immunological pathogenic effect via modulation of gene and protein expression in cardiomyocytes and other myocardial cell types. Furthermore, genetic polymorphisms of cytokine, chemokine and innate immune response genes have been associated with disease progression. We will review the molecular and immunological mechanisms of myocardial damage in human CCC in light of recent findings.

Induction of cardiac autoimmunity in Chagas heart disease: A case for molecular mimicry

Up to 18 million of individuals are infected by the protozoan parasite Trypanosoma cruzi in Latin America, one third of whom will develop chronic Chagas disease cardiomyopathy (CCC) up to 30 years after infection. Cardiomyocyte destruction is associated with a T cell-rich inflammatory infiltrate and fibrosis. The presence of such lesions in the relative scarcity of parasites in the heart, suggested that CCC might be due, in part, to a postinfectious autoimmune process. Over the last two decades, a significant amount of reports of autoimmune and molecular mimicry phenomena have been described in CCC. The authors will review the evidence in support of an autoimmune basis for CCC pathogenesis in humans and experimental animals, with a special emphasis on molecular mimicry as a fundamental mechanism of autoimmunity.

Chagas disease in Texas: Recognizing the significance and implications of evidence in the literature

Chagas disease is endemic and is recognized as a major health problem in many Latin American countries. Despite the parallels between socio-economic and environmental conditions in Texas and much of Latin America, Chagas disease is not a notifiable human disease in Texas. Based on extensive review of related literature, this paper seeks to recognize the evidence that Chagas Disease is endemic to Texas but the epidemiological, parasitological and entomological patterns of Chagas disease in Texas are both different from and parallel to other endemic regions. We find that with a growing immigrant human reservoir, the epidemiological differences may be reduced and result in increasing incidence of the disease. Chagas disease should be recognized as an emerging disease among both immigrant and indigenous populations. Without proper actions, Chagas disease will place increasing burden on the health care system. Current medical treatments consist of chemotherapies that carry the risk of serious side effects; curing the potentially fatal disease remains equivocal. Therefore, as shown in South America, prevention is paramount and can be successfully achieved through intervention and education. We conclude that biogeographical research is needed to (1) distinguish the dynamic evolution of the agent-vector-host system, (2) document locations with greater risk and identify mechanisms responsible for observed changes in risk, and (3) assist in developing a model for Triatomid vector-borne disease in states like Texas where the disease is both endemic and may be carried by a sizeable immigrant population. Tracking of Chagas disease and planning for appropriate health care services would also be aided by including Chagas disease on the list of reportable diseases for humans.

Variants in the promoter region of IKBL/NFKBIL1 gene may mark susceptibility to the development of chronic Chagas' cardiomyopathy among Trypanosoma cruzi-infected individuals

Chagas' disease, caused by Trypanosoma cruzi, is an inflammatory disorder leading to chronic Chagas cardiomyopathy (CCC). Only one third of T. cruzi-infected individuals progress to CCC while the others are considered asymptomatic (ASY). The human inhibitory kappaB-like gene (IKBL/NFKBIL1), homologous to the IkappaB family of proteins that regulate the NFkappaB family of transcription factors, is suggested as a putative inhibitor of NFkappaB. We investigated two functional polymorphisms, -62A/T and -262A/G, in the promoter of IKBL by PCR-RFLP analysis in 169 patients with CCC and 76 ASY. Genotype distributions for both -62A/T and -262A/G differed between the CCC and ASY (chi2=7.3; P=0.025 and chi2=6.8; P=0.03, respectively). Subjects, homozygous for the -62A allele, had three-fold risk of developing CCC compared with those carrying the TT genotype (P=0.0095; Odds Ratio [OR]=2.9; [95% CI 1.2-7.3]). Similar trend was observed for the -262A homozygotes (P=0.005; OR=2.7 [95% CI 1.3-6.0]. The haplotype -262A -62A was prevalent in patients with CCC (40% versus 24%; OR 2.1 [95% CI 1.4-3.3]; Pc=0.0014). The IKBL locus itself or another critical gene in this region may confer susceptibility to the development of CCC.

Lack of association of tumor necrosis factor-α polymorphisms with Chagas disease in Brazilian patients

One third of Trypanosoma cruzi-infected individuals develop chronic Chagas disease cardiomyopathy (CCC) while the majority remains asymptomatic (ASY). About 30% of CCC patients develop heart failure due to end-stage inflammatory dilated cardiomyopathy. Increased production of tumor necrosis factor (TNF)-alpha has been described in all clinical forms of Chagas disease, and the highest levels are detected in CCC patients with severe ventricular dysfunction. Genetic susceptibility may play a role in the clinical outcome of Chagas disease. We investigated TNF as a candidate gene for susceptibility to development and/or progression of CCC. We analyzed the TNFa microsatellite and the -308 TNF promoter polymorphisms, in 166 CCC compared to 80 ASY geographically and age-matched patients in an association study. To analyze the association of TNF polymorphisms with progression of the cardiomyopathy, CCC patients were also grouped in three categories according to degree of left ventricular (LV) dysfunction into severe (n=57), mild to moderate (n=21) and absent (n=88). Our results show no significant differences either between CCC and ASY patients, or among CCC patients according to severity of cardiomyopathy with respect to TNFa or -308 TNF promoter polymorphisms. These results indicate that TNF polymorphisms are associated neither to CCC development nor to progression to more severe forms of cardiomyopathy in Brazilian Chagas disease patients.

Human Genetic Diversity and the Epidemiology of Parasitic and Other Transmissible Diseases

This paper aims to review human genetic studies that are generally poorly known by parasitologists and scientists working on other pathogenic agents. The key proposals of this paper are as follows: (i) human susceptibility to transmissible diseases may often have a complex, multigenic background; (ii) recent discoveries indicate that major genomic rearrangements may be involved, possibly more so than DNA sequence; (iii) it is crucial to have a general population genetics framework of the human species based on neutral/historical markers to analyse reliably genetic susceptibility to infectious diseases; and (iv) the population level is a key factor. Ethnic diversity, a highly adaptive genetically driven phenotypic diversity, is possibly a valuable source for exploring human genetic susceptibility to transmissible diseases, since different populations have been exposed to drastically different geographic/climatic environments and different pathogens and vectors for tens of thousands of years. Studies dealing with human genetic susceptibility to transmissible diseases have mostly been based on the hypothesis that this factor is driven by only one or a few genes, and considered the individual more than the population level. Two different approaches have been developed for identifying the genes involved: (i) candidate genes and (ii) blind association studies (linkage analysis), screening the genome with a large number of high-resolution markers. Some loci involved in susceptibility to leishmaniosis, malaria and schistosomosis, for example, have already been identified. South American trypanosomosis (Chagas disease) is reviewed in detail to show the methodological problems of this classical approach. Current knowledge on the general impact of transmissible diseases on human genetic diversity, mainly HLA polymorphism, and the hopes raised by recent major international programmes such as the Human Genome Project (HGP), Human Genome Diversity Project (HGDP), International Human Haplotype Map Project (Hap Map) and extended databases, networks and networks of networks will also be reviewed.

The monocyte chemoattractant protein-1 gene polymorphism is associated with cardiomyopathy in human chagas disease

BACKGROUND

Only a subset of individuals infected with Trypanosoma cruzi develop chronic Chagas cardiomyopathy (CCC). Familial aggregation of CCC in areas of endemicity indicates that susceptibility may be genetic, which may be a plausible explanation for why only one-third of T. cruzi-infected individuals develop CCC. The monocyte chemoattractant protein-1 (CCL2/MCP-1) has been shown to enhance the uptake of T. cruzi in murine macrophages and to up-regulate the inducible nitric oxide synthase/nitric oxide system, with a consequent increased production of nitric oxide that controls the replication of the parasite.

METHODS

We assessed CCL2 variants at position -2518A/G, which are known to influence transcriptional activity, by polymerase chain reaction and restriction fragment-length polymorphism in 245 individuals, all of whom were infected with T. cruzi. One hundred sixty-nine patients had CCC, and 76 were asymptomatic.

RESULTS

Genotype distributions differed between the CCC and asymptomatic groups (chi2 = 9.4; P = .009), with an excess of genotypes with the A allele (AA + AG) in the CCC group. Among patients with CCC, 5% were homozygous for the G allele, compared with 16% of the asymptomatic subjects (odds ratio [OR], 4.1; 95% confidence interval [CI], 1.7-11; P = .001). A similar trend was observed when individuals heterozygous for the G allele were compared with individuals homozygous for the G allele between the CCC and asymptomatic groups (OR, 2.7; 95% CI, 0.97-7.2; P = .026). The A allele seems to confer susceptibility to CCC (OR, 1.9; 95% CI, 1.3-2.9; P = .001).

CONCLUSIONS

The CCL2 variant correlated with a low transcriptional level behaves as a genetic modifier of clinical outcome for T. cruzi infection, and subjects with the CCL2 -2518AA genotype have a 4-fold greater risk of developing CCC than do those without this genotype.

Weekly electrocardiographic pattern in mice infected with two different Trypanosoma cruzi strains

BACKGROUND

Chagas' disease, which is caused by Trypanosoma cruzi, affects 20 million people. The electrocardiographic alterations are usually the first evidence of disease progression. In this work, we evaluated if two different T. cruzi strains presented electrocardiographic and heart histopathological alterations that could be characteristic and only achieved to the parasite strain. The moment when the electric alterations began was also studied.

METHODS

Albino mice (n=100) were inoculated with 50 (n=50) and 500 (n=50) trypomastigotes of T. cruzi, for Tulahuen strain and SGO-Z12 isolate, respectively. Electrocardiograms were obtained before infection and once a week from 7 to 147 days post infection (d.p.i). Dipolar and unipolar leads were analyzed. Hearts were removed by necropsy on 14, 90 and 147 d.p.i. Each heart was cut horizontally into 5-mum sections and they were stained with Hematoxilin-Eosine.

RESULTS

At 147 d.p.i., 30% of Tul-infected mice were found alive, while in the SGO-Z12 infected group, 75% were alive at the same moment. The Tul-infected group showed more intraventricular blockage alterations than the other groups from 49 to 70 d.p.i, (p<0.01). No structural cardiac alterations were detected in SGO-Z12-infected mice at 7 d.p.i., while the Tul-infected group showed mononuclear cell infiltrates. At 147 d.p.i., fiber disorganization and cell infiltration were observed in the SGO-Z12 and Tul-infected groups.

CONCLUSIONS

We demonstrated that T. cruzi Tulahuen strain and SGO-Z12 isolate determined different electrocardiographic alterations which were characteristic for each stage of the experimental Chagas' disease. These results highlight the importance of the T. cruzi strain in the severity of the cardiopathy.

Cardiovascular function in elderly patients with chronic chagasic cardiopathy

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.

Ageing with Trypanosoma cruzi infection in a community where the transmission has been interrupted: the Bambuí Health and Ageing Study (BHAS)

BACKGROUND

The prevalence of Chagas' disease is decreasing in Brazil. Due to cohort effect, the disease might remain a public health problem for some time among older individuals. The present burden of Trypanosoma cruzi infection for the elderly living in areas where the transmission has been interrupted has not been studied.

METHODS

The prevalence of T. cruzi infection and its association with indicators of health status and health services use were assessed among the elderly living in one of the oldest endemic areas in Brazil (Bambuí, MG). Seropositivity was determined by blood tests (IHA and ELISA) performed in 85.6% of all residents aged 60+ (1496/1742) and in 83.1% of sampled residents aged 5-59 years (1212/1458).

RESULTS

Seropositivity showed a cohort effect, with no cases below 20 years and high prevalence among those aged 60+ years (37.7%). After adjustment for confounders, seropositivity was associated with self-rated health reasonable (OR = 1.43; 95% CI : 1.03-1.98) and bad/very bad (OR = 1.89; 95% CI : 1.30-2.75), staying in bed in past 2 weeks (OR = 1.88; 95% CI : 1.21-2.92), hospitalization in past 12 months (OR = 1.41; 95% CI : 1.05-1.89) and use of 5+ prescribed medications in past 3 months (OR = 1.75; 95% CI : 1.15-2.59).

IMPLICATIONS

Our results are an example of how survival of individuals with past exposure to infectious disease may lead to a different picture of ageing in the developing world. Policy makers need to consider the extra burden imposed by increasing rates of non-infectious disease among the elderly (as observed in Brazil) including the consequences of T. cruzi infection in areas where the infection was widespread in the past.

Predictors of unfavourable prognosis in chronic Chagas' disease

The aim of this study was to detect clinical predictors of left ventricular dysfunction, left ventricular dilatation and apical aneurysm on echocardiography, all known as independent predictors of lethal outcome for patients with chronic Chagas' disease. Seventy-four patients with a positive complement-fixation test for Chagas' disease participated; 44 (59%) had left ventricular dysfunction, 41 (55%) left ventricular dilatation and 15 (20%) apical aneurysm. A stepwise logistic regression analysis showed that systolic blood pressure (P < 0.001) and male sex (P < 0.001) were independent predictors of left ventricular dilatation on echocardiography. A receiver-operating characteristic curve provided a systolic blood pressure of 120 mmHg with a sensitivity of 70% and a specificity of 63% to predict left ventricular dilatation. The combination of male sex and systolic blood pressure of 120 mmHg had a sensitivity of 56% and a specificity of 91% to predict left ventricular dilatation. In a separate stepwise logistic regression analysis, left ventricular systolic dysfunction was independently predicted by systolic blood pressure (P = 0.006) and New York Heart Association functional class (P = 0.01). Receiver-operating curves provided a blood pressure of 120 mmHg with a sensitivity of 72% and a specificity of 59% to predict left ventricular dysfunction, whereas a New York Heart Association functional score of 2 predicted left ventricular systolic dysfunction with a sensitivity of 78% and a specificity of 50%. The combination of New York Heart Association functional class and a systolic blood pressure of 120 mmHg predicted left ventricular dysfunction with a sensitivity of 59% and a specificity of 77%. The apical aneurysm was independently predicted by myocardial necrosis on the resting ECG, but only with a sensitivity of 20%. Hence, echocardiographic markers of cardiac mortality and sudden cardiac death in Chagas' disease can be independently predicted by clinical examination. This may be useful for screening high-risk chagasic patients.

[Indeterminate form of Chagas disease: considerations about diagnosis and prognosis]

The indeterminate form of Chagas' disease is defined by the absence of clinical, radiological and electrocardiographic manifestations of cardiac or digestive involvement in Trypanosoma cruzi chronic infected persons. When submitted to advanced cardiovascular tests, these patients may present significant abnormalities. However, the indeterminate form concept was reaffirmed as valid, since diagnostic criteria are simple and prognosis is benignant. In clinical practice, diagnostic difficulties are frequent, related to subjectivity and uncertain meaning of clinical, electrocardiographic and radiological findings. Moreover, indeterminate form prognosis is not equally good: after five to 10 years, a third of patients will have cardiopathy. Sudden death, a rare complication, may be the first manifestation of Chagas' disease. It is necessary to reappraise indeterminate form concept, redefining diagnostic criteria and therapeutic management. Clinical and noninvasive evaluation may allow individual risk stratification; therapeutic interventions may be beneficial in high risk groups. Since etiologic treatment may prevent cardiopathy, its role in indeterminate form management must be reassessed.

Randomised trial of efficacy of benznidazole in treatment of early Trypanosoma cruzi infection

BACKGROUND

Benznidazole, a nitroimidazole derivative, has been recommended for the treatment of acute and congenital Trypanosoma cruzi infection (Chagas' disease). We have examined the safety and efficacy of this drug in the treatment of the early chronic phase of T cruzi infection.

METHODS

Between 1991 and 1995, we carried out a randomised, double-blind, placebo-controlled trial in a rural area of Brazil with endemic Chagas' disease. 82% of 2434 schoolchildren (aged 7-12 years) identified in a census were screened for antibodies to T cruzi by indirect immunofluorescence, indirect haemagglutination, and ELISA. 130 were positive in all tests and were randomly assigned benznidazole (7.5 mg/kg daily for 60 days by mouth) or placebo. The primary endpoint for efficacy was the disappearance of specific antibodies (negative seroconversion) by the end of 3-year follow-up. The secondary endpoint was the reduction of antibody titres on repeated serological tests. One child moved away from the area just after randomisation and was excluded from the analyses. Insecticidal measures were taken throughout the trial to reduce the risk of reinfection.

FINDINGS

Minor side-effects requiring no specific medication were recorded in a small proportion of individuals. On a chemiluminescent ELISA with purified trypomastigote glycoconjugate, serum from all participants was positive at the beginning of the trial. At the end of follow-up, 37 (58%) of the 64 benznidazole-treated participants and 3 (5%) of those who received placebo were negative for T cruzi antibodies. The efficacy of benznidazole treatment estimated by intention to treat was 55.8% (95% CI 40.8-67.0). At the end of follow-up, children who received benznidazole had five-fold lower geometric mean titres by indirect immunofluorescence than placebo-treated children (196[147-256] vs 1068[809-1408], p < 0.00001).

INTERPRETATION

The trial showed that a 60-day course of benznidazole treatment of early chronic T cruzi infection was safe and 55.8% effective in producing negative seroconversion of specific antibodies. The results are very encouraging and justify the recommendation of treatment for seropositive children as public health policy.

Autoimmunity in Chagas disease cardiopathy: biological relevance of a cardiac myosin-specific epitope crossreactive to an immunodominant Trypanosoma cruzi antigen

Heart tissue destruction in chronic Chagas disease cardiopathy (CCC) may be caused by autoimmune recognition of heart tissue by a mononuclear cell infiltrate decades after Trypanosoma cruzi infection. Indirect evidence suggests that there is antigenic crossreactivity between T. cruzi and heart tissue. As there is evidence for immune recognition of cardiac myosin in CCC, we searched for a putative myosin-crossreactive T. cruzi antigen. T. cruzi lysate immunoblots were probed with anti-cardiac myosin heavy chain IgG antibodies (AMA) affinity-purified from CCC or asymptomatic Chagas disease patient-seropositive sera. A 140/116-kDa doublet was predominantly recognized by AMA from CCC sera. Further, recombinant T. cruzi protein B13--whose native protein is also a 140- and 116-kDa double band--was identified by crossreactive AMA. Among 28 sera tested in a dot-blot assay, AMA from 100% of CCC sera but only 14% of the asymptomatic Chagas disease sera recognized B13 protein (P = 2.3 x 10(-6)). Sequence homology to B13 protein was found at positions 8-13 and 1442-1447 of human cardiac myosin heavy chain. Competitive ELISA assays that used the correspondent myosin synthetic peptides to inhibit serum antibody binding to B13 protein identified the heart-specific AAALDK (1442-1447) sequence of human cardiac myosin heavy chain and the homologous AAAGDK B13 sequence as the respective crossreactive epitopes. The recognition of a heart-specific T. cruzi crossreactive epitope, in strong association with the presence of chronic heart lesions, suggests the involvement of crossreactivity between cardiac myosin and B13 in the pathogenesis of CCC.