HLA-C(*)03 is a risk factor for cardiomyopathy in Chagas disease

Cytokine Networks as Targets for Preventing and Controlling Chagas Heart Disease

Chagas disease, a neglected disease caused by the protozoan Trypanosoma cruzi, is endemic in 21 Latin American countries, affecting 6-8 million people. Increasing numbers of Chagas disease cases have also been reported in non-endemic countries due to migration, contamination via blood transfusions or organ transplantation, characterizing Chagas as an emerging disease in such regions. While most individuals in the chronic phase of Chagas disease remain in an asymptomatic clinical form named indeterminate, approximately 30% of the patients develop a cardiomyopathy that is amongst the deadliest cardiopathies known. The clinical distinctions between the indeterminate and the cardiac clinical forms are associated with different immune responses mediated by innate and adaptive cells. In this review, we present a collection of studies focusing on the human disease, discussing several aspects that demonstrate the association between chemokines, cytokines, and cytotoxic molecules with the distinct clinical outcomes of human infection with Trypanosoma cruzi. In addition, we discuss the role of gene polymorphisms in the transcriptional control of these immunoregulatory molecules. Finally, we discuss the potential application of cytokine expression and gene polymorphisms as markers of susceptibility to developing the severe form of Chagas disease, and as targets for disease control.

Admixture mapping analysis reveals differential genetic ancestry associated with Chagas disease susceptibility in the Colombian population

Chagas disease is an infection caused by the parasite Trypanosoma cruzi, endemic in Latino America. Leveraging the three-way admixture between Native American (AMR), European (EUR) and African (AFR) populations in Latin Americans, we aimed to better understand the genetic basis of Chagas disease by performing an admixture mapping study in a Colombian population. A two-stage study was conducted, and subjects were classified as seropositive and seronegative for T. cruzi. In stage 1, global and local ancestries were estimated using reference data from the 1000 Genomes Project (1KGP) and local ancestry associations were performed by logistic regression models. The AMR ancestry showed a protective association with Chagas disease within the Major Histocompatibility Complex region (OR = 0.74, 95%CI = 0.66-0.83, lowest p-value = 4.53x10-8). The fine mapping assessment on imputed genotypes combining data from stage 1 and 2 from an independent Colombian cohort, revealed nominally associated variants in high linkage disequilibrium with the top signal (rs2032134, OR = 0.93, 95%CI = 0.90-0.97, p-value = 3.54x10-4) in the previously associated locus. To assess ancestry-specific adaptive signals, a selective sweep scan in an AMR reference population from 1KGP together with an in silico functional analysis highlighted the Tripartite Motif family and the Human Leukocyte Antigen (HLA) genes, with crucial role in the immune response against pathogens. Furthermore, these analyses emphasized the macrophages, neutrophils, and eosinophils, as key players in the defense against T. cruzi. This first admixture mapping study in Chagas disease provided novel insights underlying the host immune response in the pathogenesis of this neglected disease.

Host Genetics Background Influence in the Intragastric Trypanosoma cruzi Infection

Background

Considering the complexity of the factors involved in the immunopathology of Chagas disease, which influence the Chagas' disease pathogenesis, anti-T. cruzi immune response, and chemotherapy outcome, further studies are needed to improve our understanding about these relationships. On this way, in this article we analyzed the host genetic influence on hematological, histopathological and immunological aspects after T. cruzi infection.

Methods

BALB/c and A mice were intragastrically infected with T. cruzi SC2005 strain, isolated from a patient of an outbreak of Chagas disease. Parameters such as parasite load, survival rates, cytokines production, macrophages, T and B cell frequencies, and histopathology analysis were carried out.

Results

BALB/c mice presented higher parasitemia and mortality rates than A mice. Both mouse lineages exhibited hematological alterations suggestive of microcytic hypochromic anemia and histopathological alterations in stomach, heart and liver. The increase of CD8+ T cells, in heart, liver and blood, and the increase of CD19+ B cells, in liver, associated with a high level of proinflammatory cytokines (IL-6, TNF-α, IFN-γ), confer a resistance profile to the host. Although BALB/c animals exhibited the same findings observed in A mice, the response to infection occurred later, after a considerable parasitemia increase. By developing an early response to the infection, A mice were found to be less susceptible to T. cruzi SC2005 infection.

Conclusions

Host genetics background shaping the response to infection. The early development of a cytotoxic cellular response profile with the production of proinflammatory cytokines is important to lead a less severe manifestation of Chagas disease.

Genomic medicine in Chagas disease

Genetic approaches have been proposed for improving the understanding of the causes of differential susceptibility to Trypanosoma cruzi infection and Chagas disease outcome. Polymorphisms in genes involved in the immune/inflammatory response are being studied in order to clarify their possible role in the occurrence or severity of the cardiac and/or gastrointestinal complications. However still today, the number of significant associated genes is limited and the pathophysiological mechanisms underlying this condition are unknown. This article review the information currently available from the published scientific literature regarding the genetic variants of molecules of the immune system and other variants that can contribute to the clinical presentation of the disease. Genomic medicine will improve our knowledge about the molecular basis of Chagas disease, will open new avenues for developing biomarkers of disease progression, new therapeutic strategies to suit the requirements of individual patients, and will contribute to the control of one of the infections with the greatest socio-economic impact in the Americas.

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.

A systematic review of the Trypanosoma cruzi genetic heterogeneity, host immune response and genetic factors as plausible drivers of chronic chagasic cardiomyopathy

Chagas disease is a complex tropical pathology caused by the kinetoplastid Trypanosoma cruzi. This parasite displays massive genetic diversity and has been classified by international consensus in at least six Discrete Typing Units (DTUs) that are broadly distributed in the American continent. The main clinical manifestation of the disease is the chronic chagasic cardiomyopathy (CCC) that is lethal in the infected individuals. However, one intriguing feature is that only 30-40% of the infected individuals will develop CCC. Some authors have suggested that the immune response, host genetic factors, virulence factors and even the massive genetic heterogeneity of T. cruzi are responsible of this clinical pattern. To date, no conclusive data support the reason why a few percentages of the infected individuals will develop CCC. Therefore, we decided to conduct a systematic review analysing the host genetic factors, immune response, cytokine production, virulence factors and the plausible association of the parasite DTUs and CCC. The epidemiological and clinical implications are herein discussed.

Trypanosoma cruzi genetic diversity: Something new for something known about Chagas disease manifestations, serodiagnosis and drug sensitivity

The genetic diversity of Trypanosoma cruzi, the protozoan agent of Chagas disease, is widely recognized. At present, T. cruzi is partitioned into seven discrete typing units (DTUs), TcI-TcVI and Tcbat. This article reviews the present knowledge on the parasite population structure, the evolutionary relationships among DTUs and their distinct, but not exclusive ecological and epidemiological associations. Different models for the origin of hybrid DTUs are examined, which agree that genetic exchange among T. cruzi populations is frequent and has contributed to the present parasite population structure. The geographic distribution of the prevalent DTUs in humans from the southern United States to Argentina is here presented and the circumstantial evidence of a possible association between T. cruzi genotype and Chagas disease manifestations is discussed. The available information suggests that parasite strains detected in patients, regardless of the clinical presentation, reflect the principal DTU circulating in the domestic transmission cycles of a particular region. In contrast, in several orally transmitted outbreaks, sylvatic strains are implicated. As a consequence of the genotypic and phenotypic differences of T. cruzi strains and the differential geographic distribution of DTUs in humans, regional variations in the sensitivity of the serological tests are verified. The natural resistance to benznidazole and nifurtimox, verified in vivo and in vitro for some parasite stocks, is not associated with any particular DTU, and does not explain the marked difference in the anti-parasitic efficacy of both drugs in the acute and chronic phases of Chagas disease. Throughout this review, it is emphasized that the interplay between parasite and host genetics should have an important role in the definition of Chagas disease pathogenesis, anti-T. cruzi immune response and chemotherapy outcome and should be considered in future investigations.

Trypanosoma cruzi vaccine candidate antigens Tc24 and TSA-1 recall memory immune response associated with HLA-A and -B supertypes in Chagasic chronic patients from Mexico

Trypanosoma cruzi antigens TSA-1 and Tc24 have shown promise as vaccine candidates in animal studies. We evaluated here the recall immune response these antigens induce in Chagasic patients, as a first step to test their immunogenicity in humans. We evaluated the in vitro cellular immune response after stimulation with recombinant TSA-1 (rTSA-1) or recombinant Tc24 (rTc24) in mononuclear cells of asymptomatic Chagasic chronic patients (n = 20) compared to healthy volunteers (n = 19) from Yucatan, Mexico. Proliferation assays, intracellular cytokine staining, cytometric bead arrays, and memory T cell immunophenotyping were performed by flow cytometry. Peripheral blood mononuclear cells (PBMC) from Chagasic patients showed significant proliferation after stimulation with rTc24 and presented a phenotype of T effector memory cells (CD45RA-CCR7-). These cells also produced IFN-γ and, to a lesser extent IL10, after stimulation with rTSA-1 and rTc24 proteins. Overall, both antigens recalled a broad immune response in some Chagasic patients, confirming that their immune system had been primed against these antigens during natural infection. Analysis of HLA-A and HLA-B allele diversity by PCR-sequencing indicated that HLA-A03 and HLA-B07 were the most frequent supertypes in this Mexican population. Also, there was a significant difference in the frequency of HLA-A01 and HLA-A02 supertypes between Chagasic patients and controls, while the other alleles were evenly distributed. Some aspects of the immune response, such as antigen-induced IFN-γ production by CD4+ and CD8+ T cells and CD8+ proliferation, showed significant association with specific HLA-A supertypes, depending on the antigen considered. In conclusion, our results confirm the ability of both TSA-1 and Tc24 recombinant proteins to recall an immune response induced by the native antigens during natural infection in at least some patients. Our data support the further development of these antigens as therapeutic vaccine against Chagas disease.

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.

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 susceptibility to Chagas disease: an overview about the infection and about the association between disease and the immune response genes

Chagas disease, which is caused by the flagellate parasite Trypanosoma cruzi, affects 8-10 million people in Latin America. The disease is endemic and is characterised by acute and chronic phases that develop in the indeterminate, cardiac, and/or gastrointestinal forms. The immune response during human T. cruzi infection is not completely understood, despite its role in driving the development of distinct clinical manifestations of chronic infection. Polymorphisms in genes involved in the innate and specific immune response are being widely studied in order to clarify their possible role in the occurrence or severity of disease. Here we review the role of classic and nonclassic MHC, KIR, and cytokine host genetic factors on the infection by T. cruzi and the clinical course of Chagas disease.

Potential elucidation of a novel CTL epitope in HIV-1 protease by the protease inhibitor resistance mutation L90M

The combination of host immune responses and use of antiretrovirals facilitate partial control of human immunodeficiency virus type 1 (HIV-1) infection and result in delayed progression to Acquired Immunodeficiency Syndrome (AIDS). Both treatment and host immunity impose selection pressures on the highly mutable HIV-1 genome resulting in antiretroviral resistance and immune escape. Researchers have shown that antiretroviral resistance mutations can shape cytotoxic T-lymphocyte immunity by altering the epitope repertoire of HIV infected cells. Here it was discovered that an important antiretroviral resistance mutation, L90M in HIV protease, occurs at lower frequencies in hosts that harbor the B*15, B*48 or A*32 human leukocyte antigen subtypes. A likely reason is the elucidation of novel epitopes by L90M. NetMHCPan predictions reveal increased affinity of the peptide spanning the HIV protease region, PR 89–97 and PR 90–99 to HLA-B*15/B*48 and HLA-A*32 respectively due to the L90M substitution. The higher affinity could increase the chance of the epitope being presented and recognized by Cytotoxic T-lymphocytes and perhaps provide additional immunological pressures in the presence of antiretroviral attenuating mutations. This evidence supports the notion that knowledge of HLA allotypes in HIV infected individuals could augment antiretroviral treatment by the elucidation of epitopes due to antiretroviral resistance mutations in HIV protease.

Genetic susceptibility to chronic Chagas disease: an overview of single nucleotide polymorphisms of cytokine genes

Chagas disease is a parasitic infection that is a significant public health problem in Latin America. The mechanisms responsible for susceptibility to the infection and the mechanisms involved in the development of cardiac and digestive forms of chronic Chagas disease remain poorly understood. However, there is growing evidence that differences in susceptibility in endemic areas may be attributable to host genetic factors. The aim of this overview was to analyze the genetic susceptibility to human Chagas disease, particularly that of single nucleotide polymorphisms of cytokine genes. A review of the literature was conducted on the following databases: PubMed/MEDLINE and Scopus. The search strategy included using the following terms: "Cytokines", "Single Nucleotide Polymorphisms" and "Chagas Disease". After screening 25 citations from the databases, 19 studies were selected for the overview. A critical analysis of the data presented in the articles suggests that genetic susceptibility to Chagas disease and chronic Chagas cardiomyopathy is highly influenced by the complexity of the immune response of the host. Follow-up studies based on other populations where Chagas disease is endemic (with distinct ethnic and genetic backgrounds) need to be conducted. These should use a large sample population so as to establish what cytokine genes are involved in susceptibility to and/or progression of the disease.

Chronic Chagas' heart disease: a disease on its way to becoming a worldwide health problem: epidemiology, etiopathology, treatment, pathogenesis and laboratory medicine

Chagas' disease, caused by Trypanosoma cruzi infection, is ranked as the most serious parasitic disease in Latin America. Nearly 30% of infected patients develop life-threatening complications, and with a latency of 10-30 years, mostly Chagas' heart disease which is currently the major cause of morbidity and mortality in Latin America, enormously burdening economic resources and dramatically affecting patients' social and labor situations. Because of increasing migration, international tourism and parasite transfer by blood contact, intrauterine transfer and organ transplantation, Chagas' heart disease could potentially become a worldwide problem. To raise awareness of this problem, we reflect on the epidemiology and etiopathology of Chagas' disease, particularly Chagas' heart disease. To counteract Chagas' heart disease, in addition to the general interruption of the infection cycle and chemotherapeutic elimination of the infection agent, early and effective causal or symptomatic therapies would be indispensable. Prerequisites for this are improved knowledge of the pathogenesis and optimized patient management. From economic and logistics viewpoints, this last prerequisite should be performed using laboratory medicine tools. Consequently, we first summarize the mechanisms that have been suggested as driving Chagas' heart disease, mainly those associated with the presence of autoantibodies against G-protein-coupled receptors; secondly, we indicate new treatment strategies involving autoantibody apheresis and in vivo autoantibody neutralization; thirdly, we present laboratory medicine tools such as autoantibody estimation and heart marker measurement, proposed for diagnosis, risk assessment and patient guidance and lastly, we critically reflect upon the increase in inflammation and oxidative stress markers in Chagas' heart disease.

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.

Angiotensin-converting enzyme insertion/deletion gene polymorphism and progression of Chagas' cardiomyopathy

Chagas' disease is common in Latin America and is caused by Trypanosoma cruzi. It is usually associated with chronic cardiomyopathy, the progression of which could be related to genetic factors. As alterations in the renin-angiotensin-aldosterone system have been reported in the disease, the aim of this study was to determine whether associated genetic polymorphisms influence the development of myocardial damage. The study involved 125 patients who were divided into two groups according to whether they had mild or severe cardiomyopathy. The insertion/deletion polymorphism of the angiotensin-converting enzyme gene was investigated using standard techniques and results were correlated with disease stage. The genotypes were in Hardy-Weinberg equilibrium. After adjusting for demographic variables, no significant relationship was found between the polymorphism and progression of chronic Chagas' disease. Although our sample was limited, the results suggest that the progression of cardiomyopathy in chronic Chagas' disease is unrelated to the insertion/deletion polymorphism.

Angiotensin-converting enzyme insertion/deletion gene polymorphism and progression of Chagas' cardiomyopathy

Chagas' disease is common in Latin America and is caused by Trypanosoma cruzi. It is usually associated with chronic cardiomyopathy, the progression of which could be related to genetic factors. As alterations in the renin-angiotensin-aldosterone system have been reported in the disease, the aim of this study was to determine whether associated genetic polymorphisms influence the development of myocardial damage. The study involved 125 patients who were divided into two groups according to whether they had mild or severe cardiomyopathy. The insertion/deletion polymorphism of the angiotensin-converting enzyme gene was investigated using standard techniques and results were correlated with disease stage. The genotypes were in Hardy-Weinberg equilibrium. After adjusting for demographic variables, no significant relationship was found between the polymorphism and progression of chronic Chagas' disease. Although our sample was limited, the results suggest that the progression of cardiomyopathy in chronic Chagas' disease is unrelated to the insertion/deletion polymorphism.

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.

Association study of PTPN22 C1858T polymorphism in Trypanosoma cruzi infection

In this study we investigated a possible role for the single nucleotide polymorphism C1858T of the PTPN22 (protein tyrosine phosphatase nonreceptor 22) gene in determining the susceptibility to Trypanosoma cruzi infection, as well as in development of chagasic heart disease. This study included 316 patients with Chagas' disease and 520 healthy individuals from Colombia and Peru. Genotyping of PTPN22 was performed by the real-time polymerase chain reaction technology, using the TaqMan 5' allelic discrimination assay. No statistically significant differences in the frequency of PTPN22 C1858T gene polymorphism between chagasic patients and controls or between asymptomatic and cardiomyopathic individuals were observed. Our findings suggest that the PTPN22 polymorphism analyzed does not play a major role in the development of Chagas' disease in the Colombian and Peruvian populations.

Interleukin-1 gene cluster polymorphism in chagas disease in a Colombian case-control study

The aim of this study was to assess the possible association between the IL1A, IL1B and IL1RN gene polymorphisms and Chagas disease. Our study population consisted of 130 serologically positive cardiomyopathic patients and 130 seropositive and asymptomatic individuals from a Colombian population where Trypanosoma cruzi infection is endemic. Genotyping of the IL1A (-889C/T, +4845G/T), IL1B (-511C/T, -31T/C, +3954T/C, +5810G/A) and IL1RN (+8006T/C, +8061C/T, +11100T/C) polymorphisms was performed by polymerase chain reaction-restriction fragment length polymorphism and polymerase chain reaction sequence-specific primer methods. Statistically significant differences in the distribution of the IL1B +5810 genotypes were observed comparing cardiomyopathic patients and asymptomatic individuals (p = 0.036). Frequency of the GG genotype was higher in the cardiomyopathic patient group than in the asymptomatic group (13% versus 5%, p = 0.03, odds ratio [OR] = 2.64, 95% confidence interval [CI] = 0.99-7.33). Differences in the distribution of the allele frequencies were also observed, being the +5810G allele overrepresented in patients with cardiomyopathy (37% versus 27%, p = 0.014, OR = 1.59, 95% CI = 1.08-2.36). Examination of markers in the IL1A (-889 and +4845), IL1B (-511, -31, and +3954) and IL1RN (+11100) genes revealed that the overall distribution of alleles and genotypes in patients with chagasic cardiomyopathy and asymptomatic were not significantly different. Our results show that in Colombian population the IL1B+5810G allele was associated with an increased risk chagasic cardiomyopathy. In addition, we demonstrated that homozygosity for the IL1B +5810G risk allele increased significantly the susceptibility to cardiomyopathy. This implies that the effect of IL1B gene on chagasic cardiomyopathy predisposition is dose dependent. We found that the haplotype CT of IL1B -31 and +3954 polymorphisms showed higher association with risk to chagasic cardiomyopathy (p(c) = 0.008, OR = 12.53) and the extended haplotype (CCTCATT) was significantly more frequent in asymptomatic than in cardiomyopathic patients (p = 0.0014, p(c) = 0.011, OR = 0.17). Therefore this study suggests that IL1 gene cluster polymorphisms may play a relevant role in the susceptibility to development of chagasic chronic cardiomyopathy.

Chagas' disease susceptibility/resistance: linkage disequilibrium analysis suggests epistasis between major histocompatibility complex and interleukin-10

Association between the major histocompatibility complex (MHC) and the susceptibility/resistance to acquire Chagas' disease has been largely demonstrated. To study the role of candidate genes in this susceptibility/resistance to Chagas, we designed a population-genetic-based case-control approach (chagasic n = 104 and controls n = 60) and tested the presence of genotype and linkage disequilibrium on microsatellite loci establishing specific landmarks for the MHC, interleukin (IL)-2, IL-2Rbeta chain, IL-4, IL-10, and natural resistance-associated mactophage protein 1 (NRAMP1). After demonstrating no genetic stratification among cases and controls (F(st) were not different from 0), we found significant allelic differences among chagasic patients and controls at microsatellite locus D6S291 (MHC) and at the microsatellite pointing out the IL-10. At the MHC, we found significant differences between patients and controls in Hardy-Weinberg equilibrium-expected genotype proportions. Additionally, MHC II-locus-inferred haplotypes in chagasic patients exhibited strong significant departures from the expected proportions predicted by the second Mendelian law. The linkage disequilibrium pattern at MHC involves a region of approximately 10 cM. These results replicate previous analyses and suggest that presence of epistasis between MHC with humoral systems, such as IL-10, could be underlying the susceptibility/resistance to Chagas' disease.

Immune response to a major Trypanosoma cruzi antigen, cruzipain, is differentially modulated in C57BL/6 and BALB/c mice

BALB/c mice immunized with cruzipain, a major Trypanosoma cruzi antigen, produce specific and autoreactive immune responses against heart myosin, associated with cardiac functional and structural abnormalities. Preferential activation of the Th2 phenotype and an increase in cell populations expressing CD19+, Mac-1+ and Gr-1+ markers were found in the spleens of these mice. The aim of the present study was to investigate whether cardiac autoimmunity could be induced by cruzipain immunization of C57BL/6 mice and to compare the immune response elicited with that of BALB/c mice. We demonstrate that immune C57BL/6 splenocytes, re-stimulated in vitro with cruzipain, produced high levels of IFNgamma and low levels of IL-4 compatible with a Th1 profile. In contrast to BALB/c mice, spleens from cruzipain immune C57BL/6 mice revealed no significant changes in the number of cells presenting CD19+, Mac-1+ and Gr-1+ markers. An increased secretion of TGFbeta and a greater number of CD4+ TGFbeta+ cells were found in immune C57BL/6 but not in BALB/c mice. These findings were associated with the lack of autoreactive response against heart myosin and a myosin- or cruzipain-derived peptide. Thus, the differential immune response elicited in C57BL/6 and BALB/c mice upon cruzipain immunization is implicated in the resistance or pathogenesis of experimental Chagas' disease.

MHC class I and class II genes in mexican patients with Chagas disease

Chagas' disease contributes significantly to cardiovascular morbidity and mortality in several Latin-American countries. Previous studies have reported the effect of the human leukocyte antigen (HLA) molecules in the immune response regulation of Trypanosoma cruzi infection, and the association of HLA antigens with heart damage. We studied the major histocompatibility complex (MHC) class I (HLA-A and HLA-B), and class II (HLA-DR) genes in a sample of 66 serologically positive individuals with and without cardiomyopathy, and in 127 healthy controls. The total group of seropositive individuals revealed increased frequencies of HLA-B39 (pc=4.3x10(-5), odds ratio [OR]=3.35) and DR4 (pc=1.8x10(-5), OR=2.91) when compared to healthy controls. Increased frequencies of HLA-A68 and HLA-B39 were found in asymptomatic individuals when compared to patients with cardiomyopathy (pc=0.014, OR=4.99 and pc=0.001, OR=4.46, respectively). Also, patients with cardiomyopathy exhibited increased frequency of HLA-B35 when compared to healthy controls (pc=0.048, OR=2.56). The HLA-DR16 frequency was increased in patients with cardiomyopathy compared with asymptomatic individuals (pc=0.05, OR=No determined) and healthy controls (pc=0.02, OR=5.0). The results suggest that MHC alleles might be associated with the development of chronic infection and with heart damage in Chagas' disease. HLA-DR4 and HLA-B39 could be associated directly with the infection by T. cruzi, whereas, HLA-DR16 could be marker of susceptibility to heart damage and HLA-A68 might confer protection to develop cardiomyopathy.

Complement C3 F and BF S allotypes are risk factors for Chagas disease cardiomyopathy

The heterogeneity in the clinical expression of Chagas disease gives strong evidences for the involvement of genetic factors on its pathogenesis. Several studies have indicated different markers of genetic susceptibility to Chagas cardiomyopathy. In the present study, we present evidence of association between complement C3 and BF allotypes, and the susceptibility to Chagas disease and the development of cardiomyopathy. C3, BF, C4A, C4B and C2 polymorphism were determined in 100 seropositive Chagasic patients [cardiomyopathic (CARD), n = 57; asymptomatic indetermined (IND), n = 43] and in 100 non-related seronegative healthy controls. Patients and controls were matched according to their ethnic and geographical origin. A significantly increased frequency of C3F was observed in patients with the CARD form (8/57 14.03%), when compared with those presenting the IND form (0/43, 0%; RR 7.0) and with the healthy controls (5/100, 5%; RR 3.1). A negative association of the BF S allotype was observed in the CARD patients (19/57 33.33%) and in the Chagas total (38/100 38.0%), when compared with the controls (55/100, 55.0%; RR 0.4). All other C3, BF, C4A, C4B and C2 alleles showed no significant differences. These results suggest the allele C3F as a susceptible marker for the progression of the CARD form. On the other hand, BF S may represent a protective role against severe CARD disease. These results corroborate the importance of the alternative pathway in Trypanosoma cruzi infection and indicate possible genetic markers of Chagas cardiomyopathy.

Chronic murine Chagas' disease: the impact of host and parasite genotypes

Chagas' disease is a protozoan infection caused by the flagellate Trypanosoma cruzi. Herein we utilise experimental infections of different mouse and parasite strains to investigate the relative importance of the host and parasite genotype, respectively, in causing Chagas' disease in mice. CBA/J and BALB/c mice infected with the Tulahuen strain of T. cruzi develop a severe acute disease characterised by transient parasitaemia and a high rate of mortality. While the acute phases in these mice are indistinguishable, they display differential outcomes of the infection since CBA/J mice eventually develop polymyositis and mild myocarditis whereas BALB/c mice are resistant to chronic disease. In contrast, BALB/c mice infected with the CA-1 clone of T. cruzi exhibit a mild acute phase, develop no polymyositis but do develop severe myocarditis. Thus both the parasite and host genotype, but not the severity of the acute phase, are important in determining the eventual outcome of T. cruzi infection. We also present a murine model suitable for investigating which host factors may be necessary to induce a chronic inflammatory disease after T. cruzi infection.

Analysis of the T-cell receptor beta-chain variable-region (Vbeta) repertoire in chronic human Chagas' disease

Previous studies have shown that infection with the protozoan Trypanosoma cruzi (Chagas' disease) is associated with genetic components [human leukocyte antigen (HLA) genes and T-cell receptor (TCR) genes]. We studied the TCR Vbeta repertoire of peripheral blood lymphocytes of 23 unrelated serologically positive subjects using reverse transcriptase-polymerase chain reaction (RT-PCR). The patients, previously tested for HLA genotypes, were clinically classified as asymptomatic, arrhythmic and cardiopathic patients. Statistical analysis showed the significant increment of the Vbeta7 family in chagasics with arrhythmia compared with asymptomatic and cardiopathic patients, indicating that the frequency of this family is variable in different clinical forms of the disease and possibly that these T cells might be a marker of the progression of Chagas' disease. Based on the calculation of a Delta score the order of variability in the TCR repertoire was: patients with heart failure > asymptomatic > arrhythmic patients. The major histocompatibility complex (MHC) of the individual may influence the use of particular V genes in T-cell response to foreign antigens. We found a significant increase of the Vbeta7 family in arrhythmic patients who were DRB1*01 DQB1*0501 DPB1*0401, a marker associated with susceptibility to cardiac damage in Chagas' disease. If confirmed by further studies in a larger cohort, a possible association between the TCR Vbeta repertoire and the MHC haplotype of chagasic patients could be postulated.

Lack of association between NRAMP1 gene polymorphisms and Trypanosoma cruzi infection

Genetic analysis in mice and humans have established the key role of the human natural resistance-associated macrophage protein 1 (NRAMP1) in resistance to intracellular infections. In the present study we investigated whether four NRAMP1 polymorphisms (5'(GT)n, -236 C-->T, D543N, and 3'UTR deletion) were important in determining the susceptibility to Trypanosoma cruzi infections as well as in the development of chagasic cardiac disease. Genotyping for these variants was assessed in 83 seropositive (asymptomatic, n=51, cardiomyopathic, n=32) and 85 seronegative individuals from a Peruvian population where T. cruzi is endemic. No statistically significant differences either between patients and controls or between asymptomatic and cardiomyopathic individuals were observed with respect to NRAMP1 variants. Our data suggest that the NRAMP1 genetic polymorphism analysed do not play a major role in the pathogenesis of T. cruzi infection in this Peruvian sample.