Systemic cytokines, chemokines and growth factors reveal specific and shared immunological characteristics in infectious cardiomyopathies.

Heart disease is a major cause of death worldwide. Chronic Chagas cardiomyopathy (CCC) caused by infection with Trypanosoma cruzi leading to high mortality in adults, and rheumatic heart disease (RHD), resulting from infection by Streptococcus pyogenes affecting mainly children and young adults, are amongst the deadliest heart diseases in low-middle income countries. Despite distinct etiology, the pathology associated with both diseases is a consequence of inflammation. Here we compare systemic immune profile in patients with these cardiopathies, to identify particular and common characteristics in these infectious heart diseases. We evaluated the expression of 27 soluble factors, employing single and multivariate analysis combined with machine-learning approaches. We observed that, while RHD and CCC display higher levels of circulating mediators than healthy individuals, CCC is associated with stronger immune activation as compared to RHD. Despite distinct etiologies, univariate analysis showed that expression of TNF, IL-17, IFN-gamma, IL-4, CCL4, CCL3, CXCL8, CCL11, CCL2, PDGF-BB were similar between CCC and RHD, consistent with their inflammatory nature. Network analysis revealed common inflammatory pathways between CCC and RHD, while highlighting the broader reach of the inflammatory response in CCC. The final multivariate model showed a 100% discrimination power for the combination of the cytokines IL-12p70, IL-1Ra, IL-4, and IL-7 between CCC and RHD groups. Thus, while clear immunological distinctions were identified between CCC and RHD, similarities indicate shared inflammatory pathways in these infectious heart diseases. These results contribute to understanding the pathogenesis of CCC and RHD and may impact the design of immune-based therapies for these and other inflammatory cardiopathies that may also share immunological characteristics.

Myocardial fibrosis in chagas disease and molecules related to fibrosis.

Chronic Chagas cardiomyopathy (CCC) is responsible for the disease's greater morbidity and poor prognosis. Although understanding the pathophysiology of CCC and the fundamentals of its clinical management derives from research related to other cardiomyopathies, there are peculiarities that distinguish CCC from the others. CCC is the most fibrous heart disease, and its myocardial involvement is important as it disorganizes or disrupts the extracellular matrix, creating an environment conducive to the formation of arrhythmogenic foci. It is also considered the most arrhythmogenic of the known heart diseases, giving rise to complex arrhythmias, usually associated with varying degrees of stimulus conduction disorders. The central proposal of this review is to describe a possible association between the distribution and degree of myocardial fibrosis and cardiac arrhythmogenicity in patients with Chagas cardiomyopathy, drawing attention to the importance of noninvasive biomarkers for the quantification of myocardial fibrosis.

Regulatory T cells: Friends or foe in human Mycobacterium leprae infection?

Regulatory T cells (Tregs) are known to control immune responses by suppressing the antigen-presenting and effector T cells. Some mechanisms adopted by Tregs in combating Mycobacterium infections have been proposed. Nevertheless, in M. leprae infection, also known as leprosy or Hansen's disease, the role of Tregs has not been completely elucidated. Using multicolor flow cytometry, we evaluated the expression of different cell surface and intracellular molecules present in Tregs from peripheral blood samples of leprosy patients. Before initiating treatment, thirteen new cases of leprosy were grouped according to the Ridley-Jopling classification in to the paucibacilary (PB) or multibacilary (MB) group. Fifteen non-infected individuals (NI) were included as control subjects. Tregs were higher in the MB group than in the NI group. Tregs also co-expressed high amounts of PD1 and PDL-1, indicating that these cells could induce apoptosis of effector cells and simultaneously prevent their own apoptosis. Our data showed that compared to the NI group, Tregs from the PB group expressed higher levels of CD95L, which may be associated with other apoptotic pathways that may decrease Tregs in these patients. Correlation analysis reinforced that PD1 and CD95L are efficient apoptosis' pathway that decreased levels of Tregs in the NI and PB groups. We also observed significant differences in cytokine expression of Tregs from the PB and MB groups. Compared to the NI group, Tregs from the MB group showed higher IL-17 expression; however, compared to the PB group, the expression of IL-10 in Tregs from the MB group was lower, suggesting inefficient control of inflammation. Therefore, we concluded that different pathways were involved in Treg-induced suppression of leprosy. Moreover, Treg-mediated regulation of inflammation via IL-10 and IL-17 expression in leprosy patients was inefficient. Thus, we propose that during M. leprae infection, Tregs may impair the immune responses elicited against this bacillus, favor bacterial replication, and aid in persistence of a disseminated multibacillary disease.

Dysautonomia due to reduced cholinergic neurotransmission causes cardiac remodeling and heart failure.

Overwhelming evidence supports the importance of the sympathetic nervous system in heart failure. In contrast, much less is known about the role of failing cholinergic neurotransmission in cardiac disease. By using a unique genetically modified mouse line with reduced expression of the vesicular acetylcholine transporter (VAChT) and consequently decreased release of acetylcholine, we investigated the consequences of altered cholinergic tone for cardiac function. M-mode echocardiography, hemodynamic experiments, analysis of isolated perfused hearts, and measurements of cardiomyocyte contraction indicated that VAChT mutant mice have decreased left ventricle function associated with altered calcium handling. Gene expression was analyzed by quantitative reverse transcriptase PCR and Western blotting, and the results indicated that VAChT mutant mice have profound cardiac remodeling and reactivation of the fetal gene program. This phenotype was attributable to reduced cholinergic tone, since administration of the cholinesterase inhibitor pyridostigmine for 2 weeks reversed the cardiac phenotype in mutant mice. Our findings provide direct evidence that decreased cholinergic neurotransmission and underlying autonomic imbalance cause plastic alterations that contribute to heart dysfunction.

Trypanosoma cruzi infection induces differential modulation of costimulatory molecules and cytokines by monocytes and T cells from patients with indeterminate and cardiac Chagas' disease.

Interactions between macrophages and lymphocytes through costimulatory molecules and cytokines are essential for mounting an efficient immune response and controlling its pathogenic potential. Here we demonstrate the immunomodulatory capacity of Trypanosoma cruzi, the causative agent of Chagas' disease, through its ability to induce differential expression of costimulatory molecules and cytokines by monocytes and T cells. Costimulatory molecule and cytokine modulation was evaluated using cells from noninfected individuals and from patients with the asymptomatic indeterminate form and those with the severe cardiac clinical form of Chagas' disease. Our results show that while exposure of monocytes to live T. cruzi leads to an increase in the frequency of CD80(+) monocytes in all groups, it decreases both the frequency and intensity of CD86 expression by monocytes from patients with the cardiac form but not from those with the indeterminate form. Conversely, exposure of lymphocytes to monocytes infected with T. cruzi increased the surface expression of cytotoxic-T-lymphocyte-associated antigen 4 (CTLA-4) by T cells from indeterminate but not from cardiac patients, compared to that from control patients. These data suggest that T. cruzi induces a potentially down-regulatory environment in indeterminate subjects, which is associated with higher CD80 and CTLA-4 expression. To test the functional importance of this modulation, we evaluated the expression of cytokines after in vitro infection. Although exposure of lymphocytes to parasite-infected monocytes induced high expression of inflammatory and anti-inflammatory cytokines by T cells in all groups, indeterminate patients displayed a higher ratio of monocytes expressing interleukin 10 than tumor necrosis factor alpha following infection than did controls. These data show the ability of T. cruzi to actively change the expression of costimulatory molecules and cytokines, suggesting molecular mechanisms for the differential clinical evolution of human Chagas' disease.

Monocytes from patients with indeterminate and cardiac forms of Chagas' disease display distinct phenotypic and functional characteristics associated with morbidity.

Many studies have demonstrated that monocyte-derived macrophages display critical activities in immunity to parasites. The ability of these cells to process and present antigens, produce cytokines, and provide costimulatory signals demonstrates their pivotal role in initiating immune responses. Although potential modulatory function has been attributed to monocytes from patients with Chagas' disease, a systematic phenotypic and functional analysis of these cells has not been performed. In this work, we analyzed the ex vivo expression of important surface molecules (CD11b and HLA-DR) and immunoregulatory cytokines (interleukin-10 [IL-10], IL-12 and tumor necrosis factor alpha [TNF-alpha]) in CD14(+) and CD14(-) monocytes from Chagas' disease patients with polar clinical forms of the disease: indeterminate or severe cardiac. We also evaluated the influence of in vitro infection with T. cruzi in the expression of such molecules. We observed that monocytes from indeterminate-disease patients display lower levels of HLA-DR than those from noninfected individuals both ex vivo and after in vitro infection with T. cruzi. Although ex vivo expression of CD11b was similar among the groups, in vitro infection led to decreased expression of this molecule by monocytes from Chagas' disease patients but not from noninfected individuals. Analysis of the expression of immunoregulatory cytokines showed that while monocytes from indeterminate-disease patients are committed to IL-10 expression, a higher percentage of monocytes from cardiac-disease patients express TNF-alpha after exposure to live parasites. These results suggest that monocytes from indeterminate-disease patients display modulatory characteristics related to low HLA-DR and high IL-10 expression whereas monocytes from cardiac-disease, patients may be committed to induction of inflammatory responses related to high TNF-alpha expression.