Protection against experimental autoimmune myocarditis is mediated by interleukin-10-producing T cells that are controlled by dendritic cells

Autoimmune Myocarditis, Old Dogs and New Tricks

Autoimmunity significantly contributes to the pathogenesis of myocarditis, underscored by its increased frequency in autoimmune diseases such as systemic lupus erythematosus and polymyositis. Even in cases of myocarditis caused by viral infections, dysregulated immune responses contribute to pathogenesis. However, whether triggered by existing autoimmune conditions or viral infections, the precise antigens and immunologic pathways driving myocarditis remain incompletely understood. The emergence of myocarditis associated with immune checkpoint inhibitor therapy, commonly used for treating cancer, has afforded an opportunity to understand autoimmune mechanisms in myocarditis, with autoreactive T cells specific for cardiac myosin playing a pivotal role. Despite their self-antigen recognition, cardiac myosin-specific T cells can be present in healthy individuals due to bypassing the thymic selection stage. In recent studies, novel modalities in suppressing the activity of pathogenic T cells including cardiac myosin-specific T cells have proven effective in treating autoimmune myocarditis. This review offers an overview of the current understanding of heart antigens, autoantibodies, and immune cells as the autoimmune mechanisms underlying various forms of myocarditis, along with the latest updates on clinical management and prospects for future research.

Recurrent Adrenergic Stress Provokes Persistent Myocarditis in PD-1-Deficient Mice

It is unclear how the immune system initiates effective tissue repair responses without also simultaneously activating adaptive immune responses to self-antigens released by damaged or necrotic cells. We studied the role of repetitive adrenergic mediated stress on cardiac injury wild-type and programmed death-1-deficient (PD-1-/-) mice treated with 3 intraperitoneal low doses of isoproterenol followed by an intraperitoneal injection of high-dose ISO 7 days later (ISOprimed/ISOinjury). Repetitive adrenergic stress in ISOprimed/ISOinjury PD-1-/- mice resulted in a persistent dysregulated myocardial inflammatory response characterized by the expansion of autoreactive effector CD8+ T cells, increased cardiac hypertrophy, mild left ventricular dysfunction, and increased lethality when compared with ISOprimed/ISOinjury wild-type mice.

Emerging Roles for Dendritic Cells in Heart Failure

The field of cardio-immunology has emerged from discoveries that define roles for innate and adaptive immune responses associated with myocardial inflammation and heart failure. Dendritic cells (DCs) comprise an important cellular compartment that contributes to systemic immune surveillance at the junction of innate and adaptive immunity. Once described as a singular immune subset, we now appreciate that DCs consist of a heterogeneous pool of subpopulations, each with distinct effector functions that can uniquely regulate the acute and chronic inflammatory response. Nevertheless, the cardiovascular-specific context involving DCs in negotiating the biological response to myocardial injury is not well understood. Herein, we review our current understanding of the role of DCs in cardiac inflammation and heart failure, including gaps in knowledge and clinical relevance.

LNA oligonucleotide mediates an anti-inflammatory effect in autoimmune myocarditis via targeting lactate dehydrogenase B

Treatment of myocarditis is often limited to symptomatic treatment due to unknown pathomechanisms. In order to identify new therapeutic approaches, the contribution of locked nucleic acid antisense oligonucleotides (LNA ASOs) in autoimmune myocarditis was investigated. Hence, A/J mice were immunized with cardiac troponin I (TnI) to induce experimental autoimmune myocarditis (EAM) and treated with LNA ASOs. The results showed an unexpected anti‐inflammatory effect for one administered LNA ASO MB_1114 by reducing cardiac inflammation and fibrosis. The target sequence of MB_1114 was identified as lactate dehydrogenase B (mLDHB). For further analysis, mice received mLdhb‐specific GapmeR during induction of EAM. Here, mice receiving the mLdhb‐specific GapmeR showed increased protein levels of cardiac mLDHB and a reduced cardiac inflammation and fibrosis. The effect of increased cardiac mLDHB protein level was associated with a downregulation of genes of reactive oxygen species (ROS)‐associated proteins, indicating a reduction in ROS. Here, the suppression of murine pro‐apoptotic Bcl‐2‐associated X protein (mBax) was also observed. In our study, an unexpected anti‐inflammatory effect of LNA ASO MB_1114 and mLdhb‐specific GapmeR during induction of EAM could be demonstrated in vivo. This effect was associated with increased protein levels of cardiac mLDHB, mBax suppression and reduced ROS activation. Thus, LDHB and LNA ASOs may be considered as a promising target for directed therapy of myocarditis. Nevertheless, further investigations are necessary to clarify the mechanism of action of anti‐inflammatory LDHB‐triggered effects.

Characterization of dendritic cells in human and experimental myocarditis

Aims

Dendritic cells (DCs) are central mediators of adaptive immunity, and there is growing evidence of their role in myocardial inflammatory disease. We hypothesized that plasmacytoid and myeloid DCs are involved in the mechanisms of myocarditis and analysed these two main subtypes in human myocarditis subjects, as well as in a murine model of experimental autoimmune myocarditis (EAM).

Methods and results

Circulating DCs were analysed by flow cytometry in patients with acute myocarditis, dilated cardiomyopathy, and controls. Myocardial biopsies were immunostained for the presence of DCs and compared with non‐diseased controls. In a mouse model of acute myocarditis induced through synthetic cardiac myosine peptide injection, effects of immunomodulation including DC inhibition through MCS‐18 versus placebo treatment were tested at the peak of inflammation (Day 21), as well as 1 week later (partial recovery). Circulatory pDCs and mDCs were significantly reduced in myocarditis patients compared with controls (P < 0.01 for both) and remained so even after 6 months of follow‐up. Human myocarditis biopsies showed accumulation of pDCs (two‐fold CD304+/three‐fold CD123+, all P < 0.05) compared with controls. Myocardial pDCs and mDCs accumulated in EAM (P for both <0.0001). MCS‐18 treatment reduced pDC levels (P = 0.009), reduced myocardial inflammation (myocarditis score reduction from 2.6 to 1.8, P = 0.026), and improved ejection fraction (P = 0.03) in EAM at Day 21 (peak of inflammation). This effect was not observed during the partial recovery of inflammation on Day 28.

Conclusions

Circulating DCs are reduced in human myocarditis and accumulate in the inflamed myocardium. MCS‐18 treatment reduces DCs in EAM, leading to amelioration of inflammation and left ventricular remodelling during the acute phase of myocarditis. Our data further elucidate the role of DCs and their specific subsets in acute inflammatory cardiomyopathies.

Protosappanin A protects against experimental autoimmune myocarditis, and induces metabolically reprogrammed tolerogenic DCs

Autoimmune myocarditis is an immune-mediated myocardial injury that evolves into dilated cardiomyopathy (DCM). Protosappanin A (PrA), an immunosuppressive compound, induces immune tolerance in cardiac transplantation. However, whether PrA confers protective immunosuppression on experimental autoimmune myocarditis (EAM) is unknown. In this study, PrA treatment remarkably suppressed cardiac inflammatory cell infiltration and ameliorated cardiac remodeling in EAM mice. Additionally, PrA treatment reduced splenic T cells response, and induced expansion of immunosuppressive regulatory T cells (Tregs). Meanwhile, PrA induced the splenic dendritic cells (DCs) into a tolerogenic state with reduced co-stimulatory molecules, increased the production of tolerogenic cytokines in vivo. PrA also reprogrammed the metabolism of splenic DCs to a more glycolytic phenotype. To further investigate the effect of PrA on the functional and metabolic phenotype of DCs, the compound was added into the in vitro culture of MyHC-α-loaded DCs. These cells switched to a tolerogenic state and a metabolic profile similar to that found in cells during in ex vivo experiments. Treatment with glycolytic inhibitor 2-DG significantly reversed PrA-mediated DC tolerogenic properties, suggesting that glycolysis is indispensable for PrA-conditioned DCs to maintain their tolerogenic properties. Notably, PrA-conditioned DC vaccinations dampened EAM progress, and promoted Tregs expansion. Similarly, tolerogenic and metabolic patterns were also observed in PrA-modified human DC. In conclusion, PrA endows DC with a tolerogenic profile via glycolytic reprogramming, thereby inducing expansion of immunosuppressive Tregs, and preventing EAM progress. Our results suggested that PrA may confer immunosuppressive and protective effects on EAM by metabolically reprogramming DCs, which could contribute to the development of a new potential immunotherapy for the treatment of EAM and immune-related disorders.

Regulatory Role of CD4+ T Cells in Myocarditis

Myocarditis is an important cause of heart failure in young patients. Autoreactive, most often, infection-triggered CD4⁺ T cells were confirmed to be critical for myocarditis induction. Due to a defect in clonal deletion of heart-reactive CD4⁺ T cells in the thymus of mice and humans, significant numbers of heart-specific autoreactive CD4⁺ T cells circulate in the blood. Normally, regulatory T cells maintain peripheral tolerance and prevent spontaneous myocarditis development. In the presence of tissue damage and innate immune activation, however, activated self-antigen-loaded dendritic cells promote CD4⁺ effector T cell expansion and myocarditis. So far, a direct pathogenic role has been described for both activated Th17 and Th1 effector CD4⁺ T cell subsets, though Th1 effector T cell-derived interferon-gamma was shown to limit myocarditis severity and prevent transition to inflammatory dilated cardiomyopathy. Interestingly, recent observations point out that various CD4⁺ T cell subsets demonstrate high plasticity in maintaining immune homeostasis and modulating disease phenotypes in myocarditis. These subsets include Th1 and Th17 effector cells and regulatory T cells, despite the fact that there are still sparse and controversial data on the specific role of FOXP3-expressing Treg in myocarditis. Understanding the specific roles of these T cell populations at different stages of the disease progression might provide a key for the development of successful therapeutic strategies.

Complete Freund's adjuvant induces experimental autoimmune myocarditis by enhancing IL-6 production during initiation of the immune response

INTRODUCTION

Complete Freund's Adjuvant (CFA) emulsified with an antigen is a widely used method to induce autoimmune disease in animal models, yet the contribution of CFA to the immune response is not well understood. We compared the effectiveness of CFA with Incomplete Freund's Adjuvant (IFA) or TiterMax Gold Adjuvant (TMax) in experimental autoimmune myocarditis (EAM) in male mice.

METHODS

EAM was induced in A/J, BALB/c, and IL6KO BALB/c male mice by injection of the myocarditogenic peptide in CFA, IFA, or TMax on days 0 and 7. EAM severity was analyzed by histology on day 21. In addition, specific flow cytometry outcomes were evaluated on day 21.

RESULTS

Only mice immunized with CFA and myocarditogenic peptide on both days 0 and 7 developed substantial myocarditis as measured by histology. We observed a significantly increased level of IL6 in the spleen 3 days after CFA immunization. In the spleen and heart on day 21, there was an expansion of myeloid cells in CFA-immunized mice, as compared to IFA or TMax-immunized animals. Recombinant IL-6 at the time of IFA immunization partially restored susceptibility of the mice to EAM. We also treated EAM-resistant IL-6 knockout mice with recombinant IL-6 around the time of the first immunization, on days -1 to 2, completely restoring disease susceptibility, showing that the requirement for IL-6 coincides with primary immunization. Examining APC populations in the lymph node draining the immunization site evidenced the contribution of IL-6 to the CFA-dependence of EAM was through controlling local dendritic cell (DC) trafficking.

CONCLUSIONS

CFA used with myocarditogenic peptide twice is required to induce EAM in both A/J and Balb/c mice. Although IFA and TiterMax induce antibody responses, only CFA preferentially induced autoantigen-specific responses. CFA expands monocytes in the heart and in the spleen. IL-6 signaling is required during short window around primary immunization to induce EAM. In addition, IL-6 deficient mice resistance to EAM could be reversed by injecting IL-6 around first immunization. IL-6 expands dendritic cell and monocytic populations and ultimately leads to a robust T-cell driven immune response in CFA immunized mice.

Cardiac myosin-Th17 responses promote heart failure in human myocarditis

In human myocarditis and its sequela dilated cardiomyopathy (DCM), the mechanisms and immune phenotype governing disease and subsequent heart failure are not known. Here, we identified a Th17 cell immunophenotype of human myocarditis/DCM with elevated CD4⁺IL17⁺ T cells and Th17-promoting cytokines IL-6, TGF-β, and IL-23 as well as GM-CSF-secreting CD4⁺ T cells. The Th17 phenotype was linked with the effects of cardiac myosin on CD14⁺ monocytes, TLR2, and heart failure. Persistent heart failure was associated with high percentages of IL-17-producing T cells and IL-17-promoting cytokines, and the myocarditis/DCM phenotype included significantly low percentages of FOXP3⁺ Tregs, which may contribute to disease severity. We demonstrate a potentially novel mechanism in human myocarditis/DCM in which TLR2 peptide ligands from human cardiac myosin stimulated exaggerated Th17-related cytokines including TGF-β, IL-6, and IL-23 from myocarditic CD14⁺ monocytes in vitro, and an anti-TLR2 antibody abrogated the cytokine response. Our translational study explains how an immune phenotype may be initiated by cardiac myosin TLR ligand stimulation of monocytes to generate Th17-promoting cytokines and development of pathogenic Th17 cells in human myocarditis and heart failure, and provides a rationale for targeting IL-17A as a therapeutic option.

Emerging pharmacologic targets and treatments for myocarditis

Myocarditis is a heterogeneous group of disorders defined by inflammation of the heart muscle. The primary clinical manifestations of myocarditis are heart failure and sudden death in children and young adults. Numerous interventions have been investigated for the treatment of myocarditis, including broad spectrum alteration of the immune response and antiviral treatments; however, success has been limited. Since the myocarditis treatment trials in the 1990s there has been an improved understanding of disease progression and new facets of the immune response have been discovered. This new information provides fresh opportunities to develop therapeutics to treat myocarditis. This review analyzes previous pharmacologic approaches including immunosuppression, high dose intravenous immunoglobulin treatment, immunoadsorption and antiviral treatments, and looks forward toward recently identified immune factors that can be exploited as targets for new treatments. Such strategies include bolstering beneficial regulatory T cells or mitigating the detrimental Th17 T cells which can drive autoimmunity in the heart. The surging interest of the application of humanized monoclonal antibodies makes targeting deleterious arms of the immune response like Th17 cells a tangible goal in the near future. Promising constituents of herbal remedies have also been identified that may hold potential as new pharmacological treatments for myocarditis, however, significant work remains to elucidate the pharmacokinetics and side-effects of these compounds. Finally, advances in our understanding of the function of Matrix Metalloproteinases yield another target for altering disease progression given their role in the development of fibrosis during Dilated Cardiomyopathy. In bringing to light the various new targets and treatments available since the last myocarditis treatment trials, the aim of this review is to explore the new treatments that are possible in new myocarditis treatment trials.

Susceptibility to acute rheumatic fever based on differential expression of genes involved in cytotoxicity, chemotaxis, and apoptosis

It is unknown why only some individuals are susceptible to acute rheumatic fever (ARF). We investigated whether there are differences in the immune response, detectable by gene expression, between individuals who are susceptible to ARF and those who are not. Peripheral blood mononuclear cells (PBMCs) from 15 ARF-susceptible and 10 nonsusceptible (control) adults were stimulated with rheumatogenic (Rh+) group A streptococci (GAS) or nonrheumatogenic (Rh-) GAS. RNA from stimulated PBMCs from each subject was cohybridized with RNA from unstimulated PBMCs on oligonucleotide arrays to compare gene expression. Thirty-four genes were significantly differentially expressed between ARF-susceptible and control groups after stimulation with Rh+ GAS. A total of 982 genes were differentially expressed between Rh+ GAS- and Rh- GAS-stimulated samples from ARF-susceptible individuals. Thirteen genes were differentially expressed in the same direction (predominantly decreased) between the two study groups and between the two stimulation conditions, giving a strong indication of their involvement. Seven of these were immune response genes involved in cytotoxicity, chemotaxis, and apoptosis. There was variability in the degree of expression change between individuals. The high proportion of differentially expressed apoptotic and immune response genes supports the current model of autoimmune and cytokine dysregulation in ARF. This study also raises the possibility that a "failed" immune response, involving decreased expression of cytotoxic and apoptotic genes, contributes to the immunopathogenesis of ARF.

MCP-1and IL-1β expression in the myocardia of two young patients with Type 1 diabetes mellitus and fatal diabetic ketoacidosis

Convincing evidence exists for the early onset of diabetic cardiomyopathy and coronary artery disease (CAD) as distinct forms of cardiac disease in young patients with Type 1 diabetes mellitus (T1DM) and the pre-stages of T2DM, forms of dysregulated insulin signaling. Progression of both chronic cardiac conditions is mediated by oxidative stress and low grade inflammation. This study reports the expression of monocyte chemotactic protein-1 (MCP-1) chemokine and the interleukin (IL)-1β inflammatory cytokine in two young patients with suboptimal metabolic control and fatal diabetic ketoacidosis (DKA), two age-matched overweight/obesity cases and two age-matched controls. In addition, markers of oxidative stress, apoptosis, collagen deposition and cardiomyocyte hypertrophy were studied. Significant expression of MCP-1 and IL-1β was seen in the myocardia of the T1DM/DKA cases, with lesser amounts expressed in the overweight/obesity myocardia. All of the other markers except cardiomyocyte hypertrophy were expressed to a significantly greater extent in the T1DM/DKA and overweight/obesity cases in comparison to the age-matched controls. Cardiomyocyte hypertrophy was significantly greater in the overweight/obesity cases than in the T1DM/DKA or the control cases.

Increased systemic Th17 cytokines are associated with diastolic dysfunction in children and adolescents with diabetic ketoacidosis

Diastolic dysfunction suggestive of diabetic cardiomyopathy is established in children with T1DM, but its pathogenesis is not well understood. We studied the relationships of systemic inflammatory cytokines/chemokines and cardiac function in 17 children with T1DM during and after correction of diabetic ketoacidosis (DKA). Twenty seven of the 39 measured cytokines/chemokines were elevated at 6-12 hours into treatment of DKA compared to values after DKA resolution. Eight patients displayed at least one parameter of diastolic abnormality (DA) during acute DKA. Significant associations were present between nine of the cytokine/chemokine levels and the DA over time. Interestingly, four of these nine interactive cytokines (GM-CSF, G-CSF, IL-12p40, IL-17) are associated with a Th17 mediated cell response. Both the DA and CCL7 and IL-12p40, had independent associations with African American patients. Thus, we report occurrence of a systemic inflammatory response and the presence of cardiac diastolic dysfunction in a subset of young T1DM patients during acute DKA.

The heart of the matter: protection of the myocardium from T cells

Myocardial inflammation and damage can lead to lethal acute or chronic cardiac failure. A variety of regulatory mechanisms limit the magnitude and duration of T cell responses in the heart. Insights into these regulatory mechanisms have come from studies of specific deficiencies in central or peripheral T cell tolerance which cause or enhance the severity of myocarditis. Under non-inflammatory conditions, constitutive DC presentation of cardiac peptides to naïve T cells in cardiac draining lymph nodes tolerizes recirculating naïve T cells specific for these antigens. Cardiac antigen-specific naïve T cells, especially those specific of α-myosin heavy chain peptides, become activated and differentiate into expanded clones of effector T cells under various conditions, such as cardiac infection and/or genetic variations in peripheral tolerance. The pathology that these effector cells cause in the myocardium is limited by PD-L1 expressed on myocardial cells in response to inflammatory cytokines, and by CTLA-4 dependent mechanisms. The PD-1:PD-L1 pathway works together with other control mechanisms to keep the heart safe from T cells, and combined impairment of this pathway along with other regulatory mechanisms synergize to cause myocarditis. T cell derived IFNγ contributes to the inflammatory damage to the heart in autoimmune myocarditis, but it also engages regulatory mechanisms that limit disease, including upregulation of PD-L1, and differentiation of TNF and iNOS expressing DCs from monocytes. iNOS derived from these DCs and other IFNγ stimulated cells inhibits expansion of T cells that cause myocarditis. Regulatory T cells also appear to be critical for suppression of effector T cells specific for myocardial antigens.

Immunomodulatory effects of mesenchymal stromal cells revisited in the context of inflammatory cardiomyopathy

Myocarditis is a common inflammatory cardiomyopathy, associated with cardiomyocyte apoptosis, which can lead to chronic left ventricular dysfunction. Under conventional heart failure therapy, inflammatory cardiomyopathy typically has a progressive course, indicating a need for alternative therapeutic strategies to improve long-term outcomes. Experimental and clinical studies consistently support the application of cellular transplantation as a strategy to improve myocardial function. Mesenchymal stromal cells (MSCs) mediate distinct paracrine effects supporting endogenous regeneration, but most important are their remarkable immunoregulatory properties. In this review, an overview of current knowledge on immunopathology in myocarditis will be given. Furthermore, current research regarding the immunomodulatory properties of MSCs in the context of myocarditis will be discussed. Finally, the impact of MSC priming by the environment on their functionality and the advantages of systemic administration of MSCs under myocarditis are outlined.

Autoimmune myocarditis, valvulitis, and cardiomyopathy

Myocarditis and valvulitis are inflammatory diseases affecting myocardium and valve. Myocarditis, a viral-induced disease of myocardium, may lead to dilated cardiomyopathy and loss of heart function. Valvulitis leads to deformed heart valves and altered blood flow in rheumatic heart disease. Animal models recapitulating these diseases are important in understanding the human condition. Cardiac myosin is a major autoantigen in heart, and antibodies and T cells to cardiac myosin are evident in inflammatory heart diseases. This unit is a practical guide to induction and evaluation of experimental autoimmune myocarditis (EAM) in several mouse strains and the Lewis rat. Purification protocols for cardiac myosin and protocols for induction of EAM by cardiac myosin and its myocarditis-producing peptides, and coxsackievirus CVB3, are defined. Protocols for assessment of myocarditis and valvulitis in humans and animal models provide methods to define functional autoantibodies targeting cardiac myosin, β-adrenergic, and muscarinic receptors, and their deposition in tissues.

TLR3 deficiency induces chronic inflammatory cardiomyopathy in resistant mice following coxsackievirus B3 infection: role for IL-4

Recent findings indicate that TLR3 polymorphisms increase susceptibility to enteroviral myocarditis and inflammatory dilated cardiomyopathy (iDCM) in patients. TLR3 signaling has been found to inhibit coxsackievirus B3 (CVB3) replication and acute myocarditis in mouse models, but its role in the progression from myocarditis to iDCM has not been previously investigated. In this study we found that TLR3 deficiency increased acute (P = 5.9 × 10(-9)) and chronic (P = 6.0 × 10(-7)) myocarditis compared with WT B6.129, a mouse strain that is resistant to chronic myocarditis and iDCM. Using left ventricular in vivo hemodynamic assessment, we found that TLR3-deficient mice developed progressively worse chronic cardiomyopathy. TLR3 deficiency significantly increased viral replication in the heart during acute myocarditis from day 3 through day 12 after infection, but infectious virus was not detected in the heart during chronic disease. TLR3 deficiency increased cytokines associated with a T helper (Th)2 response, including IL-4 (P = 0.03), IL-10 (P = 0.008), IL-13 (P = 0.002), and TGF-β(1) (P = 0.005), and induced a shift to an immunoregulatory phenotype in the heart. However, IL-4-deficient mice had improved heart function during acute CVB3 myocarditis by echocardiography and in vivo hemodynamic assessment compared with wild-type mice, indicating that IL-4 impairs cardiac function during myocarditis. IL-4 deficiency increased regulatory T-cell and macrophage populations, including FoxP3(+) T cells (P = 0.005) and Tim-3(+) macrophages (P = 0.004). Thus, TLR3 prevents the progression from myocarditis to iDCM following CVB3 infection by reducing acute viral replication and IL-4 levels in the heart.

Lipopolysaccharide mediated mast cells induce IL-10 producing regulatory T cells through the ICOSL/ICOS axis

The mechanisms by which mast cells (MCs) regulate immune responses are still largely unknown. Here, we showed that MCs induced interleukin (IL)-10 producing T cells to regulate inflammatory responses. To gain insight into the molecules involved, we set up an in vitro system in which lipopolysaccharide (LPS) stimulated MCs and CD4(+) T cells were co-cultured. Induction of IL-10 producing regulatory T cells mainly relied on the inducible costimulator ligand (ICOSL)/ICOS axis. MCs stimulated with LPS for more than 6 weeks upregulated ICOSL expression, while icosl(-/-) BMMCs failed to induce IL-10 producing T cells. The LPS effect was mediated through NF-κB activation via the TLR4 signaling pathway. Ex vivo analysis of bronchoalveolar lavage fluid from mice with LPS-mediated pneumonia revealed ICOSL(+) MCs and IL-10 producing T cell induction. Additionally, adaptive transfer of ICOSL(+) BMMCs attenuated LPS-mediated inflammation in MC-deficient mice. This study provided new evidence for the regulatory role of MCs.

CD4+/CD25+ T-Lymphocytes and Th1/Th2 regulation in dilated cardiomyopathy

OBJECTIVE

Autoimmune mechanisms are often involved in the pathogenesis of Dilated Cardiomyopathy (DCM) and Th1 immune response against cardiac antigens plays a pivotal role in disease development.

METHODS

IL-2 receptor (CD4+/CD25+) and cytokines IL-2, IFN-γ, IL-10 were studied in 42 patients (17 with DCM - DCM group, 10 patients with hypertrophic cardiac disease - HCD group, and 15 healthy volunteers - Control group). DCM group was subdivided in: DCM-1 (9 patients with recent disease onset) and DCM-2 (8 patients with chronic DCM). The % CD4+/CD25+ T-lymphocytes were analyzed by double fluorescence flow cytometry both ex vivo and after phytohaemagglutinin (PHA)-cultures with/without 5 and 10 microgr of human cardiac myosin. The cytokines were measured using Enzyme-Linked Immunosorbant Assay (ELISA) method.

RESULTS

Ex vivo analysis: In DCM group, CD4+/CD25+ T-cells significantly increased compared to other groups (p<0.05), due exclusively to DCM-2 subgroup (p=0.019). In PHA cultures in DCM-2 subgroup CD4+/CD25+ T-lymphocytes were significantly increased compared to all other groups (p<0.001). The addition of myosin in the cultures of DCM-2 subgroup maintained the same result. In cultures supernatants in DCM-2 subgroup, IL-2 levels were impressively increased compared to DCM-1 subgroup (p=5.91x10-6), HCD and Control groups (p<0.001). Addition of antigen decreased significantly IL-2 levels in DCM-2 subgroup (p=0.01). IFN-γ levels followed the same pattern of alterations. IL-10 levels were significantly increased in both DCM subgroups compared to HCD and Control groups (p<0.05).

CONCLUSIONS

Increased peripheral CD4+/CD25+ T-cells found in chronic DCM could be a useful prognostic marker in DCM progress. Increased synthesis of IL-2 and IFN-γ and varying IL-10 levels reflects a Th1 pattern of immune response during chronic disease and implies active cellular immunity process, related to poor prognosis. Thus, analysis of the Th1/Th2 phenotype may be useful in disease monitoring in patients with DCM. This paper is a part of PhD thesis. It has been published at the abstract book of the Acute Cardiac Care congress 2010.

Anticardiac myosin immunity and chronic allograft vasculopathy in heart transplant recipients

Chronic allograft vasculopathy (CAV) contributes to heart transplant failure, yet its pathogenesis is incompletely understood. Although cellular and humoral alloimmunity are accepted pathogenic mediators, animal models suggest that T cells and Abs reactive to graft-expressed autoantigens, including cardiac myosin (CM), could participate. To test the relationship between CAV and anti-CM autoimmunity in humans, we performed a cross-sectional study of 72 heart transplant recipients: 40 with CAV and 32 without. Sera from 65% of patients with CAV contained anti-CM Abs, whereas <10% contained Abs to other autoantigens (p < 0.05), and only 18% contained anti-HLA Abs (p < 0.05 versus anti-CM). In contrast, 13% of sera from patients without CAV contained anti-CM Abs (p < 0.05; odds ratio [OR], associating CAV with anti-CM Ab = 13, 95% confidence interval [CI] 3.79-44.6). Multivariable analysis confirmed the association to be independent of time posttransplant and the presence of anti-HLA Abs (OR = 28, 95% CI 5.77-133.56). PBMCs from patients with CAV responded more frequently to, and to a broader array of, CM-derived peptides than those without CAV (p = 0.01). Detection of either CM-peptide-reactive T cells or anti-CM Abs was highly and independently indicative of CAV (OR = 45, 95% CI 4.04-500.69). Our data suggest detection of anti-CM immunity could be used as a biomarker for outcome in heart transplantation recipients and support the need for further studies to assess whether anti-CM immunity is a pathogenic mediator of CAV.

Circulating cardiac troponins levels and cardiac dysfunction in children with acute and fulminant viral myocarditis

OBJECTIVES

To study the correlation between cardiac troponins blood levels and degrees of cardiac dysfunction in children with acute and fulminant viral myocarditis and to study their prognostic role in predicting the outcomes and risk of having dilated cardiomyopathy.

METHODOLOGY

Troponin I & T blood levels were measured in 65 children with acute or fulminant viral myocarditis. The cardiac functions of RV & LV were assessed by Doppler echocardiography.

RESULTS

The levels of cTnI & CTnT were significantly higher in patients with fulminant myocarditis than in controls and children with acute myocarditis (p < 0.05 & <0.001* respectively). The cardiac functions were significantly impaired in fulminant myocarditis than in acute myocarditis (p < 0.001*). There were negative correlations between the cardiac troponins levels and the cardiac functions measured by echocardiography in children with acute and fulminant myocarditis. There were 3 deaths (7.5%), and 10 (25%) children developed dilated cardiomyopathy in acute myocarditis while there were eight deaths (32%) and one patient (4%) who developed dilated cardiomyopathy in fulminant myocarditis group.

CONCLUSION

Cardiac troponins levels can predict the severity of myocarditis and the prognosis on the short-term level. Fulminant myocarditis was associated with higher levels of both cTn I & cTn T than acute myocarditis. Despite that fulminant myocarditis has a more aggressive course, the risk of developing cardiomyopathy was less than in acute myocarditis.

Autoimmunity in Coxsackievirus B3 induced myocarditis: role of estrogen in suppressing autoimmunity

Picornaviruses are small, non-enveloped, single stranded, positive sense RNA viruses which cause multiple diseases including myocarditis/dilated cardiomyopathy, type 1 diabetes, encephalitis, myositis, orchitis and hepatitis. Although picornaviruses directly kill cells, tissue injury primarily results from autoimmunity to self antigens. Viruses induce autoimmunity by: aborting deletion of self-reactive T cells during T cell ontogeny; reversing anergy of peripheral autoimmune T cells; eliminating T regulatory cells; stimulating self-reactive T cells through antigenic mimicry or cryptic epitopes; and acting as an adjuvant for self molecules released during virus infection. Most autoimmune diseases (SLE, rheumatoid arthritis, Grave's disease) predominate in females, but diseases associated with picornavirus infections predominate in males. T regulatory cells are activated in infected females because of the combined effects of estrogen and innate immunity.

Impaired activation of IFN-gamma+CD4+ T cells in peripheral blood of patients with dilated cardiomyopathy

Viral persistence and autoantibodies are pathogenic components in patients with idiopathic dilated cardiomyopathy (DCM). The aim was to evaluate T-cell function in DCM using different flow cytometry based detection techniques. Following stimulation, the frequency of IFN-gamma-producing CD4+ T cells was significantly lower in patients compared with controls. In contrast, the frequency of IL-4 producing CD4+ T cells was no different. In supernatants of cultured PBMC, IFN-gamma and IL-10 were significantly lower in patients. In addition, lymphocyte proliferation was significantly lower in patients compared with controls, whereas major lymphocyte subsets were not different. IFN-gamma and IL-10 are key cytokines in the ability to mount protective immune responses and to maintain self-tolerance. A reduced activation of T-helper 1 (IFN-gamma producing) cells and a decreased capacity to produce IL-10, found in the present study, could explain parts of the autoimmune features seen in patients with DCM.

Coxsackievirus B3 infection promotes generation of myeloid dendritic cells from bone marrow and accumulation in the myocardium

Myocarditis is associated with increased number of CD4+ T cells in the myocardium after coxsackievirus B3 (CVB3) infection. Previous studies show that CD11c+ myeloid dendritic cells (mDC) loaded with myosin could induce myocarditis. This study aims to investigate the generation and accumulation of mDC in CVB3-induced myocarditis. The presence of mDC in myocardium was detected by immunohistochemisty. Bone marrow-derived mDC were generated from uninfected and CVB3-infected mice. The percentage of CD11c+ mDC on cultured cells and mean fluorescence index (MFI) of double positive cells (CD11c+CD40+, CD11c+CD80+) were measured by flow cytometry. The expression of chemokine receptors (CCR5, CCR7) on mDC and chemokines (CCL4, CCL19) in the myocardium was detected. The migration of mDC in response to CCL4 or CCL19 was measured by chemotaxis assay. Mature mDC were elevated in the myocardium from CVB3-infected mice. The percentage of mDC generated from CVB3-infected group was increased. The MFI of CD11c+CD40+ and CD11c+CD80+ was increased in CVB3-infected group. The mDC showed a down-regulation of CCR5 and unaffected CCR7 mRAN levels associated with elevated CCL4 and CCL19 in the myocardium in CVB3-infected group. Numbers of migrating bone marrow-derived mDC from CVB3-infected mice were increased in vitro. We conclude that CVB3 infection induced the greater generation of mDC from bone marrow and accumulation of mature mDC in myocardial tissues. This migration was associated with increased levels of both CCL4 and CCL19 in the heart tissue. These suggest that blocking the migration of mDC may provide a novel therapy for myocarditis.

Lower levels of the host protective IL-10 in DCM--a feature of autoimmune pathogenesis?

OBJECTIVES

To investigate whether cytokine patterns differ with respect to heart failure (HF) etiology, and to study how cytokine concentrations relate to hemodynamic alterations.

METHODS

Plasma levels of interleukin-6 (IL-6), interleukin-10 (IL-10), tumor necrosis factor alpha (TNF-alpha) and high sensitive-CRP (hs-CRP) were analysed with enzyme-linked-immunosorbent serologic assay and turbidimetry in 45 healthy subjects and 89 patients with HF, of whom 65 were diagnosed with dilated cardiomyopathy (DCM) and 24 had ischemic heart disease (IHD).

RESULTS

IL-6, IL-10 and hs-CRP were significantly higher in patients with HF as compared to healthy controls. The IL-10 was significantly lower in patients with DCM as compared to IHD, also when adjusting for clinical variables. Diastolic filling pressure correlated with IL-6, IL-10 and hs-CRP while heart rate (HR) correlated with IL-6 and TNF-alpha.

CONCLUSIONS

Proinflammatory cytokines are elevated in patients with HF and display a positive correlation with filling pressures and HR. Most significant, the regulatory and protective cytokine IL-10 was much lower in patients with DCM as compared to IHD, indicating a differentiation in cytokine patterns with respect to HF etiology.

Myocarditis

Myocarditis represents a heterogeneous final common pathway for myocardial inflammation of diverse etiologies and accounts for up to one-third of cases of dilated cardiomyopathy. The pathophysiology of viral myocarditis can be disaggregated into the effects of direct viral mediated injury, triggered acute and chronic autoimmune responses, and subsequent adverse remodeling. Recent research highlights the pathogenic role of persistent viral genome expression, Fas-ligand, tumor necrosis factor-alpha receptor 1, and antimyosin autoantibodies in the evolution of chronic systolic and diastolic heart failure. Recent refinements in endomyocardial biopsy evaluation, cardiac magnetic resonance imaging, and cytokine assays augment existing diagnostic modalities. Novel specific immunosuppressive targets aimed at interrupting myocyte injury and apoptosis, including interferon-beta seem promising to date in small clinical studies performed on selected patients.

National Institutes of Health-sponsored workshop on inflammation and immunity in dilated cardiomyopathy

Nonischemic dilated cardiomyopathy (DCM) is an uncommon cause of heart failure but has widespread importance because it is the cause of 45% of heart transplantations. Multiple experimental and clinical lines of evidence have implicated altered immunity in the pathogenesis of DCM. However, advances in the understanding of the mechanisms of altered immunity have not affected the diagnosis or treatment of DCM. In recognition of this problem, the National Institutes of Health sponsored an expert workshop with 2 aims: to review the current understanding of inflammation and immunity as they relate to DCM and to identify the most promising areas for future clinical research efforts in the field. This report summarizes the scientific opportunities, perceived needs and barriers, and workshop recommendations on research directions in DCM. The major recommendations from the members of the workshop are organized according to the following themes: cardiotropic viruses, innate and acquired immune responses, environmental factors, novel diagnostics, and novel therapeutics.