Circulating cardiac-specific autoantibodies as markers of autoimmunity in clinical and biopsy-proven myocarditis. The Myocarditis Treatment Trial Investigators

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.

Advances in research on molecular markers in immune checkpoint inhibitor-associated myocarditis

Immune checkpoint inhibitors (ICIs) play a crucial role in the immunotherapy of malignant tumors, preventing immune evasion by tumor cells and activating autoimmune cells to eliminate the tumor. Despite their proven effectiveness in antitumor therapy, potential immune-related adverse effects must be recognized, particularly ICI-associated myocarditis (ICIAM). ICIAM is the most lethal form of organ immunotoxicity, with a significant impact on short-term mortality. However, ICIAM is predominantly asymptomatic or mildly nonspecific. It is difficult to diagnose, especially due to the lack of unique molecular markers. This article aims to provide a comprehensive overview of the progress made in identifying molecular markers for ICIAM.

Pediatric Myocarditis: What Have We Learnt So Far?

Myocarditis is an inflammatory disease of the myocardium that is troublesome to diagnose and manage, especially in children. Since the introduction of endomyocardial biopsy (EMB), new diagnostic tools have provided useful data. Especially when enhanced with immunohistochemistry and polymerase chain reaction (PCR) studies, EMB remains the gold standard for the diagnosis. Notably, cardiac magnetic resonance (MRI) is a non-invasive tool that can confirm the diagnosis and has a particular usefulness during the follow-up. The causes of myocarditis are heterogeneous (mostly viral in children). The course and outcome of the illness in the pediatric population represent a complex interaction between etiologic agents and the immune system, which is still not fully understood. The clinical presentation and course of myocarditis vary widely from paucisymptomatic illness to acute heart failure refractory to therapy, arrhythmias, angina-like presentation and sudden cardiac death. In this setting, cardiac biomarkers (i.e., troponins and BNP), although unspecific, can be used to support the diagnosis. Finally, the efficacy of therapeutic strategies is controversial and not confirmed by clinical trials. In this review, we summarized the milestones in diagnosis and provided an overview of the therapeutic options for myocarditis in children.

Predictors of relapse, death or heart transplantation in myocarditis before the introduction of immunosuppression: negative prognostic impact of female gender, fulminant onset, lower ejection fraction and serum autoantibodies

AIMS

Outcome predictors in myocarditis are not well defined; we aimed at identifying predictors of death, heart transplantation (HTx) and relapse before the introduction of immunosuppression.

METHODS AND RESULTS

From 1992 to 2012 we consecutively included 466 patients (68% male, 37±17 years, single centre recruitment, median follow-up 50 months), 216 with clinically suspected and 250 with biopsy (Bx)-proven myocarditis. Serum anti heart (AHA) and antiintercalated disk (AIDA) auto-antibodies were measured by indirect immunofluorescence. We performed univariable and multivariable analysis of clinical and diagnostic features at diagnosis. Survival free from death or HTx at 10 years was 83% in the whole group and was lower in Bx- proven vs. clinically suspected myocarditis (76% vs 94% respectively, p<0.001). Female gender (hazard ratio (HR) 2.7, 95% Confidence Intervals (CI) 1.1-6.5), fulminant presentation (HR 13.77, CI 9.7-261.73), high-titre organ-specific AHA (HR 4.2, CI 1.2-14.7) and anti-nuclear antibodies (ANA) (HR 5.2, CI 2.1-12.8) were independent predictors of death or HTx; higher echocardiographic left ventricular ejection fraction (LVEF) at diagnosis was protective, with a 0.93 times risk reduction for each 1% LVEF increase (CI 0.89-0.96). History of myocarditis at diagnosis (HR 8.5, CI 3.5-20.7) was independent predictor of myocarditis relapse at follow-up; older age was protective (HR 0.95, CI 0.91-0.99). Predictors of death, HTx and relapse did not differ in Bx-proven vs. clinically suspected myocarditis.

CONCLUSIONS

Young age and a previous myocarditis were independent relapse predictors; female gender, fulminant onset, lower LVEF at presentation and high-titre organ-specific AHA and ANA were independent predictors of death and HTx, suggesting that autoimmune features predict worse prognosis.

Clinically Suspected and Biopsy-Proven Myocarditis Temporally Associated with SARS-CoV-2 Infection

We review current data on clinically suspected [European Society of Cardiology (ESC) 2013 criteria] and biopsy-proven [ESC and World Health Organization (WHO) criteria] myocarditis that is temporally associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. ESC/WHO etiological diagnosis of viral myocarditis is based on histological, and immunohistological evidence of nonischemic myocyte necrosis and monolymphocytic infiltration, i.e., myocarditis, plus the identification of a specific cardiotropic virus by molecular techniques, in particular polymerase chain reaction (PCR)/in-situ hybridization, on endomyocardial biopsy (EMB)/autopsy tissue. There is not yet definitive EMB/autopsy proof that SARS-CoV-2 causes direct cardiomyocyte damage in association with histological myocarditis. Clinical epidemiology data suggest that myocarditis is uncommon for both SARS-CoV-2-positive and -negative PCR cases. We hypothesize that the rare virus-negative biopsy-proven cases may represent new-onset immune-mediated or latent pre-existing autoimmune forms, triggered or fostered by the hyperinflammatory state of severe COVID-19. We recommend the application of the ESC/WHO definitions and diagnostic criteria in future reports to avoid low-quality scientific information leading to an inaccurate estimate of myocarditis incidence based on misdiagnosis. Expected final online publication date for the Annual Review of Medicine, Volume 73 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

SARS-CoV-2 Myocarditis: Insights Into Incidence, Prognosis, and Therapeutic Implications

Purpose of Review

In coronavirus disease 2019 (COVID-19), myocardial injury occurs frequently in severe or critically ill hospitalized patients, yet myocarditis is much less common. In this context, revisiting the definition of myocarditis is appropriate with a specific focus on diagnostic and management considerations in patients infected with SARS-CoV-2.

Recent Findings

Pathologic cardiac specimens from patients with COVID-19 suggest a mixed inflammatory response involving lymphocytes and macrophages, and importantly, cellular injury occurs predominantly at the level of pericytes and endothelial cells, less often involving direct myocyte necrosis. In COVID-19, the diagnosis of myocarditis has understandably been based predominantly on clinical criteria, and the number of patients with clinically suspected myocarditis who would meet diagnostic histological criteria is unclear. Echocardiography and cardiac magnetic resonance are important diagnostic tools, although the prognostic implications of abnormalities are still being defined. Importantly, SARS-CoV2 myocarditis should be diagnosed within an appropriate clinical context and should not be based on isolated imaging findings. Therapies in COVID-19 have focused on the major clinical manifestation of pneumonia, but the promotion of viral clearance early in the disease could prevent the development of myocarditis, and further study of immunosuppressive therapies once myocarditis has developed are indicated.

Summary

A strict and uniform approach is needed to diagnose myocarditis due to SARS-CoV-2 to better understand the natural history of this disease and to facilitate evaluation of potential therapeutic interventions. A methodological approach will also better inform the incidence of COVID-19 associated myocarditis and potential long-term health effects.

Diagnosis, treatment and predictors of prognosis of myocarditis. A narrative review

Although it has been recognized for almost two centuries, myocarditis is still a challenging diagnosis due to the wide heterogeneity of its clinical manifestations and evolution. Moreover, the diagnostic gold standard, endomyocardial biopsy (EMB), is infrequently used, making hard to determine the exact incidence of myocarditis. Clinical presentation includes a wide range of symptoms, ranging from asymptomatic or subclinical disease with mild dyspnea and chest pain to sudden death, due to cardiogenic shock or malignant ventricular arrhythmias. Equally, the evolution of myocarditis largely varies: albeit short-term prognosis is usually good, with complete or partial recovery, dilated cardiomyopathy with chronic heart failure is the major long-term consequence of myocarditis, developing often several years after the acute onset. This narrative review aims to summarize the current knowledge about myocarditis, with a particular attention to predictors of short- and long-term prognosis, in order to provide a rational and practical approach to the diagnosis, evaluation and treatment of suspected myocarditis.

Significance of Anti-Myosin Antibody Formation in Patients With Myocardial Infarction: A Prospective Observational Study

BACKGROUND

Anti-myosin antibodies (AMAs) are often formed in response to myocardial infarction (MI) and have been implicated in maladaptive cardiac remodelling. We aimed to: (1) compare AMA formation in patients with Non-ST-Elevation MI (NSTEMI) and ST-Elevation MI (STEMI); (2) evaluate factors predicting autoantibody formation; and, (3) explore their functional significance.

METHODS

Immunoglobulin M (IgM) and Immunoglobulin G (IgG) AMA titres were determined in serum samples collected at admission, 3 and 6 months post MI. The relationship between demographic and clinical data, and antibody formation, was investigated to determine factors predicting antibody formation and functional significance.

RESULTS

Forty-three (43) patients were consecutively recruited; 74.4% were positive for IgM at admission, compared with 23.3% for IgG. Mean IgG levels increased by 1.24% (±0.28) at 3 months, and 13.55% (±0.13) at 6 months post MI. Mean antibody levels were significantly higher in the NSTEMI cohort at both follow-up time points for IgG (p<0.001, p<0.0001), but not IgM (p=0.910, p=0.066). A moderately positive correlation between infarct size and increase in mean IgM concentration was observed at 3 months (r(98)=0.455; p=0.015). Anti-myosin antibody formation was not associated with an unfavourable outcome at follow-up.

CONCLUSIONS

Anti-myosin antibodies are formed in a significant proportion of patients following MI, particularly among those with NSTEMI. While IgM levels fall after infarction, IgG levels increase and persist beyond 6 months of follow-up. This raises the possibility that they may contribute to long-term myocardial damage and dysfunction. Future research should focus on the specific epitopes that are targeted by these antibodies, and their functional significance. This may result in the emergence of novel therapies to attenuate cardiac dysfunction in MI patients.

Myocarditis: A Clinical Overview

PURPOSE OF REVIEW

In this paper we will review the modern diagnostic approach to patients with clinically suspected myocarditis as well as the treatment modalities and strategy in light of up-to-date clinical experience and scientific evidence.

RECENT FINDINGS

Rapidly expanding evidence suggests that myocardial inflammation is frequently underdiagnosed or overlooked in clinical practice, although new therapeutic options have been validated. Moreover, the available evidence suggests that subclinical cardiac involvement has negative prognostic impact on morbidity and mortality and should be actively investigated and adequately treated. Myocarditis represents a growing challenge for physicians, due to increased referral of patients for endomyocardial biopsy (EMB) or cardiac magnetic resonance (CMR), and requires a highly integrated management by a team of caring physicians.

The role of anti-myosin antibodies in perpetuating cardiac damage following myocardial infarction

Recent improvements in the medical and surgical management of myocardial infarction mean that many patients are now surviving with greater impairment of cardiac function. Despite appropriate management, some of these patients subsequently develop pathological ventricular remodelling, which compounds their contractile dysfunction and can lead to congestive cardiac failure (CCF). The pathophysiological mechanism underpinning this process remains incompletely understood. One hypothesis suggests that a post-infarction autoimmune response, directed against constituents of cardiac myocytes, including cardiac myosin, may make an important contribution. Our review summarises the current literature related to the formation and clinical relevance of anti-myosin antibodies (AMAs) in patients with myocardial infarction. This discussion is supplemented with reference to a number of important animal studies, which provide evidence of the potential mechanisms underlying AMA formation and autoantibody mediated cardiac dysfunction.

Update on Myocarditis and Inflammatory Cardiomyopathy: Reemergence of Endomyocardial Biopsy

Myocarditis is defined as an inflammatory disease of the heart muscle and is an important cause of acute heart failure, sudden death, and dilated cardiomyopathy. Viruses account for most cases of myocarditis or inflammatory cardiomyopathy, which could induce an immune response causing inflammation even when the pathogen has been cleared. Other etiologic agents responsible for myocarditis include drugs, toxic substances, or autoimmune conditions. In the last few years, advances in noninvasive techniques such as cardiac magnetic resonance have been very useful in supporting diagnosis of myocarditis, but toxic, infectious-inflammatory, infiltrative, or autoimmune processes occur at a cellular level and only endomyocardial biopsy can establish the nature of the etiological agent. Furthermore, after the generalization of immunohistochemical and viral genome detection techniques, endomyocardial biopsy provides a definitive etiological diagnosis that can lead to specific treatments such as antiviral or immunosuppressive therapy. Endomyocardial biopsy is not commonly performed for the diagnosis of myocarditis due to safety reasons, but both right- and left endomyocardial biopsies have very low complication rates when performed by experienced operators. This document provides a state-of-the-art review of myocarditis and inflammatory cardiomyopathy, with special focus on the role of endomyocardial biopsy to establish specific treatments.

Localization of CD8 T cell epitope within cardiac myosin heavy chain-α334-352 that induces autoimmune myocarditis in A/J mice

BACKGROUND

Cardiac myosin heavy chain-α (Myhc), an intracellular protein expressed in the cardiomyocytes, has been identified as a major autoantigen in cardiac autoimmunity. In our studies with Myhc334-352-induced experimental autoimmune myocarditis in A/J mice (H-2a), we discovered that Myhc334-352, supposedly a CD4 T cell epitope, also induced antigen-specific CD8 T cells that transfer disease to naive animals.

METHODS AND RESULTS

In our efforts to identify the CD8 T cell determinants, we localized Myhc338-348 within the full length-Myhc334-352, leading to four key findings. (1) By acting as a dual epitope, Myhc338-348 induces both CD4 and CD8 T cell responses. (2) In a major histocompatibility complex (MHC) class I-stabilization assay, Myhc338-348 was found to bind H-2Dd-but not H-2Kk or H-2Ld-alleles. (3) The CD8 T cell response induced by Myhc338-348 was antigen-specific, as evaluated by MHC class I/H-2Dd dextramer staining. The antigen-sensitized T cells predominantly produced interferon-γ, the critical cytokine of effector cytotoxic T lymphocytes. (4) Myhc338-348 was found to induce myocarditis in immunized animals as determined by histology and magnetic resonance microscopy imaging.

CONCLUSIONS

Our data provide new insights as to how different immune cells can recognize the same antigen and inflict damage through different mechanisms.

Current state of knowledge on aetiology, diagnosis, management, and therapy of myocarditis: a position statement of the European Society of Cardiology Working Group on Myocardial and Pericardial Diseases

In this position statement of the ESC Working Group on Myocardial and Pericardial Diseases an expert consensus group reviews the current knowledge on clinical presentation, diagnosis and treatment of myocarditis, and proposes new diagnostic criteria for clinically suspected myocarditis and its distinct biopsy-proven pathogenetic forms. The aims are to bridge the gap between clinical and tissue-based diagnosis, to improve management and provide a common reference point for future registries and multicentre randomised controlled trials of aetiology-driven treatment in inflammatory heart muscle disease.

Suppressor of cytokine signaling 1 DNA administration inhibits inflammatory and pathogenic responses in autoimmune myocarditis

Myocarditis and subsequent dilated cardiomyopathy are major causes of heart failure in young adults. Myocarditis in humans is highly heterogeneous in etiology. Recent studies have indicated that a subgroup of myocarditis patients may benefit from immune-targeted therapies, because autoimmunity plays an important role in myocarditis as well as contributing to the progression to cardiomyopathy and heart failure. Suppressor of cytokine signaling (SOCS) 1 plays a key role in the negative regulation of both TLR- and cytokine receptor-mediated signaling, which is involved in innate immunity and subsequent adaptive immunity. In this study, we investigated the therapeutic effect of SOCS1 DNA administration on experimental autoimmune myocarditis (EAM) in mice. EAM was induced by s.c. immunization with cardiac-specific peptides derived from α myosin H chain in BALB/c mice. In contrast to control myocarditis mice, SOCS1 DNA-injected mice were protected from development of EAM and heart failure. SOCS1 DNA administration was effective for reducing the activation of autoreactive CD4(+) T cells by inhibition of the function of Ag-presenting dendritic cells. Our findings suggest that SOCS1 DNA administration has considerable therapeutic potential in individuals with autoimmune myocarditis and dilated cardiomyopathy.

Differences in virus prevalence and load in the hearts of patients with idiopathic dilated cardiomyopathy with and without immune-mediated inflammatory diseases

Infections with cardiotrophic viruses and immune-mediated responses against the heart have been suggested to play a dominant role in the pathogenesis of idiopathic dilated cardiomyopathy (DCM). Furthermore, immune-mediated inflammatory diseases (IMIDs) may result in DCM. It has not previously been assessed whether DCM patients with and without an IMID have different prevalences and quantities of cardiotrophic viruses in the heart. Therefore, we compared the profiles of cardiotrophic viruses in heart tissue of DCM patients with and without an IMID. Serum and myocardial tissue samples were obtained from 159 consecutive patients with DCM and 20 controls. Patients were subdivided into three groups, the first two based on the presence (n = 34) or absence (n = 125) of an IMID and the third being a control group. The parvovirus B19 virus genome was detected in equal quantities in the non-IMID DCM patients (100/125) and the control group (15/20) but in lower quantities in the IMID patients (21/34, P = 0.02). Both the non-IMID and IMID DCM patients demonstrated increased myocardial inflammation compared to controls: 12.5 ± 1.8 and 14.0 ± 3.2 CD45-positive inflammatory cells, respectively, versus 5.1 ± 0.7 for the controls (P < 0.05 for both). Importantly, significantly higher parvovirus B19 copy numbers could be amplified in non-IMID than in IMID patients (561 ± 97 versus 191 ± 92 copies/μg DNA, P < 0.001) and control subjects (103 ± 47 copies/μg DNA, P < 0.001). The present study shows decreased parvovirus B19 prevalence and copy numbers in hearts of DCM patients with an IMID compared to those without an IMID. These findings may suggest that DCM patients with an IMID have a different pathophysiologic mechanism from that which is present in the virus-induced form of DCM.

Effects of protein A immunoadsorption in patients with chronic dilated cardiomyopathy

OBJECTIVES

The objective of this study was to investigate functional effects of immunoadsorption (IA) in patients with chronic nonfamilial dilated cardiomyopathy (DCM) regarding clinical and humoral markers of heart failure.

BACKGROUND

IA has been shown to induce early hemodynamic improvement in patients with nonfamilial dilated cardiomyopathy (DCM).

METHODS

We performed IA using protein A agarose columns on five consecutive days in 51 patients with chronic DCM, congestive heart failure of NYHA class ≥ II, left ventricular ejection fraction ≤50%, and mean time since initial diagnosis of 5.0 ± 5.8 years.

RESULTS

Immediately after IA, immunoglobulin G (IgG) decreased by 89.4% and IgG3 by 66.7% (both P < 0.0001). Median NT-pro BNP was reduced from 1230.0 ng L(-1) at baseline to 829.0 ng L(-1) after 6 months (P < 0.0001). Also mean left ventricular ejection fraction (LVEF) was significantly improved (26.3% ± 9.4% to 28.7% ± 11.4% after 6 months, P = 0.016) and LVEF improved ≥5% (absolute) in 21 of 51 (41.2%) patients. After 6 months, bicycle spiroergometry showed a significant increase in exercise capacity from 82.0 ± 30.8 Watts to 93.1 ± 34.3 Watts (P = 0.008) while VO2max rose from 15.0 ± 4.1 to 16.4 ± 4.8 mL min(-1) kg(-1) (P = 0.01).

CONCLUSIONS

In this study, on heart failure patients with nonfamilial DCM, IA therapy significantly improved clinical and humoral markers of heart failure severity. These promising results may be due to the selected study population, with a shorter disease duration and the higher amount of IgG 3 reduction. Future blinded prospective multicenter studies are necessary to identify those patients that benefit most.

Clinical outcome of acute myocarditis in children according to treatment modalities

PURPOSE

There is currently little evidence to support intravenous immune globulin (IVIG) therapy for pediatric myocarditis. The purpose of our retrospective study was to assess the effects of IVIG therapy in patients with presumed myocarditis on survival and recovery of ventricular function and to determine the factors associated with its poor outcome.

METHODS

We reviewed all consecutive cases of patients with myocarditis with left ventricular dysfunction verified by echocardiogram who had visited 3 university hospitals between January 2000 and September 2009. These patients were divided into 2 groups. Group 1 consisted of 23 patients (69.6%) who received IVIG alone or IVIG in combination with steroids, and group 2 consisted of 10 patients (30.3%) who received neither IVIG nor other immunosuppressive agents. Clinical manifestations, laboratory results, echocardiographic findings, and outcomes were compared between these 2 groups.

RESULTS

One year after the initial presentation, the difference in the probability of survival did not show statistical significance in IVIG-treated patients (P=0.607). Of the echocardiographic parameters on admission, a shortening fraction of less than 15% was associated with unremitting cardiac failure. Furthermore, anemic patients were more likely to have elevated N-terminal fragment levels of the B-type natriuretic peptide (NT-proBNP) in the progressed group (P=0.036).

CONCLUSION

There was no difference between the IVIG-treated patients and the control patients in the degree of recovery of left ventricular function and survival. Prospective, randomized, clinical studies are needed to elucidate the effects of IVIG treatment during the acute stage of myocarditis on ultimate outcomes.

Fcgamma-receptor IIa polymorphism and the role of immunoadsorption in cardiac dysfunction in patients with dilated cardiomyopathy

In patients with dilated cardiomyopathy (DCM), cardiac autoantibodies are able to bind with their Fab fragment to epitopes on cardiomyocytes, but thereafter they crosslink through their Fc fragment to cardiac Fc(gamma)-receptor IIa. Polymorphic variability of the Fc(gamma)-receptor IIa is associated with modified affinity of immunoglobin G (IgG) binding and may influence therapeutic effects. In this study, 103 consecutive DCM patients were treated with immunoadsorption (IA) therapy with subsequent IgG substitution (IA/IgG). Echocardiography was performed at baseline and again at 3 and 6 months after IA/IgG. Fc(gamma)-receptor IIa polymorphism R/H131 was genotyped using a nested sequence-specific primer polymerase chain reaction (PCR). Patients with the Fc(gamma)-receptor IIa genotype R/R131 showed significantly greater improvement in left ventricular (LV) function than patients with the R/H131 or H/H131 genotypes did. Irrespective of the Fc(gamma)-receptor polymorphism, patients with shorter disease duration and a more impaired LV function responded with a greater increase in LV ejection fraction (LVEF). Therefore, the Fc(gamma)-receptor polymorphism influences the efficacy of immunomodulatory therapy involving IA/IgG.

Effects of protein A immunoadsorption in patients with advanced chronic dilated cardiomyopathy

OBJECTIVES

The objective of this study was to investigate functional effects of immunoadsorption (IA) in severely limited study patients with chronic nonfamilial dilated cardiomyopathy (DCM), and to analyze the prevalence of Troponin I (TNI) autoantibodies.

BACKGROUND

Immunoadsorption (IA) has been shown to induce early hemodynamic improvement in patients with nonfamilial DCM.

METHODS

We performed IA using Immunosorba columns on five consecutive days in 27 patients with chronic DCM, congestive heart failure of NYHA class >or=II, left ventricular ejection fraction below 40%, and mean time since initial diagnosis of 7.2 +/- 6.8 years.

RESULTS

Immediately after IA, IgG decreased by 87.7% and IgG3 by 58.5%. Median NT-pro BNP was reduced from 1740.0 ng/L at baseline to 1504.0 ng/L after 6 months (P = 0.004). Mean left ventricular ejection fraction (LVEF) was not significantly improved overall (24.1 +/- 7.8% to 25.4 +/- 10.4% after 6 months, P = 0.38), but LVEF improved >or=5% (absolute) in 9 of 27 (33%) patients. Bicycle spiroergometry showed a significant increase in exercise capacity from 73.7 +/- 29.4 Watts to 88.8 +/- 31.1 Watts (P = 0.003) after 6 months while VO2max rose from 13.7 +/- 3.8 to 14.9 +/- 3.0 mL/min kg after 6 months (P = 0.09). Subgroup analysis revealed a higher NT-pro BNP reduction in patients with shorter disease duration (P = 0.03) and without TNI autoantibodies at baseline (P = 0.05). All 9 patients with an absolute increase of LVEF of >or=5.0% were diabetic (P = 0.0001).

CONCLUSIONS

In this study, on severely limited heart failure patients with nonfamilial DCM, IA therapy moderately improved markers of heart failure severity in a limited subgroup of patients. This may be due to the selected study population with end-stage heart failure patients and the lower reduction of IgG3 compared to previous studies. Future blinded multicenter studies are necessary to identify those patients that benefit most.

Consequences of unlocking the cardiac myosin molecule in human myocarditis and cardiomyopathies

Myocarditis, often initiated by viral infection, may progress to autoimmune inflammatory heart disease, dilated cardiomyopathy and heart failure. Although cardiac myosin is a dominant autoantigen in animal models of myocarditis and is released from the heart during viral myocarditis, the characterization, role and significance of anti-cardiac myosin autoantibodies is poorly defined. In our study, we define the human cardiac myosin epitopes in human myocarditis and cardiomyopathies and establish a mechanism to explain how anti-cardiac myosin autoantibodies may contribute to heart disease. We show that autoantibodies to cardiac myosin in sera from myocarditis and dilated cardiomyopathies in humans targeted primarily epitopes in the S2 hinge region of cardiac myosin. In addition, anti-cardiac myosin antibodies in sera or purified IgG from myocarditis and cardiomyopathy targeted the beta-adrenergic receptor and induced antibody-mediated cAMP-dependent protein kinase A (PKA) cell signaling activity in heart cells. Antibody-mediated PKA activity in sera was abrogated by absorption with anti-human IgG. Antibody-mediated cell signaling of PKA was blocked by antigen-specific inhibition by human cardiac myosin or the beta-adrenergic receptor but not the alpha adrenergic receptor or bovine serum albumin. Propranolol, a beta blocker and inhibitor of the beta-adrenergic receptor pathway also blocked the antibody-mediated signaling of the beta-adrenergic receptor and PKA. The data suggest that IgG antibody against human cardiac myosin reacts with the beta-adrenergic receptor and triggers PKA signaling in heart cells. In summary, we have identified a new class of crossreactive autoantibodies against human cardiac myosin and the beta-adrenergic receptor in the heart. In addition, we have defined disease specific peptide epitopes in the human cardiac myosin rod S2 region in human myocarditis and cardiomyopathy as well as a mechanistic role of autoantibody in the pathogenesis of disease.

Anti-heart autoantibodies in familial dilated cardiomyopathy

Familial aggregation is a feature of myocarditis and dilated cardiomyopathy (DCM). Myocarditis, a clinically polymorphic inflammatory disease of the myocardium, is diagnosed by endomyocardial biopsy (EMB) and may lead to DCM. Mutations in several genes encoding myocyte structural proteins are known monogenic DCM causes, but because of high etiologic and genetic heterogeneity, the gene defects identified so far account for a minority of cases. In the last decade, it has been discovered that autoimmunity plays a pivotal role in myocarditis and DCM that are thought to represent different stages of an organ-specific autoimmune disease in genetically predisposed individuals. None of the available genetic studies in familial DCM has taken into account the autoimmune phenotype markers in the characterization of index patients and relatives, thus it is not known whether or not the described gene defects are involved in the autoimmune form of the disease. In animal models autoimmune myocarditis/DCM can be induced by viral infection, immunization with heart-specific autoantigens, or develop spontaneously in genetically predisposed strains. It may be cell or antibody-mediated; susceptibility is based upon multiple MHC and non-MHC genes. In patients, the diagnosis of autoimmune myocarditis/DCM requires exclusion of viral genome on EMB and detection of serum heart-reactive autoantibodies. They are found in index patients and relatives from about 60% of both familial and non-familial pedigrees and predict DCM development among healthy relatives. Some antibodies have functional effects on cardiac myocytes in vitro, in animal models and possibly in a DCM subset without inflammation, responsive to extracorporeal immunoadsorption. Cardiac-specific autoantibodies, which are shown to be disease-specific for myocarditis/DCM, can be used as biomarkers for identifying patients in whom, in the absence of active infection of the myocardium, immunosuppression and/or immunomodulation may be beneficial and their relatives at risk. Future studies should clarify genetic basis of human autoimmune myocarditis/DCM as well as genotype/immune phenotype correlations.

Genetically determined myocarditis: clinical presentation and immunological characteristics

PURPOSE OF REVIEW

Myocarditis is a clinically heterogeneous myocardial inflammatory disease, diagnosed by endomyocardial biopsy; it may be idiopathic, infectious, or autoimmune and may lead to dilated cardiomyopathy. Myocarditis and dilated cardiomyopathy represent different stages of an organ-specific autoimmune disease in genetically predisposed individuals.

RECENT FINDINGS

In animal models, cell-mediated or antibody-mediated autoimmune myocarditis/dilated cardiomyopathy can be induced by viral infection or immunization with heart-specific autoantigens, or can develop spontaneously in genetically predisposed strains. Susceptibility is based on multiple major histocompatibility complex and nonmajor histocompatibility complex genes. In patients the diagnosis of autoimmune myocarditis/dilated cardiomyopathy requires exclusion of viral genome on endomyocardial biopsy and detection of serum heart-reactive autoantibodies. They are directed against multiple antigens that are found in patients and relatives from about 60% of familial and nonfamilial pedigrees. They predict dilated cardiomyopathy development among relatives, years before disease. Some antibodies have functional effects on cardiac myocytes in vitro, in animals and possibly in a dilated cardiomyopathy subset, responsive to extracorporeal immunoadsorption.

SUMMARY

In myocarditis/dilated cardiomyopathy, cardiac-specific and disease-specific antibodies of IgG class are potential biomarkers for identifying 'at risk' relatives as well as those patients in whom, in the absence of active infection of the myocardium, immunosuppression, and/or immunomodulation may be beneficial. Future studies should better define the genetic basis of human autoimmune myocarditis/dilated cardiomyopathy.

Acute viral myocarditis

Acute myocarditis is one of the most challenging diagnosis in cardiology. At present, no diagnostic gold standard is generally accepted, due to the insensitivity of traditional diagnostic tests. This leads to the need for new diagnostic approaches, which resulted in the emergence of new molecular tests and a more detailed immunohistochemical analysis of endomyocardial biopsies. Recent findings using these new diagnostic tests resulted in increased interest in inflammatory cardiomyopathies and a better understanding of its pathophysiology, the recognition in overlap of virus-mediated damage, inflammation, and autoimmune dysregulation. Novel results also pointed towards a broader spectrum of viral genomes responsible for acute myocarditis, indicating a shift of enterovirus and adenovirus to parvovirus B19 and human herpes virus 6. The present review proposes a general diagnostic approach, focuses on the viral aetiology and associated autoimmune processes, and reviews treatment options for patients with acute viral myocarditis.

Molecular biology and pathogenesis of viral myocarditis

Myocarditis is a cardiac disease associated with inflammation and injury of the myocardium. Several viruses have been associated with myocarditis in humans. However, coxsackievirus B3 is still considered the dominant etiological agent. The observed pathology in viral myocarditis is a result of cooperation or teamwork between viral processes and host immune responses at various stages of disease. Both innate and adaptive immune responses are crucial determinants of the severity of myocardial damage, and contribute to the development of chronic myocarditis and dilated cardiomyopathy following acute viral myocarditis. Advances in genomics and proteomics, and in the use of informatics and biostatistics, are allowing unbiased initial evaluations that can be the basis for testable hypotheses about virus pathogenesis and new therapies.

Myopericarditis: Etiology, management, and prognosis

Acute pericarditis is often accompanied by some degree of myocarditis. In clinical practice both pericarditis and myocarditis coexist because they share common etiologic agents, mainly cardiotropic viruses. The term "myopericarditis" indicates a primarily "pericarditic syndrome" and it is responsible for the majority of cases. The clinical presentation is varied, reflecting the variability of myocardial involvement, that may be focal or diffuse, affecting any or all cardiac chambers. Probably many cases may be subclinical and subtle cardiac symptoms and signs may be overshadowed by the systemic manifestations of the viral infection. Echocardiography is essential for the diagnosis of left ventricular dysfunction in even subclinical cases and for follow-up of patients with apparently normal left ventricular function. Magnetic resonance imaging holds promise for an effective non-invasive diagnostic tool. Either for acute pericarditis or myopericarditis there is a lack for adequate controlled clinical trials. In myopericarditis the use of NSAID should be cautious, because in animal models of myocarditis, NSAID are not effective and may actually enhance the myocarditic process and increase mortality. In clinical practice lower anti-inflammatory doses are mainly considered to control symptoms. The natural history of myopericarditis in large populations is not known with accuracy. On follow-up, the majority of these cases had objective normalization of echocardiography, electrocardiography, laboratory testing, and functional status, although up to 14% may report atypical, non-limiting chest discomfort. Unfortunately, few data have been published on myopericarditis, the paper reviews current available evidence on the presentation, management, and prognosis of myopericarditis.

Clinical implications of anti-heart autoantibodies in myocarditis and dilated cardiomyopathy

Dilated cardiomyopathy (DCM), a leading cause of heart failure and heart transplantation in younger adults, is characterized by dilatation and impaired contraction of the left or both ventricles; it may be idiopathic, familial/genetic (20-30%), viral, and/or immune. On endomyocardial biopsy there is chronic inflammation in 30-40% of cases. Mutations in genes encoding myocyte structural proteins, cardiotoxic noxae and infectious agents are known causes; due to high aetiologic and genetic heterogeneity, the gene defects identified so far account for a tiny proportion of the familial cases. In at least two thirds of patients, DCM remains idiopathic. Myocarditis may be idiopathic, infectious or autoimmune and may heal or lead to DCM. Circulating heart-reactive autoantibodies are found in myocarditis/DCM patients and symptom-free relatives at higher frequency than in normal or noninflammatory heart disease control groups. These autoantibodies are directed against multiple antigens, some of which are expressed only in the heart (organ-specific); some autoantibodies have functional effects on cardiac myocytes in vitro as well as in animal models. Depletion of nonantigen-specific antibodies by extracorporeal immunoadsorption is associated with improved ventricular function and reduced cardiac symptoms in some DCM patients, suggesting that autoantibodies may also have a functional role in humans. Immunosuppression seems beneficial in patients who are virus-negative and cardiac autoantibody positive. Prospective family studies have shown that cardiac-specific autoantibodies are present in at least 60% of both familial and non familial pedigrees and predict DCM development among asymptomatic relatives, years before clinical and echocardiographic evidence of disease. Animal models have shown that autoimmune myocarditis/DCM can be induced by virus as well as reproduced by immunization with a well-characterized autoantigen, cardiac myosin. Thus, in a substantial proportion of patients, myocarditis and DCM represent different stages of an organ-specific autoimmune disease, that represents the final common pathogenetic pathway of infectious and noninfectious myocardial injuries in genetically predisposed individuals.

Th1-type immune responses by Toll-like receptor 4 signaling are required for the development of myocarditis in mice with BCG-induced myocarditis

The immunological aspects of autoimmune myocarditis are difficult to understand because of the existence of many infectious agents and animal models suggesting different mechanisms in autoimmune myocarditis. To overcome these difficulties, two strains of mice, C3H/HeN and C3H/HeJ, showing different immune responses to mycobacteria, were immunized with myosin mixed with BCG. The C3H/HeN mice with a wild-type Toll-like receptor 4 (TLR4) showed severe myocarditis, whereas the C3H/HeJ mice with nonfunctional mutated TLR4 did not. CD4(+) cells from both strains of mice exhibited appreciable proliferative responses following myosin stimulation; however, the cytokines from these cells differed between these two strains. The C3H/HeN mice showed T helper (Th)1-type cytokine responses, whereas the expressions of mRNA in C3H/HeJ mice were Th2-type cytokine. When both of these strains of immunized mice were inoculated with a plasmid encoding cDNA of interleukin (IL)-4 or agonistic IL-4, the development of myocarditis was inhibited in C3H/HeN mice. Moreover, C3H/HeJ mice, in which development of myocarditis was not induced by immunization of myosin mixed with BCG, showed myocarditis after injection of IL-4 antagonistic mutant DNA for the induction of Th1-type immune responses. The results suggested that the induction of autoimmune myocarditis by myosin is affected by Th1-type immune responses.

Myocarditis

Viruses are the most common cause of myocarditis in economically advanced countries.

Enteroviruses and adenoviruses are the most common etiologic agents.

Viral myocarditis is a triphasic process. Phase 1 is the period of active viral replication in the myocardium during which the symptoms of myocardial damage range from none to cardiogenic shock. If the disease process continues, it enters phase 2, which is characterized by autoimmunity triggered by viral and myocardial proteins. Heart failure often appears for the first time in phase 2. Phase 3, dilated cardiomyopathy, is the end result in some patients. Diagnostic procedures and treatment should be tailored to the phase of disease.

Viral myocarditis is a significant cause of dilated cardiomyopathy, as proved by the frequent presence of viral genomic material in the myocardium, and by improvement in ventricular function by immunomodulatory therapy.

Myocarditis of any etiology usually presents with heart failure, but the second most common presentation is ventricular arrhythmia. As a result, myocarditis is one of the most common causes of sudden death in young people and others without preexisting structural heart disease.

Myocarditis can be definitively diagnosed by endomyocardial biopsy. However, it is clear that existing criteria for the histologic diagnosis need to be refined, and that a variety of molecular markers in the myocardium and the circulation can be used to establish the diagnosis.

Treatment of myocarditis has been generally disappointing. Accurate staging of the disease will undoubtedly improve treatment in the future. It is clear that immunosuppression and immunomodulation are effective in some patients, especially during phase 2, but may not be as useful in phases 1 and 3. Since myocarditis is often selflimited, bridging and recovery therapy with circulatory assistance may be effective. Prevention by immunization or receptor blocking strategies is under development.

Giant cell myocarditis is an unusually fulminant form of the disease that progresses rapidly to heart failure or sudden death. Rapid onset of disease in young people, especially those with other autoimmune manifestations, accompanied by heart failure or ventricular arrhythmias, suggests giant cell myocarditis.

Peripartum cardiomyopathy in economically developed countries is usually the result of myocarditis.

Clinical implications of anti-cardiac immunity in dilated cardiomyopathy

Criteria of organ-specific autoimmunity are fulfilled in a subset of patients with myocarditis/dilated cardiomyopathy (DCM). In particular, circulating heart-reactive autoantibodies are found in such patients and symptom-free relatives. These autoantibodies are directed against multiple antigens, some of which are expressed in the heart (organ-specific), others in heart and some skeletal muscle fibres (partially heart-specific) or in heart and skeletal muscle (muscle-specific). Distinct autoantibodies have different frequency in disease and normal controls. Different techniques detect one or more antibodies, thus they cannot be used interchangeably for screening. It is unknown whether the same patients produce more antibodies or different patient groups develop autoimmunity to distinct antigens. IgG antibodies, shown to be cardiac- and disease-specific for myocarditis/DCM, can be used as autoimmune markers for relatives at risk as well as for identifying patients in whom immunosuppression may be beneficial. Some autoantibodies may also have a functional role, but further work is needed.

Autoimmune myocarditis and dilated cardiomyopathy: focus on cardiac autoantibodies

Criteria of organ-specific autoimmunity are fulfilled in a subset of patients with myocarditis/dilated cardiomyopathy (DCM). In particular, circulating heart-reactive autoantibodies are found in patients and symptom-free relatives. These autoantibodies are directed against multiple antigens, some of which are expressed in the heart (organ-specific), others in heart and some skeletal muscle fibres (partially-heart specific) or in heart and skeletal muscle (muscle-specific). Distinct autoantibodies have different frequency in disease and normal controls. Different techniques detect one or more antibodies, thus they cannot be used interchangeably for screening. It is unknown whether the same patients produce more antibodies or different patient groups develop autoimmunity to distinct antigens. IgG antibodies, shown to be cardiac and disease-specific for myocarditis/DCM, can be used as autoimmune markers for identifying patients in whom immunosuppression may be beneficial and relatives at risk. Some autoantibodies may also have a functional role, but further work is needed.

Two Autoimmune Diabetes Loci Influencing T Cell Apoptosis Control Susceptibility to Experimental Autoimmune Myocarditis

The pathogenesis of immune-mediated myocarditis depends on genetic and environmental factors. To study the genetic mechanisms, we have developed a model of experimental autoimmune myocarditis in the A.SW mouse. Here we provide evidence that loci on murine chromosome 6, and possibly chromosome 1, are involved in regulating susceptibility. Moreover, these loci overlap with loci implicated in other autoimmune diseases including diabetes in the NOD mouse. These two loci also regulate apoptosis in thymocytes as well as peripheral T cells in the NOD mouse, and we report further that A.SW mice demonstrate the same characteristics in apoptosis. These results suggest that common pathogenetic mechanisms involving apoptosis of both thymic and peripheral T cells are shared by multiple autoimmune diseases.

Successful treatment of enterovirus-induced myocarditis with interferon-alpha

No randomized, placebo-controlled studies have investigated interferon-alpha therapy in enterovirus-proven myocarditis. This report describes 2 patients with enterovirus-induced myocarditis (1 with associated Churg-Strauss syndrome) who at follow-up endomyocardial biopsy showed clinical and hemodynamic improvement and viral clearance (using polymerase chain reaction) after interferon-alpha therapy.

Cardiac autoantibodies to myosin and other heart-specific autoantigens in myocarditis and dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is characterized by dilation and impaired contraction of the left ventricle or both; it is a relevant cause of heart failure and a common indication for heart transplantation. It may be idiopathic, familial/genetic, viral, autoimmune or immune-mediated, associated with a viral infection. Myocarditis is an inflammatory disease of the myocardium; it may be idiopathic, infectious or autoimmune and may heal or lead to DCM. Thus, in a patient subset, myocarditis and DCM are thought to represent the acute and chronic stages of an organ-specific autoimmune disease of the myocardium. In keeping with this hypothesis, autoimmune features in patients with myocarditis/DCM include: familial aggregation, a weak association with HLA-DR4, abnormal expression of HLA class II on cardiac endothelium on endomyocardial biopsy, detection of organ- and disease-specific cardiac autoantibodies in the sera of affected patients and of symptom-free relatives. The organ-specific cardiac autoantibodies detected by immunofluorescence are directed against multiple antigens. One of these, first identified using immunoblotting and confirmed by ELISA, is the cardiac-specific alpha-myosin isoform. Myosin fulfils the expected criteria for organ-specific autoimmunity, in that immunization with cardiac but not skeletal myosin reproduces, in susceptible mouse strains, the human disease phenotype of myocarditis/DCM; in addition, alpha-myosin is entirely cardiac-specific. The organ-specific cardiac autoantibodies detected by immunofluorescence in symptom-free relatives were associated with echocardiographic features suggestive of early disease. Short-term follow-up is in keeping with this interpretation, although extended follow-up is necessary to define better the role of the antibody as predictor of disease susceptibility in healthy subjects at risk of myocarditis/DCM, such as first-degree relatives.

Circulating cardiac autoantibodies in dilated cardiomyopathy and myocarditis: pathogenetic and clinical significance

Dilated cardiomyopathy (DCM) is a relevant cause of heart failure and a common indication for heart transplantation. It may be idiopathic, familial/genetic, viral, autoimmune or immune-mediated associated with a viral infection. Myocarditis is an inflammatory disease of the myocardium; it may be idiopathic, infectious or autoimmune and may heal or lead to DCM. Thus, in a patient subset, myocarditis and DCM are thought to represent the acute and chronic stages of an organ-specific autoimmune disease of the myocardium. In keeping with this hypothesis, autoimmune features in patients with myocarditis/DCM include: familial aggregation; a weak association with HLA-DR4; abnormal expression of HLA class II on cardiac endothelium on endomyocardial biopsy; and detection of organ- and disease-specific cardiac autoantibodies of the IgG class in the sera of affected patients and symptom-free relatives. The cardiac autoantibodies detected by immunofluorescence are directed against multiple antigens. Two of these, first identified using immunoblotting and confirmed by ELISA, are the atrial-specific alpha- and the ventricular and skeletal muscle beta-heavy chain isoform. The alpha-myosin isoform fulfils the expected criteria for organ-specific autoimmunity, in that immunization with cardiac, but not skeletal myosin reproduces, in susceptible mouse strains, the human disease phenotype of myocarditis/DCM; in addition, alpha-myosin is entirely cardiac-specific. Additional antigenic targets of heart-reactive autoantibodies include unknown sarcolemmal proteins, mitochondrial enzymes, beta-adrenergic and muscarinic receptors. For some of these antibodies, there is in vitro evidence for a functional role. The organ-specific cardiac autoantibodies detected by immunofluorescence in symptom-free relatives were associated with echocardiographic features suggestive of early disease. Mid-term follow-up suggests that these antibodies are predictive markers of progression to DCM among symptom-free relatives with or without abnormal echocardiographic findings.

Pathophysiology of viral myocarditis: the role of humoral immune response

The pathophysiology of viral myocarditis is still a matter of debate. Humoral autoimmunity in postviral heart disease remains an attractive but complex hypothesis. Antigenic mimicry with or without cytolytic antibody properties has been shown to play a role in the immunopathogenesis of myocarditis with respect to sarcolemmal/myolemmal epitopes (including the beta-receptor), myosin and some mitochondrial proteins including the antinucleotide translocator (ANT)-carrier and dihydrolipoamid dehydrogenase. Today, refined two-dimensional Western blots are able to identify receptors and enzymes that are target of a humoral immune response or the consequence of an "immunization process." A humoral immune response to an invading agent will most likely lead to immunodestruction first. After conversion to IgG, the continuing antibody response may indicate the healing or healed process and last for many years or life-long. This paper reviews our present knowledge on the humoral immune response in myocarditis and its interplay with the viral agents and the other components of the immune system.

Interleukin-12 receptor/STAT4 signaling is required for the development of autoimmune myocarditis in mice by an interferon-gamma-independent pathway

BACKGROUND

Interleukin (IL)-12 exerts a potent proinflammatory effect by stimulating T-helper (Th) 1 responses. This effect is believed to be mediated primarily through the activation of STAT4 and subsequent production of interferon (IFN)-gamma. Methods and Results- We examined the role of IL-12 receptor (IL-12R) signaling in the development of murine experimental autoimmune myocarditis (EAM) induced by cardiac myosin immunization. Both IL-12Rbeta1-deficient mice and STAT4-deficient mice were resistant to the induction of myocarditis. Treatment with exogenous IL-12 exacerbated disease. We questioned whether IFN-gamma is required for the disease-promoting activity of IL-12. On the contrary, we found that IFN-gamma suppresses EAM. Lack of IFN-gamma due to either depletion with an antibody or a genetic deficiency exacerbated myocarditis. Spleens from IFN-gamma-deficient mice immunized with cardiac myosin showed increased cellularity; greater numbers of CD3+, CD4+, CD8+, and IL-2-producing cells; and heightened ability to produce cytokines on stimulation in vitro. Treatment of mice with recombinant IFN-gamma suppressed the development of myocarditis.

CONCLUSIONS

IL-12/IL-12R/STAT4 signaling promotes the development of EAM. In contrast, IFN-gamma plays a protective role. The disease-limiting effects of IFN-gamma might be explained by its ability to control the expansion of activated T lymphocytes.