Long-term follow up of patients with dilated heart muscle disease treated with human leucocytic interferon alpha or thymic hormones initial results

Implication of microRNA as a potential biomarker of myocarditis

Myocarditis was previously attributed to an epidemic viral infection. Additional harmful reagents, in addition to viruses, play a role in its etiology. Coronavirus disease 2019 (COVID-19) vaccine-induced myocarditis has recently been described, drawing attention to vaccine-induced myocarditis in children and adolescents. Its pathology is based on a series of complex immune responses, including initial innate immune responses in response to viral entry, adaptive immune responses leading to the development of antigen-specific antibodies, and autoimmune responses to cellular injury caused by cardiomyocyte rupture that releases antigens. Chronic inflammation and fibrosis in the myocardium eventually result in cardiac failure. Recent advancements in molecular biology have remarkably increased our understanding of myocarditis. In particular, microRNAs (miRNAs) are a hot topic in terms of the role of new biomarkers and the pathophysiology of myocarditis. Myocarditis has been linked with microRNA-221/222 (miR-221/222), miR-155, miR-10a*, and miR-590. Despite the lack of clinical trials of miRNA intervention in myocarditis yet, multiple clinical trials of miRNAs in other cardiac diseases have been aggressively conducted to help pave the way for future research, which is bolstered by the success of recently U.S. Food and Drug Administration-approved small-RNA medications. This review presents basic information and recent research that focuses on myocarditis and related miRNAs as a potential novel biomarker and the therapeutics.

Fulminant myocarditis in adults: a narrative review

Fulminant myocarditis (FM) is an uncommon syndrome characterized by sudden and severe hemodynamic compromise secondary to acute myocardial inflammation, often presenting as profound cardiogenic shock, life-threatening ventricular arrhythmias and/or electrical storm. FM may be refractory to conventional therapies and require mechanical circulatory support (MCS). The immune system has been recognized as playing a pivotal role in the pathophysiology of myocarditis, leading to an increased focus on immunosuppressive treatment strategies. Recent data have highlighted not only the fact that FM has significantly worse outcomes than non-FM, but that prognosis and management strategies of FM are heavily dependent on histological subtype, placing greater emphasis on the role of endomyocardial biopsy in diagnosis. The impact of subtype on severity and prognosis will likewise influence how aggressively the myocarditis is managed, including whether MCS is warranted. Many patients with refractory cardiogenic shock secondary to FM end up requiring MCS, with venoarterial extracorporeal membrane oxygenation demonstrating favorable survival rates, particularly when initiated prior to the development of multiorgan failure. Among the challenges facing the field are the need to more precisely identify immunopathophysiological pathways in order to develop targeted therapies, and the need to better optimize the timing and management of MCS to minimize complications and maximize outcomes.

Efficacy of immunosuppressive therapy in myocarditis: A 30-year systematic review and meta analysis

AIMS

Myocarditis is an inflammation of the heart muscle, due to infectious, toxic or autoimmune causes. Literature reported controversial results in relation to the effect of immunosuppression (IS)/immunomodulation (IM). We aimed at assessing the effect of IS/IM by meta analysis.

METHODS AND RESULTS

Using the P.R.I.S.M.A. approach, two researchers searched for relevant studies on PubMed, Embase, and the Central Registry of Controlled Trials of the Cochrane Library. Proposed MeSH terms were: "immunotherapy OR immune therapy OR immune modeling OR Immunosuppressive Agents" AND "combination OR combined with OR plus" AND "myocarditis OR cardiomyopathies OR inflammatory cardiomyopathy". The language was restricted to English. Reference lists of included articles and those relevant to the topic were hand searched for the identification of additional, potentially relevant articles. The cutoff date was from 1987 until 30th Nov 2019. Reported survival or mortality events or change of left ventricular ejection fraction (LVEF) after IS/IT were primary outcomes of the study; in addition, improvement of New York Heart Association class, follow-up biopsy (Bx) findings, viral genome clearance on Bx and recurrence of myocarditis were recorded if reported. Statistical analysis was conducted using Review Manager 5.3; 5452 studies were screened, of these 73 were assessed for eligibility, including 8 randomized control studies, 26 retrospective studies, 2 prospective studies and 1 case control study, 34 case reports and 2 case series. In prospective studies, the difference in mortality between the IS and control groups tended to be lower in the combined IS groups (12.5% vs. 18.2%) (95% CI of odds ratio 0.7(0.3, 1.64)) and the pooled difference of the increase of LVEF between the IS and control groups tended to be higher in the combined IS groups (95% CI 7.26 (-2.29, 16.81)). In retrospective studies, the difference of survival between the IS and control group was significantly in favor of IS (95%CI Hazard ratio 0.82(0.69, 0.96)).

CONCLUSIONS

A tailored IS may be considered in myocarditis, depending on the phase of the disease, and the type of underlying autoimmune or immune-mediated form.

Recognition and Initial Management of Fulminant Myocarditis: A Scientific Statement From the American Heart Association

Fulminant myocarditis (FM) is an uncommon syndrome characterized by sudden and severe diffuse cardiac inflammation often leading to death resulting from cardiogenic shock, ventricular arrhythmias, or multiorgan system failure. Historically, FM was almost exclusively diagnosed at autopsy. By definition, all patients with FM will need some form of inotropic or mechanical circulatory support to maintain end-organ perfusion until transplantation or recovery. Specific subtypes of FM may respond to immunomodulatory therapy in addition to guideline-directed medical care. Despite the increasing availability of circulatory support, orthotopic heart transplantation, and disease-specific treatments, patients with FM experience significant morbidity and mortality as a result of a delay in diagnosis and initiation of circulatory support and lack of appropriately trained specialists to manage the condition. This scientific statement outlines the resources necessary to manage the spectrum of FM, including extracorporeal life support, percutaneous and durable ventricular assist devices, transplantation capabilities, and specialists in advanced heart failure, cardiothoracic surgery, cardiac pathology, immunology, and infectious disease. Education of frontline providers who are most likely to encounter FM first is essential to increase timely access to appropriately resourced facilities, to prevent multiorgan system failure, and to tailor disease-specific therapy as early as possible in the disease process.

Immunomodulatory treatment for lymphocytic myocarditis-a systematic review and meta-analysis

Deleterious inflammatory responses are seen to be the trigger of heart failure in myocarditis and therapies directed towards immunomodulation have been assumed to be beneficial. The objective of the present review was to systematically assess the effect of immunomodulation in lymphocytic myocarditis. Studies were included if diagnosis of lymphocytic myocarditis was based on EMB as well as on the exclusion of other etiologies of heart failure and if the patients had at least moderately decreased left ventricular ejection fraction (< 45%). All immunomodulatory treatments at any dose that target the cause of myocarditis leading to cardiomyopathy were included. Retrieval of PUBMED, SCOPUS, Cochrane Central Register of Controlled Trials, and LILACs from January 1950 to January 2016 revealed 444 abstracts of which nine studies with a total of 612 patients were included. As primary effectivity endpoint, a change in left ventricular ejection was chosen. No benefits of corticosteroids or intravenous immunoglobulin alone were reported. Immunoadsorption and subsequent IVIG substitution was associated with a greater improvement in left ventricular ejection fraction (LVEF) in one study. Single studies found a beneficial effect of interferon and statins on LVEF. We performed a meta-analysis for the combination of corticosteroids with immunosuppressants and found a non-significant increase of LVEF of + 13.06% favoring combined treatment (95%CI 1.71 to + 27.84%, p = 0.08). The current evidence does not support the routine use of immunosuppression in traditional lymphocytic myocarditis. Nevertheless, in histologically proven virus-negative myocarditis of high-risk patients, combined immunosuppression might be beneficial. Future research should focus on translation of these effects to clinical outcome.

Immunosuppressive treatment for myocarditis: a meta-analysis of randomized controlled trials

BACKGROUND

Immunosuppressive treatment for myocarditis is controversial. Several small-scale randomized controlled trials (RCTs) reported inconsistent outcomes for patients with myocarditis.

METHODS

We searched on the Medline, Embase, and Cochrane databases for articles in English language between January 1966 and May 2013, as well as on the China National Knowledge Internet (CNKI, 1979 to May 2012) and the Chinese Biomedical Literature Database (CBM, 1978 to May 2013) for articles in Chinese language. Statistical analysis was performed using Review Manager 5.0.

RESULTS

Nine articles were finally selected, in which 342 patients were in immunosuppressive treatment group and 267 patients in conventional treatment group. The immunosuppressive treatment group showed a significant improvement in left ventricular ejection fraction at both short-term (≤3 months) [difference: 0.08, 95% confidence interval (CI): 0.05-0.10) and long-term (difference: 0.10, 95% CI: 0.00-0.21)] follow-up. Moreover, left ventricular end-diastolic dimension decreased significantly in the immunosuppressive treatment group after short-term follow-up (difference: -1.85 mm, 95% CI: -3.18 to -0.52 mm), but a long-term beneficial effect was not sustained (difference: -5.79 mm, 95% CI: -15.30 to 3.72 mm). There was no difference, however, between the two groups in the rate of death or heart transplantation (odds ratio: 1.33, 95% CI: 0.77, 2.31).

CONCLUSION

Immunosuppressive treatment might be beneficial for improving left ventricular systolic function and remodeling in patients with myocarditis, which could be considered as a therapeutic alternative when optimal conventional therapy is not effective. More large RCTs, however, are required.

Update on myocarditis

Myocarditis is an inflammatory disease of the heart frequently resulting from viral infections and/or post-viral immune-mediated responses. It is one of the important causes of dilated cardiomyopathy worldwide. The diagnosis is presumed on clinical presentation and noninvasive diagnostic methods such as cardiovascular magnetic resonance imaging. Endomyocardial biopsy remains the gold standard for in vivo diagnosis of myocarditis. The therapeutic and prognostic benefits of endomyocardial biopsy results have recently been demonstrated in several clinical trials. Although remarkable advances in diagnosis, understanding of pathophysiological mechanisms, and treatment of acute myocarditis were gained during the last years, no standard treatment strategies could be defined as yet, apart from standard heart failure therapy and physical rest. In severe cases, mechanical support or heart transplantation may become necessary. There is some evidence that immunosuppressive and immunomodulating therapy are effective for chronic, virus-negative inflammatory cardiomyopathy. Further investigations by controlled, randomized studies are needed to definitively determine their role in the treatment of myocarditis.

A single-amino-acid polymorphism in reovirus protein μ2 determines repression of interferon signaling and modulates myocarditis

Myocarditis is indicated as the second leading cause of sudden death in young adults. Reovirus induces myocarditis in neonatal mice, providing a tractable model system for investigation of this important disease. Alpha/beta-interferon (IFN-α/β) treatment improves cardiac function and inhibits viral replication in patients with chronic myocarditis, and the host IFN-α/β response is a determinant of reovirus strain-specific differences in induction of myocarditis. Virus-induced IFN-β stimulates a signaling cascade that establishes an antiviral state and further induces IFN-α/β through an amplification loop. Reovirus strain-specific differences in induction of and sensitivity to IFN-α/β are associated with the viral M1, L2, and S2 genes. The reovirus M1 gene-encoded μ2 protein is a strain-specific repressor of IFN-β signaling, providing one possible mechanism for the variation in resistance to IFN and induction of myocarditis between different reovirus strains. We report here that μ2 amino acid 208 determines repression of IFN-β signaling and modulates reovirus induction of IFN-β in cardiac myocytes. Moreover, μ2 amino acid 208 determines reovirus replication, both in initially infected cardiac myocytes and after viral spread, by regulating the IFN-β response. Amino acid 208 of μ2 also influences the cytopathic effect in cardiac myocytes after spread. Finally, μ2 amino acid 208 modulates myocarditis in neonatal mice. Thus, repression of IFN-β signaling mediated by reovirus μ2 amino acid 208 is a determinant of the IFN-β response, viral replication and damage in cardiac myocytes, and myocarditis. These results demonstrate that a single amino acid difference between viruses can dictate virus strain-specific differences in suppression of the host IFN-β response and, consequently, damage to the heart.

IFN-alpha expression and antiviral effects are subtype and cell type specific in the cardiac response to viral infection

The interferon-beta (IFN-beta) response is critical for protection against viral myocarditis in several mouse models, and IFN-alpha or -beta treatment is beneficial against human viral myocarditis. The IFN-beta response in cardiac myocytes and cardiac fibroblasts forms an integrated network for organ protection; however, the different IFN-alpha subtypes have not been studied in cardiac cells. We developed a quantitative RT-PCR assay that distinguishes between 13 highly conserved IFN-alpha subtypes and found that reovirus T3D induces five IFN-alpha subtypes in primary cardiac myocyte and fibroblast cultures: IFN-alpha1, -alpha2, -alpha4, -alpha5, and -alpha8/6. Murine IFN-alpha1, -alpha2, -alpha4, or -alpha5 treatment induced IRF7 and ISG56 and inhibited reovirus T3D replication in both cell types. This first investigation of IFN-alpha subtypes in cardiac cells for any virus demonstrates that IFN-alpha is induced in cardiac cells, that it is both subtype and cell type specific, and that it is likely important in the antiviral cardiac response.

Complication Rate of Right Ventricular Endomyocardial Biopsy via the Femoral Approach

Background— An unequivocal diagnosis of myocarditis and cardiac virus persistence is based on histological, immunohistological, and molecular biological analyses of endomyocardial biopsies (EMBs). Biopsy-based diagnosis of myocarditis has become increasingly important because recent studies have demonstrated the beneficial effects of biopsy-based causal treatment strategies (immunosuppressive or antiviral). Because the risks of major complications caused by EMB procedures have not yet been well defined, we evaluated the incidence of major and minor complications of right ventricular EMB procedures in this retrospective and prospective single-center study.

Methods and Results— With the use of a modified Cordis bioptome, 1919 patients underwent 2505 EMB procedures retrospectively over a 9-year period (January 1995 to December 2003), and 496 patients underwent 543 EMB procedures prospectively between January 2004 and December 2005. A total of 2415 patients had 3048 EMB procedures via the right femoral vein approach under biplane fluoroscopic control to evaluate unexplained left ventricular dysfunction (retrospective left ventricular ejection fraction, 49.8±18.8%; prospective, 48.8±19.7%) after exclusion of secondary causes. During each EMB procedure, an average of 8.2±0.8 EMBs were obtained retrospectively and 10.1±0.6 specimens prospectively for a total of 26 025 specimens. No patient died or required emergency cardiac surgery. Other major complications like cardiac tamponade requiring pericardiocentesis or complete atrioventricular block requiring permanent pacing were very rare: 0.12% in the retrospective study and 0% in the prospective study. Minor complications such as pericardial effusion, conduction abnormalities, or arrhythmias occurred in 0.20% of the EMB procedures in the retrospective study and 5.5% in the prospective study.

Conclusions— The EMB procedure via the femoral vein approach under fluoroscopic guidance has a very low complication rate when performed by experienced operators.

Fulminant myocarditis

Fulminant myocarditis is an inflammatory process that occurs in the myocardium and causes acute-onset heart failure. If patients with fulminant myocarditis are aggressively supported in a timely manner, nearly all can have an excellent recovery. In this Review, we discuss the clinical and histological distinguishing features of fulminant myocarditis and contrast this disease entity with nonfulminant myocarditis. The epidemiology, pathophysiology, clinical presentation, methods of diagnosis, management options and prognosis of fulminant myocarditis are reviewed in detail.

Molecular diagnosis of the viral component in cardiomyopathies: pathophysiological, clinical and therapeutic implications

BACKGROUND

Myocarditis is defined as the inflammation of myocardium associated with cardiac dysfunction. Despite this clear-cut definition, diagnosis and etiologic treatment continue to create considerable debate. Viral infections are frequent causes of myocarditis and there is evidence that persistent viral infection is associated with poor prognosis in different subtypes of cardiomyopathy.

OBJECTIVE

To review methods for diagnosis of viral myocarditis and present the use of polymerase chain reaction (PCR)-based protocols for evaluating viral infection in myocarditis/cardiomyopathies.

METHODS

A review of published literature.

RESULTS/CONCLUSION

There is increasing evidence that PCR-based protocols can provide reliable molecular evidence for the presence of viral infection in myocardium. Thus application of molecular techniques will allow collection and analysis of more information on the epidemiology of viral cardiomyopathies, patient risk stratification and appropriate medical treatment.

Basal expression levels of IFNAR and Jak-STAT components are determinants of cell-type-specific differences in cardiac antiviral responses

Viral myocarditis is an important human disease, and reovirus-induced murine myocarditis provides an excellent model system for study. Cardiac myocytes, like neurons in the central nervous system, are not replenished, yet there is no cardiac protective equivalent to the blood-brain barrier. Thus, cardiac myocytes may have evolved a unique antiviral response relative to readily replenished cell types, such as cardiac fibroblasts. Our previous comparisons of these two cell types revealed a conundrum: reovirus T3D induces more beta-interferon (IFN-beta) mRNA in cardiac myocytes, yet there is a greater induction of IFN-stimulated genes (ISGs) in cardiac fibroblasts. Here, we investigated possible underlying molecular determinants. We found that greater basal expression of IFN-beta in cardiac myocytes results in greater basal activated nuclear STAT1 and STAT2 and greater basal ISG mRNA expression and provides greater basal antiviral protection relative to cardiac fibroblasts. Conversely, cardiac fibroblasts express greater basal IFN-alpha/beta receptor 1 (IFNAR1) and greater basal cytoplasmic Jak1, Tyk2, STAT2, and IRF9, leading to a greater increase in reovirus T3D- or IFN-induced nuclear activated STAT1 and STAT2 and greater induction of ISGs for a greater IFN-induced antiviral protection relative to cardiac myocytes. Our results suggest that high basal IFN-beta expression in cardiac myocytes prearms this vulnerable, nonreplenishable cell type, while high basal expression of IFNAR1 and latent Jak-STAT components in adjacent cardiac fibroblasts renders these cells more responsive to IFN and prevents them from inadvertently serving as a reservoir for viral replication and spread to cardiac myocytes. These studies provide the first indication of an integrated network of cell-type-specific innate immune components for organ protection.

Cytokines in HIV-associated cardiomyopathy

Among the multiple cardiac manifestations occurring in HIV-infected patients, cardiomyopathy is one of the most challenging. Its incidence has only slightly decreased since the introduction of highly active antiretroviral therapy (HAART). Also, its pathogenesis remains relatively unclear. Although several studies demonstrated the presence of HIV genome in the heart of patients, more recent developments found that viral infection plays an indirect role only, as well as they recognized the contribution of proinflammatory cytokines in the progression of the disease. Experimental studies on animals and cultured myocytes have established the signalling pathway triggered by proinflammatory cytokines in heart failure and cardiomyopathy. Tumor necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1) and IL-6 promote expression of inducible nitric oxide synthase (iNOS) in cardiomyocytes through activation of p38 mitogen-activated protein kinase (p38 MAPK) and nuclear factor kappaB (NFkappaB). TNF-alpha and high concentrations of NO also induce cardiomyocyte apoptosis by TNF type 1 receptor activation. This biological framework, which is also involved in progression of cardiomyopathy in humans, is more pronounced in HIV-infected patients, in whom proinflammatory cytokines TNF-alpha, IL-1 and IL-6 are increased, resulting in an enhanced expression of cardiac iNOS, especially in patients with a low CD4 T cell count. This may account for the worse outcome of heart failure in HIV-infected patients. However, there are only few data today to support future therapeutic implications of cytokines antagonism in treatment of HIV-infected patients with cardiomyopathy. Whether modulation of TNF production or selective inhibition of p38 MAPK pathway could be useful approaches remains uncertain.

Coxsackievirus-induced myocarditis: new trends in treatment

Myocarditis is a common inflammatory heart disease in children and young adults that may result in chronically dilated cardiomyopathy. Coxsackievirus B3 is the major etiologic agent of this disease. Current treatments for patients with viral myocarditis are almost entirely supportive. In recent years, some promising therapeutic candidates have emerged, including novel treatments and improvements of existing drugs. Among these are molecules that specially target virus entry, such as pleconaril, WIN 54954 and CAR-Fc; nucleic acid-based antiviral agents that inhibit viral translation and/or transcription, such as antisense oligodeoxynucleotide and short interfering RNA; and immunomodulatory agents that augment the host-protective immune responses to effectively clear viruses from target tissues, including interferons and immunoglobulins. In addition, certain new antiviral strategies, still in the early stages, include modulation of signal transduction pathways responsible for viral replication using enzyme inhibitors, which have revealed potential therapeutic targets for viral myocarditis. Finally, the progress in cellular cardiomyoplasty for end-stage therapy, in particular the preliminary clinical trials, is also discussed with respect to its potential future application.

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.

Anti-viral treatment in patients with virus-induced cardiomyopathy

Ongoing viral persistence in the myocardium is associated with an adverse prognosis of cardiomyopathy eventually resulting in a reduced capacity for work and thus it is associated with enormous social costs. Experimental and clinical data highlight that an imbalance of the cytokine network and a defect in the cytokine-induced immune response may constitute major causes leading to the development of virus persistence and progression of myocardial dysfunction. Reversibility of cardiac impairment during the early stages of the disease and the arising chance of specific treatment options demand early diagnosis and treatment of the disease. Our pilot data on anti-viral treatment using INF-beta showed beneficial clinical effects and suggest that some of the ventricular dysfunction and wall motion abnormalities resolved after elimination of the responsible agents. The data also suggest that elimination of cardiotropic viruses and associated clinical effects may occur even in DCM patients presenting with a long history.

Basal and reovirus-induced beta interferon (IFN-beta) and IFN-beta-stimulated gene expression are cell type specific in the cardiac protective response

Viral myocarditis is an important human disease, with a wide variety of viruses implicated. Cardiac myocytes are not replenished yet are critical for host survival and thus may have a unique response to infection. Previously, we determined that the extent of reovirus induction of beta interferon (IFN-beta) and IFN-beta-mediated protection in primary cardiac myocyte cultures was inversely correlated with the extent of reovirus-induced cardiac damage in a mouse model. Surprisingly, and in contrast, the IFN-beta response did not determine reovirus replication in skeletal muscle cells. Here we compared the IFN-beta response in cardiac myocytes to that in primary cardiac fibroblast cultures, a readily replenished cardiac cell type. We compared basal and reovirus-induced expression of IFN-beta, IRF-7 (an interferon-stimulated gene [ISG] that further induces IFN-beta), and another ISG (561) in the two cell types by using real-time reverse transcription-PCR. Basal IFN-beta, IRF-7, and 561 expression was higher in cardiac myocytes than in cardiac fibroblasts. Reovirus T3D induced greater expression of IFN-beta in cardiac myocytes than in cardiac fibroblasts but equivalent expression of IRF-7 and 561 in the two cell types (though fold induction for IRF-7 and 561 was higher in fibroblasts than in myocytes because of the differences in basal expression). Interestingly, while reovirus replicated to equivalent titers in cardiac myocytes and cardiac fibroblasts, removal of IFN-beta resulted in 10-fold-greater reovirus replication in the fibroblasts than in the myocytes. Together the data suggest that the IFN-beta response controls reovirus replication equivalently in the two cell types. In the absence of reovirus-induced IFN-beta, however, reovirus replicates to higher titers in cardiac fibroblasts than in cardiac myocytes, suggesting that the higher basal IFN-beta and ISG expression in myocytes may play an important protective role.

PKR's protective role in viral myocarditis

Reovirus-induced murine myocarditis provides an excellent model for the human disease. Previously, we showed that reovirus induction of and sensitivity to interferon-beta (IFN-beta) are important determinants of protection against cardiac damage. IFN-beta induces a number of genes with antiviral activities, including the dsRNA-activated protein kinase, PKR. Once bound to viral dsRNA, PKR becomes activated and phosphorylates eukaryotic initiation factor-2 alpha (eIF2 alpha) leading to the cessation of host cell translation. Additionally, activated PKR can exert its antiviral effects by inducing phosphorylation of I kappa B, leading to the activation of the transcription factor NF kappa B and subsequent induction of IFN-beta. Thus, activated PKR can both induce and be induced by IFN-beta. Recently, numerous reports have shown PKR to be dispensable for both induction of IFN as well as protection against disease. However, both PKR's role in the heart in response to viral infection and its ability to prevent cardiac damage have gone largely unexplored. Here, we demonstrate PKR to be critical for viral induction of IFN-beta in primary cardiac myocyte cultures. Additionally, we show that loss of PKR leads to an increase in virulence for both myocarditic and nonmyocarditic reoviruses. Finally, we demonstrate PKR to be critical for protection against reovirus-induced viral myocarditis.

Interferon-beta treatment eliminates cardiotropic viruses and improves left ventricular function in patients with myocardial persistence of viral genomes and left ventricular dysfunction

BACKGROUND

Viral infections are important causes of myocarditis and may induce cardiac dysfunction and finally lead to dilated cardiomyopathy. We investigated whether interferon (IFN)-beta therapy is safe and may achieve virus clearance and prevent deterioration of left ventricular (LV) function in patients with myocardial virus persistence.

METHODS AND RESULTS

In this phase II study, 22 consecutive patients with persistence of LV dysfunction (history of symptoms, 44+/-27 months) and polymerase chain reaction-proven enteroviral or adenoviral genomes were treated with 18x10(6) IU/week IFN-beta (Beneferon) subcutaneously for 24 weeks. Histological and immunohistological analysis of endomyocardial biopsies was used to characterize myocardial inflammation. LV diameters and ejection fraction were assessed by echocardiography and angiography, respectively. During the treatment period, IFN-beta was well tolerated by all patients. No patient deteriorated. Clearance of viral genomes was observed in 22 of 22 of patients after antiviral therapy. Virus clearance was paralleled by a significant decrease of LV end diastolic and end systolic diameters, decreasing from 59.7+/-11.1 to 56.5+/-10.0 mm (P<0.001) and 43.2+/-13.6 to 39.4+/-12.1 mm (P<0.001), respectively. LV ejection fraction increased from 44.6+/-15.5% to 53.1+/-16.8% (P<0.001).

CONCLUSIONS

A 6 months, IFN-beta treatment was safe in patients with myocardial enteroviral or adenoviral persistence and LV dysfunction and resulted in elimination of viral genomes (22 of 22 patients) and improved LV function (15 of 22 patients).

An approach to the treatment of pediatric myocarditis

The newest treatment strategies for pediatric myocarditis have evolved from an understanding of the pathophysiology of myocyte damage. Although the initial stages of viral myocarditis apparently result from the direct cytopathic effects on the atrial and ventricular myocardium, later stages of progressive decompensation result from immune-mediated myocyte destruction common to many forms of myocarditis. Despite advances in the understanding of the role of genetics, immunologic mechanisms, and infectious causes of myocarditis, supportive therapy continues to remain the cornerstone of treatment. Presently, therapies include supportive management with anticongestive agents, antiviral medications, and therapies that attempt to interrupt the immunologic cascade. Clinical studies have yet to provide convincing evidence that the use of immunosuppressants and gamma-globulin favorably alters the outcome for pediatric patients with acute myocarditis. Ventricular assist devices and heart transplantation remain as treatment options for all pediatric patients with severe myocarditis resistant to all other therapies. Although this review will focus on viral myocarditis, the supportive strategies and surgical treatment options apply to most forms of cardiomyopathy.

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.

The role of interferon regulatory factors in the cardiac response to viral infection

Reovirus-induced murine myocarditis provides an excellent model for the human disease. Cardiac tissue damage varies between reovirus strains, and is caused by a direct viral cytopathogenic effect. One determinant of virus-induced cardiac tissue damage is the cardiac interferon-beta (IFN-beta) response to viral infection. Nonmyocarditic reoviruses induce more IFN-beta and/or are more sensitive to the antiviral effects of IFN-beta in cardiac cells than myocarditis reoviruses. The roles of interferon regulatory factors (IRFs) in the cardiac response to viral infection are reviewed, and results suggest possible cardiac-specific variations in IRF-3 and IRF-1 function. In addition, data are presented indicating that the role of IRF-2 in regulation of IFN-beta expression is cell type-specific and differs between skeletal and cardiac muscle cells. Together, results suggest that the heart may provide a unique environment for IRF function, critical for protection against virus-induced cardiac damage.

Innovative drug treatments for viral and autoimmune myocarditis

Myocarditis is a common cause of cardiomyopathy and is thought to account for 25% of all cases in humans. Unfortunately, the disease is difficult to detect clinically before a myopathic process ensues. Management of myocarditis-induced heart failure includes the standard regimen of diuretics, digoxin, angiotensin-converting enzyme inhibitors, angiotensin-II receptor blockers, and beta-adrenergic blockers. The management of myocarditis itself is dependent on the etiology of the illness. Treatments that are currently under investigation include immunosuppressants, nonsteroidal antiinflammatory agents, immunoglobulins, immunomodulation, antiadrenergics, calcium-channel blockers, angiotensin-converting enzyme inhibitors, nitric oxide inhibitors (e.g., aminoguanidine), and antivirals. Despite advances in treatment, more work needs to be done in the early detection of myocarditis. Additionally, better means need to be established for distinguishing between viral and noninfectious autoimmune forms of the disease, so that appropriate treatment can be instituted.

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.

Diagnosis and treatment of pediatric viral myocarditis

Acute myocarditis is characterized by the rapid development of life-threatening congestive heart failure and arrhythmias. Although the initial stages of this disorder apparently result from direct cytopathic effects on the atrial and ventricular myocardium, later stages of progressive decompensation may result from immune-mediated myocyte destruction. There has been recent improvement in understanding the role of this immunologic cascade. As a result, treatment now begins earlier in the course of the disease and can target both the virus and the immune response. Our ability to implement mechanical support in children as a bridge to transplant or recovery, even in children presenting in the final stages of their disease, has led to an improved outcome regarding morbidity and mortality.

Improved reliability for echocardiographic measurement of left ventricular volume using harmonic power imaging mode combined with contrast agent

Harmonic power imaging (HPI) is a new echocardiographic modality that enhances the detection of contrast agents in the left ventricle. The endocardium can be delineated by conventional echocardiography using ultrasound contrast agents, although the images tend to be faint. The present study was designed to assess left ventricular volume using HPI after intravenous injection of the contrast agent Levovist (Schering SA, Berlin, Germany) in 25 unselected patients. End-diastolic volume, end-systolic volume, and ejection fraction were determined for each patient with angiography and with 4 different ultrasound modalities: (1) conventional mode without contrast, (2) contrast conventional mode, (3) contrast harmonic intermittent imaging mode, and (4) contrast triggered HPI. The use of HPI improved correlations between the echographic and angiographic measurements for all parameters as well as precision and bias determined by Bland and Altman analysis. The relative errors for interobserver variability were also lower with HPI. This study demonstrates that echocardiographic determination of left ventricular volumes and ejection fraction is more accurate and reproducible using HPI combined with Levovist.

Interferon regulatory factor 3 is required for viral induction of beta interferon in primary cardiac myocyte cultures

Viral myocarditis affects an estimated 5 to 20% of the human population. The antiviral cytokine beta interferon (IFN-beta) is critical for protection against viral myocarditis in mice. That is, nonmyocarditic reoviruses induce myocarditis in mice that lack IFN-alpha/beta, and nonmyocarditic reoviruses both induce more IFN-beta and are more sensitive to the antiviral effects of IFN-beta than myocarditic reoviruses in primary cardiac myocyte cultures. Induction of IFN-beta in certain cell types involves viral activation of the transcription factor interferon regulatory factor 3 (IRF-3). To address whether IRF-3 can induce IFN-beta in cardiac myocytes, primary cardiac myocyte cultures and control L929 cells were transfected with a plasmid constitutively expressing IRF-3. Overexpression of IRF-3 resulted in induction of IFN-beta in the absence of viral infection in both cell types. To address whether IRF-3 is required for viral induction of IFN-beta, cell cultures were transfected with a plasmid constitutively expressing a dominant negative IRF-3 protein. The dominant negative IRF-3 reduced reovirus induction of IFN-beta in control L929 cells and completely eliminated induction in primary cardiac myocyte cultures. This provides the first identification of a cardiac cellular factor required for viral induction of IFN-beta and the first report of any cell type requiring IRF-3 for this response.

Innovative drug treatments for viral and autoimmune myocarditis

Myocarditis has been shown to be a common cause of cardiomyopathy and is believed to account for 25% of all cases in human beings. Unfortunately, the disease is difficult to detect before a myopathic process ensues. Treatment of myocarditis-induced heart failure includes the standard regimen of diuretics, digoxin, angiotensin-converting enzyme inhibitors, and currently, beta-adrenergic blockers. Treatment of myocarditis itself is dependent on the etiology of the illness. Treatments under investigation include immunosuppressants, nonsteroidal antiinflammatory agents, immunoglobulins, immunomodulation, antiadrenergics, calcium-channel blockers, angiotensin-converting enzyme inhibitors, nitric oxide inhibition (e.g., aminoguanidine), and antiviral agents. Despite advances in treatment, more work needs to be done in the early detection of myocarditis. Additionally, better means need to be established for distinguishing between viral and autoimmune forms of the disease, so that appropriate treatment can be instituted.