Autoimmunity in myocarditis: relevance of animal models

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.

Update on COVID-19 Myocarditis

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) gained worldwide attention at the end of 2019 when it was identified to cause severe respiratory distress syndrome. While it primarily affects the respiratory system, we now have evidence that it affects multiple organ systems in the human body. Cardiac manifestations may include myocarditis, life threatening arrhythmias, acute coronary syndrome, systolic heart failure, and cardiogenic shock. Myocarditis is increasingly recognized as a complication of Coronavirus-19 (COVID-19) and may result from direct viral injury or from exaggerated host immune response. The diagnosis is established similar to other etiologies, and is based on detailed history, clinical exam, laboratory findings and non-invasive imaging studies. When available, cardiac MRI is the preferred imaging modality. Endomyocardial biopsy may be performed if the diagnosis remains uncertain. Current management is mainly supportive with the potential addition of interventions recommended for severe COVID-19 disease, such as remdesivir, steroids, and convalescent plasma. In the setting of cardiogenic shock and refractory, life-threatening arrhythmias that persist despite medical therapy, advanced mechanical circulatory support devices should be considered. Ultimately, early recognition and aggressive intervention are key factors in reducing morbidity and mortality. Our management strategy is expected to evolve further as we learn more about COVID-19 disease and the associated cardiac complications.

Sphingolipid Mediators of Myocardial Pathology

Cardiomyopathy is the leading cause of mortality worldwide. While the causes of cardiomyopathy continue to be elucidated, current evidence suggests that aberrant bioactive lipid signaling plays a crucial role as a component of cardiac pathophysiology. Sphingolipids have been implicated in the pathophysiology of cardiovascular disease, as they regulate numerous cellular processes that occur in primary and secondary cardiomyopathies. Experimental evidence gathered over the last few decades from both in vitro and in vivo model systems indicates that inhibitors of sphingolipid synthesis attenuate a variety of cardiomyopathic symptoms. In this review, we focus on various cardiomyopathies in which sphingolipids have been implicated and the potential therapeutic benefits that could be gained by targeting sphingolipid metabolism.

Ferumoxytol-enhanced cardiovascular magnetic resonance detection of early stage acute myocarditis

BACKGROUND

The diagnostic utility of cardiovascular magnetic resonance (CMR) is limited during the early stages of myocarditis. This study examined whether ferumoxytol-enhanced CMR (FE-CMR) could detect an earlier stage of acute myocarditis compared to gadolinium-enhanced CMR.

METHODS

Lewis rats were induced to develop autoimmune myocarditis. CMR (3 T, GE Signa) was performed at the early- (day 14, n = 7) and the peak-phase (day 21, n = 8) of myocardial inflammation. FE-CMR was evaluated as % myocardial dephasing signal loss on gradient echo images at 6 and 24 h (6 h- & 24 h-FE-CMR) following the administration of ferumoxytol (300μmolFe/kg). Pre- and post-contrast T2* mapping was also performed. Early (EGE) and late (LGE) gadolinium enhancement was obtained after the administration of gadolinium-DTPA (0.5 mmol/kg) on day 14 and 21. Healthy rats were used as control (n = 6).

RESULTS

Left ventricular ejection fraction (LVEF) was preserved at day 14 with inflammatory cells but no fibrosis seen on histology. EGE and LGE at day 14 both showed limited myocardial enhancement (EGE: 11.7 ± 15.5%; LGE: 8.7 ± 8.7%; both p = ns vs. controls). In contrast, 6 h-FE-CMR detected extensive myocardial signal loss (33.2 ± 15.0%, p = 0.02 vs. EGE and p < 0.01 vs. LGE). At day 21, LVEF became significantly decreased (47.4 ± 16.4% vs control: 66.2 ± 6.1%, p < 0.01) with now extensive myocardial involvement detected on EGE, LGE, and 6 h-FE-CMR (41.6 ± 18.2% of LV). T2* mapping also detected myocardial uptake of ferumoxytol both at day 14 (6 h R2* = 299 ± 112 s- 1vs control: 125 ± 26 s- 1, p < 0.01) and day 21 (564 ± 562 s- 1, p < 0.01 vs control). Notably, the myocardium at peak-phase myocarditis also showed significantly higher pre-contrast T2* (27 ± 5 ms vs control: 16 ± 1 ms, p < 0.001), and the extent of myocardial necrosis had a strong positive correlation with T2* (r = 0.86, p < 0.001).

CONCLUSIONS

FE-CMR acquired at 6 h enhance detection of early stages of myocarditis before development of necrosis or fibrosis, which could potentially enable appropriate therapeutic intervention.

Established and novel treatment options in acute myocarditis, with or without heart failure

INTRODUCTION

Acute myocarditis is a disorder characterized by an unpredictable clinical course which ranges from asymptomatic, incidentally discovered forms, to cases with fulminant course and adverse outcome. The most challenging issues in the context of acute myocarditis are the appearance of difficult to treat heart failure in the acute phase and the potential progression in the long-term to dilated cardiomyopathy. Areas covered: With respect to available treatment options in acute myocarditis, in the absence of specific guidelines, management is supportive and overall empirical, especially for the oligo- or asymptomatic patients with preserved ejection fraction. Haemodynamically instable patients should be treated in referral centers with capability of advanced cardiopulmonary support. Patients with heart failure but without haemodynamic impairment should be treated according to the heart failure guidelines. Endomyocardial biopsy may be performed in an individualized basis both for diagnostic purposes and to guide treatment, based on the detection or not of viral genome. Expert commentary: Apart from the already established treatments, novel therapies against several targets are currently investigated and are expected to contribute to a more efficacious management options in the future. Increased awareness among medical professionals is essential for the early diagnosis and best care of acute myocarditis patients.

Effects of zileuton on the development of autoimmune myocarditis in an experimental rat model

BACKGROUND

Myocarditis is associated with high morbidity and mortality in childhood, but the pathogenesis of this disease is still unclear. Current knowledge indicates that complex immunopathogenic mechanisms are involved. It is understood that leukotrienes play an important role in the inflammation associated with asthma, and recent reports indicate that leukotrienes participate in immune processes and in autoimmunity.

OBJECTIVE

The aim of this study was to assess the role of leukotriene synthesis in the development of myocardial inflammation and necrosis during myocarditis.

METHODS

The effect of zileuton, a leukotriene synthesis inhibitor, was assessed in an experimental model of autoimmune myocarditis in rats. Healthy adult (10-week-old) male Wistar albino rats were randomly divided into 3 groups. Groups A and B received injections of 1.0 mg porcine cardiac myosin to induce autoimmune myocarditis and group C (the control group) received phosphate-buffered saline. Group B also received zileuton by oral gavage at 100 mg/kg · d(-1). Myocardial inflammation was assessed biochemically via serum concentrations of creatine kinase MB subunit (CK-MB) and troponin T. Cardiac tissue was assessed macroscopically (0 = no inflammation; 1 = a small discolored focus; 2 = diffuse discolored areas covering less than half of the cardiac surface; 3 = diffuse discolored areas covering more than half of the cardiac surface) and microscopically (0 = no inflammation; 1 = ⪯5% infiltration; 2 = 5% to <10% infiltration; 3 = 10% to < 20% infiltration; 4 = >20% infiltration).

RESULTS

Twenty-four rats were divided equally into 3 groups. All rats survived the duration of the study. After 21 days, all rats were euthanized. No significant differences were found between groups A and B in terms of serum concentrations of CK-MB or troponin T. The microscopic pathology score was significantly lower in group B (myosin + zileuton) than in group A (myosin only) (0.12 [0.35] vs 1.25 [1.03]; P = 0.023). The microscopic pathology score was significantly higher in group A than in group C (1.25 [1.03] vs 0; P < 0.01), but the difference between groups B and C was not statistically significant. The macroscopic pathology score was significantly higher in group A than in group B (1.37 [0.91] vs 0.37 [0.51]; P = 0.029). The macroscopic pathology score was significantly higher in group A than in group C (1.37 [0.91] vs 0; P < 0.01). There was no significant difference in macroscopic scores between groups B and C (0.37 [0.51] vs 0).

CONCLUSIONS

In this study of the effects of zileuton in an experimental rat model of autoimmune myocarditis, no significant differences were found in the serum concentrations of the biochemical markers in the 2 groups administered myosin. However, lower macroscopic and microscopic inflammation scores in the zileuton-treated group (group B) compared with the group administered only myosin (group A) suggest that zileuton, a leukotriene-synthesis inhibitor, may suppress the development of experimental autoimmune myocarditis in rats.

Autoimmune myocarditis, valvulitis, and cardiomyopathy

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

Toll-like receptors and myocardial inflammation

Toll-like receptors (TLRs) are a member of the innate immune system. TLRs detect invading pathogens through the pathogen-associated molecular patterns (PAMPs) recognition and play an essential role in the host defense. TLRs can also sense a large number of endogenous molecules with the damage-associated molecular patterns (DAMPs) that are produced under various injurious conditions. Animal studies of the last decade have demonstrated that TLR signaling contributes to the pathogenesis of the critical cardiac conditions, where myocardial inflammation plays a prominent role, such as ischemic myocardial injury, myocarditis, and septic cardiomyopathy. This paper reviews the animal data on (1) TLRs, TLR ligands, and the signal transduction system and (2) the important role of TLR signaling in these critical cardiac conditions.

Spontaneous autoimmune myocarditis and cardiomyopathy in HLA-DQ8.NODAbo transgenic mice

Most individuals have viral infections at some point in their life, however, only few develop autoreactivity to cardiac myosin following infection suggesting a genetic predisposition. Population studies have shown that among all the genetic factors linked with autoimmune disease development, MHC class II genes are the most significant genetic factors. Experimental autoimmune myocarditis resembling human Dilated cardiomyopathy can be induced in susceptible mice by infection with coxsackie virus as well as immunization with purified foreign and murine cardiac specific a-myosin. We generated transgenic mice lacking endogenous class II molecules, HLA-DR3.Abo and HLA-DQ8.Abo transgenic mice in NOD and HLA-DQ8.Abo in B10 background, to study the role of MHC in spontaneous autoimmunity. The HLA molecules in these mice are expressed on cell surface and can positively select CD4+ T cells expressing various Vb T cell receptors. NOD.DQ8 female mice spontaneously developed myocarditis and dilated cardiomyopathy. Histopathology of heart revealed mononuclear infiltrate consisting of CD4 and Mac-1+ cells and myocyte necrosis. NOD.DQ8 mice showed cellular and humoral autoreactive response to self cardiac myosin.. Depletion of CD8 and CD4 + cells suggested that CD8 T cells may act as regulatory cells while CD4 cells are required as effector cells. NOD.DR3 and B10.DQ8 mice did not develop any cardiac pathology suggesting DQ8 is required for predisposition to the spontaneous autoreactivity while NOD background influences onset and progression of disease. Thus these mice provide powerful tools to understand the role of HLA class II molecules in predisposition and onset of human diseases and to develop immunotherapy.

Oral tolerization with cardiac myosin peptide (614-629) ameliorates experimental autoimmune myocarditis: role of STAT 6 genes in BALB/CJ mice

INTRODUCTION

Experimental autoimmune myocarditis (EAM) is mediated by myocardial infiltration by myosin-specific T cells secreting inflammatory cytokines.

MATERIALS AND METHODS

To clarify the role of cytokines in EAM, we compared STAT 6-deficient ((-/-)) with STAT 4(-/-) and wild-type (BALB/CJ) mice following immunization with cardiac myosin peptide (614-629).

RESULTS

Wild-type mice developed severe disease with a small increase in severity in STAT 6(-/-) mice, while STAT 4(-/-) mice were resistant to EAM. STAT 6(-/-) mice had increased splenocyte proliferation and INF-gamma production versus wild type, while STAT 4(-/-) mice had decreased proliferation and INF-gamma. Following oral administration of myosin (614-629), tolerization was induced in wild-type mice evidenced by amelioration of myocarditis and up-regulation of IL-4. Adoptive transfer of splenocytes from orally tolerized mice resulted in inhibition of disease in STAT 6(-/-) mice.

CONCLUSION

These results demonstrate that oral tolerization ameliorates EAM in BALB/CJ mice and indicate a down-regulatory role for STAT 6 genes.

The role of infections in autoimmune disease

Autoimmunity occurs when the immune system recognizes and attacks host tissue. In addition to genetic factors, environmental triggers (in particular viruses, bacteria and other infectious pathogens) are thought to play a major role in the development of autoimmune diseases. In this review, we (i) describe the ways in which an infectious agent can initiate or exacerbate autoimmunity; (ii) discuss the evidence linking certain infectious agents to autoimmune diseases in humans; and (iii) describe the animal models used to study the link between infection and autoimmunity.

Role of the innate immune system in acute viral myocarditis

Although the adaptive immune system is thought to play an important role in the pathogenesis of viral myocarditis, the role of the innate immune system has not been well defined. To address this deficiency, we employed a unique line of mice that harbor a genomic "knock in" of a mutated TNF gene lacking the AU rich element (TNF(ARE/ARE)) that is critical for TNF mRNA stability and translation, in order to examine the contribution of the innate immune system in encephalomyocarditis-induced myocarditis (EMCV). Heterozygous mice (TNF(ARE/+)) were infected with 500 plaque-forming units of EMCV. TNF(ARE/+)mice had a significantly higher 14-day mortality and myocardial inflammation when compared to littermate control mice. Virologic studies showed that the viral load at 14 days was significantly lower in the hearts of TNF(ARE/+) mice. TNF(ARE/+) mice had an exaggerated proinflammatory cytokine and chemokine response in the heart following EMCV infection. Modulation of the innate immune response in TNF(ARE/+) mice by the late administration of prednisolone resulted in a significant improvement in survival and decreased cardiac inflammation, whereas early administration of prednisolone resulted in a blunted innate response and increased mortality in littermate control mice. Viewed together, these data suggest that the duration and degree of activation of the innate immune system plays a critical role in determining host outcomes in experimental viral myocarditis.

Remission of CVB3-induced viral myocarditis by in vivo Th2 polarization via hydrodynamics-based interleukin-4 gene transfer

BACKGROUND

Regulation of Th polarization was critical for the prevention of Coxsackievirus B3 (CVB3) induced myocarditis. In the present study, interleukin (IL)-4 was over-expressed by hydrodynamics-based gene transfection (HGT) to induce the in vivo Th2 bias and evaluate the influence of Th polarization on the pathogenesis of CVB3-myocaditis.

METHODS

IL-4 expressing plasmid was delivered into BALB/c mice by HGT after CVB3 infection. In vivo Th polarization was evaluated by detecting expression of Th1/Th2 cytokine, antibody isotype and Th related transcription factor, as well as the proliferation of CD8(+) T cells. The severity of myocarditis was assessed by weight loss, serological index of myocarditis, pathological feature, as well as survival rate.

RESULTS

HGT of IL-4 plasmid resulted in high-level and long-lasting expression of IL-4 in different organs, which rescued mice from severe heart inflammation and death. This may due to the induction of a Th2-bised immune response specified with decreased expression of tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma but increased expression of IL-10 and IL-4 in serum and heart tissue, more IL-4 but less IFN-gamma secreting splenic CD4+ T cells, an immunoglobulin G1 isotype switch, increased expression of GATA-3 and low proliferation of CD8+ T cells, without significant change of virus titer in heart tissue.

CONCLUSIONS

CVB3-induced myocarditis could be remitted through in vivo Th2 polarization, which has implications for our understanding of the role of Th2 population in immunity to CVB3 infection and for the development of new therapies for CVB3-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.

Autoimmunity in coxsackievirus B3 induced myocarditis

Virus infections are implicated in several autoimmune diseases. Multiple mechanisms of autoimmunity induction have been proposed including antigenic mimicry, production of cryptic epitopes and infection acting as both adjuvant for self-antigens and the mechanism of releasing these cell antigens. Evidence for these mechanisms in coxsackievirus B3 induced myocarditis is discussed.

Spontaneous myocarditis mimicking human disease occurs in the presence of an appropriate MHC and non-MHC background in transgenic mice

Most individuals have viral infections at some point in their life, however, only few develop autoreactivity to cardiac myosin following infection resulting in myocarditis suggesting a genetic predisposition. Most mouse models of myocarditis are induced by viral infection or by immunization with cardiac myosin. We generated HLA-DR3.Abetao and HLA-DQ8.Abetao transgenic mice in NOD and HLA-DQ8.Abetao in B10 background to study spontaneous autoimmunity. A high mortality was observed in NOD.DQ8 female mice 16 weeks or older. Echocardiography showed marked systolic dysfunction. Histopathology of various organs revealed an enlarged heart with mononuclear infiltrate consisting of CD4 and Mac-1+ cells and myocyte necrosis. The autoimmunity was associated with the presence of spontaneous autoreactive T cells and antibodies to cardiac myosin. Serologically, mice were negative for all known mouse viruses. NOD.DR3.Abetao, the transgene negative littermates, NOD, and B10.DQ8 Abetao mice had no gross or microscopic cardiac pathology. Spontaneous cellular and humoral response to cardiac myosin suggests that NOD.DQ8 may harbor autoreactive cells that can lead to spontaneous myocarditis and dilated cardiomyopathy. HLA-DQ8 is required for the predisposition to the spontaneous autoreactivity while NOD background influences onset and progression of disease. This model of myocarditis occurs predominantly in female mice and may provide insight into the pathogenesis of heart disease in women.

Longitudinal study of a natural outbreak of heart and skeletal muscle inflammation in Atlantic salmon, Salmo salar L

Heart and skeletal muscle inflammation (HSMI) is a transmissible disease of farmed Atlantic salmon, Salmo salar L. It is characterized by significant epi-, endo- and myocarditis, as well as myositis, particularly involving red skeletal muscle. The aetiology of HSMI is currently unresolved, though a viral cause is suspected. Since its discovery in 1999, HSMI has become an increasing problem for the Norwegian farming industry, with some farms experiencing yearly outbreaks and subsequent economic losses. In the present study an Atlantic salmon farm was studied from December 2003 to April 2005. Samples from apparently healthy as well as clinically diseased fish were collected monthly and examined histopathologically. The first fish to be diagnosed with HSMI was sampled in May, 8 months after transfer to sea. A clinical outbreak of HSMI followed in June, when all fish in the sample had lesions consistent with HSMI. Subsequent samples revealed that cardiac lesions decreased in severity 2 months after the start of the outbreak, but that multiple foci of cellular infiltration and necrosis persisted throughout the year. There appeared to be a shift in lesion location from being most severe in the compact myocardium in early stages of disease to a greater involvement of the atrium and spongy layer of the ventricle in later samples. Late samples also showed increased fibrosis of cardiac tissue. In conclusion, HSMI appears to be a severe disease with elevated mortality, morbidity close to 100% and prolonged duration.

PROTECTING THE PUMP: Controlling Myocardial Inflammatory Responses

Because of the anatomy, function, and nonregenerative nature of the myocardium, inflammation in this tissue is not well tolerated. Nevertheless, various diseases of the heart are characterized by inflammatory responses involving the effector mechanisms of innate and adaptive (lymphocyte-dependent) immunity. The innate immune response to ischemia-reperfusion injury is, by far, the most common cause of myocardial inflammation. Innate responses may have beneficial influences that preserve myocardial function in the short term but may be maladaptive in chronic states. Adaptive responses in the myocardium occur with infection or loss of tolerance, and lead to myocarditis. Given the narrow margin for benefit of cardiac inflammation, special regulatory mechanisms likely raise the threshold, compared to other tissues, for the induction and persistence of adaptive immune responses. These mechanisms include strong central and peripheral T cell tolerance to heart antigens and induction of anti-inflammatory feedback mechanisms involving cytokines such as interferon-gamma.

Inflammatory cardiomyopathy: there is a specific matrix destruction in the course of the disease

Cardiomyopathies are responsible for a high proportion of cases of congestive heart failure and sudden death, as well as for the need for transplantation. Understanding of the causes of these disorders has been sought in earnest over the past decade. We hypothesized that DCM is a disease of the cytoskeleton/sarcolemma, which affects the sarcomere. Evaluation of the sarcolemma in DCM and other forms of systolic heart failure demonstrates membrane disruption; and, secondarily, the extracellular matrix architecture is also affected. Disruption of the links from the sarcolemma to ECM at the dystrophin C-terminus and those to the sarcomere and nucleus via N-terminal dystrophin interactions could lead to a "domino effect" disruption of systolic function and development of arrhythmias. We also have suggested that dystrophin mutations play a role in idiopathic DCM in males. The T-cap/MLP/alpha-actinin/titin complex appears to stabilize Z-disc function via mechanical stretch sensing. Loss of elasticity results in the primary defect in the endogenous cardiac muscle stretch sensor machinery. The over-stretching of individual myocytes leads to activation of cell death pathways, at a time when stretch-regulated survival cues are diminished due to defective stretch sensing, leading to progression of heart failure. Genetic DCM and the acquired disorder viral myocarditis have the same clinical features including heart failure, arrhythmias, and conduction block, and also similar mechanisms of disease based on the proteins targeted. In dilated cardiomyopathy, the process of progressive ventricular dilation and changes of the shape of the ventricle to a more spherical shape, associated with changes in ventricular function and/or hypertrophy, occurs without known initiating disturbance. In those cases in which resolution of cardiac dysfunction does not occur, chronic DCM results. It has been unclear what the underlying etiology of this long-term sequela could be, but viral persistence and autoimmunity have been widely speculated.

Human cardiac inflammatory responses triggered by Coxsackie B viruses are mainly Toll-like receptor (TLR) 8-dependent

The group B coxsackieviruses are single-stranded RNA viruses that have been implicated in viral myocarditis. Viral infection of the myocardium, as well as the associated inflammatory response are important determinants of the virus-associated myocardial damage. Although these viruses are known as cytopathic viruses that cause death of the host cell, their viral RNA has been shown to persist in cardiac muscle contributing to a chronic inflammatory cardiomyopathy. Thus, it is essential that we understand the mechanism by which Coxasckie B viruses (CBVs) trigger this inflammatory response. In this study we investigated the involvement of Toll-like receptors (TLRs) in the recognition of CBV virions as well as CBV single-stranded RNA. Here we report that the CBV-induced inflammatory response is mediated through TLR8 and to a lesser extent through TLR7.

5'-Terminal deletions occur in coxsackievirus B3 during replication in murine hearts and cardiac myocyte cultures and correlate with encapsidation of negative-strand viral RNA

Adult human enteroviral heart disease is often associated with the detection of enteroviral RNA in cardiac muscle tissue in the absence of infectious virus. Passage of coxsackievirus B3 (CVB3) in adult murine cardiomyocytes produced CVB3 that was noncytolytic in HeLa cells. Detectable but noncytopathic CVB3 was also isolated from hearts of mice inoculated with CVB3. Sequence analysis revealed five classes of CVB3 genomes with 5' termini containing 7, 12, 17, 30, and 49 nucleotide deletions. Structural changes (assayed by chemical modification) in cloned, terminally deleted 5'-nontranslated regions were confined to the cloverleaf domain and localized within the region of the deletion, leaving key functional elements of the RNA intact. Transfection of CVB3 cDNA clones with the 5'-terminal deletions into HeLa cells generated noncytolytic virus (CVB3/TD) which was neutralized by anti-CVB3 serum. Encapsidated negative-strand viral RNA was detected using CsCl-purified CVB3/TD virions, although no negative-strand virion RNA was detected in similarly treated parental CVB3 virions. The viral protein VPg was detected on CVB3/TD virion RNA molecules which terminate in 5' CG or 5' AG. Detection of viral RNA in mouse hearts from 1 week to over 5 months postinoculation with CVB3/TD demonstrated that CVB3/TD virus strains replicate and persist in vivo. These studies describe a naturally occurring genomic alteration to an enteroviral genome associated with long-term viral persistence.

Fulminant myocarditis demonstrating uncommon morphology--a report of two autopsy cases

Two autopsy cases of fulminant myocarditis demonstrating uncommon morphology were studied. Subjects included two male patients: a 42-year-old (case 1) and a 39-year-old (case 2). Both cases had fever, chest or epigastric pain, electrocardiographic abnormalities, prominent elevation of serum glutamic oxaloacetic transaminase, glutamic pyruvic transaminase, lactic dehydrogenase and creatine phosphokinase. They were treated with intra-aortic balloon pumping and percutaneous cardiopulmonary support, and they died at 3 days and 4 days after admission (total course of 10 days and 9 days), respectively. Case 1 showed focal necrosis, severe myocardial dystrophic calcification positive for Kossa stain, inflammatory edema, lymphocyte and macrophage infiltration and extravasation of erythrocytes. Case 2 showed acute inflammation and severe myocardial necrosis with neutrophilic abscess, lymphocyte and macrophage infiltration, cell debris and purulent exudate. Calcified, degenerative and necrotic cardiac myocytes and macrophages were reacted with anti-Enterovirus antibody (clone 5-D8/1), which recognizes an epitope on the VP1 peptide of most Coxsackievirus, echovirus, poliovirus and enterovirus strains. Therefore, the present two cases may be compatible with fulminant enterovirus-associated myocarditis. Using reverse transcriptase-semi-nested polymerase chain reaction, picornaviral RNA was detected in the amplified products extracted from the paraffin-embedded myocardial sample of case 1 but not in case 2.

Characterization of an infectious cDNA copy of the genome of a naturally occurring, avirulent coxsackievirus B3 clinical isolate

Group B coxsackieviruses (CVB) cause numerous diseases, including myocarditis, pancreatitis, aseptic meningitis and possibly type 1 diabetes. To date, infectious cDNA copies of CVB type 3 (CVB3) genomes have all been derived from pathogenic virus strains. An infectious cDNA copy of the well-characterized, non-pathogenic CVB3 strain GA genome was cloned in order to facilitate mapping of the CVB genes that influence expression of a virulence phenotype. Comparison of the sequence of the parental CVB3/GA population, derived by direct RT-PCR-mediated sequence analysis, to that of the infectious CVB3/GA progeny genome demonstrated that an authentic copy was cloned; numerous differences were observed in coding and non-coding sequences relative to other CVB3 strains. Progeny CVB3/GA replicated similarly to the parental strain in three different cell cultures and was avirulent when inoculated into mice, causing neither pancreatitis nor myocarditis. Inoculation of mice with CVB3/GA protected mice completely against myocarditis and pancreatitis induced by cardiovirulent CVB3 challenge. The secondary structure predicted for the CVB3/GA domain II, a region within the 5′ non-translated region that is implicated as a key site affecting the expression of a cardiovirulent phenotype, differs from those predicted for cardiovirulent and pancreovirulent CVB3 strains. This is the first report characterizing a cloned CVB3 genome from an avirulent strain.

Type I IFN-beta gene therapy suppresses cardiac CD8+ T-cell infiltration during autoimmune myocarditis

Gene therapy using DNA encoding type I IFN subtypes IFNA6, IFNA9 and IFNB suppresses murine cytomegalovirus (MCMV)-myocarditis, a predominantly cell-mediated disease in BALB/c mice. CD8(+) T cells are the principal cell type within the inflamed myocardium. As such, we investigated the effects of IFN subtype treatment on this T-cell subset and other cell types in the cardiac infiltrate. In the acute phase of disease, IFNA6 and IFNA9 treatments significantly reduced the number of CD8(+) T cells within the foci of cellular infiltration in the heart. During the chronic phase, which is primarily autoimmune in nature, IFNB treatment significantly reduced CD8(+) T cells. B-cell and neutrophil numbers in the cardiac infiltrate were also reduced following IFNB immunotherapy. Although early inflammatory responses are important for resolution of virus infection, high numbers of lymphocytes persisting in the myocardium may lead to exacerbation of disease. Our data suggests that type I IFN DNA therapy regulates cardiac cellular infiltration. Thus, treatment with IFN-beta administered prophylactically to high-risk patients in acquiring CMV infection may reduce the development of chronic autoimmune myocarditis.

beta2-microglobulin-associated regulation of interferon-gamma and virus-specific immunoglobulin G confer resistance against the development of chronic coxsackievirus myocarditis

To gain insight into the strategies of the immune system to confer resistance against the development of chronic coxsackievirus B3 (CVB3) myocarditis we compared the course of the disease in C57BL/6 mice, beta2-microglobulin knockout (beta2m(-/-)) mice, and perforin-deficient (perforin(-/-)) mice. We found that perforin(-/-) mice as well as immunocompetent C57BL/6 mice reveal a resistant phenotype with complete elimination of the virus from the heart in the course of acute myocarditis. In contrast, myocardial CVB3 infection of beta2m(-/-) mice was characterized by a significantly higher virus load associated with a fulminant acute inflammatory response and, as a consequence of virus persistence, by the development of chronic myocarditis. Interferon-gamma secretion of stimulated spleen cells was found to be significantly delayed in beta2m(-/-) mice compared to perforin(-/-) mice and C57BL/6 control mice during acute myocarditis. In addition, generation of virus-specific IgG and neutralizing antibodies were found to be significantly decreased in beta2m(-/-) mice during acute infection. From these results we conclude that protection against the development of chronic myocarditis strongly depends on the expression of beta2m, influencing the catabolism of IgG as well as the production of protective cytokines, such as interferon-gamma. Moreover, CVB3-induced cardiac injury and prevention of chronic myocarditis was found to be unrelated to perforin-mediated cytotoxicity in our model system.

Viral causes of cardiac inflammation

Over the past year there have been few significant breakthroughs in the understanding of the etiologies of viral myocarditis or dilated cardiomyopathy (DCM). One interesting trend has been the increasing number of reports of myocarditis associated with parvovirus B19 infection. Whether this is simply a result of improved diagnostics, or reflects an underlying change in the etiology is unclear. However, studies of the underlying mechanisms of these disorders have resulted in several reports linking the acquired and viral forms. Over the past few years the cytoarchitecture has been a focus of study for familial DCM. During the last year, one key molecule, dystrophin, has been shown to be disrupted in patients with end-stage cardiomyopathy, irrespective or etiology, mutated in patients with sporadic forms of disease and identified as a potential susceptibility gene for viral infection of the myocardium. The shared cellular receptor, the Coxsackievirus B-Adenovirus receptor (CAR), for the two most common viral agents associated with acquired myocarditis and DCM, was shown to be up-regulated in patients with DCM, potentially making the expression of this protein a marker of susceptibility to virus infection. However, a study of the CAR gene in patients with DCM or myocarditis did not identify any genetic mutations in these patients. Finally a receptor for viral double stranded RNA (TLR-3) was identified. The role of this receptor in the innate immune response against cardiotropic viruses has yet to be elucidated.

IL-12 is required for differentiation of pathogenic CD8+ T cell effectors that cause myocarditis

Cardiac antigen-specific CD8(+) T cells are involved in the autoimmune component of human myocarditis. Here, we studied the differentiation and migration of pathogenic CD8(+) T cell effector cells in a new mouse model of autoimmune myocarditis. A transgenic mouse line was derived that expresses cardiac myocyte restricted membrane-bound ovalbumin (CMy-mOva). The endogenous adaptive immune system of CMy-mOva mice displays tolerance to ovalbumin. Adoptive transfer of naive CD8(+) T cells from the ovalbumin-specific T cell receptor-transgenic (TCR-transgenic) OT-I strain induces myocarditis in CMy-mOva mice only after subsequent inoculation with ovalbumin-expressing vesicular stomatitis virus (VSV-Ova). OT-I effector T cells derived in vitro in the presence or absence of IL-12 were adoptively transferred into CMy-mOva mice, and the consequences were compared. Although IL-12 was not required for the generation of cytolytic and IFN-gamma-producing effector T cells, only effectors primed in the presence of IL-12 infiltrated CMy-mOva hearts in significant numbers, causing lethal myocarditis. Furthermore, analysis of OT-I effectors collected from a mediastinal draining lymph node indicated that only effectors primed in vitro in the presence of IL-12 proliferated in vivo. These data demonstrate the importance of IL-12 in the differentiation of pathogenic CD8(+) T cells that can cause myocarditis.

Expansion of specific alphabeta+ T-cell subsets in the myocardium of patients with myocarditis and idiopathic dilated cardiomyopathy associated with Coxsackievirus B infection

Idiopathic dilated cardiomyopathy (IDC) is one of the major causes of death in humans and has been linked to Coxsackievirus B (CVB) infection. The aim of this study was to analyze phenotypes of heart-infiltrating immune cells in patients suffering from myocarditis and IDC associated with CVB infections. We found that the myocardium of these patients was infiltrated by CD4(+) and CD8(+) T lymphocytes as well as macrophages. Evidence of CVB3/4 infections was also found. In the majority of patients, the T-cell receptor repertoire (TCR) of the infiltrating lymphocytes was restricted, with a polyclonal expansion of the Vbeta7 gene family. We also found that human leukocyte antigen (HLA) class II alleles associated with susceptibility to type 1 diabetes (HLA-DR4 and HLA-DQA1*04/05/06 alleles) were remarkably infrequent in IDC patients (p < 0.005), thus suggesting that they might confer protection against IDC. Finally, mRNA for interleukin-1beta, interferon-gamma, and tumor necrosis factor-alpha was detected in the cardiac specimens, although at a lower level compared with specimens from hearts without signs of viral infections. We conclude that CVB infection of the human myocardium is associated with a selective, yet polyclonal activation of different T-cell subsets in genetically susceptible individuals. This immune response may play a critical role in modulating disease progression after viral infections.

Cardiac disease in transgenic mice expressing human immunodeficiency virus-1 nef in cells of the immune system

We previously reported that a severe acquired immune deficiency syndrome-like disease develops in transgenic (Tg) mice expressing the human immunodeficiency virus-1 in its natural target cells: immature and mature CD4(+) T cells and cells of the macrophage/dendritic lineage. Here, we show that these mice also develop cardiac disease, characterized most prominently by a focal myocytolysis, occasionally by myocarditis and by deposition of endogenous immunoglobulin on cardiomyocytes. Microfil perfusion demonstrated widespread coronary arteriospasm and echocardiographic analysis revealed depressed cardiac function in Tg mice. A higher (but still modest) level of cardiomyocyte apoptosis was detected in Tg as compared to non-Tg hearts. Tg expression was detected in some of the infiltrating mononuclear cells, but not in cardiomyocytes or in cells of the heart vessels, suggesting a human immunodeficiency virus-1-induced disease process mediated by cells of the immune system. The similarity of the heart disease observed in these Tg mice to that observed in acquired immune deficiency syndrome patients suggests a common pathogenesis.

Characterisation of murine cytomegalovirus myocarditis: cellular infiltration of the heart and virus persistence

Myocarditis triggered by a viral infection has integral viral and immunological aspects associated with the pathogenesis of disease. The present study was performed to analyse the cellular inflammatory response in the heart and cytomegalovirus replication during the development of myocarditis in vivo. We examined murine cytomegalovirus in an animal model of myocarditis using both susceptible BALB/c and resistant C57BL/6 mice. The heart infiltrating cells of BALB/c mice were found to comprise predominantly CD8+ T cells, with other cells of the CD4+ T cell, macrophage, B cell and neutrophil phenotype. Infectious MCMV titres in the heart were low and replicative virus could not be isolated beyond the first week post-infection (p.i.). Direct viral lysis of myocytes in vitro and apoptosis of cardiac cells in vivo was observed. Furthermore, viral DNA was detected in the heart of both mouse strains throughout the development of chronic disease. Viral gB RNA was detected during the first 35 days p.i. However, viral transcript for ie1 RNA but not gB RNA was found in the heart during the late stage of disease, suggesting latent viral infection of the heart. Our findings suggest that maintenance of the chronic phase of myocarditis involving post-viral immunological responses can occur in the presence of little infectious virus replication in the heart.

The group B coxsackieviruses and myocarditis

The six serotypes of the group B coxsackieviruses (CVB) are common human enteroviruses linked etiologically to inflammatory cardiomyopathies. This has been demonstrated by molecular detection of enteroviral RNA in human heart tissue, serologic associations with disease, and virus isolation from cases of fulminant myocarditis. The murine model of CVB-associated myocarditis has demonstrated that CVB can be attenuated through mutations at different genomic sites. Human CVB3 isolates demonstrate varying degrees of cardiovirulence in the murine model; one site of virulence determination has been mapped to domain II of the 5' non-translated region. The interplay of CVB replication and the immune response to that replication in the heart is a complex interaction determining the extent to which the virus replication is limited and the degree to which a pathogenic inflammation of cardiac muscle occurs. Studies of CVB3-induced myocarditis in murine strains lacking subsets of the immune system or genes regulating the immune response have demonstrated a pivotal role of the T cell response to the generation of myocarditis. While CVB are associated with 20-25% of cases of myocarditis or cardiomyopathy, the severity of the disease and the existence of attenuated strains shown to generate protective immunity in animal models indicates that vaccination against the CVBs would be valuable.

From infection to autoimmunity

We have investigated two models of virally-induced autoimmune myocarditis in mice using widely different infectious agents. Infection of susceptible BALB/c mice with either Coxsackievirus or murine cytomegalovirus results in the development of acute myocarditis from day 7-14 after infection, and chronic myocarditis from day 28 onwards. The chronic phase of myocarditis is associated with mononuclear infiltration of the myocardium and the production of autoantibodies to cardiac myosin, although infectious virus cannot be detected past day 14 of infection. T cells and autoantibodies have been shown to be important for the development of autoimmune myocarditis. Many researchers have investigated the role of molecular mimicry in the development of myocarditis after viral infection. This review explores the 'adjuvant' effect of infection on the innate immune response and how this determines the progression to autoimmune disease. We show that NK cells protect against the development of disease, while complement and complement receptors are involved in the development of autoimmune myocarditis induced by inoculation with virus or cardiac myosin, respectively. Our results suggest that the innate immune response to viral and self-antigens may determine whether susceptible strains of mice progress to chronic autoimmune disease. These findings have broad implications for understanding the role of infection in inducing autoimmune disease.

Ganciclovir and cidofovir treatment of cytomegalovirus-induced myocarditis in mice

The cardiovascular disease myocarditis is characterized by inflammation and necrosis of cardiac muscle. This disease has been associated with various viral etiologies, including cytomegalovirus (CMV). Murine CMV (MCMV) infection of adult BALB/c mice produces a disease with acute and chronic phases similar to that found in humans. In our murine model, we have investigated the therapeutic efficacy of antiviral drug administration on myocarditis. Two drugs commonly used for CMV treatment, ganciclovir and cidofovir, were subjected to trials, with both drugs showing potent antiviral activity against MCMV both in vitro and in vivo. The acute phase of myocarditis was significantly reduced when antiviral therapy commenced 24 h postinfection. Such treatment also reduced the severity of the chronic phase of myocarditis. In contrast, antiviral treatment commencing after the acute phase had no effect on chronic myocarditis. Reinfection of mice with MCMV caused exacerbation of myocardial inflammation. Such an increase in severity of myocarditis could be prevented with either ganciclovir or cidofovir treatment, but the preexisting inflammation and necrosis of the myocardium persisted. These data highlight possible therapeutic uses of antiviral drugs in viral myocarditis as well as further elucidating the pathogenic nature of the disease.

Prevention of autoimmune myocarditis through the induction of antigen-specific peripheral immune tolerance

BACKGROUND

Autoimmunity to cardiac antigens, in particular cardiac myosin, has been observed in humans with myocarditis and in animals with experimental inflammatory heart disease. Current treatments for myocarditis are in many cases immunosuppressive and might lead to increased cardiac damage by reducing host defenses against infectious agents. Therefore, we sought to develop an antigen-specific approach to inhibit autoimmunity in mice with myosin-induced experimental autoimmune myocarditis.

METHODS AND RESULTS

Syngeneic splenocytes, coupled with cardiac myosin by use of ethylene carbodiimide, were administered intravenously before disease induction, and the effects of this peripheral tolerization on myosin-induced myocarditis were assessed. This antigen-specific immunotherapy significantly reduced both the incidence and severity of myocarditis, with the prevention of myocyte necrosis, mononuclear cell infiltration, and fibrosis. Myosin-specific delayed-type hypersensitivity and antibody production were significantly reduced, demonstrating that peripheral tolerance affected both T- and B-cell responsiveness to the autoantigen.

CONCLUSIONS

These results suggest that the induction of antigen-specific peripheral immune tolerance may be an effective approach for the treatment of myocarditides with autoimmune involvement.

Apolipoprotein J/clusterin limits the severity of murine autoimmune myocarditis

Apolipoprotein J/clusterin (apoJ/clusterin), an intriguing protein with unknown function, is induced in myocarditis and numerous other inflammatory injuries. To test its ability to modify myosin-induced autoimmune myocarditis, we generated apoJ-deficient mice. ApoJ-deficient and wild-type mice exhibited similar initial onset of myocarditis, as evidenced by the induction of two early markers of the T cell-mediated immune response, MHC-II and TNF receptor p55. Furthermore, autoantibodies against the primary antigen cardiac myosin were induced to the same extent. Although the same proportion of challenged animals exhibited some degree of inflammatory infiltrate, inflammation was more severe in apoJ-deficient animals. Inflammatory lesions were more diffuse and extensive in apoJ-deficient mice, particularly in females. In marked contrast to wild-type animals, the development of a strong generalized secondary response against cardiac antigens in apoJ-deficient mice was predictive of severe myocarditis. Wild-type mice with a strong Ab response to secondary antigens appeared to be protected from severe inflammation. After resolution of inflammation, apoJ-deficient, but not wild-type, mice exhibited cardiac function impairment and severe myocardial scarring. These results suggest that apoJ limits progression of autoimmune myocarditis and protects the heart from postinflammatory tissue destruction.

Chronic myocarditis induced by T cells reactive to a single cardiac myosin peptide: persistent inflammation, cardiac dilatation, myocardial scarring and continuous myocyte apoptosis

Recent recognition that an autoimmune myocarditis may precede, and result in, dilated cardiomyopathy has focused attention on immune mechanisms of myocardial injury. In this paper, we describe a model of chronic autoimmune myocarditis in the Lewis rat. The production of myocarditis has been previously described by this group and in brief is accomplished by a single tail vein infusion of activated T cells specific for a 17-amino acid peptide from rat cardiac myosin. In this report, animals were followed for approximately 6 months post-T-cell infusion. Hearts from animals which received cardiac myosin specific T cells all showed extensive fibrosis associated with ongoing inflammation. Apoptosis, identified by TdT-mediated dUTP nick end labelling (TUNEL), was identified as a mode of myocyte death in hearts with acute and chronic myocarditis but not in age- and sex-matched controls. Immunohistochemistry was used to characterize the immune infiltrate and adhesion molecules in hearts with chronic myocarditis and these findings were compared to hearts with acute myocarditis. We propose that this rat model of chronic myocarditis mimics human disease, since inflammation results in ventricular dilatation and myocyte hypertrophy reminiscent of dilated cardiomyopathy. This model offers potential for further investigation of immune, functional and possible therapeutic aspects of autoimmune related cardiomyopathies.

Giant cell myocarditis: most fatal of autoimmune diseases

OBJECTIVE

To increase awareness of giant cell myocarditis (GCM), its pathogenesis, and treatment.

METHODS

Review of relevant publications from the English-language literature.

RESULTS

GCM is a rare, frequently fatal inflammatory disorder of cardiac muscle of unknown origin, characterized by widespread degeneration and necrosis of myocardial fibers.Congestive heart failure and ventricular tachycardia are common clinical manifestations. GCM occurs primarily in previously healthy adults, although it is frequently associated with various systemic diseases, primarily of autoimmune causes. The inflammatory infiltrate is characterized by the presence of multinucleated giant cells and is distinct from cardiac sarcoidosis. Animal models of GCM are similar to models of other autoimmune disorders such as rheumatoid arthritis. The prognosis, which is poor despite partial responsiveness to immunosuppressive medications, is improved with cardiac transplantation.

CONCLUSIONS

The clinical and immunopathogenetic similarities with classical rheumatologic diseases, the differential diagnosis with sarcoidosis and other inflammatory conditions, and the use of standard immunosuppressive medications make GCM a disease process that should be added to the rheumatologist's expertise.

Expression of an antigenic adenovirus epitope in a group B coxsackievirus

Group B coxsackieviruses (CVB) cause human myocarditis, while human adenovirus type 2 (Ad2) is implicated as an agent of this disease. The L1 loop of the Ad2 hexon protein has been demonstrated to be antigenic in rabbits. To evaluate the feasibility of a multivalent vaccine strain against the CVB and Ad2, we cloned the sequence encoding the Ad2 hexon L1 loop, flanked by dissimilar sequences encoding the protease 2A (2Apro) recognition sites, into the genome of an attenuated strain of CVB type 3 (CVB3/0) at the junction of 2Apro and the capsid protein 1D. Progeny virus (CVB3-PL2-Ad2L1) was obtained following transfection of the construct into HeLa cells. Replication of CVB3-PL2-Ad2L1 in diverse cell cultures demonstrated that the yield of the chimeric virus was between 0.5 to 2 log units less than the parental strain. Western blot analyses of the CVB3 capsid protein 1D in CVB3-PL2-Ad2L1-infected HeLa cells demonstrated production of the expected capsid protein. Viral proteins were detected earlier and in approximately fourfold greater amounts in CVB3-PL2-Ad2L1-infected HeLa cells than in CVB3/0-infected cells. Cleavage of the CVB3-PL2-Ad2L1 polyprotein by 2Apro was slowed, accompanied by an accumulation of the fusion 1D-L1 loop protein. Reverse transcription-PCR sequence analysis of CVB3-PL2-Ad2L1 RNA demonstrated that the Ad2 hexon polypeptide coding sequence was maintained in the chimeric viral genome through at least 10 passages in HeLa cells. Mice inoculated with CVB3-PL2-Ad2L1 demonstrated a brief viremia with no replication detectable in the heart but prolonged replication of virus in the pancreas in the absence of pathologic changes in either organ. CVB3-PL2-Ad2L1 induced binding and neutralizing anti-Ad2 antibodies, in addition to antibodies against CVB3 in mice. CVB3-PL2-Ad2L1 was used to challenge mice previously inoculated with CVB3/0 and with preexisting anti-CVB3 neutralizing-antibody titers; anti-Ad2 neutralizing and binding antibodies were induced in these mice at higher levels than in mice without anti-CVB3 immunity. The data demonstrate that a CVB vector can stably express an antigenic polypeptide of Ad2 from within the CVB open reading frame that results in the induction of protective immune responses against both viruses.

The role of inflammatory mediators in chronic heart failure: cytokines, nitric oxide, and endothelin-1

There is now considerable evidence to suggest that neurohormonal and immune mechanisms may play a central role in the pathogenesis of chronic heart failure (CHF), which is likely to have important implications for the management of this condition. It has been proposed that CHF is a state of immune activation with inflammatory cytokines contributing to both the central and the peripheral manifestations of this syndrome. The immune system is the body's natural defence mechanism against infection and other stresses, which has several different components that interact with each other in a complex manner. The main components which are thought to be relevant to the pathogenesis of CHF are: cytokines, adhesion molecules, autoantibodies, nitric oxide, and endothelin-1, and this review will concentrate on these factors. This article will also discuss the potential role of anti-cytokine therapies in the treatment of CHF.