Peptides derived from cardiovascular G-protein-coupled receptors induce morphological cardiomyopathic changes in immunized rabbits

Autoantibodies and Cardiomyopathy: Focus on Beta-1 Adrenergic Receptor Autoantibodies

ABSTRACT

Antibody response to self-antigens leads to autoimmune response that plays a determinant role in cardiovascular disease outcomes including dilated cardiomyopathy (DCM). Although the origins of the self-reactive endogenous autoantibodies are not well-characterized, it is believed to be triggered by tissue injury or dysregulated humoral response. Autoantibodies that recognize G protein-coupled receptors are considered consequential because they act as modulators of downstream receptor signaling displaying a wide range of unique pharmacological properties. These wide range of pharmacological properties exhibited by autoantibodies has cellular consequences that is associated with progression of disease including DCM. Increase in autoantibodies recognizing beta-1 adrenergic receptor (β1AR), a G protein-coupled receptor critical for cardiac function, is observed in patients with DCM. Cellular and animal model studies have indicated pathological roles for the β1AR autoantibodies but less is understood about the molecular basis of their modulatory effects. Despite the recognition that β1AR autoantibodies could mediate deleterious outcomes, emerging evidence suggests that not all β1AR autoantibodies are deleterious. Recent clinical studies show that β1AR autoantibodies belonging to the IgG3 subclass is associated with beneficial cardiac outcomes in patients. This suggests that our understanding on the roles the β1AR autoantibodies play in mediating outcomes is not well-understood. Technological advances including structural determinants of antibody binding could provide insights on the modulatory capabilities of β1AR autoantibodies in turn, reflecting their diversity in mediating β1AR signaling response. In this study, we discuss the significance of the diversity in signaling and its implications in pathology.

The Role of B Cells in Cardiomyopathy and Heart Failure

PURPOSE OF REVIEW

To summarize the current knowledge on the role that B lymphocytes play in heart failure.

RECENT FINDINGS

Several studies from murine models have shown that B cells modulate cardiac adaptation to injury and ultimately affect the degree of cardiac dysfunction after acute ischemic damage. In addition, a B cell-modulating small molecule was recently shown to have beneficial effects in humans with heart failure with preserved ejection fraction. B lymphocytes are specialized immune cells present in all jawed vertebrates. They are characteristically known for their ability to produce antibodies, but they have other functions and are important players in virtually all forms of immune responses. A growing body of evidence indicates that B cells are intimately connected with the heart and that B cell dysregulation might play a role in the pathogenesis and progression of both heart failure with reduced ejection fraction and heart failure with preserved ejection fraction. B cells are therefore gathering attention as potential targets for the development of novel immunomodulatory-based treatments for heart failure.

The Incidence of Myocarditis and Pericarditis in Post COVID-19 Unvaccinated Patients—A Large Population-Based Study

Myocarditis and pericarditis are potential post-acute cardiac sequelae of COVID-19 infection, arising from adaptive immune responses. We aimed to study the incidence of post-acute COVID-19 myocarditis and pericarditis. Retrospective cohort study of 196,992 adults after COVID-19 infection in Clalit Health Services members in Israel between March 2020 and January 2021. Inpatient myocarditis and pericarditis diagnoses were retrieved from day 10 after positive PCR. Follow-up was censored on 28 February 2021, with minimum observation of 18 days. The control cohort of 590,976 adults with at least one negative PCR and no positive PCR were age- and sex-matched. Since the Israeli vaccination program was initiated on 20 December 2020, the time-period matching of the control cohort was calculated backward from 15 December 2020. Nine post-COVID-19 patients developed myocarditis (0.0046%), and eleven patients were diagnosed with pericarditis (0.0056%). In the control cohort, 27 patients had myocarditis (0.0046%) and 52 had pericarditis (0.0088%). Age (adjusted hazard ratio [aHR] 0.96, 95% confidence interval [CI]; 0.93 to 1.00) and male sex (aHR 4.42; 95% CI, 1.64 to 11.96) were associated with myocarditis. Male sex (aHR 1.93; 95% CI 1.09 to 3.41) and peripheral vascular disease (aHR 4.20; 95% CI 1.50 to 11.72) were associated with pericarditis. Post COVID-19 infection was not associated with either myocarditis (aHR 1.08; 95% CI 0.45 to 2.56) or pericarditis (aHR 0.53; 95% CI 0.25 to 1.13). We did not observe an increased incidence of neither pericarditis nor myocarditis in adult patients recovering from COVID-19 infection.

Immunomodulatory Treatment Strategies Targeting B Cells for Heart Failure

Cardio-oncology, a nascent specialty, has evolved as a concerted strategy to address the cardiovascular complications of cancer therapies. On the other hand, emerging evidence has shown that some anti-tumor drugs, such as CD20-targeted rotuximab, also have markedly cardioprotective effects in addition to treating cancers. Rituximab is a CD20-targeted monoclonal antibody and kill tumor B-cells through antibody-mediated and antibody-independent pathways, indicating that B cells participate and promote the progression of cardiovascular diseases. In this review, we mainly present the evidence that B cells contribute to the development of hypertrophy, inflammation, and maladaptive tissue remodeling, with the aim of proposing novel immunomodulatory therapeutic strategies targeting B cells and their products for the treatment of heart failure.

Impact of autoantibodies against the M2-muscarinic acetylcholine receptor on clinical outcomes in peripartum cardiomyopathy patients with standard treatment

Objectives

To evaluate the impact of autoantibodies against the M2-muscarinic receptor (anti-M2-R) on the clinical outcomes of patients receiving the standard treatment for peripartum cardiomyopathy (PPCM).

Methods

A total of 107 PPCM patients who received standard heart failure (HF) treatment between January 1998 and June 2020 were enrolled in this study. According to anti-M2-R reactivity, they were classified into negative (n = 59) and positive (n = 48) groups, denoted as the anti-M2-R (−) and anti-M2-R (+) groups. Echocardiography, 6-min walk distance, serum digoxin concentration (SDC), and routine laboratory tests were performed regularly for 2 years. The all-cause mortality, cardiovascular mortality, and rehospitalisation rate for HF were compared between the two groups.

Results

A total of 103 patients were included in the final data analysis, with 46 in the anti-M2-R (+) group and 57 in the anti-M2-R (−) group. Heart rate was lower in the anti-M2-R (+) group than in the anti-M2-R (−) group at the baseline (102.7 ± 6.1 bpm vs. 96.0 ± 6.4 bpm, p < 0.001). The initial SDC was higher in the anti-M2-R (+) group than in the anti-M2-R (−) group with the same dosage of digoxin (1.25 ± 0.45 vs. 0.78 ± 0.24 ng/mL, p < 0.001). The dosages of metoprolol and digoxin were higher in the anti-M2-R (−) patients than in the anti-M2-R (+) patients (38.8 ± 4.6 mg b.i.d. vs. 27.8 ± 5.3 mg b.i.d., p < 0.0001, respectively, for metoprolol; 0.12 ± 0.02 mg/day vs. 0.08 ± 0.04 mg/day, p < 0.0001, respectively, for digoxin). Furthermore, there was a greater improvement in cardiac function in the anti-M2-R (−) patients than in the anti-M2-R (+) patients. Multivariate analysis identified negativity for anti-M2-R as the independent predictor for the improvement of cardiac function. Rehospitalisation for HF was lower in the anti-M2-R (−) group, but all-cause mortality and cardiovascular mortality were the same.

Conclusions

There were no differences in all-cause mortality or cardiovascular mortality between the two groups. Rehospitalisation rate for HF decreased in the anti-M2-R (−) group. This difference may be related to the regulation of the autonomic nervous system by anti-M2-R.

The Emerging Role of B Lymphocytes in Cardiovascular Disease

B cells are traditionally known for their ability to produce antibodies in the context of adaptive immune responses. However, over the last decade B cells have been increasingly recognized as modulators of both adaptive and innate immune responses, as well as players in an important role in the pathogenesis of a variety of human diseases. Here, after briefly summarizing our current understanding of B cell biology, we present a systematic review of the literature from both animal models and human studies that highlight the important role that B lymphocytes play in cardiac and vascular disease. While many aspects of B cell biology in the vasculature and, to an even greater extent, in the heart remain unclear, B cells are emerging as key regulators of cardiovascular adaptation to injury.

Autoantibodies as Endogenous Modulators of GPCR Signaling

Endogenous self-reactive autoantibodies (AAs) recognize a range of G-protein-coupled receptors (GPCRs). They are frequently associated with cardiovascular, neurological, and autoimmune disorders, and in some cases directly impact disease progression. Many GPCR AAs modulate receptor signaling, but molecular details of their modulatory activity are not well understood. Technological advances have provided insight into GPCR biology, which now facilitates deeper understanding of GPCR AA function at the molecular level. Most GPCR AAs are allosteric modulators and exhibit a broad range of pharmacological properties, altering both receptor signaling and trafficking. Understanding GPCR AAs is not only important for defining how these unusual GPCR modulators function in disease, but also provides insight into the potential use and limitations of using therapeutic antibodies to modulate GPCR signaling.

Diagnostic and prognostic value of autoantibodies against β1-adrenoreceptors in patients with heart failure following acute myocardial infarction: A 5-year prospective study

A number of studies have suggested that autoantibodies against β₁-adrenoreceptors (β₁R-AAbs) have an important role in pathophysiological processes of heart failure. The aim of the present study was to determine whether β₁R-AAbs are implicated in cardiac dysfunction following acute myocardial infarction (AMI) and their association with prognosis. A total of 33 cases with systolic heart failure (SHF), 49 with diastolic heart failure (DHF) and 44 with normal heart function following AMI were recruited. β₁R-AAbs were detected by ELISA and major adverse cardiac events (MACEs) were recorded during the 5-year follow-up. The positive rate of β₁R-AAbs in the SHF group (45.5%) was significantly higher compared with that in the DHF (22.4%; P<0.05) and normal (15.9%; P<0.05) groups. The area under the receiver operating characteristics curve for the diagnosis of SHF was 0.630 (95% CI: 0.514–0.747, P=0.026). During a median follow-up period of 51.0±15.4 months, the positive rate of β₁R-AAbs in the MACEs group was significantly higher compared with that in the non-MACEs group (P<0.05). Multivariate logistic regression analysis indicated that the left ventricular ejection fraction and diabetes were independent predictors of 5-year MACEs following AMI, whereas β₁R-AAbs were not. Kaplan-Meier analysis revealed that the cumulative MACEs-free survival rate was the lowest in the SHF group, followed by the DHF and normal groups (P<0.05). Therefore, β₁R-AAbs were indicated to be of value for early diagnosis of SHF after AMI but not as independent predictors for the prognosis of patients with AMI.

Multiple Autoantibodies against Cardiovascular Receptors as Biomarkers in Hypertensive Heart Disease

OBJECTIVES

The pathogenesis of hypertensive heart disease (HHD) remains unclear, which might include autoimmunity. The aim of the present study was to determine whether a relationship exists between the presence of autoantibodies against β1, β2, α1 adrenoreceptors, M2-muscarinic receptors, angiotensin II type1 receptors and HHD.

METHODS

In the present study, 44 patients diagnosed with HHD, 36 patients with hypertension, and 40 controls were also enrolled. The measurement of these 5 autoantibodies was performed by enzyme-linked immunosorbent assay.

RESULTS

The frequencies of autoantibodies against β1, β2, α1 adrenoreceptors, autoantibodies against M2-muscarinic receptors and autoantibodies against angiotensin II type1 receptors were significantly higher in patients with HHD, when compared to patients with hypertension and normal controls (all p < 0.001). In addition, the titers of these 5 autoantibodies significantly increased in patients with HHD. Patients who were positive for all 5 autoantibodies had larger left ventricular end-diastolic diameter (60.5 ± 4.9 vs. 57.8 ± 5.0 vs. 52.5 ± 5.3 mm) and worse left ventricular ejection fraction (45.0 ± 11.0 vs. 56.6 ± 10.4 vs. 57.8 ± 5.3%), when compared to patients not positive for all the 5 autoantibodies and patients negative for all the 5 autoantibodies (χ2 = 9.524, p = 0.009 and χ2 = 7.689, p = 0.021). Furthermore, a significant positive correlation was observed between each 2 autoantibodies of these 5 autoantibodies (all p < 0.001).

CONCLUSION

Multiple autoantibodies of cardiovascular receptors may be involved in the pathogenesis and may be predictive factors of HHD.

Association of Autoantibodies against M2-Muscarinic Acetylcholine Receptor with Atrial Fibrosis in Atrial Fibrillation Patients

Objectives

To investigate the association of serum autoantibodies against M2-muscarinic acetylcholine receptor (anti-M2-R) with atrial fibrosis in long-standing persistent atrial fibrillation (AF) patients.

Methods

Twenty-four long-standing persistent AF patients, scheduled to undergo hybrid ablation surgery, were enrolled in the study. Twenty-six patients with sinus rhythm, scheduled to undergo coronary artery bypass grafting surgery, were enrolled into the non-AF group. We detected serum anti-M2-R levels. Left atrial appendages were subjected to histological and molecular biological assays. Patients in the AF group received follow-up for two years.

Results

The AF group showed significantly higher serum anti-M2-R levels compared to the non-AF group (496.2 ± 232.5 vs. 86.3 ± 25.7 pmol/L, p < 0.001). The AF group exhibited severe fibrosis in the left atrial appendages, as indicated by increased collagen volume fraction (45.2 ± 4.7% vs. 27.6 ± 8.3%, p < 0.001), and higher levels of collagen I (0.52 ± 0.04 vs. 0.24 ± 0.06, p < 0.001) and collagen III (0.51 ± 0.07 vs. 0.36 ± 0.09, p < 0.001). TGF-β1 and CTGF were also upregulated in the AF group. A positive correlation between serum anti-M2-R levels and fibrosis of the left atrial appendage and fibrogenic indexes was observed.

Conclusions

Serum anti-M2-R levels are higher in AF patients and are associated with the severity of atrial fibrosis. In addition, serum anti-M2-R levels are positively correlated to TGF-β1 and CTGF expression in the left atrial appendage.

No evidence for humoral autoimmunity against cardiomyocytes, adrenergic or muscarinic receptors in patients with Tako-Tsubo cardiomyopathy

BACKGROUND

An association between Tako-Tsubo cardiomyopathy (TTC) and underlying malignancies has been observed, suggesting that TTC might be the consequence of paraneoplastic phenomena. This study investigates the presence of autoantibodies against cardiomyocytes as well as adrenergic (β₁, β₂) and muscarinic (M2) receptors in patients with TTC.

METHODS AND RESULTS

Serum from 20 TTC patients and 20 controls with ischemic heart disease was obtained. Indirect immunofluorescence testing for intracellular autoantibodies against cardiomyocytes showed a homogenous distribution, as in both groups 9 of 20 sera displayed a characteristic binding pattern of antibodies including vascular walls and intracellular structures. Flow cytometry analysis revealed no difference between TTC and controls in the binding of autoantibodies to the surface antigens of cardiomyocyte HL-1 cells (p = 0.569, t-test). Flow cytometry analysis of nontransfected wild type cells (p = 0.633, t-test), M2 receptor-transfected cells (p = 0.687, t-test), β₁ receptor-transfected cells (p = 0.444, t-test) and β₂ receptor-transfected cells (p = 0.632, t-test) showed similar results for control and TTC sera. Likewise, the binding pattern of TTC patients with a history of neoplasia compared to those without or to controls did not differ significantly (p > 0.05, u-test).

CONCLUSION

Findings suggest that the presumed paraneoplastic etiology of TTC cannot be attributed to the formation of these antibodies.

Cyclic peptide RD808 reduces myocardial injury induced by β1-adrenoreceptor autoantibodies

Autoantibodies against the second extracellular loop of β₁-adrenergic receptor (β₁-AA) have been shown to be involved in the development of cardiovascular diseases. Recently, there has been considerable interest in strategies to remove these autoantibodies, particularly therapeutic peptides to neutralize β₁-AA. Researchers are investigating the roles of cyclic peptides that mimic the structure of relevant epitopes on the β₁-AR-EC_II in a number of immune-mediated diseases. Here, we used a cyclic peptide, namely, RD808, to neutralize β₁-AA, consequently alleviating β₁-AA-induced myocardial injury. We investigated the protective effects of RD808 on the myocardium both in vitro and in vivo. RD808 was found to increase the survival rate of cardiomyocytes; furthermore, it decreased myocardial necrosis and apoptosis and improved the cardiac function of BalB/c mice in a β₁-AA transfer model. In vitro and in vivo experiments showed that myocardial autophagy was increased in the presence of RD808, which might contribute to its cardioprotective effects. Our findings indicate that RD808 reduced myocardial injury induced by β₁-AA.

Immunization with plasmids encoding M2 acetylcholine muscarinic receptor epitopes impairs cardiac function in mice and induces autophagy in the myocardium

Autoantibodies against the M2 subtype of muscarinic acetylcholine receptors with functional activities have been found in the sera of patients with dilated cardiomyopathy (DCM), and the second extracellular loop has been established as the predominant epitope. However, it has been shown that the third intracellular loop is recognized by Chagas disease patients with severe cardiac dysfunction. In this work, BALB/c mice were immunized with plasmids encoding these two epitopes, and a control group received the empty plasmid (pcDNA3 vector). Serum from these DNA-immunized animals had elevated and persistent titres of antibodies against respective antigens. Heart echocardiography indicated diminished left ventricular wall thickness and reduced ejection fraction for both epitope-immunized groups, and ergospirometry tests showed a significant decrease in the exercise time and oxygen consumption. Transfer of serum from these immunized mice into naïve recipients induced the same alterations in cardiac structure and function. Furthermore, electron microscopy analysis of donor-immunized animals revealed several ultrastructural alterations suggestive of autophagy and mitophagy, suggesting novel roles for these autoantibodies. Overall, greater functional and structural impairment was observed in the donor and recipient epitope groups, implicating the third intracellular loop epitope in the pathological effects for the first-time. Therefore, the corresponding peptides could be useful for autoimmune DCM diagnosis and targeted therapy.

β1-Adrenergic Receptor Contains Multiple IAk and IEk Binding Epitopes That Induce T Cell Responses with Varying Degrees of Autoimmune Myocarditis in A/J Mice

Myocarditis/dilated cardiomyopathy (DCM) patients can develop autoantibodies to various cardiac antigens and one major antigen is β1-adrenergic receptor (β₁AR). Previous reports indicate that animals immunized with a β₁AR fragment encompassing, 197–222 amino acids for a prolonged period can develop DCM by producing autoantibodies, but existence of T cell epitopes, if any, were unknown. Using A/J mice that are highly susceptible to lymphocytic myocarditis, we have identified β₁AR 171–190, β₁AR 181–200, and β₁AR 211–230 as the major T cell epitopes that bind major histocompatibility complex class II/IA^k or IE^k alleles, and by creating IA^k and IE^k dextramers, we demonstrate that the CD4 T cell responses to be antigen-specific. Of note, all the three epitopes were found also to stimulate CD8 T cells suggesting that they can act as common epitopes for both CD4 and CD8 T cells. While, all epitopes induced only mild myocarditis, the disease-incidence was enhanced in animals immunized with all the three peptides together as a cocktail. Although, antigen-sensitized T cells produced mainly interleukin-17A, their transfer into naive animals yielded no disease. But, steering for T helper 1 response led the T cells reacting to one epitope, β₁AR 181–200 to induce severe myocarditis in naive mice. Finally, we demonstrate that all three β₁AR epitopes to be unique for T cells as none of them induced antibody responses. Conversely, animals immunized with a non-T cell activator, β₁AR 201–220, an equivalent of β₁AR 197–222, had antibodies comprising of all IgG isotypes and IgM except, IgA and IgE. Thus, identification of T cell and B cell epitopes of β₁AR may be helpful to determine β₁AR-reactive autoimmune responses in various experimental settings in A/J mice.

MRI Assessment of Cardiomyopathy Induced by β1-Adrenoreceptor Autoantibodies and Protection Through β3-Adrenoreceptor Overexpression

The cardiopathogenic role of autoantibodies (aabs) directed against β1-adrenoreceptors (β1-AR) is well established. In mouse models, they cause progressive dilated cardiomyopathy (DCM) whose characterization with echocardiography requires prolonged protocols with numerous animals, complicating the evaluation of new treatments. Here, we report on the characterization of β1-aabs-induced DCM in mice using 11.7T MRI. C57BL/6J mice (n = 10 per group) were immunized against the β1-AR and left ventricular (LV) systolic function was assessed at 10, 18 and 27 weeks. Increase in LV mass/tibial length ratio was detected as the first modification at 10 weeks together with dilation of cavities, thereby outperforming echocardiography. Significant impairment in diastolic index was also observed in immunized animals before the onset of systolic dysfunction. Morphometric and histological measurements confirmed these observations. The same protocol performed on β3-AR-overexpressing mice and wild-type littermates (n = 8–12 per group) showed that transgenic animals were protected with reduced LV/TL ratio compared to wild-type animals and maintenance of the diastolic index. This study demonstrates that MRI allows a precocious detection of the subtle myocardial dysfunction induced by β1-aabs and that β3-AR stimulation blunts the development of β1-aabs-induced DCM, thereby paving the way for the use of β3AR-stimulating drugs to treat this autoimmune cardiomyopathy.

Cardiomyopathy - An approach to the autoimmune background

Autoimmunity is increasingly accepted as the origin or amplifier of various diseases. In contrast to classic autoantibodies (AABs), which induce immune responses resulting in the destruction of the affected tissue, an additional class of AABs is directed against G-protein-coupled receptors (GPCRs; GPCR-AABs). GPCR-AABs functionally affect their related GPCRs for activation of receptor mediated signal cascades. Diseases which are characterized by the presence of GPCR-AABs with evidence for disease-specific pathogenic activity could be named "functional autoantibody disease". We briefly summarize here the historical view on autoimmunity in cardiomyopathy, followed by an approach to the mechanistic autoimmunity background. Furthermore, autoantibodies with outstanding importance for cardiomyopathies as a functional autoantibody disease, such as GPCR-AABs, and mainly those directed against the beta1-adrenergic and muscarinic 2 receptor autoantibodies, are introduced. Anti-cardiac myosin and anti-cardiac troponin autoantibodies, as further potential players in autoimmune cardiomyopathy, are additionally taken into account. The basic view on the autoantibodies, their related receptor interactions and pathogenic consequences are presented. Focused specifically on GPCR-AABs, "pros and cons" of assays such as indirect assays (functional changes of cell preparations are monitored after GPCR-AAB receptor binding) and direct assays based on the ELISA technologies (GPCR epitope mimics for GPCR-AAB binding) are critically discussed. Last but not least, treatment strategies for "functional autoantibody disease", such as for GPCR-AAB removal (therapeutic plasma exchange, immunoadsorption) and in vivo GPCR-AAB attack such as intravenous IgG treatment (IVIG), B-cell depletion and GPCR-AAB binding and neutralization, are critically reflected with respect to their patient benefits.

Combined analysis of cross-reacting antibodies anti-β1AR and anti-B13 in advanced stages of Chagas heart disease

OBJECTIVE

Autoantibodies cross-reacting with the β1 adrenergic receptor (anti-β1AR and anti-p2β) and cardiac myosin antigens (anti-B13) have been related to the pathogenesis of chronic Chagas heart disease (CCHD). Studies exploring their levels in different stages are scarce. We aimed to evaluate the relationship of these autoantibodies with the clinical profile of chronic patients, especially regarding their classificatory accuracy in severe presentation with heart failure.

METHODS AND RESULTS

We conducted a cross-sectional study of 155 T. cruzi-seropositive patients and 26 age- and gender-matched healthy controls. They were categorised in three stages of CCHD. Serum antibodies were measured by specific immunoassays. Symptomatic individuals showed increased levels of anti-β1AR and anti-B13, while anti-p2β antibodies were similar between groups. A composite logistic regression model including anti-B13, anti-β1AR antibody levels and age was able to predict systolic heart failure yielding an area under the curve of 83% (sensitivity of 67% and specificity of 89%).

CONCLUSIONS

In our study, anti-β1AR and anti-B13 antibodies were higher in individuals with chronic Chagas heart disease stage III, mainly in those with dilated cardiomyopathy associated with systolic heart failure. Logistic regression analysis showed that both antibodies were good predictors of severe CCHD. As well as being involved in disease progression, anti-β1AR and anti-B13 antibodies may be used as a serum marker of poor prognosis in terms of heart compromise.

Anti-calreticulin antibodies and calreticulin in sera of patients diagnosed with dilated or hypertrophic cardiomyopathy

Distinct cellular level of the Ca²⁺-binding chaperone calreticulin (CRT) is essential for correct embryonal cardiac development and postnatal function. However, CRT is also a potential autoantigen eliciting formation of antibodies (Ab), whose role is not yet clarified. Immunization with CRT leads to cardiac injury, while overexpression of CRT in cardiomyocytes induces dilated cardiomyopathy (DCM) in animals. Hence, we analysed levels of anti-CRT Ab and calreticulin in the sera of patients with idiopatic DCM and hypertrophic cardiomyopathy (HCM). ELISA and immunoblot using human recombinant CRT and Pepscan with synthetic, overlapping decapeptides of CRT were used to detect anti-CRT Ab. Serum CRT concentration was tested by ELISA. Significantly increased levels of anti-CRT Ab of isotypes IgA (p < 0.001) and IgG (p < 0.05) were found in patients with both DCM (12/34 seropositive for IgA, 7/34 for IgG) and HCM (13/38 seropositive for IgA, 11/38 for IgG) against healthy controls (2/79 for IgA, 1/79 for IgG). Titration analysis in seropositive DCM and HCM patients documented anti-CRT Ab detected at 1/1600 dilution for IgG and 1/800 for IgA (and IgA1) and at least at 1/200 dilution for IgA2, IgG1, IgG2 and IgG3. Pepscan identified immunogenic CRT epitopes recognized by IgA and IgG Ab of these patients. Significantly increased levels of CRT relative to healthy controls were found in sera of patients with HCM (p < 0.01, 5/19). These data extend the knowledge of seroprevalence of anti-CRT Ab and CRT, and suggest possible involvement of autoimmune mechanisms directed to CRT in some forms of cardiomyopathies, which are clinically heterogeneous.

Autoantibodies and cardiovascular dysfunction: cause or consequence?

There has been a long history of the exploration into autoimmunity as a possible pathogenic factor of cardiovascular diseases from unknown cause represented by dilated cardiomyopathy (DCM). Autoantibodies (AAbs) have emerged either as humoral responses provoked by the release of "self-antigens" due to tissue damage or dysregulated humoral immunity itself. The pathogenic roles of some AAbs have been suggested by the findings from basic research using in vitro and in vivo disease models as well as clinical studies including immunoadsorption studies removing AAbs from patients with DCM. In this context, the importance of AAbs belonging to IgG3 subclass has also been implicated. In this review article, we summarize the findings accumulated to date regarding AAbs which have been considered to be involved in the pathology of DCM or pregnancy-related cardiovascular disease. Furthermore, we discuss the significance of AAbs as a possible cause of DCM and their potential roles as a novel therapeutic target.

Defective circulating CD4+LAP+ regulatory T cells in patients with dilated cardiomyopathy

There has been increasing evidence that chronic immune activation plays critical roles in the pathogenesis of DCM. CD4(+) LAP(+) Tregs are a newly identified T cell subset with suppressive function on the immune response. This study was designed to investigate whether the circulating frequency and function of CD4(+)LAP(+) Tregs would be impaired in patients with DCM. The results demonstrated that DCM patients had a significantly lower frequency of circulating CD4(+)LAP(+) Tregs compared with control donors. CD4(+)LAP(+) Tregs from DCM patients showed compromised function to suppress proliferation of CD4(+) LAP(-)CD25(int/low) T cells and proliferation and IgG production of B cells. Moreover, B cell proliferation and IgG subset production could be directly suppressed by CD4(+) LAP(+) Tregs. TGF-β and contact-dependent mechanisms were involved in CD4(+)LAP(+) Treg-mediated suppression. Correlation analysis suggested that CD4(+)LAP(+) Treg frequency was positively correlated with LVEF and negatively correlated with serum IgG3 and NT-proBNP concentration in patients with DCM. Our results are the first to demonstrate that the frequencies of CD4(+)LAP(+) Tregs in patients with DCM are reduced and that their suppressive function is compromised. Defective CD4(+) LAP(+) Tregs may be an underlying mechanism of immune activation in DCM patients.

Immunoadsorption therapy in dilated cardiomyopathy

Dilated cardiomyopathy is a common myocardial disease characterized by ventricular chamber enlargement and systolic dysfunction that result in heart failure. In addition to genetic predisposition, viral infection and myocardial inflammation play a causal role in the disease process of dilated cardiomyopathy. Experimental and clinical studies suggest that activation of the humoral immune system, with production of circulating cardiac autoantibodies, plays an important functional role in the development and progression of cardiac dysfunction in patients with dilated cardiomyopathy. Small open-controlled studies showed that removal of circulating antibodies by immunoadsorption results in improvement of cardiac function and decrease in myocardial inflammation. At present, immunoadsorption is an experimental treatment option for improvement of cardiac function - therapy that calls for confirmation by a placebo-controlled multicenter study.

Agonistic autoantibodies directed against G-protein-coupled receptors and their relationship to cardiovascular diseases

Agonistic autoantibodies (AABs) against G-protein-coupled receptor (GPCR) are present mainly in diseases of the cardiovascular system or in diseases associated with cardiovascular disturbances. The increasing knowledge about the role of autoantibodies against G-protein-coupled receptor (GPCR-AABs) as pathogenic drivers, the resulting development of strategies aimed at their removal or neutralization, and the evidenced patient benefit associated with such therapies have created the need for a summary of GPCR-AAB-associated diseases. Here, we summarize the present knowledge about GPCR-AABs in cardiovascular diseases. The identity of the GPCR-AABs and their prevalence in each of several specific cardiovascular diseases are documented. The structure of GPCR is also briefly discussed. Using this information, differences between classic agonists and GPCR-AABs in their GPCR binding and activation are presented and the resulting pathogenic consequences are discussed. Furthermore, treatment strategies that are currently under study, most of which are aimed at the removal and in vivo neutralization of GPCR-AABs, are indicated and their patient benefits discussed. In this context, immunoadsorption using peptides/proteins or aptamers as binders are introduced. The use of peptides or aptamers for in vivo neutralization of GPCR-AABs is also described. Particular attention is given to the GPCR-AABs directed against the adrenergic beta1-, beta2-, and α1-receptor as well as the muscarinic receptor M2, angiotensin II-angiotensin receptor type I, endothelin1 receptor type A, angiotensin (1-7) Mas-receptor, and 5-hydroxytryptamine receptor 4. Among the diseases associated with GPCR-AABs, special focus is given to idiopathic dilated cardiomyopathy, Chagas' cardiomyopathy, malignant and pulmonary hypertension, and kidney diseases. Relationships of GPCR-AABs are indicated to glaucoma, peripartum cardiomyopathy, myocarditis, pericarditis, preeclampsia, Alzheimer's disease, Sjörgren's syndrome, and metabolic syndrome after cancer chemotherapy.

The correlation between peripartum cardiomyopathy and autoantibodies against cardiovascular receptors

Background

Peripartum cardiomyopathy (PPCM) is characterized by left ventricular systolic dysfunction and heart failure. However, its pathogenesis is not clear. Our preliminary study revealed that autoantibodies against β₁-adrenergic receptors (β₁R-AABs) and M₂-muscarinic receptors (M₂R-AABs) participated in heart failure regardless of primary heart disease. Whether β₁R-AABs and M₂R-AABs participate in the pathogenesis of PPCM is still unknown.

Methods

Totally 37 diagnosed PPCM patients and 36 normal pregnant women were enrolled in this study. Clinical assessment and 2-dimensional echocardiographic studies as well as the measurement of β₁R-AABs or M₂R-AABs by enzyme linked immunosorbent assay (ELISA) were performed.

Results

The positive rates for β₁R-AABs and M₂R-AABs were 59.5% (22/37) and 45.9% (17/37) in PPCM patients, and 19.4% (7/36) (P<0.001) and 16.67% (6/36) (P<0.001) in normal pregnant women, respectively. Both β₁R-AABs and M₂R-AABs had a positive correlation with serum expression level of NT-proBNP, left ventricular dimension and NYHA FC (rs: 0.496–0.892, P<0.01). In addition, a negative correlation between the activity of β₁R-AABs and M₂R-AABs and LVEF, LVFS was observed (rs: −0.488–0.568, P<0.01). Moreover, autoantibodies against cardiovascular receptors increased the risk of the onset of PPCM (OR = 18.786, 95% confidence interval 1.926–183.262, P = 0.012).

Conclusions

The β₁R-AABs and M₂R-AABs reveal a significant elevation and are correlated with the increased left ventricular dimension and worse cardiac contraction function. The autoantibodies of cardiovascular receptors are independent risk factors for the onset of PPCM.

β1-selective adrenoceptor antagonists increase plasma levels of anti-p2β antibodies and decrease cardiac involvement in chronic progressive Chagas heart disease

BACKGROUND

Studies indicate that antibodies cross-reacting with cardiac β1 adrenergic receptors are likely to play a role in the development of chronic Chagas heart disease (CCHD). In parallel, clinical trials have shown that β1 antagonist drugs exert beneficial effects in the prognosis of patients with CCHD. In a group of patients with CCHD undergoing therapy with β1-blockers, we have now evaluated the levels of anti-p2β antibodies and the severity of CCHD.

METHODS

We performed a cross-sectional study in Trypanosoma cruzi seropositive patients categorized according to a standard CCHD classification. All individuals were subjected to a complete clinical examination.

RESULTS

There was no association between CCHD stages, electrocardiographic conduction disturbances, and echocardiogram pathological signs with the levels of autoantibodies. However, when patients were analyzed according to selective cardio-β1-blocker therapy, those receiving treatment had higher levels of anti-p2β. Patients from CCHD stage III treated with combined therapy of cardio-β1-selective blockers, enalapril, and statins, presented decreased cardiac involvement and lower score of risk of mortality than individuals from the same group who were not treated.

CONCLUSIONS

Our results suggest that selective cardio-β1-blockers might modify the autoantibody anti-p2β levels, and that combined therapy in patients with stage III CCHD might be associated with lower cardiac involvement and risk score of mortality in patients with heart failure. Longitudinal studies will help to ascertain the proper role of β1-blockers in the immunopathological processes underlying chronic Chagas disease.

Autoantibodies against the β3-adrenoceptor protect from cardiac dysfunction in a rat model of pressure overload

β₃-adrenoceptors (β₃-ARs) mediate a negative inotropic effect in human ventricular cardiomyocytes, which is opposite to that of β₁- and β₂-ARs. It has been previously demonstrated that autoantibodies against the β_1/β₂-AR exist in the sera of some patients with heart failure (HF) and these autoantibodies display agonist-like effects. Our aim in this study was to observe whether autoantibodies against the β₃-AR (β₃-AR Abs) exist in the sera of patients with HF and to assess the effects of β₃-AR Abs on rat model of pressure overload cardiomyopthy. In the present study, the level of β₃-AR Abs in the sera of HF patients was screened by ELISA. β₃-AR Abs from HF patients were administrated to male adult rats with abdominal aortic banding (AAB), and the cardiac function was measured by echocardiographic examination and hemodynamic studies. The biological effects of this autoantibody on cardiomyocytes were evaluated using a motion-edge detection system, intracellular calcium transient assay, and patch clamp techniques. Compared to healthy subjects, the frequency of occurrence and titer of β₃-AR Abs in the sera of HF patients were greatly increased, and β₃-AR Abs could prevent LV dilation and improve the cardiac function of rats with AAB. β₃-AR Abs exhibited negative chronotropic and inotropic effects and were accompanied by a decreased intracellular Ca²⁺ transient and membrane L-type Ca²⁺ current in cardiomyocytes. Our results demonstrated the existence of β₃-AR Abs in the sera of patients with HF and found that this autoantibody could alleviate the cardiac dysfunction induced by pressure-overload in AAB rats.

Implications of a vasodilatory human monoclonal autoantibody in postural hypotension

Functional autoantibodies to the autonomic receptors are increasingly recognized in the pathophysiology of cardiovascular diseases. To date, no human activating monoclonal autoantibodies to these receptors have been available. In this study, we describe for the first time a β2-adrenergic receptor (β2AR)-activating monoclonal autoantibody (C5F2) produced from the lymphocytes of a patient with idiopathic postural hypotension. C5F2, an IgG3 isotype, recognizes an epitope in the N terminus of the second extracellular loop (ECL2) of β2AR. Surface plasmon resonance analysis revealed high binding affinity for the β2AR ECL2 peptide. Immunoblotting and immunofluorescence demonstrated specific binding to β2AR in H9c2 cardiomyocytes, CHO cells expressing human β2AR, and rat aorta. C5F2 stimulated cyclic AMP production in β2AR-transfected CHO cells and induced potent dilation of isolated rat cremaster arterioles, both of which were specifically blocked by the β2AR-selective antagonist ICI-118551 and by the β2AR ECL2 peptide. This monoclonal antibody demonstrated sufficient activity to produce postural hypotension in its host. Its availability provides a unique opportunity to identify previously unrecognized causes and new pharmacological management of postural hypotension and other cardiovascular diseases.

Assessment of cross-reactive host-pathogen antibodies in patients with different stages of chronic Chagas disease

INTRODUCTION AND OBJECTIVES

Trypanosoma cruzi infection has been shown to induce humoral autoimmune responses against host antigens tissues. Particularly, antibodies cross-reacting with myocardial antigens may play a role in the development of the severe forms of chronic Chagas disease. The aim of this study was to determine the association between clinical stage of the disease and the presence of autoantibodies in patients with chronic Chagasic disease.

METHODS

We performed a cross-sectional study in T. cruzi-seropositive patients divided into 3 groups according to the classic classification of chronic Chagas heart of Storino et al. All participants underwent complete clinical examination and their sera were used to measure autoantibody levels.

RESULTS

All patients had detectable levels of anti-p2β and anti-B13 autoantibodies but none had anti-Na-K-ATPase antibodies. No association was observed between electrocardiographic conduction disturbances and autoantibody levels. Patients with chronic Chagas disease stage III had the highest levels of anti-B13 antibodies and a high risk of mortality score, showing a clear association between disease stage and this score.

CONCLUSIONS

Anti-B13 antibodies were significantly higher in chronic Chagas disease stage III patients, suggesting that these antibodies may be involved in disease progression and that they might be a useful marker of poor prognosis in terms of heart compromise. Our results also reveal an important correlation between the level of anti-B13 autoantibodies and symptomatic heart failure and/or dilated cardiomyopathy.

The diagnostic and clinical significance of anti-muscarinic receptor autoantibodies

The role of autoimmunity in cardiovascular diseases has become one of the focal points of research studies. Autoimmune response and autoreactive autoantibodies have been found in dilated cardiomyopathy, heart failure, rheumatic fever, myocarditis, atherosclerosis, and other diseases. Autoantibodies may appear due to tissue injury and exposure of autoantigens, in addition to molecular mimicry and cross-reactivity with antigens found in infectious agents in predisposed individuals. In the early 1990s, autoantibodies reacting with the M2 muscarinic receptor were found in patients with dilated cardiomyopathy and subsequently, in patients with Chagas heart disease and arrhythmic disorders. Immunization of animals with the corresponding antigen triggered cardiac abnormalities also appearing in dilated cardiomyopathy of humans. It has been suggested that antibodies against M2 muscarinic receptors play a role in the pathogenesis of cardiac diseases and may also alter the electrophysiological properties of cardiac tissue. Herein, we review the current knowledge of antibodies against M2 muscarinic receptors and the possible use of a targeted therapy against these autoantibodies.

Administration of the cyclic peptide COR-1 in humans (phase I study): ex vivo measurements of anti-β1-adrenergic receptor antibody neutralization and of immune parameters

AIMS

A novel concept for the treatment of heart failure is the neutralization of antibodies against the β(1)-adrenergic receptor (anti-β(1)AR-ab). In a rat model of autoimmune cardiomyopathy, the cyclic peptide COR-1 (given i.v. once monthly) neutralized anti-β(1)AR-abs and prevented anti-β(1)AR-ab-induced myocardial damage, and completely reverted cardiac dysfunction over 3-6 months.

METHODS AND RESULTS

A clinical phase I trial was designed as a single-blinded, placebo-controlled study. Fifty human volunteers received COR-1 or matching placebo as a single i.v. administration with ascending doses (10-240 mg). Primary endpoints were safety and tolerability, while the pharmacokinetic profile of COR-1 was assessed as a secondary endpoint. All five investigated dose groups were well tolerated; no drug-related side effects occurred. Pharmacokinetics revealed a favourable profile with an almost complete plasma clearance within 60 min after administration. Pharmacodynamic investigation showed dose-dependent efficacy with almost complete scavenging of pathological anti-β(1)AR-abs ex vivo at the two highest doses. No anti-COR-1 autoantibodies occurred. No other effects on the immune system (such as an increase of crucial cytokines) were observed up to 43 days after drug administration, nor upon incubation of anti-β(1)AR-ab-positive patient blood samples with COR-1 ex vivo.

CONCLUSIONS

COR-1 was shown to be safe after i.v. administration in vivo; no relevant side effects occurred. Efficacy was estimated from ex vivo investigation of the potency to neutralize specific anti-β(1)-AR-abs.

TRIAL REGISTRATION

NCT 01043146, Eudra CT 2008-007745-31.

Autoantibodies in Heart Failure and Cardiac Dysfunction

Human heart failure is a disease with multifactorial causes, considerable morbidity, and high mortality. Several circulating autoantibodies, some of them being heart-specific, play a crucial role in the progression and induction of heart failure. However the precise mechanisms on how these autoantibodies perpetuate or even induce an organ specific autoimmune response are not yet fully understood. Also it is being a matter of current research to elucidate a potential pathophysiological role of the innate immune system in generating auto-reactive antibodies. In this review we will summarize the current available literature on circulating autoantibodies which are related to human heart failure. We will present clinical and animal studies that demonstrate the occurrence and pathophysiological relevance of several autoantibodies in heart failure, as well as point out biological mechanisms on molecular and cellular level. Finally the beneficial therapeutic effects of numerous clinical studies that target the humoral arm of the immune system by using either intravenous immunoglobulins and/or immunoadsorption will be critically discussed.

Immunoadsorption therapy for patients with dilated cardiomyopathy and heart failure

Several autoantibodies directed against cardiac cellular proteins including G-protein-linked receptors, contractile proteins and mitochondrial proteins, have been identified in patients with dilated cardiomyopathy (DCM). Among these autoantibodies, anti-β1-adrenoreceptor (AR) antibodies have long been discussed in terms of their pathogenetic role in DCM. Anti-β1-AR antibody-positive patients with DCM showed significant deterioration of NYHA functional class as well as reduced cardiac function compared to those in autoantibody-negative patients. Various studies with a limited number of patients indicate that the use of immunoadsorption to eliminate immunoglobulin G (IgG) significantly improves cardiac performance and clinical status in heart failure patients. Since removal of autoantibodies of the IgG3 subclass induces hemodynamic improvement and an increase in the left ventricular ejection fraction, antibodies belonging to IgG3 such as anti-β1-AR antibodies might play an important role in reducing cardiac function in patients with DCM. According to a recent report, however, the effect of hemodynamic improvement by immunoadsorption threapy was similar among patients who were positive and negative for anti-β1-AR antibodies, indicating that the beneficial effects of immunoadsorption might be not directly associated with the selective elimination of the β1-AR autoantibodies. Immunoadsorption therapy is a new therapeutic option for patients with DCM and heart failure, but further investigations are required to elucidate the specific antigens of cardiac autoantibodies responsible for the hemodynamic effects.

Interleukin-6-deficient mice resist development of experimental autoimmune cardiomyopathy induced by immunization of β1-adrenergic receptor

BACKGROUND

IL-6 is known to be an important mediator in immune response and is now suggested to be involved in the pathogenesis of autoimmune diseases. However, little is known about the role of IL-6 in β(1)-adrenergic receptor induced autoimmune cardiomyopathy.

MATERIALS AND METHODS

Twenty IL-6-deficient (IL-6(-/-)) mice and fifty-one wild type C57BL/6J (WT) mice were immunized with a synthetic peptide corresponding to the second extracellular loop of the β(1) (β(1)AR ECII) at 0, 1, 5, 9, 13 weeks and observed until 25 weeks. Another forty-one WT mice and twenty IL-6(-/-) mice were used as controls receiving vehicle in the same manner.

RESULTS

As compared with IL-6(-/-) immunized and control mice, WT immunized mice showed increased end-systolic left ventricular dimension and end-diastolic left ventricular dimension as well as decreased fractional shortening and circumferential fiber shortening in the end of the experiment, which was accompanied by significantly increased antibody level. Moreover, mRNAs encoding for β(1)-adrenergic receptor kinase (GRK2), B-type natriuretic peptide (BNP) and β(1) adrenergic receptor (Adrb1) in heart tissues from WT immunized group were increased. There was a significant positive correlation among end-diastolic left ventricular dimension, autoantibody titer and mRNA expressions of BNP, Adrb1 and GRK2.

CONCLUSION

Our results demonstrated that immunization with β1AR ECII was unable to induce an early stage phenotype of cardiomyopathy in IL-6(-/-) mice, being different from wild type in which cardiomyopathy was observed, suggesting that IL-6 plays a key role in the regulation of β(1)AR induced autoimmune cardiomyopathy possibly through its enhanced antibody production.

Animal models of cardiac disease and stem cell therapy

Animal models that mimic cardiovascular diseases are indispensable tools for understanding the mechanisms underlying the diseases at the cellular and molecular level. This review focuses on various methods in preclinical research to create small animal models of cardiac diseases, such as myocardial infarction, dilated cardiomyopathy, heart failure, myocarditis and cardiac hypertrophy, and the related stem cell treatment for these diseases.

Cardiac gene expression and systemic cytokine profile are complementary in a murine model of post-ischemic heart failure

After myocardial infarction (MI), activation of the immune system and inflammatory mechanisms, among others, can lead to ventricular remodeling and heart failure (HF). The interaction between these systemic alterations and corresponding changes in the heart has not been extensively examined in the setting of chronic ischemia. The main purpose of this study was to investigate alterations in cardiac gene and systemic cytokine profile in mice with post-ischemic HF. Plasma was tested for IgM and IgG anti-heart reactive repertoire and inflammatory cytokines. Heart samples were assayed for gene expression by analyzing hybridization to AECOM 32k mouse microarrays. Ischemic HF significantly increased the levels of total serum IgM (by 5.2-fold) and total IgG (by 3.6-fold) associated with a relatively high content of anti-heart specificity. A comparable increase was observed in the levels of circulating pro-inflammatory cytokines such as IL-1beta (3.8X) and TNF-alpha (6.0X). IFN-gamma was also increased by 3.1-fold in the MI group. However, IL-4 and IL-10 were not significantly different between the MI and sham-operated groups. Chemokines such as MCP-1 and IL-8 were 1.4- and 13-fold increased, respectively, in the plasma of infarcted mice. We identified 2079 well annotated unigenes that were significantly regulated by post-ischemic HF. Complement activation and immune response were among the most up-regulated processes. Interestingly, 21 of the 101 quantified unigenes involved in the inflammatory response were significantly up-regulated and none were down-regulated. These data indicate that post-ischemic heart remodeling is accompanied by immune-mediated mechanisms that act both systemically and locally.

Transfer of immune components from rabbit autoimmune cardiomyopathy into severe combined immunodeficiency (SCID) mice induces cardiomyopathic changes

BACKGROUND

Growing evidence suggests that autoimmune mechanism plays an important role in the pathogenesis of cardiomyopathy. The purpose of this study was to investigate whether passive transfer of IgG and/or lymphocytes from rabbits with autoimmune cardiomyopathy is able to reproduce cardiomyopathic changes in severe combined immunodeficiency (SCID) mice.

METHODS AND RESULTS

SCID mice were injected intraperitoneally with IgG and/or peripheral blood lymphocytes (PBL) from either rabbits immunized with both beta1-adrenoceptor peptide and M2-muscarinic receptor peptide (beta1+M2 group) or rabbits with adjuvant (N group). Thirty five SCID mice were divided into seven groups; N-IgG, N-PBL, N-IgG & PBL, (beta1+M2)-IgG, (beta1+M2)-PBL, (beta1+M2)-IgG & PBL and control groups. Heart weight in three (beta1+M2) groups were significantly increased. All mice in three (beta1+M2) groups showed high titer of rabbit anti-beta1 adrenoceptor autoantibodies, and 4 mice in the (beta1+M2)-PBL group and 3 mice in the (beta1+M2)-IgG & PBL group showed a significant increase in titer of rabbit anti-M2-muscarinic receptor autoantibodies. Focal infiltration of inflammatory cells in the myocardium was observed in the (beta1+M2)-IgG & PBL group. In the (beta1+M2)-PBL group and (beta1+M2)-IgG & PBL group, cardiomyocyte diameters were significantly increased. Some myocytes of the (beta1+M2)-IgG & PBL group exhibited intracellular edema, clumps of Z-band and increased numbers of mitochondria by using electron microscopy.

CONCLUSION

Transfer of IgG and PBL from rabbits immunized with combined beta1 and M2 peptides was able to reproduce the early stage of cardiomyopathic changes in SCID mice.

Beneficial Effect on Cardiac Function by Intravenous Immunoglobulin Treatment in Patients with Dilated Cardiomyopathy is not due to Neutralization of Anti-receptor Autoantibody

Anti-beta1-adrenoceptor (beta1AR) autoantibodies have been shown to be pathophysiologically important in idiopathic dilated cardiomyopathy (DCM). Treatment with intravenous immunoglobulin (IVIG) has shown beneficial effects in both DCM and ischemic cardiomyopathy. However, the underlying mechanism has not been clarified. In the present study, we therefore examined whether the improvement of cardiac function was due to neutralization of functional beta1AR autoantibodies by anti-idiotypic antibodies. Autoantibodies against the beta1AR was analysed in sera from patients with DCM and coronary artery disease (CAD) treated with IVIG or placebo before, 6 and 12 months. Six month after treatment, DCM patients showed increase in beta1AR autoantibodies, mostly in IgG1 and IgG2, whereas in CAD patients mostly in IgG2. No changes in beta1AR autoantibodies after 12 months were detected. In summary, our results indicate that improvement of cardiac function by IVIG is not due to neutralization of beta1AR autoantibodies.

Inflammation as a therapeutic target in heart failure? A scientific statement from the Translational Research Committee of the Heart Failure Association of the European Society of Cardiology

The increasing prevalence of heart failure poses enormous challenges for health care systems worldwide. Despite effective medical interventions that target neurohumoral activation, mortality and morbidity remain substantial. Evidence for inflammatory activation as an important pathway in disease progression in chronic heart failure has emerged in the last two decades. However, clinical trials of 'anti-inflammatory' therapies (such as anti-tumor necrosis factor-alpha approaches) have to date failed to show benefit in heart failure patients. The Heart Failure Association of the European Society of Cardiology recently organized an expert workshop to address the issue of inflammation in heart failure from a basic science, translational and clinical perspective, and to assess whether specific inflammatory pathways may yet serve as novel therapeutic targets for this condition. This consensus document represents the outcome of the workshop and defines key research questions that still need to be addressed as well as considering the requirements for future clinical trials in this area.

Throat infection, neck and chest pain and cardiac response: a persistent infection-related clinical syndrome

Dizziness, chest discomfort, chest depression and dyspnea are a group of symptoms that are common complaints in clinical practice. Patients with these symptoms are usually informed that while neurosis consequent to coronary heart disease is excluded nonetheless they remain unhealthy with no rational explanation or treatment. 165 cases of these symptoms and 85 control subjects were reviewed and underwent further medical history inquiry, routine EKG test and cardiac ultrasound examination. Thirty-five patients received coronary artery angiography to exclude coronary heart disease. Serum myocardial autoantibodies against beta(1)-adrenoceptor, alpha-myosin heavy chain, M(2)-muscarinic receptor and adenine-nucleotide translocator were tested, and inflammatory cytokines and high sensitivity C-reaction protein were measured and lymphocyte subclass was assayed by flow cytometry. All patients had a complex of four symptoms or tetralogy: (1) persistent throat or upper respiratory tract infection, (2) neck pain, (3) chest pain and (4) chest depression or dyspnea, some of them with anxiety. Anti-myocardial autoantibodies (AMCAs) were present in all patients vs. 8% in controls. TNF-alpha, IL-1 and IL-6 were significantly higher in patients than in controls (P<0.01). CD3(+) and CD4-CD8(+) lymphocytes were significantly higher and CD56(+) lymphocytes lower in patients than those in controls (P<0.01). The ratio of serum pathogen antibodies positive against Coxsackie virus-B, cytomegalovirus, Mycoplasma pneumoniae and Chlamydia pneumoniae were all markedly higher in patients. These data led to identification of a persistent respiratory infection-related clinical syndrome, including persistent throat infection, neck spinal lesion, rib cartilage inflammation, symptoms of cardiac depression and dyspnea with or without anxiety.

Autoimmunity and idiopathic dilated cardiomyopathy: where we stand?

Idiopathic dilated cardiomyopathy (DCM) with its heterogeneous phenotype and genotype remains one of the leading causes of severe heart failure particularly in the younger. Even in the elderly, it appears around 15% of heart failure is due to DCM. Despite great improvements in heart failure therapy, prognoses remains poor. One of the most important reasons is that the present heart failure management is aimed mostly at restoration of neurohormonal balance, rather than targeting primary causes of the disease. As a matter of fact, a substantial subgroup of DCM and chronic heart failure is accompanied by autoimmune mechanism, in particular a wide spectrum of autoantibodies. For almost two decades, the autoimmune hypothesis has been considered a "fairy tale". Today, we have better understanding of autoimmune mechanism in DCM. This focused issue is aimed to summarize what has happened in the last two decades in the context of basic understanding of underlying mechanisms and clinical relevance.