Role of immunoglobulin G3 subclass in dilated cardiomyopathy: results from protein A immunoadsorption

β1 Adrenergic Receptor Autoantibodies and IgG Subclasses: Current Status and Unsolved Issues

A wide range of anti-myocardial autoantibodies have been reported since the 1970s. Among them, autoantibodies against the β1-adrenergic receptor (β1AR-AAb) have been the most thoroughly investigated, especially in dilated cardiomyopathy (DCM). Β1AR-Aabs have agonist effects inducing desensitization of β1AR, cardiomyocyte apoptosis, and sustained calcium influx which lead to cardiac dysfunction and arrhythmias. Β1AR-Aab has been reported to be detected in approximately 40% of patients with DCM, and the presence of the antibody has been associated with worse clinical outcomes. The removal of anti-myocardial autoantibodies including β1AR-AAb by immunoadsorption is beneficial for the improvement of cardiac function for DCM patients. However, several studies have suggested that its efficacy depended on the removal of AAbs belonging to the IgG3 subclass, not total IgG. IgG subclasses differ in the structure of the Fc region, suggesting that the mechanism of action of β1AR-AAb differs depending on the IgG subclasses. Our previous clinical research demonstrated that the patients with β1AR-AAb better responded to β-blocker therapy, but the following studies found that its response also differed among IgG subclasses. Further studies are needed to elucidate the possible pathogenic role of IgG subclasses of β1AR-AAbs in DCM, and the broad spectrum of cardiovascular diseases including HF with preserved ejection fraction.

Immunoadsorption therapy in refractory heart failure patients with dilated cardiomyopathy: a potential therapeutic option

OBJECTIVE

Removal of cardiac autoantibodies by immunoadsorption might confer clinical improvement in dilated cardiomyopathy. In this pilot study, we investigated the efficacy and safety of immunoadsorption therapy in refractory heart failure patients with dilated cardiomyopathy.

METHODS

This study consisted of 9 heart failure patients with dilated cardiomyopathy, NYHA III-IV, left ventricular ejection fraction <30%, unresponsive to heart failure therapy, and with cardiac autoantibodies. Patients underwent immunoadsorption therapy for five consecutive days using a tryptophan column. Changes in cardiac function (left ventricular ejection fraction, left ventricular end-diastolic diameter, left ventricular end-systolic diameter), exercise capacity (6-minute walk distance), neurohormonal (N-terminal pro-brain natriuretic peptide), proinflammatory (high-sensitive C-reactive protein), and myocardial (cardiac troponin-I), biochemical, and hematological variables were obtained at baseline and after 3 and 6 months of immunoadsorption therapy.

RESULTS

Mean left ventricular ejection fraction and 6-minute walk distance significantly increased at 3 months (from 23.27±5.09 to 32.1±1.7%, p=0.01 for left ventricular ejection fraction and from 353±118 to 434±159 m, p=0.04 for 6-minute walk distance) and further increased at 6 months after immunoadsorption therapy (to 34.5±7.7%, p=0.02 for ejection fraction and to 441±136 m, p=0.04 for 6-minute walk distance). NT-proBNP level reduced from 1161(392.8-3034) to 385(116.1-656.5) ng/L (p=0.04), and high-sensitive C-reactive protein decreased from 9.74±0.96 to 4.3±5.8 mg/L (p=0.04) at 6 months. Left ventricular end-diastolic diameter (66.1±5.8 vs. 64.7±8.9 mm) and left ventricular end-systolic diameter (56.1±8.6 vs. 52.3±10.8 mm) tended to decrease but did not reach statistical significance. No significant worsening was observed in creatinine, cardiac troponin-I, and hemoglobin levels after the immunoadsorption procedure.

CONCLUSION

In dilated cardiomyopathy patients with refractory heart failure, immunoadsorption may be considered a potentially useful therapeutic option to improve a patient's clinical status.

Dilated cardiomyopathy and chronic cardiac inflammation: Pathogenesis, diagnosis and therapy

Dilated cardiomyopathy (DCM) is typically defined by left ventricular dilation and systolic dysfunction in the absence of a clear precipitant. Idiopathic disease is common; up to 50% of patients with DCM have no cause found despite imaging, genetic and biopsy assessments. Treatment remains focused on managing symptoms, reducing the risk of sudden cardiac death and ameliorating the structural and electrical complications of disease progression. In the absence of aetiology-specific treatments, the condition remains associated with a poor prognosis; mortality is approximately 40% at 10 years. The role of immune-mediated inflammatory injury in the development and progression of DCM was first proposed over 30 years ago. Despite the subsequent failures of three large clinical trials of immunosuppressive treatment (ATTACH, RENEWAL and the Myocarditis Treatment Trial), evidence for an abnormal adaptive immune response in DCM remains significant. In this review, we summarise and discuss available evidence supporting immune dysfunction in DCM, with a specific focus on cellular immunity. We also highlight current clinical and experimental treatments. We propose that the success of future immunosuppressive treatment trials in DCM will be dependent on the deep immunophenotyping of patients, to identify those with active inflammation and/or an abnormal immune response who are most likely to respond to therapy.

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.

Immunoadsorption treatment for dilated cardiomyopathy: A PRISMA-compliant systematic review and meta-analysis

BACKGROUND

As one of the leading causes of heart failure, dilated cardiomyopathy (DCM) is characterized by dysfunctional muscle contraction and enlarged ventricular chamber. Patients with DCM have been shown to respond well to immunoadsorption (IA) therapies. However, the efficacy and safety of IA treatment for DCM patients remained to be evaluated.

METHODS

This study was designed in accordance with the Preferred Reporting Items for Systematic Review and Meta-analysis. We searched the databases such as Cochrane library, Cochrane Central Register of Controlled Trials, Embase, OVID, and Web of Science from January 1990 to March 20, 2020, and performed meta-analysis using Stata MP Version 13.0.

RESULTS

We performed meta-analysis on 12 studies that included a total of 395 patients with DCM. Overall, IA treatment significantly improved the left ventricular ejection fraction (6.01, 95% confidence interval [CI] [4.84-7.19]), reduced the left ventricular end diastolic diameter (-3.62, 95% CI [-4.06 to -3.19]), reduced severity of symptoms according to the New York Heart Association (NYHA) functional classification (-1.37, 95% CI [-1.73 to -1.02]) as compared with the controls, but had no effect on values for safety parameters (1.13, 95% CI [0.58-2.19]).

CONCLUSIONS

Results of this meta-analysis indicated that the IA treatment can improve the left ventricular ejection fraction, reduce left ventricular end diastolic diameter, and thus improve clinical outcome in DCM patients. However, further evidence are required to validate the relative safety of IA treatment. Multi-center, double blind studies should be conducted to elucidate the precise effect of IA treatment in DCM patients.

Vibrational spectroscopy as a powerful tool for follow-up immunoadsorption therapy treatment of dilated cardiomyopathy - a case report

Dilated cardiomyopathy (DCM) is a leading cardiomyopathy condition and is the leading reason for heart transplantation. Due to high etiologic and genetic heterogeneity of the pathologies, different therapeutic treatment strategies are available and have been successful for different treatments. Immunoadsorption (IA) therapy removes the circulating anticardiac antibodies and improves the left ventricular function in substantial proportion of DCM patients. Powerful, non-invasive analytical tools are highly desired to investigate the efficiency and success of IA therapy. In this contribution, we followed the changes of a female DCM patient undergoing IA therapy at different treatment time points in a label-free, non-invasive manner from blood samples (plasma and serum) on the basis of vibrational spectroscopy (Raman scattering and IR absorption). Chemometric methods, including dimension reduction and statistical modeling, were used to interpret spectral data. The impact of different time points of the IA treatment can be identified in both the plasma and serum, using both techniques, with high accuracy. The removal of antibodies of immunoglobulin G (IgG) group during IA therapy and their restoration was reflected in both Raman and FTIR spectra. Relative changes in the spectral bands assigned to IgG agreed well with the immunoturbidimetry measurement of total IgG. Successful clinical treatment was accompanied by spectral differences between vibrational spectra obtained at initial disease state and 11 months after the IA treatment. The long-term follow-up of the patient reveals the stabilization of the health state after therapy. It is noteworthy that the treatment time points were distinguished with a better accuracy using spectra from plasma compared to those from serum samples, which might indicate the involvement of corresponding proteins in the coagulation. Vibrational spectroscopy is a powerful tool for personalized medicine to follow-up the treatment success of IA therapy for the DCM disorder.

Apheresis therapies for NMOSD attacks: A retrospective study of 207 therapeutic interventions

Objective

To analyze whether 1 of the 2 apheresis techniques, therapeutic plasma exchange (PE) or immunoadsorption (IA), is superior in treating neuromyelitis optica spectrum disorder (NMOSD) attacks and to identify predictive factors for complete remission (CR).

Methods

This retrospective cohort study was based on the registry of the German Neuromyelitis Optica Study Group, a nationwide network established in 2008. It recruited patients with neuromyelitis optica diagnosed according to the 2006 Wingerchuk criteria or with aquaporin-4 (AQP4-ab)-antibody-seropositive NMOSD treated at 6 regional hospitals and 16 tertiary referral centers until March 2013. Besides descriptive data analysis of patient and attack characteristics, generalized estimation equation (GEE) analyses were applied to compare the effectiveness of the 2 apheresis techniques. A GEE model was generated to assess predictors of outcome.

Results

Two hundred and seven attacks in 105 patients (87% AQP4-ab-antibody seropositive) were treated with at least 1 apheresis therapy. Neither PE nor IA was proven superior in the therapy of NMOSD attacks. CR was only achieved with early apheresis therapy. Strong predictors for CR were the use of apheresis therapy as first-line therapy (OR 12.27, 95% CI: 1.04-144.91, p = 0.047), time from onset of attack to start of therapy in days (OR 0.94, 95% CI: 0.89-0.99, p = 0.014), the presence of AQP4-ab-antibodies (OR 33.34, 95% CI: 1.76-631.17, p = 0.019), and monofocal attack manifestation (OR 4.71, 95% CI: 1.03-21.62, p = 0.046).

Conclusions

Our findings suggest early use of an apheresis therapy in NMOSD attacks, particularly in AQP4-ab-seropositive patients. No superiority was shown for one of the 2 apheresis techniques.

Classification of evidence

This study provides Class IV evidence that for patients with NMOSD, neither PE nor IA is superior in the treatment of attacks.

Inflammatory Cardiomyopathic Syndromes

Inflammatory activation occurs in nearly all forms of myocardial injury. In contrast, inflammatory cardiomyopathies refer to a diverse group of disorders in which inflammation of the heart (or myocarditis) is the proximate cause of myocardial dysfunction, causing injury that can range from a fully recoverable syndrome to one that leads to chronic remodeling and dilated cardiomyopathy. The most common cause of inflammatory cardiomyopathies in developed countries is lymphocytic myocarditis most commonly caused by a viral pathogenesis. In Latin America, cardiomyopathy caused by Chagas disease is endemic. The true incidence of myocarditis is unknown to the limited utilization and the poor sensitivity of endomyocardial biopsies (especially for patchy diseases such as lymphocytic myocarditis and sarcoidosis) using the gold-standard Dallas criteria. Emerging immunohistochemistry criteria and molecular diagnostic techniques are being developed that will improve diagnostic yield, provide additional clues into the pathophysiology, and offer an application of precision medicine to these important syndromes. Immunosuppression is recommended for patients with cardiac sarcoidosis, giant cell myocarditis, and myocarditis associated with connective tissue disorders and may be beneficial in chronic viral myocarditis once virus is cleared. Further trials of immunosuppression, antiviral, and immunomodulating therapies are needed. Together, with new molecular-based diagnostics and therapies tailored to specific pathogeneses, the outcome of patients with these disorders may improve.

Safety and Efficacy of Immunoadsorption as an Add-On to Medical Treatment in Patients with Severe Idiopathic Pulmonary Arterial Hypertension

BACKGROUND

Despite optimized medical therapy, severe idiopathic pulmonary arterial hypertension (IPAH) is a devastating disease with a poor outcome. Autoantibodies have been detected in IPAH that can contribute to worsening of the disease.

OBJECTIVES

The objective of this prospective, open-label, single-arm, multicenter trial was to evaluate the safety and efficacy of immunoadsorption (IA) as an add-on to optimized medical treatment for patients with IPAH.

METHODS

A total of 10 IPAH patients received IA over 5 days. Their clinical parameters, including hemodynamics measured by right heart catheter, were assessed at baseline and after 3 and 6 months. The primary endpoint was the change in pulmonary vascular resistance (PVR). Secondary endpoints included the change in 6-min walking distance, quality of life, safety, and plasma levels of IgG and autoantibodies.

RESULTS

The evaluation of the 10 IPAH patients (75% female; 51 ± 12 years; 166 ± 10 cm; WHO functional class III; 53% on combination therapy) revealed that IA was a safe procedure that efficiently removed IgG and autoantibodies from the circulation. After 3 months, the mean PVR improved significantly by 13.2% (p = 0.03) and the cardiac index improved by 13.1%, but no significant changes were found in 6-min walking distance. The quality of life physical functioning subscale score significantly improved after 6 months. The serious adverse events in 3 patients were possibly related to IA and included pneumonia, temporary disturbance in attention, and thrombocytopenia.

CONCLUSIONS

IA as an add-on to targeted medical treatment for IPAH is a safe procedure with beneficial effects on hemodynamics, especially in patients with high levels of autoantibodies. Larger-scale controlled studies are needed to assess its efficacy in IPAH and to identify responders.

Role of Adaptive Immunity in the Development and Progression of Heart Failure: New Evidence

Heart failure (HF) is considered the endpoint of a variety of cardiac diseases, which are the leading cause of death in adults and considered a growing pandemic worldwide. Independent of the initial form of cardiac injury, there is evidence linking the involvement of the immune system. In HF there is evidence of the participation of T_H1, and T_H17 cells, which account for sustained pathological chronic inflammation, cell migration, and the induction of specific pathological phenotypes of mononuclear cells. Of equal or even higher relevance are the B lymphocyte activation mechanisms that include production of pro-inflammatory cytokines, chemokines, and cardiac autoantibodies with or without activation of the complement proteins. Both of these unbalanced T- and B-cell pathways of the adaptive immune system are associated with cardiomyocyte death and tissue remodeling by fibrosis leading to a dysfunctional heart. At this time, therapy with neutralizing antibodies and the use of anti-cytokine immunomodulators to counteract the immune system effects have reached a plateau of mixed results in clinical trials. Nevertheless, recent evidence showed promising results in animal models that suggest that modulation of the adaptive immune system cells more than some of their effector molecules could have benefits in HF patients. This review summarizes the role of the adaptive immunity cells in HF, considering the sustained activation of adaptive immune system as a potential contributor to disease progression in humans and experimental models where its regulation provides a new therapeutic target.

Autoantibodies Specifically Against β1 Adrenergic Receptors and Adverse Clinical Outcome in Patients With Chronic Systolic Heart Failure in the β-Blocker Era: The Importance of Immunoglobulin G3 Subclass

OBJECTIVE

To elucidate the prevalence and role of β1 adrenergic receptor autoantibodies (β1AR-AAb) belonging to the immunoglobulin (Ig)G3 subclass in patients with heart failure (HF) treated with β-adrenergic blockers.

BACKGROUND

Several cardiac AAbs have been reported to be present in sera from patients with dilated cardiomyopathy and other etiologies. Among AAbs, those recognizing β1AR-AAbs show agonist-like effects, have detrimental effects on cardiomyocytes, and may induce persistent myocardial damage.

METHODS

We quantify total IgG and IgG3 subclass β1AR-AAb in subjects with chronic stable HF with long-term follow-up.

RESULTS

In our study cohort of 121 subjects, non-IgG3-β1AR-AAb and IgG3-β1AR-AAb were found to be positive in 20 (17%) and 26 patients (21%), respectively. The positive rate of IgG3-β1AR-AAb was significantly higher for those with nonischemic compared with ischemic HF etiology (27% vs 8%, P = .01), but the positive rate for non-IgG3-β1AR-AAb was similar between the 2 groups (18% vs 16%, respectively, P = NS). There were no significant differences in clinical and echocardiographic measures among total β1AR-AAb negative, non-IgG3-β1AR-AAb positive, and IgG3-β1AR-AAb positive groups at baseline. During 2.2 ± 1.2 years of follow-up, we observed similar rates of the composite endpoint of all-cause mortality, cardiac transplantation, or hospitalization resulting from HF between total IgG-β1AR-AAb negative and positive patients. However, the composite endpoint events were significantly more common in the patients without than in those with IgG3-β1AR-AAb (P = .048, log-rank test).

CONCLUSIONS

Presence of IgG3-β1AR-AAb, not total IgG, was associated with paradoxically more favorable outcomes in our cohort of patients with chronic systolic HF largely treated by β-blockers.

Immunoadsorption therapy for dilated cardiomyopathy using tryptophan column-A prospective, multicenter, randomized, within-patient and parallel-group comparative study to evaluate efficacy and safety

Over the past few decades, several cardiac autoantibodies have been reported in sera from patients with dilated cardiomyopathy (DCM). Immunoadsorption (IA) therapy is one of the therapeutic tools to remove such autoantibodies. The objective of this study was to investigate functional effects of IA therapy using a tryptophan column in severe DCM patients. Of 49 patients enrolled, 44 were randomized from 10 sites in Japan. IA therapy was conducted in 40 patients with DCM (refractory to standard therapy for heart failure, New York Heart Association [NYHA] class III/IV, left ventricular ejection fraction [LVEF] <30%). Mean echocardiographic LVEF was significantly improved (23.8 ± 1.3% to 25.9 ± 1.3%, P = 0.0015). However, mean radionuclide LVEF over 3 months of IA therapy was not significantly improved (20.8 ± 1.1% to 21.9 ± 1%, P = 0.0605). The cardiothoracic ratio was also significantly decreased (P = 0.0010). NYHA functional class (P < 0.0001), subjective symptoms assessed by a quality of life questionnaire (P = 0.0022), maximum oxygen consumption (P = 0.0074), and 6‐minute walk distance (P = 0.0050) were improved after IA therapy. Subgroup analysis revealed improvement of echocardiographic LVEF in patients with higher baseline autoantibody scores but not in those with lower scores. IA therapy improved subjective symptoms and exercise capacity in patients with refractory heart failure resulting from DCM. Favorable effect on cardiac function was noted in patients with higher autoantibody scores. J. Clin. Apheresis 31:535–544, 2016. © 2015 Wiley Periodicals, Inc.

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.

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.

High proportion of patients with end-stage heart failure regardless of aetiology demonstrates anti-cardiac antibody deposition in failing myocardium: humoral activation, a potential contributor of disease progression

AIMS

Various reports have raised the possibility of humoral immune responses as contributors for the progression of heart failure. Previous studies, however, have focused on the analysis of serum and documented circulating antibodies against a variety of cardiac proteins. However, there is little evidence on whether anti-cardiac antibodies are deposited in end-stage failing myocardium. Our objective was to determine whether or not there was evidence of deposition of anti-cardiac antibodies and/or activated complement components in end-stage failing human myocardium.

METHODS AND RESULTS

Myocardial samples were obtained from 100 end-stage heart failure patients and 40 donor control biopsies. Sections were cut and stained using standard fluorescent immunohistochemistry techniques with anti-human immunoglobulin G (IgG), IgG3, and C3c. Gel electrophoresis and protein identification by mass spectrometry were used to confirm the presence of IgG and its antigen. Immunoglobulin G was localized to the sarcolemma in 71% of patients, 48% of those being positive for the subtype IgG3. The proportion of patients with ischaemic heart disease that was positive for IgG was 65% and among those with non-ischaemic aetiologies was 76%. In a subgroup analysis, the presence of IgG and its subunits were confirmed by mass spectrometry and adenosine triphosphate synthase β subunit identified as an antigen. Complement was activated in 31% of all patients. The presence of IgG, IgG3, and C3c was directly correlated with the length of disease (r = 0.451, P = 0.006).

CONCLUSION

Evidence of anti-cardiac antibodies and complement activation was found in a large number of patients with end-stage cardiomyopathy regardless of the aetiology. Adenosine triphosphate synthase appears to be a new prominent antigenic stimulus; but more interestingly, the simultaneous co-existence of activated complement components suggests that this humoral mechanism may participate in disease progression.

The role of B-cells in heart failure

Heart failure is a complex disease that has great impact on morbidity and mortality in the general population. No recent therapies have proven to be effective; however, the discovery of new potential pathophysiological mechanisms involved in heart failure expression and progression could offer novel therapeutic strategies. A number of studies have shown that the immune system may be a central mediator in the development and progression of heart failure, and here we describe how the B-cell and B-cell-mediated pathways play specific roles in the heart failure state. Therapies aimed at B-cells, either blocking antibody production or inactivating B-cell function, may suggest potential new treatment strategies.

Targeting anti-beta-1-adrenergic receptor antibodies for dilated cardiomyopathy

Anti-beta-1-adrenergic receptor antibodies (anti-β1AR Abs) have long been implicated in the pathogenesis of dilated cardiomyopathy (DCM). It is believed that these autoantibodies bind to and constitutively stimulate the β1AR to promote pathological cardiac remodelling and β1AR desensitization and downregulation. The prevalence of anti-β1AR Abs in patients with DCM ranges from 26% to 60%, and the presence of these autoantibodies correlates with a poor prognosis. Several small studies have shown improvements in functional status, haemodynamics, and biomarkers of heart failure upon removal or neutralization of these antibodies from the sera of affected patients. Traditionally, removal of anti-β1AR Abs required immunoadsorption therapy with apheresis columns directed against human immunoglobulins (Igs) and subsequent i.v. Ig infusion, thereby essentially performing a plasma exchange transfusion. However, recent advances have allowed the development of small peptides and nucleotide sequences that specifically target and neutralize anti-β1AR Abs, providing a hopeful avenue for future drug development to treat DCM. Herein, we briefly review the clinical literature of therapy directed against anti-β1AR Abs and highlight the opportunity for further research and development in this area.

Measurement of antibody effects on cellular function of isolated cardiomyocytes

Dilated cardiomyopathy (DCM) is one of the main causes for heart failure in younger adults. Although genetic disposition and exposition to toxic substances are known causes for this disease in about one third of the patients, the origin of DCM remains largely unclear. In a substantial number of these patients, autoantibodies against cardiac epitopes have been detected and are suspected to play a pivotal role in the onset and progression of the disease. The importance of cardiac autoantibodies is underlined by a hemodynamic improvement observed in DCM patients after elimination of autoantibodies by immunoadsorption. A variety of specific antigens have already been identified and antibodies against these targets may be detected by immunoassays. However, these assays cannot discriminate between stimulating (and therefore functionally effective) and blocking autoantibodies. There is increasing evidence that this distinction is crucial. It can also be assumed that the targets for a number of cardiotropic antibodies are still unidentified and therefore cannot be detected by immunoassays. Therefore, we established a method for the detection of functionally active cardiotropic antibodies, independent of their respective antigen. The background for the method is the high homology usually observed for functional regions of cardiac proteins in between mammals. This suggests that cardiac antibodies directed against human antigens will cross-react with non-human target cells, which allows testing of IgG from DCM patients on adult rat cardiomyocytes. Our method consists of 3 steps: first, IgG is isolated from patient plasma using sepharose coupled anti-IgG antibodies obtained from immunoadsorption columns (PlasmaSelect, Teterow, Germany). Second, adult cardiomyocytes are isolated by collagenase perfusion in a Langendorff perfusion apparatus using a protocol modified from previous works. The obtained cardiomyocytes are attached to laminin-coated chambered coverglasses and stained with Fura-2, a calcium-selective fluorescent dye which can be easily brought into the cell to observe intracellular calcium (Ca(2+)) contents. In the last step, the effect of patient IgG on the cell shortening and Ca(2+) transients of field stimulated cardiomyocytes is monitored online using a commercial myocyte calcium and contractility monitoring system (IonOptix, Milton, MA, USA) connected to a standard inverse fluorescent microscope.

The number of regulatory T cells correlates with hemodynamic improvement in patients with inflammatory dilated cardiomyopathy after immunoadsorption therapy

Inflammatory DCM (iDCM) may be related to autoimmune processes. An immunoadsorption (IA) has been reported to improve cardiac hemodynamics. The benefit of IA is probably related to the removal of autoantibodies. A recent study suggests additional effects of IA on the T cell-mediated immune reactions, especially on regulatory T cells (Tregs). In this prospective study, the correlation between the level of Tregs and improvement of myocardial contractility in response to IA in patients with iDCM was investigated. Patients (n = 18) with iDCM, reduced left ventricular (LV) ejection fraction (<35%), were enrolled for IA. Before and 6 months after IA, LV systolic function was assessed by echocardiography, and blood levels of Tregs were quantified by FACS analysis. Patients (n = 12) with chronic ischaemic heart failure and comparable reduced LV-EF served as controls. IA improved LV-EF in 12 of 18 patients at 6-month follow-up. These patients were classified as 'IA responder'. In 6 patients, LV-EF remained unchanged. At baseline, IA responder and non-responder subgroups showed similar values for C-reactive protein, white blood cells, lymphocytes and T helper cells, but they differ for the number of circulating Tregs (responder: 2.32 ± 1.38% versus non-responder: 4.86 ± 0.28%; P < 0.01). Tregs increased significantly in the IA responders, but remained unchanged in the IA non-responders. In patients with ischaemic cardiomyopathy, none of these values changed over time. A low level of Tregs in patients with chronic iDCM may characterize a subset of patients who do best respond to IA therapy.

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.

Specific immunoadsorption therapy using a tryptophan column in patients with refractory heart failure due to dilated cardiomyopathy

BACKGROUND

Certain cardiac-specific autoantibodies found in patients with dilated cardiomyopathy (DCM) play a role in mediating myocardial damage and fatal ventricular arrhythmias resulting in sudden cardiac death. Immunoadsorption therapy (IA) is one of the therapeutic tools to remove such autoantibodies. Clinical studies from Germany have shown that nonspecific IA using columns loaded by sheep antihuman IgG or protein A improved hemodynamic data and affected favorably cardiac function and survival in patients with heart failure (HF) due to DCM. The goal of this study is to determine if IA therapy using the high-profile tryptophan column, which has high affinity for IgG3 subclass, affects favorably cardiac function in patients with severe HF who are refractory to conventional therapy.

METHODS AND RESULTS

IA therapy was conducted in 16 patients with DCM (age 53 ± 4, male 8, New York Heart Association functional class III/IV, mean ejection fraction 18 ± 2%). Study subjects had autoantibodies directed against either β1-adrenergic or M2-muscarinic receptors. Plasma brain natriuretic peptide levels were significantly decreased after IA (P = 0.016). Plasma inflammatory cytokines including interleukin-6 and tumor necrosis factor-α did not change after each session of IA. Six-minute walk distance was significantly increased after IA (P = 0.01). Left ventricular ejection fraction increased by 3% 3 months after IA (P = 0.039).

CONCLUSIONS

Our initial experience demonstrated safety and short-term efficacy of IA using a new IgG3-specific tryptophan column for patients with advanced HF due to DCM. Long-term follow-up is needed to confirm the effects on cardiac function and morbidity/mortality in such patients.

Impact of troponin I-autoantibodies in chronic dilated and ischemic cardiomyopathy

The aim of this study was to investigate the prognostic value of circulating troponin I (TNI)-autoantibodies in plasma of patients with chronic heart failure. Sera of 390 heart failure patients were tested for the presence of anti-TNI antibodies by enzyme-linked immunosorbent assay (ELISA), including 249 (63.8% of total) patients with dilated cardiomyopathy (DCM) and 141 (36.2% of total) patients with ischemic cardiomyopathy (ICM). A total of 72 patients (18.5% of total) were female and 318 (81.5% of total) were male. Mean patient age was 54.6 ± 11.3 years and mean follow-up time was 3.8 ± 3.2 years. TNI-autoantibodies (titer of ≥1:40) were detected in 73 out of 390 patients (18.7% of total). In TNI-autoantibody positive patients mean left ventricular ejection fraction (LVEF) was 27.6 ± 5.8%, compared to 25.8 ± 5.9% in TNI-autoantibody negative patients, P = 0.03. The combined end-point of death (n = 118, 30.3% of total) or heart transplantation (HTX) (n = 44, 11.3% of total) was reached in 162 patients (41.5% of total). Kaplan-Meier analysis demonstrated superior survival (combined end-point of death or HTX) in patients with DCM versus ICM (P = 0.0198) and TNI-autoantibody positive patients versus TNI-autoantibody negative patients (P = 0.0348). Further subgroup analysis revealed a favorable outcome in TNI-positive patients with heart failure if the patients suffered from DCM (P = 0.0334), whereas TNI-autoantibody status in patients with ICM was not associated with survival (P = 0.8486). In subsequent multivariate Weibull-analysis, a positive TNI serostatus was associated with a significantly lower all-cause mortality in DCM patients (P = 0.0492). The presence of TNI-autoantibodies in plasma is associated with an improved survival in patients with chronic DCM, but not ICM. This might possibly indicate a prophylactic effect of TNI-autoantibodies in this subgroup of patients, encouraging further studies into possible protective effects of antibodies against certain cardiac target structures.

Guidelines on the use of therapeutic apheresis in clinical practice--evidence-based approach from the Apheresis Applications Committee of the American Society for Apheresis

The American Society for Apheresis (ASFA) Apheresis Applications Committee is charged with a review and categorization of indications for therapeutic apheresis. Beginning with the 2007 ASFA Special Issue (fourth edition), the subcommittee has incorporated systematic review and evidence-based approach in the grading and categorization of indications. This Fifth ASFA Special Issue has further improved the process of using evidence-based medicine in the recommendations by refining the category definitions and by adding a grade of recommendation based on widely accepted GRADE system. The concept of a fact sheet was introduced in the Fourth edition and is only slightly modified in this current edition. The fact sheet succinctly summarizes the evidence for the use of therapeutic apheresis. The article consists of 59 fact sheets devoted to each disease entity currently categorized by the ASFA as category I through III. Category IV indications are also listed.

Effects of protein A immunoadsorption in patients with chronic dilated cardiomyopathy

OBJECTIVES

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Immunoadsorption in dilated cardiomyopathy: long-term reduction of cardiodepressant antibodies

BACKGROUND

Disturbances of humoral immunity have been described in dilated cardiomyopathy (DCM), and a number of antibodies against cardiac cell proteins have been identified. Previous studies showed that immunoadsorption therapy with subsequent IgG substitution (IA/IgG) enhances cardiac function, and that removal of cardiodepressant antibodies may represent one essential mechanism of this therapy. The long-term effect of IA/IgG on the level of cardiodepressant antibodies remains to be elucidated.

METHODS

A total of 17 patients with DCM were observed up to 12 months after IA/IgG. Echocardiographic measurements were performed at baseline, 3, 6 and 12 months after therapy. Cardiodepressant antibodies were detected by incubation of rat cardiomyocytes with purified patients' IgG and recording of contractility and Ca(2+) ratio.

RESULTS

In contrast to patients without cardiodepressant antibodies before IA/IgG, patients with negative inotropic antibodies showed an improvement of left ventricular ejection fraction (LVEF) from 33.8 +/- 1.7% to 44.7 +/- 2.7%; 44.5 +/- 2.3% and 51.8 +/- 1.7% after 3, 6 and 12 months (P < 0.001 vs. baseline, P < 0.05 vs. LVEF of non-cardiodepressant group). Immediately after IA/IgG therapy, no cardiodepressant effects of patients' IgG on isolated cardiomyocytes were detectable, and this effect remained diminished until 6 months after IA/IgG (P < 0.001 for contractility and Ca(2+) ratio). Compared with the levels after 3 and 6 months, cardiodepressant antibodies reoccured after 12 months (P = 0.067 for contractility, P < 0.05 for Ca(2+) ratio vs. 6 months after IA/IgG). However, the negative inotropic reaction is still diminished compared with the reaction before IA/IgG.

CONCLUSION

IA/IgG therapy induces long-term reduction of negative inotropic antibodies. After 12 months, however, re-increase of negative inotropic antibodies cannot be excluded.

Complete elimination of cardiodepressant IgG3 autoantibodies by immunoadsorption in patients with severe heart failure

BACKGROUND

Cardiodepressant IgG3 autoantibodies (CD-Abs) can be targeted by apheresis. Using blinded measurements of CD-Abs before and after immunoadsorption (IA), the cardiac function of patients who did or did not achieve complete CD-Abs elimination was compared.

METHODS AND RESULTS

Autoantibodies were completely removed from 18 patients with heart failure (New York Heart Association class 3 or 4, left ventricular ejection fraction (LVEF) <30%) using a selective IgG3 adsorption column. All patients had anti-beta1-adrenergic and/or M2-muscarinic autoantibodies before IA, and all LVEF were measured on radionuclide ventriculography. CD-Abs were measured before and after IA, and patient status was blinded until all measurements were collected. Treatment was defined as complete when CD-Abs status changed from positive to negative after IA. Other instances were defined as incomplete. Six-min walk test results and brain natriuretic peptide levels improved significantly after IA (P<0.01). The increase in LVEF 3 months after IA was significantly greater after complete treatment in comparison to the incomplete treatment group (19+/-8-29+/-9% vs 18+/-9-17+/-8%, P<0.01). Cardiac insufficiency events were also more frequent in the incomplete treatment group.

CONCLUSIONS

Complete elimination of CD-Abs with apheresis may be related to improved cardiac function in the treatment of heart failure.

Myocarditis

Myocarditis is an uncommon, potentially life-threatening disease that presents with a wide range of symptoms in children and adults. Viral infection is the most common cause of myocarditis in developed countries, but other etiologies include bacterial and protozoal infections, toxins, drug reactions, autoimmune diseases, giant cell myocarditis, and sarcoidosis. Acute injury leads to myocyte damage, which in turn activates the innate and humeral immune system, leading to severe inflammation. In most patients, the immune reaction is eventually down-regulated and the myocardium recovers. In select cases, however, persistent myocardial inflammation leads to ongoing myocyte damage and relentless symptomatic heart failure or even death. The diagnosis is usually made based on clinical presentation and noninvasive imaging findings. Most patients respond well to standard heart failure therapy, although in severe cases, mechanical circulatory support or heart transplantation is indicated. Prognosis in acute myocarditis is generally good except in patients with giant cell myocarditis. Persistent, chronic myocarditis usually has a progressive course but may respond to immunosuppression.

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

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

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

OBJECTIVES

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Immunoadsorption as treatment option in dilated cardiomyopathy

Abnormalities of the cellular and humoral immune system have been described in patients with dilated cardiomyopathy (DCM). Various circulating cardiac autoantibodies have been detected among DCM patients. Circulating antibodies are extractable by immunoadsorption (IA). Recent open controlled pilot studies have consequently shown that removal of circulating antibodies by IA induces improvement of cardiac function in DCM. IA, furthermore, decreases myocardial inflammation. In vitro data indicate that cardiodepressive antibodies play an important role in cardiac dysfunction of DCM patients; removal of these antibodies may accordingly represent the essential mechanism of IA in DCM. Furthermore, detection of cardiodepressive antibodies predicts hemodynamic benefits during IA. These antibodies belong to immunoglobulin G subclass 3. Recent data indicate that newly detected sarcolemmal Fc(gamma) receptors IIa are involved in the functional effects of cardiac autoantibodies.

Recent insights into the role of autoimmunity in idiopathic dilated cardiomyopathy

Dilated cardiomyopathy is a devastating disease associated with poor outcomes. Although the etiology of this disease remains largely unknown, so-called "idiopathic" dilated cardiomyopathy (iDCM) is associated with evidence of an autoimmune process that may be contributing to the pathophysiology of this disease. Indeed, iDCM shares many characteristics with other autoimmune diseases, including an association with systemic and organ-specific inflammation, an association with viral infections, a genetic predisposition, and a correlation with specific human leukocyte antigen subtypes. Additionally, numerous pathologic cardiac-specific autoantibodies have been associated with iDCM, including those against alpha-myosin, the beta(1)-adrenoceptor, and cardiac troponin I. This review highlights the emerging evidence regarding autoimmune characteristics of iDCM, and summarizes the data of specific immunomodulatory therapies used to target autoimmune mechanisms in the treatment of patients with this devastating disease.

Recommendations for the use of immunoapheresis in the treatment of autoimmune bullous diseases

Despite the use of high-dose systemic corticosteroids in combination with other immunosuppressants, in some patients with autoimmune bullous diseases only insufficient improvement is achieved. In these cases and in acute severe disease, adjuvant immunoapheresis has been increasingly used. A consensus meeting was held in mid-2005 in Hamburg, aiming at developing guidelines for the use of immunoapheresis in the treatment of autoimmune bullous diseases. This paper summarizes the experts' recommendations.