Detection of anti-β1-AR autoantibodies in heart failure by a cell-based competition ELISA

Adrenoceptors and Hypertension

Hypertension is a very prevalent condition associated with high mortality and morbidity, secondary to changes resulting in blood vessels and resultant end-organ damage. Haemodynamic changes, including an initial rise in cardiac output followed by an increase in total peripheral resistance, denote the early changes associated with borderline or stage 1 hypertension, especially in young men. Increased sodium reabsorption leading to kidney damage is another mechanism proposed as one of the initial triggers for essential hypertension. The underlying pathophysiological mechanisms include catecholamine-induced α1- and ß1-adrenoceptor stimulation, and renin-angiotensin-aldosterone system activation leading to endothelial dysfunction which is believed to lead to persistent blood pressure elevation.α1 blockers, α2 agonists, and ß blockers were among the first oral anti-hypertensives. They are no longer first-line therapy after outcome trials did not demonstrate any benefits over and above other agents, despite similar blood pressure reductions. Angiotensin-converting enzyme inhibitors (or angiotensin receptor blockers), calcium channel blockers, and thiazide-like diuretics are now considered the first line of therapy, although adrenoceptor agents still have a role as second- or third-line therapy. The chapter also highlights hypertension in specific medical conditions such as pregnancy, phaeochromocytoma, hyperthyroidism, portal hypertension, pulmonary arterial hypertension, and ocular hypertension, to provide an overview for clinicians and researchers interested in the role of adrenoceptors in the pathophysiology and management of hypertension.

S100a9 inhibits Atg9a transcription and participates in suppression of autophagy in cardiomyocytes induced by β1-adrenoceptor autoantibodies

BACKGROUND

Cardiomyocyte death induced by autophagy inhibition is an important cause of cardiac dysfunction. In-depth exploration of its mechanism may help to improve cardiac dysfunction. In our previous study, we found that β1-adrenergic receptor autoantibodies (β1-AAs) induced a decrease in myocardial autophagy and caused cardiomyocyte death, thus resulting in cardiac dysfunction. Through tandem mass tag (TMT)-based quantitative proteomics, autophagy-related S100a9 protein was found to be significantly upregulated in the myocardial tissue of actively immunized mice. However, whether S100a9 affects the cardiac function in the presence of β1-AAs through autophagy and the specific mechanism are currently unclear.

METHODS

In this study, the active immunity method was used to establish a β1-AA-induced mouse cardiac dysfunction model, and RT-PCR and western blot were used to detect changes in gene and protein expression in cardiomyocytes. We used siRNA to knockdown S100a9 in cardiomyocytes. An autophagy PCR array was performed to screen differentially expressed autophagy-related genes in cells transfected with S100a9 siRNA and negative control siRNA. Cytoplasmic nuclear separation, co-immunoprecipitation (Co-IP), and immunofluorescence were used to detect the binding of S100a9 and hypoxia inducible factor-1α (HIF-1α). Finally, AAV9-S100a9-RNAi was injected into mice via the tail vein to knockdown S100a9 in cardiomyocytes. Cardiac function was detected via ultrasonography.

RESULTS

The results showed that β1-AAs induced S100a9 expression. The PCR array indicated that Atg9a changed significantly in S100a9siRNA cells and that β1-AAs increased the binding of S100a9 and HIF-1α in cytoplasm. Knockdown of S100a9 significantly improved autophagy levels and cardiac dysfunction.

CONCLUSION

Our research showed that β1-AAs increased S100a9 expression in cardiomyocytes and that S100a9 interacted with HIF-1α, which prevented HIF-1α from entering the nucleus normally, thus inhibiting the transcription of Atg9a. This resulted in autophagy inhibition and cardiac dysfunction.

Prognostic Value of β1 Adrenergic Receptor Autoantibody and Soluble Suppression of Tumorigenicity-2 in Patients With Acutely Decompensated Heart Failure

Background

Both β1 adrenergic receptor autoantibody (β1-AA) and soluble suppression of tumorigenicity-2 (sST2) take a role in the pathological remodeling of heart failure. However, limited studies investigated the correlation between the expression of β1-AA and sST2 in patients with acutely decompensated heart failure (ADHF).

Objective

To explore the correlation between β1-AA and sST2, and evaluate their prognostic value in patients with ADHF.

Methods

Patients who were admitted for ADHF were included. The N-terminal pro-brain natriuretic peptide (NT-proBNP), sST2, and β1-AA in blood samples were tested at hospital admission and then followed up for assessing the outcomes. Pearson correlation analysis was used to explore the correlation between β1-AA and sST2. The effects of β1-AA, sST2, or the combination of them on the all-cause mortality of patients with ADHF were assessed by Multivariate Cox regression analysis.

Results

There were 96 patients with ADHF and 96 control populations enrolled. The β1-AA was significantly higher in ADHF than in the control group (0.321 ± 0.06 vs. 0.229 ± 0.04, P = 0.000). Pearson correlation analysis showed that β1-AA was positively correlated with sST2 (r = 0.593), NT-proBNP (r = 0.557), Procalcitonin (r = 0.176), and left ventricular end-diastolic diameter (r = 0.315), but negatively correlated with triglycerides (r = −0.323), and left ventricular ejection fraction (r = −0.430) (all P < 0.05) in ADHF. Patients with ADHF, complicated with both high β1-AA and sST2, showed the highest all-cause mortality during an average of 25.5 months of follow-up. Multivariate Cox regression showed the combination of both high β1-AA and sST2 independently correlated with the all-cause mortality after adjustment for other risk factors (hazard ratio 3.348, 95% CI 1.440 to 7.784, P = 0.005). After adding with β1-AA and sST2, the area under the curves for the prognostic all-cause mortality could increase from 0.642 to 0.748 (P = 0.011).

Conclusion

The β1-AA is positively correlated with sST2 in patients with ADHF. Elevated plasma β1-AA and sST2 level in patients with ADHF are associated with poorer prognoses.

Unmasking features of the auto-epitope essential for β1 -adrenoceptor activation by autoantibodies in chronic heart failure

Aims

Chronic heart failure (CHF) can be caused by autoantibodies stimulating the heart via binding to first and/or second extracellular loops of cardiac β₁‐adrenoceptors. Allosteric receptor activation depends on conformational features of the autoantibody binding site. Elucidating these features will pave the way for the development of specific diagnostics and therapeutics. Our aim was (i) to fine‐map the conformational epitope within the second extracellular loop of the human β₁‐adrenoceptor (β₁EC_II) that is targeted by stimulating β₁‐receptor (auto)antibodies and (ii) to generate competitive cyclopeptide inhibitors of allosteric receptor activation, which faithfully conserve the conformational auto‐epitope.

Methods and results

Non‐conserved amino acids within the β₁EC_II loop (compared with the amino acids constituting the EC_II loop of the β₂‐adrenoceptor) were one by one replaced with alanine; potential intra‐loop disulfide bridges were probed by cysteine–serine exchanges. Effects on antibody binding and allosteric receptor activation were assessed (i) by (auto)antibody neutralization using cyclopeptides mimicking β₁EC_II ± the above replacements, and (ii) by (auto)antibody stimulation of human β₁‐adrenoceptors bearing corresponding point mutations. With the use of stimulating β₁‐receptor (auto)antibodies raised in mice, rats, or rabbits and isolated from exemplary dilated cardiomyopathy patients, our series of experiments unmasked two features of the β₁EC_II loop essential for (auto)antibody binding and allosteric receptor activation: (i) the NDPK^211–214 motif and (ii) the intra‐loop disulfide bond C²⁰⁹↔C²¹⁵. Of note, aberrant intra‐loop disulfide bond C²⁰⁹↔C²¹⁶ almost fully disrupted the functional auto‐epitope in cyclopeptides.

Conclusions

The conformational auto‐epitope targeted by cardio‐pathogenic β₁‐receptor autoantibodies is faithfully conserved in cyclopeptide homologues of the β₁EC_II loop bearing the NDPK^211–214 motif and the C²⁰⁹↔C²¹⁵ bridge while lacking cysteine C²¹⁶. Such molecules provide promising tools for novel diagnostic and therapeutic approaches in β₁‐autoantibody‐positive CHF.

Autoantibodies Against β1-Adrenoceptor Exaggerated Ventricular Remodeling by Inhibiting CTRP9 Expression

Background

Autoantibodies against the second extracellular loop of the β₁‐adrenoceptor (β₁‐AA) act similarly to agonist of β₁‐adrenergic receptor, which plays an important role in the pathophysiological characteristics of ventricular remodeling. Recently, considerable lines of evidence have suggested that CTRP9 (C1q tumor necrosis factor–related protein 9) is a potent cardioprotective cardiokine and protects the heart from ventricular remodeling. The aim of this study was to determine the role of CTRP9 in ventricular remodeling induced by β₁‐AA.

Methods and Results

Blood samples were collected from 131 patients with coronary heart disease and 131 healthy subjects. The serum levels of β₁‐AA and CTRP9 were detected using ELISA. The results revealed that CTRP9 levels in β₁‐AA–positive patients were lower than those in β₁‐AA–negative patients, and serum CTRP9 concentrations were inversely correlated with β₁‐AA. β₁‐AA monoclonal antibodies (β₁‐AAmAbs) were administered in mice with and without rAAV9‐cTnT‐Full Ctrp9‐FLAG virus for 8 weeks. Reverse transcription–polymerase chain reaction/Western analysis showed that cardiomyocyte CTRP9 expression was significantly reduced in β₁‐AAmAb–treated mice. Moreover, compared with the β₁‐AAmAb alone group, cardiac‐specific CTRP9 overexpression improved cardiac function, attenuated adverse remodeling, and ameliorated cardiomyocyte apoptosis and fibrosis. Mechanistic studies demonstrated that CTRP9 overexpression decreased the levels of G‐protein–coupled receptor kinase 2 and promoted the activation of AMP‐dependent kinase pathway. However, cardiac‐specific overexpression of CTRP9 had no effect on the levels of cAMP and protein kinase A activity elevated by β₁‐AAmAb.

Conclusions

This study provides the first evidence that the long‐term existence of β₁‐AAmAb suppresses cardiac CTRP9 expression and exaggerates cardiac remodeling, suggesting that CTRP9 may be a novel therapeutic target against pathologic remodeling in β₁‐AA–positive patients with coronary heart disease.

The inflammation-based modified Glasgow prognostic score is associated with survival in stable heart failure patients

AIMS

The progression of heart failure is presumably dependent on the individual inflammatory host response. The combination of the inflammatory markers, albumin, and C-reactive protein, termed modified Glasgow prognostic score (mGPS), has been derived from cancer patients and validated in multiple cohorts. This study aimed to investigate the impact of the easily available mGPS on survival of stable patients with heart failure with reduced ejection fraction (HFrEF).

METHODS AND RESULTS

Patients with stable HFrEF undergoing routine ambulatory care between January 2011 and November 2017 have been identified from a prospective registry at the Medical University of Vienna. Comorbidities, laboratory data as well as the nutritional risk index at baseline were assessed. All-cause mortality was defined as the primary study end point. The mGPS was calculated, and its association with heart failure severity and impact on overall survival were determined. Data were analysed for a total of 443 patients. The mGPS was 0 for 352 (80%), 1 for 76 (17%), and 2 for 14 (3%) patients, respectively. Elevation of mGPS was associated with worsening of routine laboratory parameters linked to prognosis, especially NT-proBNP [median 1830 pg/mL (IQR 764-3455) vs. 4484 pg/mL (IQR 1565-8003) vs. 6343 pg/mL (IQR 3750-15401) for mGPS 0, 1, and 2, respectively; P < 0.001] and nutritional risk index. In the Cox regression analysis, the increase of mGPS was associated with adverse outcome in the univariate analysis [crude hazard ratio 3.00 (95% CI 2.14-4.21), P < 0.001] and after adjustment for multiple covariates as age, gender, body mass index, and glomerular filtration rate as well as heart failure severity reflected by NT-proBNP and New York Heart Association class [adj. hazard ratio 1.87 (95% CI 1.19-2.93), P = 0.006].

CONCLUSIONS

Enhanced inflammation and nutritional depletion are more common in advanced heart failure. The inflammation-based score mGPS predicts survival in HFrEF patients independently of NT-proBNP emphasizing the significance of the individual pro-inflammatory response on prognosis.

Endoplasmic reticulum stress contributed to β1-adrenoceptor autoantibody-induced reduction of autophagy in cardiomyocytes

Autophagy reduction has been confirmed as an important mechanism in apoptosis induction. Our previous study showed that decreased autophagy induced by β1-adrenoceptor autoantibodies (β1-AAs) enhanced cardiomyocyte apoptosis and contributed to heart failure progression. Endoplasmic reticulum stress (ERS) is known to be an important mechanism in intracellular homeostasis and is closely related to autophagy. However, ERS in β1-AA-induced autophagy dysfunction of cardiomyocytes remains unclear. In this study, we used an active immunization rat model and H9c2 cardiomyocytes to study the role of ERS in β1-AA-induced autophagy. Results showed that prolonged action of β1-AAs significantly reduced the autophagy of myocardial tissues and H9c2 cardiomyocytes, and ERS and its related apoptotic pathways were significantly activated. Moreover, mRFP-GFP-LC3 double-labeled adenoviruses were used to detect cardiomyocyte autophagic flux to confirm that β1-AAs caused a significant decrease in autophagic flux in H9c2 cardiomyocytes. The ERS inhibitor, 4-phenylbutyrate (4-PBA), partially attenuated the β1-AA-induced reduction of cardiomyocyte autophagy, consistent with the effect of the mammalian target of rapamycin inhibitor rapamycin (Rapa). Compared to the pretreatment with 4-PBA or Rapa alone, pretreatment with the combination of 4-PBA and Rapa had a greater effect on attenuating the β1-AA-induced decrease in autophagy and β1-AA-induced apoptosis in cardiomyocytes. This study provides an experimental basis for the role of β1-AAs in the homeostatic maintenance of cardiomyocytes in patients with heart failure with respect to autophagy and ERS.

Cyclopeptide COR-1 to treat beta1-adrenergic receptor antibody-induced heart failure

RATIONALE

Despite advances in pharmacotherapy, heart failure still incurs significant morbidity and mortality. Stimulating antibodies directed against the secondextracellular loop of the human ß1-adrenergic receptor (anti-ß1EC2) cause myocyte damage and heart failure in rats. This receptor domain is 100% homologous between rats and humans.

OBJECTIVE

ß1EC2-mimicking cyclopeptides (25-meric) markedly improved the development and/or course of anti-ß1EC2-mediated cardiomyopathy. Further developments should be investigated.

METHODS AND RESULTS

The shortened 18-meric cyclic peptide COR-1, in which one of the two disulphide bonds was removed to enable reproducible GMP production, can also be used to treat cardiomyopathic rats. Echocardiography, catheterization and histopathology of the rat hearts revealed that monthly intravenous administrations of COR-1 almost fully reversed the cardiomyopathic phenotype within 6 months at doses of 1 to 4 mg/kg body weight. Administration of COR-1 resulted in markedly reduced anti-ß1EC2-expressing memory B lymphocytes in the spleen despite continued antigenic boosts, but did not significantly decrease overall peripheral anti-ß1EC2 titers. COR-1 did not induce any anti-ß1EC2 or other immune response in naïve rats (corresponding to findings in healthy human volunteers). It did not cause any toxic side effects in GLP studies in dogs, rats or mice, and the "no observed adverse effect level" (NOAEL) exceeded the therapeutic doses by 100-fold.

CONCLUSION

The second generation immunomodulating epitope-mimicking cyclopeptide COR-1 (also termed JNJ-5442840) offers promise to treat immune-mediated cardiac diseases.

Decreased autophagy induced by β1-adrenoceptor autoantibodies contributes to cardiomyocyte apoptosis

It has been recognized that myocardial apoptosis is one major factor in the development of heart dysfunction and autophagy has been shown to influence the apoptosis. In previous studies, we reported that anti-β₁-adrenergic receptor autoantibodies (β₁-AABs) decreased myocardial autophagy, but the role of decreased autophagy in cardiomyocyte apoptosis remains unclear. In the present study, we used a β₁-AAB-immunized rat model to investigate the role of decreased autophagy in cardiomyocyte apoptosis. We reported that the level of autophagic flux increased early and then decreased in an actively β₁-AAB-immunized rat model. Rapamycin, an mTOR inhibitor, restored myocardial apoptosis in the presence of β₁-AABs. Further, we found that the early increase of autophagy was an adaptive stress response that is possibly unrelated to β₁-AR, and the activation of the β₁-AR and PKA contributed to late decreased autophagy. Then, after upregulating or inhibiting autophagy with rapamycin, Atg5 overexpression adenovirus or 3-methyladenine in cultured primary neonatal rat cardiomyocytes, we found that autophagy decline promoted myocardial apoptosis effectively through the mitochondrial apoptotic pathway. In conclusion, the reduction of apoptosis through the proper regulation of autophagy may be important for treating patients with β₁-AAB-positive heart dysfunction.

Cyclic Peptides for Effective Treatment in a Long-Term Model of Graves Disease and Orbitopathy in Female Mice

A model for human Graves disease in mice was used to compare several treatment approaches. The mice received regular adenovirus (Ad) thyroid-stimulating hormone receptor (TSHR) A subunit immunizations (injections every 4 weeks). The generation of anti-TSHR antibodies, enlarged thyroid sizes (goiter), elevated serum thyroxine levels, retro-orbital fibrosis, and cardiac involvement (tachycardia and hypertrophy) were consistently observed over 9 months. Treatment of established disease in these mice using cyclic peptides that mimic one of the cylindrical loops of the TSHR leucine-rich repeat domain improved or cured all investigated parameters after six consecutive monthly injections. The first significant beneficial effects were observed 3 to 4 months after starting these therapies. In immunologically naïve mice, administration of any of the cyclic peptides did not induce any immune response. In contrast, monthly injections of the full antigenic TSHR A domain as fusion protein with immunoglobulin G crystallizable fragment induced clinical signs of allergy in Ad-TSHR-immunized mice and anti-TSHR antibodies in naïve control mice. In conclusion, cyclic peptides resolved many clinical findings in a mouse model of established Graves disease and orbitopathy. In contrast to blocking TSHR by allosteric modulation, the approach does not incur a direct receptor antagonism, which might offer a favorable side effect profile.

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.

Pharmacokinetics and Safety of Single Intravenous Doses of JNJ-54452840, an Anti-β1-Adrenergic Receptor Antibody Cyclopeptide, in Healthy Male Japanese and Caucasian Participants

AIM

To evaluate the pharmacokinetics and safety of single intravenous doses of JNJ-54452840 infused over 1 minute in healthy male Japanese and Caucasian participants. JNJ-54452840 is a novel peptide for the treatment of chronic heart failure, with a proposed mechanism of action of binding interference and decreased production of anti-β1-adrenergic receptor (anti-β1-AR) antibodies, which stimulate the cardiac β1-AR.

METHODS

In this randomized, single-centre, double-blind, placebo-controlled, four-way crossover study, 32 male Japanese and Caucasian participants (16 in each group) received single intravenous doses of JNJ-54452840 20, 80 and 240 mg, and placebo, each separated by a ≥7-day washout period. Pharmacokinetics and safety were assessed predose and at specified timepoints for 24 h. Anti-β1-AR antibodies were monitored.

RESULTS

The mean JNJ-54452840 maximum observed plasma concentration (C max) and area under the concentration-time curve from time zero to infinity with extrapolation of the terminal phase (AUCinf) values increased linearly with dose, with rapid elimination in both groups. Dose proportionality criteria were not met between the 20 and 240 mg doses for both study cohorts. The median time to reach C max (T max) ranged from 1 to 5 minutes. The mean total systemic clearance after intravenous administration (CL), volume of distribution at steady state (V ss), mean residence time (MRT) and terminal half-life (T ½) values were similar for both groups. The mean T ½ values ranged from 5.9 to 26.1 min in a dose-dependent manner. The overall prevalence of antibodies was 9.4 % at baseline; antibodies not present at baseline developed in five Caucasians (15.6 %) but not in Japanese participants. One participant in each group experienced a serious thromboembolic event (pulmonary embolism, ischaemic stroke).

CONCLUSION

JNJ-54452840 demonstrated similar pharmacokinetics in both groups. JNJ-54452840 was possibly immunogenic, and two participants reported thromboembolic serious adverse events. The relationship between these events and antibody formation is not known.

Proliferation in cardiac fibroblasts induced by β1-adrenoceptor autoantibody and the underlying mechanisms

Chronic sustained stimulation of β-adrenoceptor is closely related to cardiac fibrosis which is bad for cardiac function. Growing evidence showed that the high prevalence of β₁-adrenoceptor autoantibody (β₁-AA) in the sera of patients with various types of cardiovascular diseases decreased cardiac function. In the current study, we demonstrated that β₁-AA impaired the cardiac function evaluated by echocardiography and that β₁-AA triggered cardiac fibrosis in terms of increased expression of α-smooth muscle actin as the marker of myofibroblast and collagen deposition in a passive β₁-AA immunized mice model during 16 weeks. Further, we showed that β₁-AA activated β₁-AR/cAMP/PKA pathway and promoted proliferation in primary cardiac fibroblasts through specific binding to β₁-AR but not to β₂-AR. Moreover, β₁-AA was also likely to promote proliferation in cardiac fibroblasts through activating p38MAPK and ERK1/2 as p38MAPK inhibitor SB203580 and ERK1/2 inhibitor PD98059 partially reversed the proliferative effect. The persistent activating signalling of PKA and P38MAPK in 1 h induced by β₁-AA was associated with lacking agonist-induced desensitization phenomena. The conditioned medium from β₁-AA-stimulated cardiac fibroblasts induced cardiomyocyte apoptosis, which indicated that β₁-AA changed the secretion of cardiac fibroblasts contributing to cardiac injury. These findings will contribute to our understanding of the pathological mechanisms of β₁-AA.

Chronic Heart Failure and Inflammation

As a greater proportion of patients survive their initial cardiac insult, medical systems worldwide are being faced with an ever-growing need to understand the mechanisms behind the pathogenesis of chronic heart failure (HF). There is a wealth of information about the role of inflammatory cells and pathways during acute injury and the reparative processes that are subsequently activated. We discuss the different causes that lead to chronic HF development and how the sum of initial inflammatory and reparative responses only sets the trajectory for disease progression. Unfortunately, comparatively little is known about the contribution of the immune system once the trajectory has been set, and chronic HF has been established—which clinically represents the majority of patients. It is known that chronic HF is associated with circulating inflammatory cytokines that can predict clinical outcomes, yet the causative role inflammation plays in disease progression is not well defined, and the majority of clinical trials that target aspects of inflammation in patients with chronic HF have largely been negative. This review will present what is currently known about inflammation in chronic HF in both humans and animal models as a means to highlight the gap in our knowledge base that requires further examination.

Simultaneous quantification of Escherichia coli O157:H7 and Shigella boydii using a visual-antibody-macroarray

Being high throughput, rapid, automated, economical, convenient to operate and highly sensitive, protein arrays have been widely used in the analysis of tumor markers and veterinary drug residues. Pathogenic microbes also can be detected qualitatively by DNA array or protein array; however, their high throughput detection and quantification remains a big obstacle. To evaluate the potentiality of protein arrays for multiple quantitative detection of microorganisms with naked eye examination without the help of any equipment, here we developed a visual-antibody-macroarray (VAMA) aiming at rapid and simultaneous quantification of Escherichia coli O157:H7 and Shigella boydii. The results show that this VAMA is highly specific and is able to distinguish mixed Escherichia coli O157:H7 and Shigella boydii synchronously. The detection limits are equivalent to 3.4 × 10(5) CFU mL(-1) and 3.2 × 10(5) CFU mL(-1), respectively, which conform to the results of plate counting and ELISA. Importantly, the examination can be solely performed with the naked eye. Therefore, we provide an easy, reliable and rapid method for quantitative analysis of microorganisms.

Applications of cell-based bioassays measuring the induced expression of endogenous genes

Cell-based bioassays are used to determine the biological activity of complex biotherapeutic products, to assign potency and to assure the quality and consistency of the manufacturing process. Clinically, these assays are used to assess bioactivity in patient samples, particularly for the detection of antidrug neutralizing antibodies. Owing to their versatility, cellular assays that measure endogenous gene expression by quantitative reverse transcription PCR offer a rapid and automatable alternative to assays measuring functional, late-stage responses. Notably, detection of immediate early gene expression represents a direct response of the cell to receptor ligation by the biotherapeutic. We review current developments in the use of this approach and demonstrate its application to the detection of receptor-binding autoantibodies using, as a case study, the detection of autoantibodies to the thyroid-stimulating hormone receptor.

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.

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.

Impact of human autoantibodies on β1-adrenergic receptor conformation, activity, and internalization

Aims

Autoantibodies against second extracellular loops of β₁-adrenergic receptors frequent in dilated cardiomyopathy confer myocardial dysfunction presumably via cAMP stimulation. Here, we investigate the autoantibody impact on receptor conformation and function.

Methods and results

IgG was prepared from patients with dilated cardiomyopathy, matched healthy donors (10 each) or commercial IgG preparations (2). IgG binding to β₁-adrenergic receptor peptides was detected in 5 of 10 patients and 2 of 10 controls. IgG colocalization with the native receptor was detected in 8 of 10 patients and 1 of 10 controls (10 of 10 patients and 7 of 10 controls at >30 mg IgG/L). All IgGs exhibiting receptor colocalization triggered changes in receptor conformation (determined with fluorescent sensors) not stringently correlated to cAMP stimulation, suggesting the induction of more or less active receptor conformations. Receptor-activating IgG was detected in 8 of 10 patients but only 1 of 10 controls. In addition, IgG from 8 of 10 patients and 3 of 10 controls attenuated receptor internalization (measured by total internal reflection fluorescence microscopy). IgG-inducing inactive receptor conformations had no effect on subsequent cAMP stimulation by isoproterenol. IgG-inducing active receptor conformations dampened or augmented subsequent cAMP stimulation by isoproterenol, depending on whether receptor internalization was attenuated or not. Corresponding IgG effects on the basal beating rate and chronotropic isoproterenol response of embryonic human cardiomyocytes were observed.

Conclusions

(i) Autoantibodies trigger conformation changes in the β₁-adrenergic receptor molecule. (ii) Some also attenuate receptor internalization. (iii) Combinations thereof increase the basal beating rate of cardiomyocytes and optionally entail dampening of their chronotropic catecholamine responses. (iv) The latter effects seem specific for patient autoantibodies, which also have higher levels.