Otavio Cabral-Marques

Mechanisms of Autoantibody-Induced Pathology

Autoantibodies are frequently observed in healthy individuals. In a minority of these individuals, they lead to manifestation of autoimmune diseases, such as rheumatoid arthritis or Graves’ disease. Overall, more than 2.5% of the population is affected by autoantibody-driven autoimmune disease. Pathways leading to autoantibody-induced pathology greatly differ among different diseases, and autoantibodies directed against the same antigen, depending on the targeted epitope, can have diverse effects. To foster knowledge in autoantibody-induced pathology and to encourage development of urgently needed novel therapeutic strategies, we here categorized autoantibodies according to their effects. According to our algorithm, autoantibodies can be classified into the following categories: (1) mimic receptor stimulation, (2) blocking of neural transmission, (3) induction of altered signaling, triggering uncontrolled (4) microthrombosis, (5) cell lysis, (6) neutrophil activation, and (7) induction of inflammation. These mechanisms in relation to disease, as well as principles of autoantibody generation and detection, are reviewed herein.

Vascular hypothesis revisited: Role of stimulating antibodies against angiotensin and endothelin receptors in the pathogenesis of systemic sclerosis.

Systemic sclerosis (SSc) is a connective tissue disorder of unknown etiology characterized by the presence of multiple autoantibodies, including those against angiotensin and endothelin receptors. Patients with SSc can develop heterogeneous clinical manifestations including microvascular damage, the dysregulation of innate and adaptive immunity, and generalized fibrosis of multiple organs. Autoantibodies against angiotensin II type I receptor (AT1R) and endothelin-1 type A receptor (ETAR) play important roles in the pathogenesis of SSc. These autoantibodies regulate physiological processes ranging from production of collagen by skin fibroblasts to angiogenesis modulation. Understanding the mechanisms behind autoantibodies against AT1R and ETAR could provide insight to future novel therapies for SSc patients. In this review, we focus on elucidating the immunopathological mechanisms triggered by anti-AT1R and anti-ETAR autoantibodies to summarize current knowledge about vascular abnormalities resulting in progressive damage of organs seen in patients with SSc.

Long-term outcomes of 176 patients with X-linked hyper-IgM syndrome treated with or without hematopoietic cell transplantation

Background: X‐linked hyper‐IgM syndrome (XHIGM) is a primary immunodeficiency with high morbidity and mortality compared with those seen in healthy subjects. Hematopoietic cell transplantation (HCT) has been considered a curative therapy, but the procedure has inherent complications and might not be available for all patients. Objectives: We sought to collect data on the clinical presentation, treatment, and follow‐up of a large sample of patients with XHIGM to (1) compare long‐term overall survival and general well‐being of patients treated with or without HCT along with clinical factors associated with mortality and (2) summarize clinical practice and risk factors in the subgroup of patients treated with HCT. Methods: Physicians caring for patients with primary immunodeficiency diseases were identified through the Jeffrey Modell Foundation, United States Immunodeficiency Network, Latin American Society for Immunodeficiency, and Primary Immune Deficiency Treatment Consortium. Data were collected with a Research Electronic Data Capture Web application. Survival from time of diagnosis or transplantation was estimated by using the Kaplan‐Meier method compared with log‐rank tests and modeled by using proportional hazards regression. Results: Twenty‐eight clinical sites provided data on 189 patients given a diagnosis of XHIGM between 1964 and 2013; 176 had valid follow‐up and vital status information. Sixty‐seven (38%) patients received HCT. The average follow‐up time was 8.5 ± 7.2 years (range, 0.1‐36.2 years). No difference in overall survival was observed between patients treated with or without HCT (P = .671). However, risk associated with HCT decreased for diagnosis years 1987‐1995; the hazard ratio was significantly less than 1 for diagnosis years 1995‐1999. Liver disease was a significant predictor of overall survival (hazard ratio, 4.9; 95% confidence limits, 2.2‐10.8; P < .001). Among survivors, those treated with HCT had higher median Karnofsky/Lansky scores than those treated without HCT (P < .001). Among patients receiving HCT, 27 (40%) had graft‐versus‐host disease, and most deaths occurred within 1 year of transplantation. Conclusion: No difference in survival was observed between patients treated with or without HCT across all diagnosis years (1964‐2013). However, survivors treated with HCT experienced somewhat greater well‐being, and hazards associated with HCT decreased, reaching levels of significantly less risk in the late 1990s. Among patients treated with HCT, treatment at an early age is associated with improved survival. Optimism remains guarded as additional evidence accumulates.

Environmental factor and inflammation-driven alteration of the total peripheral T-cell compartment in granulomatosis with polyangiitis.

Autoimmune diseases are initiated by a combination of predisposing genetic and environmental factors resulting in self-perpetuating chronic inflammation and tissue damage. Autoantibody production and an imbalance of effector and regulatory T-cells are hallmarks of autoimmune dysregulation. While expansion of circulating effector memory T-cells is linked to disease pathogenesis and progression, the causes driving alterations of the peripheral T-cell compartment have remained poorly understood so far. In granulomatosis with polyangiitis (GPA), a prototypical autoimmune disorder of unknown aetiology, we performed for the first time a combined approach using phenotyping, transcriptome and functional analyses of T-cell populations to evaluate triggers of memory T-cell expansion. In more detail, we found increased percentages of circulating CD4+CD28-, CD8+CD28- and CD4+CD161+ single-positive and CD4+CD8+ double-positive T-cells in GPA. Transcriptomic profiling of sorted T-cell populations showed major differences between GPA and healthy controls reflecting antigen- (bacteria, viruses, fungi) and cytokine-driven impact on T-cell populations in GPA. Concomitant cytomegalovirus (CMV) and Epstein-Barr virus (EBV) - positivity was associated with a significant increase in the percentage of CD28- T-cells in GPA-patients compared to sole CMV- or EBV-positivity or CMV- and EBV-negativity. T-cells specific for other viruses (influenza A virus, metapneumovirus, respiratory syncytial virus) and the autoantigen proteinase 3 (PR3) were infrequently detected in GPA. Antigen-specific T-cells were not specifically enriched in any of the T-cell subsets. Altogether, on a genetic and cellular basis, here we show that alterations of the peripheral T-cell compartment are driven by inflammation and various environmental factors including concomitant CMV and EBV infection. Our study provides novel insights into mechanisms driving autoimmune disease and on potential therapeutic targets.

Antibodies against angiotensin II type 1 receptor (AT1R) and endothelin receptor type A (ETAR) in systemic sclerosis (SSc)-response.

31 32 33 34 We gratefully thankWallukat et al. for their attention and interest on our studies concerning the role of antibodies against angiotensin II type 1 receptor (AT1R) and endothelin receptor type A (ETAR) in systemic sclerosis (SSc). Althoughwe agreewithmany of their statements, we do not completely share their enthusiasm about the role of immunoapheresis (IA) according to our limited experiencewith IA in SSc. In SSc, antibodies (ab) are very refractory to IA and their concentrations showed only slightly and short-term reduction which increased very shortly after IA discontinuation. This fact was probably due to the profile of systemic autoimmune disease. In SSc, we have cross reacting and synergistic ab against AT1R and ETAR. As the authors showed in their model using rat cardiomyocytes measuring chronotopic activity, anti-AT1R ab increases while anti-ETAR ab reduces this activity. Whether chronotropy is in fact an adequate in vitro outcome parameter in SSc seems to be questionable. In addition to the ab concentrations, receptor expression is a very important parameter that also needs to be considered. As

Expanding the clinical and genetic spectrum of G6PD deficiency: The occurrence of BCGitis and novel missense mutation

Glucose-6-phosphate dehydrogenase (G6PD) is a key enzyme in the pentose phosphate pathway that ensures sufficient production of coenzyme nicotinamide adenine dinucleotide phosphate (NADPH) by catalyzing the reduction of NADP+ to NADPH. Noteworthy, the latter mediates the production of reactive oxygen species (ROS) by phagocytic cells such as neutrophils and monocytes. Therefore, patients with severe forms of G6PD deficiency may present impaired NADPH oxidase activity and become susceptible to recurrent infections. This fact, highlights the importance to characterize the immunopathologic mechanisms underlying the susceptibility to infections in patients with G6PD deficiency. Here we report the first two cases of G6PD deficiency with Bacille Calmette-Guérin (BCG) adverse effect, besides jaundice, hemolytic anemia and recurrent infections caused by Staphylococcus aureus. The qualitative G6PD screening was performed and followed by oxidative burst analysis using flow cytometry. Genetic and in silico analyses were carried out by Sanger sequencing and mutation pathogenicity predicted using bioinformatics tools, respectively. Activated neutrophils and monocytes from patients displayed impaired oxidative burst. The genetic analysis revealed the novel missense mutation c.1157T>A/p.L386Q in G6PD. In addition, in silico analysis indicated that this mutation is pathogenic, thereby hampering the oxidative burst of neutrophils and monocytes from patients. Our data expand the clinical and genetic spectrum of G6PD deficiency, and suggest that impaired oxidative burst in this severe primary immune deficiency is an underlying immunopathologic mechanism that predisposes to mycobacterial infections.

Functional autoantibodies directed against cell surface receptors in systemic sclerosis

Systemic sclerosis (SSc) is a complex and heterogeneous systemic autoimmune disease characterized by the presence of high serum levels of antibodies targeting a variety of self-antigens. In addition to autoantibodies directed against nuclear antigens, patients with SSc also develop high serum levels of functional autoantibodies that target cell surface receptors when compared to healthy subjects. Following binding to extracellular receptors, these functional autoantibodies trigger the activation of signal transducing pathways, resulting in a stimulatory or suppressive effect. For example, stimulatory autoantibodies toward platelet-derived growth factor receptor (PDGFR) or antibodies targeting G protein–coupled receptors (e.g., angiotensin II receptor type 1 and endothelin receptor type A) have pleiotropic roles in the pathogenesis of SSc. High levels of these functional autoantibodies dysregulate the response of non-immune cells (e.g., fibroblasts and endothelial cells) as well as innate and adaptive immune cells, including myeloid cells and lymphocytes, respectively. Thus, the immunobiology of such autoantibodies clarifies why patients with SSc develop clinical features such as extensive fibrosis, vasculopathies and abnormal immune responses. Future interventions that modulate the natural production of functional autoantibodies that target cell surface receptors or neutralize such autoantibodies would be essential in reducing morbidity and mortality rates presented by SSc patients.

Antibodies against chemokine receptors CXCR3 and CXCR4 predict progressive deterioration of lung function in patients with systemic sclerosis

BackgroundThe chemokine receptors CXCR3 and CXCR4 are involved in the pathogenesis of fibrosis, a key feature of systemic sclerosis (SSc). It is hypothesized that immunoglobulin (Ig)G antibodies (abs) against these two receptors are present in patients with SSc and are associated with clinical findings.MethodsAnti-CXCR3 and anti-CXCR4 ab levels were measured in 449 sera from 327 SSc patients and in 234 sera from healthy donors (HD) by enzyme-linked immunosorbent assay (ELISA). In SSc, ab levels were compared with clinical data in a cross-sectional and longitudinal setting. Protein expression of CXCR3 and CXCR4 on peripheral blood mononuclear cells (PBMCs) was analyzed in 17 SSc patients and 8 HD by flow cytometry.ResultsAnti-CXCR3 and anti-CXCR4 ab levels were different among SSc subgroups compared with HD and were highest in diffuse SSc patients. The ab levels strongly correlated with each other (r = 0.85). Patients with SSc-related interstitial lung disease (SSc-ILD) exhibited higher ab levels which negatively correlated with lung function parameters (e.g., r = −0.5 and r = −0.43 for predicted vital capacity, respectively). However, patients with deterioration of lung function showed lower anti-CXCR3/4 ab levels compared with those with stable disease. Frequencies and median fluorescence intensities (MFI) of CXCR3+ and CXCR4+ PBMCs were lower in SSc patients compared with HD and correlated with the severity of skin and lung fibrosis. They correlated with the severity of skin and lung fibrosis.ConclusionsAnti-CXCR3/4 abs and their corresponding receptors are linked with the severity of SSc-ILD. Antibody levels discriminate patients with stable or decreasing lung function and could be used for risk stratification.

Functional autoantibodies targeting G protein-coupled receptors in rheumatic diseases

G protein-coupled receptors (GPCRs) comprise the largest and most diverse family of integral membrane proteins that participate in different physiological processes such as the regulation of the nervous and immune systems. Besides the endogenous ligands of GPCRs, functional autoantibodies are also able to bind GPCRs to trigger or block intracellular signalling pathways, resulting in agonistic or antagonistic effects, respectively. In this Review, the effects of functional GPCR-targeting autoantibodies on the pathogenesis of autoimmune diseases, including rheumatic diseases, are discussed. Autoantibodies targeting β1 and β2 adrenergic receptors, which are expressed by cardiac and airway smooth muscle cells, respectively, have an important role in the development of asthma and cardiovascular diseases. In addition, high levels of autoantibodies against the muscarinic acetylcholine receptor M3 as well as those targeting endothelin receptor type A and type 1 angiotensin II receptor have several implications in the pathogenesis of rheumatic diseases such as Sjögren syndrome and systemic sclerosis. Expanding the knowledge of the pathophysiological roles of autoantibodies against GPCRs will shed light on the biology of these receptors and open avenues for new therapeutic approaches.

Antibodies to Signaling Molecules and Receptors in Alzheimer’s Disease are Associated with Psychomotor Slowing, Depression, and Poor Visuospatial Function

BACKGROUND Alzheimers disease (AD) is associated with several antibodies as well as signaling molecules and receptors. These may be detrimental in the presence of a disrupted blood-brain barrier (BBB). OBJECTIVE To investigate whether the levels of antibodies toward 33 signaling molecules involved in neurotransmitter, vascular, and immune functions were associated with AD and, within the AD group; cognitive function and mood. METHODS Antibodies in sera from patients with mild AD [(n = 91) defined as a Mini-Mental State Examination ≥ 20 or a Clinical Dementia Rating Scale≤1] and healthy controls (n = 102) were measured with enzyme-linked immunosorbent assays. Levels in AD and controls were compared by Mann-Whitney test. In the AD group, associations between antibodies and psychometric test scores were analyzed by robust regression. The false discovery threshold was set to 0.05. RESULTS Antibodies to serotonin receptors [5-HT2AR (effect size (r) = 0.21, p = 0.004), 5-HT2CR (r = 0.25, p = 0.0005) and 5-HT7R (r = 0.21, p = 0.003)], vascular endothelial growth factor receptor 1 [VEGFR1 (r = 0.29, p < 0.001)] and immune-receptors (Stabilin-1 (r = 0.23, p = 0.001) and C5aR1 (r = 0.21, p = 0.004) were higher in AD. Psychomotor speed was associated with D1R-abs (β 0.49, p < 0.001), depression with ETAR-abs (β 0.31, p < 0.001), and visuospatial function with 5-HT1AR-abs (β 0.27, p = 0.004) despite similar antibody levels compared to controls. CONCLUSIONS Antibody levels to VEGFR1, serotonergic receptors, and receptors in the immune system were increased in AD. Antibodies at similar levels as in controls were associated cognitive dysfunction and depression in AD.