Functionally Active Antibodies to the Angiotensin II Type 1-Receptor Measured by a Luminometric Bioassay Do Not Correlate With Clinical Manifestations in Systemic Sclerosis: A Comparison With Antibodies to Vascular Receptors and Topoisomerase I Detected by ELISA

Immunoglobulins G from Patients with Systemic Sclerosis Modify the Molecular Signatures of Endothelial Cells

OBJECTIVE

Antinuclear antibodies (ANA) are powerful biomarkers in systemic sclerosis (SSc). Functional antibodies (FA) might be implicated in vasculopathy, in which endothelial cells (EC) are key players. We aimed to explore the effect of purified IgG from patients with SSc on omics signatures of EC and examine the influence of ANA serotypes and FA.

METHODS

EC were cultured in the presence of purified IgG from patients with SSc, patients with systemic lupus erythematosus (SLE) or healthy controls (HC). EC omics profiles were analysed by liquid chromatography with tandem mass spectrometry (LC-MS/MS) and RNA sequencing. EC proteome induced by IgG from patients with SSc was confirmed with an external validation cohort.

RESULTS

In the derivation cohort, principal component analysis (PCA) using proteomics data showed three distinct groups of subjects: a first one including mostly anti-topoisomerase-I positive patients (ATA+), a second one including mostly anti-centromere positive patients and a third group comprising anti-RNA polymerase-III positive patients, SLE and HC. In transcriptomics, PCA distinguished one group composed of ATA+patients only from a second group mixing ATA+patients with other individuals. The validation cohort confirmed the existence of two groups of distinct EC proteome profiles and clinical severity in ATA+patients. In both SSc cohorts, no association between FA presence and proteomic profiles was observed. Quantitative proteomics measured the most discriminant proteins in EC exposed to purified IgG.

CONCLUSION

Purified IgG from patients with SSc can modify EC proteome and transcriptome. The observed changes closely associate with ANA serotype.

Absence of Functional Autoantibodies Targeting Angiotensin II Receptor Type 1 and Endothelin-1 Type A Receptor in Circulation and Purified IgG From Patients With Systemic Sclerosis

OBJECTIVE

Systemic sclerosis (SSc) is a rare but severe autoimmune disease characterized by immune dysregulation, fibrosis, and vasculopathy. Although previous studies have highlighted the presence of functional autoantibodies targeting the angiotensin II receptor type 1 (AT1) and endothelin-1 type A receptor (ETAR), leading to autoantibody-mediated receptor stimulation and subsequent activation of endothelial cells (ECs), a comprehensive understanding of the direct interaction between these autoantibodies and their receptors is currently lacking. Moreover, existing data confirming the presence of these autoantibodies in SSc often rely on similar methodologies and assays. Our aim was to replicate previous findings and to investigate the functional effects of IgG derived from patients with SSc (SSc IgG) on AT1 and ETAR signaling, the downstream EC response, and the presence of AT1-binding autoantibodies in circulation.

METHODS

Quantitative polymerase chain reaction and cytokine enzyme-linked immunosorbent assay, alongside a real-time cell analyzer, were used to assess receptor-specific functional characteristics of purified SSc IgG (n = 18). Additionally, a novel protein capture assay using solubilized epitope-tagged AT1 was developed to detect AT1-binding autoantibodies in plasma samples from patients with SSc (n = 28) and healthy donors (n = 14).

RESULTS

No evidence for EC activation in an AT1- or ETAR-dependent manner was revealed. Furthermore, stimulation with SSc IgG did not induce receptor activation or alter G protein-coupled receptor signaling on agonist stimulation in a model with receptor overexpression. Lastly, no AT1-binding autoantibodies were detected in plasma samples from patients with SSc when using epitope-tagged solubilized AT1.

CONCLUSION

Overall, our study did not provide evidence to support the presence of AT1- or ETAR-activating autoantibodies in purified SSc IgG or AT1-binding autoantibodies in the circulation of patients with SSc.

Clinical conundrums in pediatric kidney transplantation: What we know about the role of angiotensin II type I receptor antibodies in pediatric kidney transplantation and the path forward

Antibodies to angiotensin II type 1 receptor (AT1R-Abs) are among the most well-studied non-HLA antibodies in renal transplantation. These antibodies have been shown to be common in pediatric kidney transplantation and associated with antibody-mediated rejection (AMR), vascular inflammation, development of human leukocyte donor-specific antibodies (HLA DSA), and allograft loss. As AT1R-Ab testing becomes more readily accessible, evidence to guide clinical practice for testing and treating AT1R-Ab positivity in pediatric kidney transplant recipients remains limited. This review discusses the clinical complexities of evaluating AT1R-Abs given the current available evidence.

Intensive receptor blockade and plasma exchange to treat refractory scleroderma renal crisis in patients with agonistic autoantibodies targeting the angiotensin II type 1 and endothelin-1 type A receptors

Scleroderma renal crisis is a rare complication of systemic sclerosis characterized by a rapid decline in kidney function due to acute renal vascular injury. Recently, activating autoantibodies targeting the angiotensin II type 1 receptor and the endothelin-1 type A receptor have been implicated in the pathophysiology of scleroderma renal crisis by sensitizing the angiotensin II type 1 receptor and endothelin-1 type A receptor in renal resistance arteries to their natural ligands. Here, we describe a cohort of 10 patients with scleroderma renal crisis refractory to standard treatment, including blockade of the renin-angiotensin system. Multimodal therapy was initiated, targeting at the removal of anti-angiotensin II type 1 receptor and anti-endothelin-1 type A receptor autoantibodies by plasma exchange and the reduction of vasoconstrictive activity. Further treatment options included angiotensin II type 1 receptor and endothelin-1 type A receptor blockade, iloprost, intravenous immunoglobulins, and immunosuppression. Six patients were hypertensive. On kidney biopsy, concentric intimal sclerosis was present in all patients, whereas acute vascular injury was evident in eight. Levels of anti-angiotensin II type 1 receptor and anti-endothelin-1 type A receptor autoantibodies were significantly reduced by multimodal treatment. Kidney function improved in three patients with histological signs of severe acute renal vascular damage. This report demonstrates that intensive multimodal therapy taking account of potentially pathogenic anti-angiotensin II type 1 receptor and anti-endothelin-1 type A receptor autoantibodies in concert with other vasodilatory interventions provides a salvage option for patients with refractory scleroderma renal crisis.

Comprehensive autoantibody profiles in systemic sclerosis: Clinical cluster analysis

Background

Systemic sclerosis (SSc) belongs to the group of connective tissue diseases and is associated with the occurrence of disease-specific autoantibodies. Although it is still controversial whether these antibodies contribute to pathogenesis, there are new insights into the development of these specific antibodies and their possible pathophysiological properties. Interestingly, they are associated with specific clinical manifestations, but for some rarer antibodies this association is not fully clarified. The aim of this study is a comprehensive analysis of the serum autoantibody status in patients with SSc followed by correlation analyses of autoantibodies with the clinical course of the disease.

Methods

Serum from SSc patients was analyzed using a line blot (EUROLINE, EUROIMMUN AG) for SSc-related autoantibodies. Autoantibodies to centromere, Topo-1, antimitochondrial antibodies (AMA) M2 subunit, angiotensin II type 1 receptors (AT1R) and endothelin-1 type-A-receptors (ETAR) were also determined by ELISA. We formed immunological clusters and used principal components analysis (PCA) to assign specific clinical characteristics to these clusters.

Results

A total of 372 SSc patients were included. 95.3% of the patients were antinuclear antibody positive and in 333 patients at least one SSc specific antibody could be detected. Four immunological clusters could be found by PCA. Centromere, Topo-1 and RP3 all formed own clusters, which are associated with distinct clinical phenotypes. We found that patients with an inverted phenotype, such as limited cutaneous SSc patients within the Topo-1 cluster show an increased risk for interstital lung disease compared to ACA positive patients. Anti-AT1R and anti-ETAR autoantibodies were measured in 176 SSc patients; no association with SSc disease manifestation was found. SSc patients with AMA-M2 antibodies showed an increased risk of cardiovascular events.

Conclusion

In our in large cluster analysis, which included an extended autoantibody profile, we were able to show that serologic status of SSc patients provides important clues to disease manifestation, co-morbidities and complications. Line blot was a reliable technique to detect autoantibodies in SSc and detected rarer autoantibodies in 42% of our patients.