HLA and autoantibodies define scleroderma subtypes and risk in African and European Americans and suggest a role for molecular mimicry

A Prospective Observational Study of Disease Severity and Mortality in Hispanic American Patients With Systemic Sclerosis

OBJECTIVE

To characterize disease manifestations in Hispanic American patients with systemic sclerosis (SSc) in comparison with non-Hispanic White and Black patients.

METHODS

Longitudinal clinical characteristics were collected prospectively in the Genetics versus Environment in Scleroderma Outcome Study cohort. All patients fulfilled the classification criteria for SSc and had a disease duration less than five years at enrollment.

RESULTS

A cohort of 427 patients, consisting of 124 Hispanic, 220 non-Hispanic White, and 83 non-Hispanic Black participants were examined. At enrollment, Hispanic patients were significantly younger but had longer disease duration, higher frequency of U1-RNP positivity as well as concurrent systemic lupus erythematosus (SLE) diagnosis, and lower income and educational levels in comparison to non-Hispanic White patients. Compared with non-Hispanic Black patients, Hispanic patients had more frequently limited cutaneous involvement and anticentromere antibodies. In the longitudinal analysis, Hispanic patients had significantly lower forced vital capacity percents predicted (point estimate, -9.3%; P < 0.001) than non-Hispanic White but not Black patients. Hispanic patients had similar longitudinal modified Rodnan Skin Scores like non-Hispanic White patients but lower measurements than non-Hispanic Black patients (point estimate, -3.2; P = 0.029). Hispanic patients had significantly higher serially obtained perceived functional disability scores than White patients (point estimate, 0.29; P < 0.001). Hispanic patients also had higher mortality rates than White Americans even after adjustment for age, gender, and socioeconomic statuses.

CONCLUSION

Hispanic patients have higher likelihood of having U1-RNP positivity and SLE overlap, more severe restrictive lung disease, as well as higher rate of mortality than non-Hispanic White patients.

SLIDE: Significant Latent Factor Interaction Discovery and Exploration across biological domains

Modern multiomic technologies can generate deep multiscale profiles. However, differences in data modalities, multicollinearity of the data, and large numbers of irrelevant features make analyses and integration of high-dimensional omic datasets challenging. Here we present Significant Latent Factor Interaction Discovery and Exploration (SLIDE), a first-in-class interpretable machine learning technique for identifying significant interacting latent factors underlying outcomes of interest from high-dimensional omic datasets. SLIDE makes no assumptions regarding data-generating mechanisms, comes with theoretical guarantees regarding identifiability of the latent factors/corresponding inference, and has rigorous false discovery rate control. Using SLIDE on single-cell and spatial omic datasets, we uncovered significant interacting latent factors underlying a range of molecular, cellular and organismal phenotypes. SLIDE outperforms/performs at least as well as a wide range of state-of-the-art approaches, including other latent factor approaches. More importantly, it provides biological inference beyond prediction that other methods do not afford. Thus, SLIDE is a versatile engine for biological discovery from modern multiomic datasets.

Genetically transitional disease: conceptual understanding and applicability to rheumatic disease

In genomic medicine, the concept of genetically transitional disease (GTD) refers to cases in which gene mutation is necessary but not sufficient to cause disease. In this Perspective, we apply this novel concept to rheumatic diseases, which have been linked to hundreds of genetic variants via association studies. These variants are in the 'grey zone' between monogenic variants with large effect sizes and common susceptibility alleles with small effect sizes. Among genes associated with rare autoinflammatory diseases, many low-frequency and/or low-penetrance variants are known to increase susceptibility to systemic inflammation. In autoimmune diseases, hundreds of HLA and non-HLA genetic variants have been revealed to be modest- to moderate-risk alleles. These diseases can be reclassified as GTDs. The same concept could apply to many other human diseases. GTD could improve the reporting of genetic testing results, diagnostic yields, genetic counselling and selection of therapy, as well as facilitating research using a novel approach to human genetic diseases.

Phenotypes of patients with systemic sclerosis in the Chinese Han population: a cluster analysis

OBJECTIVE

Systemic sclerosis (SSc) is a heterogeneous connective tissue disease that is commonly subdivided into limited cutaneous SSc (lcSSc) and diffuse cutaneous SSc (dcSSc) based on the extent of skin involvement. This subclassification may not reflect the full range of clinical phenotypic variation. This study aimed to investigate clinical features and aggregation of patients with SSc in Chinese based on SSc manifestations and organ involvements, in order to achieve precise treatment of SSc early prevention of complications.

METHODS

In total 287 SSc patients were included in this study. A cluster analysis was applied according to 13 clinical and serologic variables to determine subgroups of patients. Survival rates between obtained clusters and risk factors affecting prognosis were also compared.

RESULT

In this study, six clusters were observed: cluster 1 (n = 66) represented the skin type, with all patients showing skin thickening. In cluster 2 (n = 56), most patients had vascular and articular involvement. Cluster 3 (n = 14) individuals mostly had cardiac and pulmonary involvement. In cluster 4 (n = 52), the gastrointestinal type, 50 patients presented with stomach symptoms and 28 patients presented with esophageal symptoms. In cluster 5 (n = 50), patients barely had any major organ involvement. Cluster 6 (n = 49) included 46% of all patients presenting with renal crisis.

CONCLUSION

The results of our cluster analysis study implied that limiting SSc patient subgroups to those based only on skin involvement might not capture the full heterogeneity of the disease. Organ damage and antibody profiles should be considered when identifying homogeneous patient groups with a specific prognosis. Key Points • Provides a new method of categorizing SSc patients. • Can better explain disease progression and guide subsequent treatment.

Males and females with scleroderma: A comparative study in a Brazilian sample

Objectives

This study aimed to evaluate the clinical and serological profile in systemic sclerosis (SSc) by comparing females and males.

Patients and methods

This retrospective study was conducted with 215 SSc patients (193 females, 22 males; mean age: 50.1±14.5 years; range, 16 to 88 years) between September 2005 and September 2020. Disease severity was calculated by the Medsger severity score. Males and females were compared for clinical and serological markers.

Results

Females more frequently had esophageal involvement (p=0.003), telangiectasias (p=0.03), and antinuclear antibodies (p=0.04). Males more frequently had fingertip scars (p=0.03), digital ulcers (p=0.006), and a worse median Medsger severity score (6 in males vs. 4 in females, p=0.05).

Conclusion

In the studied sample, males had more severe disease than females with greater repercussions in periferic circulatory system.

Human leukocyte antigen-DQ risk heterodimeric haplotypes of left ventricular dysfunction in cardiac sarcoidosis: an autoimmune view of its role

Cardiac sarcoidosis (CS) is the scarring of heart muscles by autoimmunity, leading to heart abnormalities and patients with sarcoidosis with cardiac involvements have poor prognoses. Due to the small number of patients, it is difficult to stratify all patients of CS by human leukocyte antigen (HLA) analysis. We focused on the structure of antigen-recognizing pockets in heterodimeric HLA-class II, in addition to DNA sequences, and extracted high-affinity combinations of antigenic epitopes from candidate autoantigen proteins and HLA. Four HLA heterodimer-haplotypes (DQA1*05:03/05:05/05:06/05:08-DQB1*03:01) were identified in 10 of 68 cases. Nine of the 10 patients had low left ventricular ejection fraction (< 50%). Fourteen amino-acid sequences constituting four HLA anchor pockets encoded by the HLA haplotypes were all common, suggesting DQA1*05:0X-DQB1*03:01 exhibit one group of heterodimeric haplotypes. The heterodimeric haplotypes recognized eight epitopes from different proteins. Assuming that autoimmune mechanisms might be activated by molecular mimicry, we searched for bacterial species having peptide sequences homologous to the eight epitopes. Within the peptide epitopes form the SLC25A4 and DSG2, high-homology sequences were found in Cutibacterium acnes and Mycobacterium tuberculosis, respectively. In this study, we detected the risk heterodimeric haplotypes of ventricular dysfunction in CS by searching for high-affinity HLA-class II and antigenic epitopes from candidate cardiac proteins.

Biomarkers in the Pathogenesis, Diagnosis, and Treatment of Systemic Sclerosis

Systemic sclerosis (SSc) is a complex autoimmune disease characterized by vascular damage, vasoinstability, and decreased perfusion with ischemia, inflammation, and exuberant fibrosis of the skin and internal organs. Biomarkers are analytic indicators of the biological and disease processes within an individual that can be accurately and reproducibly measured. The field of biomarkers in SSc is complex as recent studies have implicated at least 240 pathways and dysregulated proteins in SSc pathogenesis. Anti-nuclear antibodies (ANA) are classical biomarkers with well-described clinical classifications and are present in more than 90% of SSc patients and include anti-centromere, anti-Th/To, anti-RNA polymerase III, and anti-topoisomerase I antibodies. Transforming growth factor-β (TGF-β) is central to the fibrotic process of SSc and is intimately intertwined with other biomarkers. Tyrosine kinases, interferon-1 signaling, IL-6 signaling, endogenous thrombin, peroxisome proliferator-activated receptors (PPARs), lysophosphatidic acid receptors, and amino acid metabolites are new biomarkers with the potential for developing new therapeutic agents. Other biomarkers implicated in SSc-ILD include signal transducer and activator of transcription 4 (STAT4), CD226 (DNAX accessory molecule 1), interferon regulatory factor 5 (IRF5), interleukin-1 receptor-associated kinase-1 (IRAK1), connective tissue growth factor (CTGF), pyrin domain containing 1 (NLRP1), T-cell surface glycoprotein zeta chain (CD3ζ) or CD247, the NLR family, SP-D (surfactant protein), KL-6, leucine-rich α2-glycoprotein-1 (LRG1), CCL19, genetic factors including DRB1 alleles, the interleukins (IL-1, IL-4, IL-6, IL-8, IL-10 IL-13, IL-16, IL-17, IL-18, IL-22, IL-32, and IL-35), the chemokines CCL (2,3,5,13,20,21,23), CXC (8,9,10,11,16), CX3CL1 (fractalkine), and GDF15. Adiponectin (an indicator of PPAR activation) and maresin 1 are reduced in SSc patients. A new trend has been the use of biomarker panels with combined complex multifactor analysis, machine learning, and artificial intelligence to determine disease activity and response to therapy. The present review is an update of the various biomarker molecules, pathways, and receptors involved in the pathology of SSc.

Antivinculin Antibodies in Systemic Sclerosis: Associations With Slow Gastric Transit and Extraintestinal Clinical Phenotype

OBJECTIVE

The gastrointestinal (GI) tract is commonly affected in systemic sclerosis (SSc). A positive association between antivinculin antibody levels and GI symptom severity is reported in SSc. We sought to examine whether antivinculin antibodies associate with measures of GI dysmotility and extraintestinal clinical phenotype in SSc.

METHODS

A total of 88 well-characterized patients with SSc and GI disease were assayed for antivinculin antibodies by enzyme-linked immunosorbent assay. Whole-gut scintigraphy, GI symptom scores, and clinical features of SSc were compared between patients with and without antibodies.

RESULTS

Twenty of 88 (23%) patients had antivinculin antibodies, which were more prevalent in patients with slow gastric transit (35% versus 22%). In the univariate analyses, patients who were positive for antivinculin antibodies were more likely to have limited cutaneous disease (odds ratio [OR] 9.60 [95% confidence interval (95% CI) 1.19, 77.23]) and thyroid disease (OR 4.09 [95% CI 1.27, 13.21]). Such patients were also less likely to have lung involvement based on a Medsger Severity Score of ≥2 (OR 0.25 [95% CI 0.07, 0.92]). Higher levels of antivinculin autoantibodies were associated with less gastric emptying (β coefficient -3.41 [95% CI -6.72, -0.09]). The association between antivinculin antibodies and each of these clinical features remained significant in the multivariable model. In particular, the presence of antivinculin antibodies (β coefficient -6.20 [95% CI -12.33, -0.063]) and higher levels of antivinculin antibodies (β coefficient -3.64 [95% CI -7.05, -0.23]) were each significantly associated with slower gastric transit.

CONCLUSION

Antivinculin antibodies associate with slower gastric transit in SSc and may provide insight into GI complications of SSc.

Human leukocyte antigen association in systemic sclerosis patients: our experience at a tertiary care center in North India

Introduction

Systemic sclerosis (SSc) is a chronic multisystem autoimmune rheumatic disease of unknown etiology. Several studies have established that SSc is triggered by a dynamic interplay between genetic factors and environmental stimuli. In the present study, we aimed to study the association of human leukocyte antigen (HLA) with familial and non-familial SSc patients [limited cutaneous SSc (lcSSc) and diffuse cutaneous SSc (dcSSc)] from North India.

Methods

The HLA-A, B, DRB1, and DQB1 genotyping of 150 (70 lcSSc and 80 dcSSc) adult-onset SSc patients and 150 age-gender-matched healthy controls were performed with sequence-specific oligonucleotide (SSO) typing kits using the luminex platform. HLA typing for HLA class I (A, B, and C) and II (DRB1, DQB1, and DPB1) in five North Indian families consisting of parent-child/sibling pairs affected with SSc or overlap syndrome was performed by Next Generation Sequencing (NGS) with Illumina MiniSeq.

Rseults

Among the non-familial SSc patients, HLA- DRB1*11 (P = 0.001, OR: 2.38, P c = 0.01) was identified as a risk allele, and DRB1*12 (P = .0001, OR: 0.00, P c = 0.001) as a protective allele. There was no statistical association found with HLA-DQB1*. Also, no significant association was observed between HLA antigens and different clinical subsets (lcSSc and dcSSc) of SSc. Two cases of familial SSc patients had the DRB1*11 allele. The DRB1*12 allele was absent in all the familial SSc patients.

Discussion

HLA DRB1*11 (risk allele) and DRB1*12 (protective allele) were found to be strongly associated with non-familial SSc patients and partially explain the disease's familial clustering, supporting the susceptible genetic background theory for SSc development. The study also indicates the HLA allele as a common genetic risk factor in distinct autoimmune diseases contributing to overlap syndrome or polyautoimmunity.

Can Pharmacogenetic Variants in TPMT, MTHFR and SLCO1B1 Genes Be Used as Potential Markers of Outcome Prediction in Systemic Sclerosis Patients?

Systemic sclerosis (SSc) is a rare connective tissue disorder with highest morbidity and mortality among rheumatologic diseases. Disease progression is highly heterogeneous between patients, implying a strong need for individualization of therapy. Four pharmacogenetic variants, namely TPMT rs1800460, TPMT rs1142345, MTHFR rs1801133 and SLCO1B1 rs4149056 were tested for association with severe disease outcomes in 102 patients with SSc from Serbia treated either with immunosuppressants azathioprine (AZA) and methotrexate (MTX) or with other types of medications. Genotyping was performed using PCR-RFLP and direct Sanger sequencing. R software was used for statistical analysis and development of polygenic risk score (PRS) model. Association was found between MTHFR rs1801133 and higher risk for elevated systolic pressure in all patients except those prescribed with MTX, and higher risk for kidney insufficiency in patients prescribed with other types of drugs. In patients treated with MTX, variant SLCO1B1 rs4149056 was protective against kidney insufficiency. For patients receiving MTX a trend was shown for having a higher PRS rank and elevated systolic pressure. Our results open a door wide for more extensive research on pharmacogenomics markers in patients with SSc. Altogether, pharmacogenomics markers could predict the outcome of patients with SSc and help in prevention of adverse drug reactions.

Immune-mediated lung diseases: A narrative review

The role of immunity in the pathogenesis of various pulmonary diseases, particularly interstitial lung diseases (ILDs), is being increasingly appreciated as mechanistic discoveries advance our knowledge in the field. Immune-mediated lung diseases demonstrate clinical and immunological heterogeneity and can be etiologically categorized into connective tissue disease (CTD)-associated, exposure-related, idiopathic, and other miscellaneous lung diseases including sarcoidosis, and post-lung transplant ILD. The immunopathogenesis of many of these diseases remains poorly defined and possibly involves either immune dysregulation, abnormal healing, chronic inflammation, or a combination of these, often in a background of genetic susceptibility. The heterogeneity and complex immunopathogenesis of ILDs complicate management, and thus a collaborative treatment team should work toward an individualized approach to address the unique needs of each patient. Current management of immune-mediated lung diseases is challenging; the choice of therapy is etiology-driven and includes corticosteroids, immunomodulatory drugs such as methotrexate, cyclophosphamide and mycophenolate mofetil, rituximab, or other measures such as discontinuation or avoidance of the inciting agent in exposure-related ILDs. Antifibrotic therapy is approved for some of the ILDs (e.g., idiopathic pulmonary fibrosis) and is being investigated for many others and has shown promising preliminary results. A dire need for advances in the management of immune-mediated lung disease persists in the absence of standardized management guidelines.

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.

Systemic sclerosis in adults. Part I: Clinical features and pathogenesis

Systemic sclerosis (SSc), also referred to as systemic scleroderma or scleroderma, is a rare, complex immune-mediated connective tissue disease characterized by progressive skin fibrosis and other clinically heterogenous features. The etiopathogenesis of SSc involves vasculopathy and immune system dysregulation occurring on a permissive genetic and epigenetic background, ultimately leading to fibrosis. Recent developments in our understanding of disease-specific autoantibodies and bioinformatic analyses has led to a reconsideration of the purely clinical classification of diffuse and limited cutaneous SSc subgroups. Autoantibody profiles are predictive of skin and internal organ involvement and disease course. Early diagnosis of SSc, with commencement of disease-modifying treatment, has the potential to improve patient outcomes. In SSc, many of the clinical manifestations that present early signs of disease progression and activity are cutaneous, meaning dermatologists can and should play a key role in the diagnosis and management of this significant condition. The first article in this continuing medical education series discusses the epidemiology, clinical characteristics, and pathogenesis of SSc in adults, with an emphasis on skin manifestations, the important role of dermatologists in recognizing these, and their correlation with systemic features and disease course.

Autoantibodies as Biomarker and Therapeutic Target in Systemic Sclerosis

Systemic sclerosis (SSc) is a rare connective tissue disorder characterized by immune dysregulation evoking the pathophysiological triad of inflammation, fibrosis and vasculopathy. In SSc, several alterations in the B-cell compartment have been described, leading to polyclonal B-cell hyperreactivity, hypergammaglobulinemia and autoantibody production. Autoreactive B cells and autoantibodies promote and maintain pathologic mechanisms. In addition, autoantibodies in SSc are important biomarkers for predicting clinical phenotype and disease progression. Autoreactive B cells and autoantibodies represent potentially promising targets for therapeutic approaches including B-cell-targeting therapies, as well as strategies for unselective and selective removal of autoantibodies. In this review, we present mechanisms of the innate immune system leading to the generation of autoantibodies, alterations of the B-cell compartment in SSc, autoantibodies as biomarkers and autoantibody-mediated pathologies in SSc as well as potential therapeutic approaches to target these.

Scleroderma autoantibodies in guiding monitoring and treatment decisions

PURPOSE OF REVIEW

One of the key clinical challenges of systemic sclerosis (SSc) is diversity in clinical presentation, organ involvement and disease progression. Antinuclear autoantibodies (ANA) are central to the diagnosis of SSc. ANA specificities associated with distinct clinical patterns of organ and skin involvement. Understanding of the molecular differences and pathogenesis of scleroderma has helped further inform clinical acumen. Here, we provide an update on ANA on clinical profiling, management and future direction of SSc.

RECENT FINDINGS

There has been further development in delineating clinical patterns in ANA, genetic susceptibility and antigen triggers predisposing to ANA subtypes. Sub-group analysis of recent clinical trials shows differing treatment responses to novel therapeutics.

SUMMARY

ANA subtyping is likely to be firmly embedded into future classification systems. Beyond informing current management and monitoring of scleroderma patients, ANA subsets have implication on future research and clinical trial design.

Association of HLA-DRB1*15:02:01, DQB1*05:01:24 and DPB1*13:01:01 in Thai patients with systemic sclerosis

INTRODUCTION

HLA studies in patients with systemic sclerosis (SSc) have shown variable results. This study aimed to examine the association of HLA class I and II risk alleles in Thai SSc patients, and clarify the contribution of risk HLA alleles to the pathogenesis and clinical manifestations.

METHODS

Blood samples from 92 SSc patients and 135 healthy controls (HCs) were collected. Eleven loci of the HLA class I (HLA-A, B, and C) and class II (HLA-DR, DP, and DQ) genes were determined by a 3-field (6-digit) analysis using the Next Generation DNA Sequencing (NGS) method. Anti-topoisomerase-I antibodies (ATA) and anti-centromere antibodies (ACA) were identified by ELISA methods.

RESULTS

Allele frequencies (AFs) of HLA-DRB1*15:02:01, DRB5*01:02:01, DQB1*05:01:24, DPB1*13:01:01, and DQA1*01:01:01 were increased significantly in the whole SSc and SSc patients with positive ATA, but with negative ACA (SSc/ATA+/ACA-). Of these, DPB1*13:01:01 was the most susceptible allele. The DRB1*15:02:01, DQB1:05:01:24, and DPB1*13:01:01 alleles were estimated to locate on the unique haplotype, and haplotype frequency was estimated to be significantly higher than those in the HCs (p=0.002). The linkage analysis of DRB1*15/16 revealed that most of the DRB1*15:02:01 alleles were linked to DRB5*01:02:01 or DRB5*01:08:01N. The linkage of DRB1*16:02:01 to DRB5*01:01:01 was observed frequently. The associations of risk alleles with several SSc clinical features were observed.

CONCLUSION

HLA-DRB1*15:02:01, DRB5*01:02:01, DQB1*05:01:24, and DPB1*13:01:01 on the unique haplotype were associated with the pathogenesis and clinical features of SSc in Thai patients. The linkage of DRB1*15:02:01 to DRB5*01:08:01N was observed commonly in northern Thai patients. This article is protected by copyright. All rights reserved.

Recent advances in elucidating the genetic basis of systemic sclerosis

PURPOSE OF REVIEW

Systemic sclerosis (SSc) is a complex autoimmune disorder that affects the connective tissue and causes severe vascular damage and fibrosis of the skin and internal organs. There are recent advances in the field that apply novel methods to high throughput genotype information of thousands of patients with SSc and provide promising results towards the use of genomic data to help SSc diagnosis and clinical care.

RECENT FINDINGS

This review addresses the development of the first SSc genomic risk score, which can contribute to differentiating SSc patients from healthy controls and other immune-mediated diseases. Moreover, we explore the implementation of data mining strategies on the results of genome-wide association studies to highlight subtype-specific HLA class II associations and a strong association of the HLA class I locus with SSc for the first time. Finally, the combination of genomic data with transcriptomics informed drug repurposing and genetic association studies in well characterized SSc patient cohorts identified markers of severe complications of the disease.

SUMMARY

Early diagnosis and clinical management of SSc and SSc-related complications are still challenging for rheumatologists. The development of predictive models and tools using genotype data may help to finally deliver personalized clinical care and treatment for patients with SSc in the near future.

Can Antinuclear Antibodies Have a Pathogenic Role in Systemic Sclerosis?

Systemic sclerosis (SSc) is a connective tissue disease characterized by extensive fibrosis of the skin and internal organs, associated with vasculopathy and autoimmune features. Antinuclear antibodies (ANA) are found in almost all SSc patients and constitute strong diagnosis and prognosis biomarkers. However, it remains unclear whether ANA are simple bystanders or if they can have a role in the pathophysiology of the disease. One might think that the nuclear nature of their targets prevents any accessibility to autoantibodies. Nevertheless, recent data suggest that ANA could be pathogenic or at least contribute to the perennation of the disease. We review here first the indirect clues of the contribution of ANA to SSc: they are associated to the disease subtypes, they may precede disease onset, their titer correlates with disease activity and severity, there is an association between molecular subsets, and some patients can respond to B-cell targeting therapy. Then, we describe in a second part the mechanisms of ANA production in SSc from individual genetic background to post-transcriptional modifications of neoantigens. Finally, we elaborate on the potential mechanisms of pathogenicity: ANA could be pathogenic through immune-complex-mediated mechanisms; other processes potentially involve molecular mimicry and ANA penetration into the target cell, with a focus on anti-topoisomerase-I antibodies, which are the most probable candidate to play a role in the pathophysiology of SSc. Finally, we outline some technical and conceptual ways to improve our understanding in this field.

Contribution of HLA and KIR Alleles to Systemic Sclerosis Susceptibility and Immunological and Clinical Disease Subtypes

Systemic sclerosis (SSc) is an autoinflammatory, fibrotic condition of unknown aetiology. The presence of detectable autoantibodies against diverse nuclear antigens, as well as strong HLA associations with disease, suggest autoimmune involvement, however the links between endogenous and exogenous risk factors and SSc pathology remain undetermined. We have conducted a genetic analysis of HLA inheritance in two independent and meta-analysed cohorts of 1,465 SSc cases and 13,273 controls, including stratified association analyses in clinical and autoantibody positive subgroups of disease. Additionally, we have used patient genotypes to impute gene dosages across the KIR locus, encoding paired activating and inhibitory lymphocyte receptors for Class I HLA ligands, to conduct the largest analysis of KIR-HLA epistatic interactions in SSc to date. We confirm previous Class II HLA associations with SSc risk and report a new Class I association with haplotype HLA-B*44:03-HLA-C*16:01 at genome-wide significance (GWS). We further report statistically significant HLA associations with clinical and serological subtypes of disease through direct case-case comparison, and report a new association of HLA-DRB1*15:01, previously shown to bind topoisomerase-1 derived peptides, with anti-topoisomerase (ATA) positive disease. Finally, we identify genetic epistasis between KIRs and HLA class I ligands, suggesting genetic modulation of lymphocyte activation may further contribute to an individual’s underlying disease risk. Taken together, these findings support future functional investigation into endogenous immunological and environmental stimuli for disrupted immune tolerance in SSc.

A Summary on the Genetics of Systemic Lupus Erythematosus, Rheumatoid Arthritis, Systemic Sclerosis, and Sjögren's Syndrome

Systemic lupus erythematosus, systemic sclerosis, rheumatoid arthritis, and Sjögren's syndrome are four major autoimmune rheumatic diseases characterized by the presence of autoantibodies, caused by a dysregulation of the immune system that leads to a wide variety of clinical manifestations. These conditions present complex etiologies strongly influenced by multiple environmental and genetic factors. The human leukocyte antigen (HLA) region was the first locus identified to be associated and still represents the strongest susceptibility factor for each of these conditions, particularly the HLA class II genes, including DQA1, DQB1, and DRB1, but class I genes have also been associated. Over the last two decades, the genetic component of these disorders has been extensively investigated and hundreds of non-HLA risk genetic variants have been uncovered. Furthermore, it is widely accepted that autoimmune rheumatic diseases share molecular disease pathways, such as the interferon (IFN) type I pathways, which are reflected in a common genetic background. Some examples of well-known pleiotropic loci for autoimmune rheumatic diseases are the HLA region, DNASEL13, TNIP1, and IRF5, among others. The identification of the causal molecular mechanisms behind the genetic associations is still a challenge. However, recent advances have been achieved through mouse models and functional studies of the loci. Here, we provide an updated overview of the genetic architecture underlying these four autoimmune rheumatic diseases, with a special focus on the HLA region.

A Narrative Review of Pathogenetic and Histopathologic Aspects, Epidemiology, Classification Systems, and Disease Outcome Measures in Systemic Sclerosis

Systemic sclerosis (SSc) is a rare systemic autoimmune disease, characterized by the presence of three main actors: vasculopathy, immune activation, and fibrosis. This pathologic process is then translated in a clinical picture with great variability among different patients in terms of type of organ involvement, disease severity and prognosis. This heterogeneity is a main feature of SSc, which, in addition to the presence of early phases of the disease characterized by mild symptoms, can explain the high difficulty in establishing classification criteria, and in defining patients' subsets and disease outcomes. The definition of disease outcomes is particularly relevant in the setting of clinical trials, where the aim is to provide reliable endpoints, able to measure the magnitude of the efficacy of a certain drug or intervention. For this reason, in the last years, increasing efforts have been done to design measures of disease activity, damage, severity, and response to treatment, often in the context of composite indexes. When considering disease outcomes, the experience of the patient represents a relevant and complementary aspect. The tools able to capture this experience, the patient-reported outcomes, have been increasingly used in the last years in clinical practice and in clinical trials, both as primary and secondary endpoints. This comprehensive narrative review on SSc will therefore cover pathogenetic and histopathologic aspects, epidemiology, classification systems, and disease outcome measures, in order to focus on issues that are relevant for clinical research and design of clinical trials.

Association with HLA-DRβ1 position 37 distinguishes juvenile Dermatomyositis from adult-onset myositis

Objectives

Juvenile dermatomyositis (JDM) is a rare, severe autoimmune disease and the most common idiopathic inflammatory myopathy (IIM) of children. JDM and adult-onset dermatomyositis (DM) have similar clinical, biological and serological features, although these features differ in prevalence between childhood-onset and adult-onset disease, suggesting age of disease onset may influence pathogenesis. Therefore, a JDM-focused genetic analysis was performed using the largest collection of JDM samples to date.

Methods

Caucasian JDM samples (n = 952) obtained via international collaboration were genotyped using the Illumina HumanCoreExome chip. Additional non-assayed HLA loci and genome-wide SNPs were imputed.

Results

HLA-DRB1*03:01 was confirmed as the classical HLA allele most strongly associated with JDM (OR 1.66; 95% CI 1.46, 1.89; P = 1.4 × 10−14), with an independent association at HLA-C*02:02 (OR = 1.74; 95% CI 1.42, 2.13, P = 7.13 × 10−8). Analyses of amino acid positions within HLA-DRB1 indicated the strongest association was at position 37 (omnibus P = 3.3 × 10−19), with suggestive evidence this association was independent of position 74 (omnibus P = 5.1 × 10−5), the position most strongly associated with adult-onset DM. Conditional analyses also suggested the association at position 37 of HLA-DRB1 was independent of some alleles of the Caucasian HLA 8.1 ancestral haplotype (AH8.1) such as HLA-DQB1*02:01 (OR = 1.62; 95% CI 1.36, 1.93; P = 8.70 × 10−8), but not HLA-DRB1*03:01 (OR = 1.49; 95% CR 1.24, 1.80; P = 2.24 × 10−5). No associations outside the HLA region were identified.

Conclusions

Our findings confirm previous associations with AH8.1 and HLA-DRB1*03:01, HLA-C*02:02 and identify a novel association with amino acid position 37 within HLA-DRB1 which may distinguish JDM from adult DM.

Molecular Basis of Accelerated Aging with Immune Dysfunction-Mediated Inflammation (Inflamm-Aging) in Patients with Systemic Sclerosis

Systemic sclerosis (SSc) is a chronic connective tissue disorder characterized by immune dysregulation, chronic inflammation, vascular endothelial cell dysfunction, and progressive tissue fibrosis of the skin and internal organs. Moreover, increased cancer incidence and accelerated aging are also found. The increased cancer incidence is believed to be a result of chromosome instability. Accelerated cellular senescence has been confirmed by the shortening of telomere length due to increased DNA breakage, abnormal DNA repair response, and telomerase deficiency mediated by enhanced oxidative/nitrative stresses. The immune dysfunctions of SSc patients are manifested by excessive production of proinflammatory cytokines IL-1, IL-6, IL-17, IFN-α, and TNF-α, which can elicit potent tissue inflammation followed by tissue fibrosis. Furthermore, a number of autoantibodies including anti-topoisomerase 1 (anti-TOPO-1), anti-centromere (ACA or anti-CENP-B), anti-RNA polymerase enzyme (anti-RNAP III), anti-ribonuclear proteins (anti-U1, U2, and U11/U12 RNP), anti-nucleolar antigens (anti-Th/T0, anti-NOR90, anti-Ku, anti-RuvBL1/2, and anti-PM/Scl), and anti-telomere-associated proteins were also found. Based on these data, inflamm-aging caused by immune dysfunction-mediated inflammation exists in patients with SSc. Hence, increased cellular senescence is elicited by the interactions among excessive oxidative stress, pro-inflammatory cytokines, and autoantibodies. In the present review, we will discuss in detail the molecular basis of chromosome instability, increased oxidative stress, and functional adaptation by deranged immunome, which are related to inflamm-aging in patients with SSc.

Insights into origins and specificities of autoantibodies in systemic sclerosis

PURPOSE OF REVIEW

Autoantibodies are hallmark findings in systemic sclerosis (SSc), often present prior to disease onset. Clinical diagnosis and prognosis of SSc have long relied on the antitopoisomerase - anticentromere - anti-RNA polymerase antibody trichotomy. However, many more autoantibodies found in SSc are being actively investigated for insights into triggering events, mechanisms of tolerance break, and connections to tissue damage. This review examines recent studies on SSc autoantibodies and the early events that lead to their development.

RECENT FINDINGS

Recent work has elucidated potential connections between human cytomegalovirus infection, silicone breast implants, and malignancy to SSc autoantibody development. At the level of the dendritic cell:T cell interaction, where tolerance is broken, new studies identified shared motifs in the peptide-binding domains of SSc-associated human leukocyte antigen alleles. Immunological analysis of SSc patient B cells has uncovered several anomalies in the regulatory capacities of SSc naïve and memory B cell populations. Expanding efforts to uncover new SSc autoantibodies revealed anti-CXCL4, anticollagen V, and other autoantibodies as potential players in disease pathogenesis.

SUMMARY

Further research into the role of autoantibodies in SSc development may uncover new mechanism-guided therapeutic targets. In addition, a better understanding of autoantibody associations with SSc disease outcomes will improve clinical care.

Development of Lupus Erythematosus Tumidus During the Course of Systemic Sclerosis

A man with systemic sclerosis (SS), manifested by characteristic skin lesions, gastro-esophageal reflux disease, and pulmonary fibrosis producing progressive respiratory failure, and a positive antinuclear antibody consistent with reactivity to fibrillarin, developed skin lesions with the clinical and histological characteristics of lupus erythematosus tumidus (LET) 10 years after the diagnosis of SS. His respiratory failure progressed and he expired from sepsis after tracheal intubation and mechanical ventilation two years after developing LET. The association of SS and LET, not described until now, raises questions about its pathogenesis and its prognostic significance.

Similarities between COVID-19 and systemic sclerosis early vasculopathy: A "viral" challenge for future research in scleroderma

OBJECTIVE

To review similarities between COVID-19 and systemic sclerosis (SSc) early vasculopathy to provide novel insights into both diseases.

METHODS

A narrative review of the literature supplemented with expert opinion.

RESULTS

There is clear evidence that the endothelium is at the centre stage in SSc and COVID-19, with endothelial cell activation/injury and dysfunction creating the crucial evolving step in the pathogenesis of both diseases. The angiotensin system has also been implicated in the early stages of both COVID-19 and SSc. Autoptic studies provide novel insights into the effects of SARS-CoV-2 on the endothelium. Normal endothelium and endothelial dysfunction in COVID-19 and SSc are discussed. It is debated whether SARS-CoV-2 infection triggers autoimmunity with production of autoantibodies which is of mechanistic interest because other viral illnesses are potentially involved in endothelial dysfunction and in SSc pathogenesis.

CONCLUSION

COVID-19 is due to a direct assault of SARS-CoV-2 on the vascular system as an acute infection, whereas SSc remains a chronic/sub-acute autoimmune disease of largely unknown etiology Further study and exploration of the SARS-CoV-2 pathogenic mechanisms might provide further useful milestones in the understanding of the early SSc pathogenesis.

Current Concepts on the Pathogenesis of Systemic Sclerosis

From the clinical standpoint, systemic sclerosis (SSc) is characterized by skin and internal organ fibrosis, diffuse fibroproliferative vascular modifications, and autoimmunity. Clinical presentation and course are highly heterogenous and life expectancy variably affected mostly dependent on lung and heart involvement. SSc touches more women than men with differences in disease severity and environmental exposure. Pathogenetic events originate from altered homeostasis favored by genetic predisposition, environmental cues and a variety of endogenous and exogenous triggers. Epigenetic modifications modulate SSc pathogenesis which strikingly associate profound immune-inflammatory dysregulation, abnormal endothelial cell behavior, and cell trans-differentiation into myofibroblasts. SSc myofibroblasts show enhanced survival and enhanced extracellular matrix deposition presenting altered structure and altered physicochemical properties. Additional cell types of likely pathogenic importance are pericytes, platelets, and keratinocytes in conjunction with their relationship with vessel wall cells and fibroblasts. In SSc, the profibrotic milieu is favored by cell signaling initiated in the one hand by transforming growth factor-beta and related cytokines and in the other hand by innate and adaptive type 2 immune responses. Radical oxygen species and invariant receptors sensing danger participate to altered cell behavior. Conventional and SSc-specific T cell subsets modulate both fibroblasts as well as endothelial cell dysfunction. Beside autoantibodies directed against ubiquitous antigens important for enhanced clinical classification, antigen-specific agonistic autoantibodies may have a pathogenic role. Recent studies based on single-cell RNAseq and multi-omics approaches are revealing unforeseen heterogeneity in SSc cell differentiation and functional states. Advances in system biology applied to the wealth of data generated by unbiased screening are allowing to subgroup patients based on distinct pathogenic mechanisms. Deciphering heterogeneity in pathogenic mechanisms will pave the way to highly needed personalized therapeutic approaches.

Comprehensive analysis of the major histocompatibility complex in systemic sclerosis identifies differential HLA associations by clinical and serological subtypes

OBJECTIVE

The greatest genetic effect reported for systemic sclerosis (SSc) lies in the major histocompatibility complex (MHC) locus. Leveraging the largest SSc genome-wide association study, we aimed to fine-map this region to identify novel human leucocyte antigen (HLA) genetic variants associated with SSc susceptibility and its main clinical and serological subtypes.

METHODS

9095 patients with SSc and 17 584 controls genome-wide genotyped were used to impute and test single-nucleotide polymorphisms (SNPs) across the MHC, classical HLA alleles and their composite amino acid residues. Additionally, patients were stratified according to their clinical and serological status, namely, limited cutaneous systemic sclerosis (lcSSc), diffuse cutaneous systemic sclerosis (dcSSc), anticentromere (ACA), antitopoisomerase (ATA) and anti-RNApolIII autoantibodies (ARA).

RESULTS

Sequential conditional analyses showed nine SNPs, nine classical alleles and seven amino acids that modelled the observed associations with SSc. This confirmed previously reported associations with HLA-DRB1*11:04 and HLA-DPB1*13:01, and revealed a novel association of HLA-B*08:01. Stratified analyses showed specific associations of HLA-DQA1*02:01 with lcSSc, and an exclusive association of HLA-DQA1*05:01 with dcSSc. Similarly, private associations were detected in HLA-DRB1*08:01 and confirmed the previously reported association of HLA-DRB1*07:01 with ACA-positive patients, as opposed to the HLA-DPA1*02:01 and HLA-DQB1*03:01 alleles associated with ATA presentation.

CONCLUSIONS

This study confirms the contribution of HLA class II and reveals a novel association of HLA class I with SSc, suggesting novel pathways of disease pathogenesis. Furthermore, we describe specific HLA associations with SSc clinical and serological subtypes that could serve as biomarkers of disease severity and progression.

Antigen Processing, Presentation, and Tolerance: Role in Autoimmune Skin Diseases

Autoreactive T cells pose a constant risk for the emergence of autoimmune skin diseases in genetically predisposed individuals carrying certain HLA risk alleles. Immune tolerance mechanisms are opposed by broad HLA-presented self-immunopeptidomes, a predefined repertoire of polyspecific TCRs, the continuous generation of new antibody specificities by somatic recombination of Ig genes in B cells, and heightened proinflammatory reactivity. Increased autoantigen presentation by HLA molecules, cross-activation of pathogen-induced T cells against autologous structures, altered metabolism of self-proteins, and excessive production of proinflammatory signals may all contribute to the breakdown of immune tolerance and the development of autoimmune skin diseases.

Incidence and prevalence of systemic sclerosis globally: a comprehensive systematic review and meta-analysis

OBJECTIVES

We aimed to conduct a systematic review and meta-analysis on the incidence and prevalence of SSc covering the entire literature.

METHODS

This study followed the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement of 2009. We conducted a systematic search in MEDLINE, Web of Science and Embase to identify articles reporting incidence and/or prevalence of SSc. Two authors conducted the search, reviewed articles for inclusion and extracted relevant data. We used random-effects models to estimate the pooled prevalence and incidence of SSc and performed subgroup analyses by sex, case definition and region to investigate heterogeneity. We explored the association between calendar period and reported estimates using meta-regression.

RESULTS

Among 6983 unique records identified, we included 61 studies of prevalence and 39 studies of incidence in the systematic review. The overall pooled prevalence of SSc was 17.6 (95% CI 15.1, 20.5) per 100 000 and the overall pooled incidence rate of SSc was 1.4 (95% CI 1.1, 1.9) per 100 000 person-years. We observed significant regional variations in reported estimates; studies conducted in North America reported considerably higher estimates than other regions. The pooled incidence and prevalence in women were five times higher than in men. More recent studies reported higher estimates than older ones.

CONCLUSION

In this comprehensive review of the incidence and prevalence of SSc across the world, there was large heterogeneity among estimates, which should be taken into consideration when interpreting the results.

Updates on genetics in systemic sclerosis

Systemic sclerosis (SSc) is a complex disease, in which an interaction of genetic and environmental factors plays an important role in its development and pathogenesis. A number of genetic studies, including candidate gene analysis and genome-wide association study, have found that the associated genetic variants are mainly localized in noncoding regions in the expression quantitative trait locus and influence corresponding gene expression. The gene variants identified as a risk for SSc susceptibility include those associated with innate immunity, adaptive immune response, and cell death, while there are only few SSc-associated genes involved in the fibrotic process or vascular homeostasis. Human leukocyte antigen class II genes are associated with SSc-related autoantibodies rather than SSc itself. Since the pathways between the associated genotype and phenotype are still poorly understood, further investigations using multi-omics technologies are necessary to characterize the complex molecular architecture of SSc, identify biomarkers useful to predict future outcomes and treatment responses, and discover effective drug targets.

Relapsing Polychondritis Presenting 2 Years after Systemic Sclerosis with Pulmonary Arterial Hypertension

Relapsing polychondritis (RPC) is a systemic immune-mediated disease characterized by recurrent and progressive inflammation of cartilaginous tissues. 64% of RPC patients concurrent with other autoimmune disorders, there are very few reports about the concomitant RPC patients with systemic sclerosis (SSc). Herein we report a case of RPC in a 50-year-old female following SSc with pulmonary arterial hypertension (PAH) 2 years ago. She was treated with corticosteroids, immunosuppressive drugs, oral endothelin-A receptor antagonist and phosphodiesterase type 5 inhibitors. Her ocular and auricular symptoms disappeared quickly. The hemodynamic parameters were also significantly improved after treatment. To our knowledge, this is the first RPC complicated with SSc-PAH reported.

Expression Quantitative Trait Locus Analysis in Systemic Sclerosis Identifies New Candidate Genes Associated With Multiple Aspects of Disease Pathology

OBJECTIVE

To identify the genetic variants that affect gene expression (expression quantitative trait loci [eQTLs]) in systemic sclerosis (SSc) and to investigate their role in the pathogenesis of the disease.

METHODS

We performed an eQTL analysis using whole-blood sequencing data from 333 SSc patients and 524 controls and integrated them with SSc genome-wide association study (GWAS) data. We integrated our findings from expression modeling, differential expression analysis, and transcription factor binding site enrichment with key clinical features of SSc.

RESULTS

We detected 49,123 validated cis-eQTLs from 4,539 SSc-associated single-nucleotide polymorphisms (SNPs) (P_GWAS < 10^-5 ). A total of 1,436 genes were within 1 Mb of the 4,539 SSc-associated SNPs. Of those 1,436 genes, 565 were detected as having ≥1 eQTL with an SSc-associated SNP. We developed a strategy to prioritize disease-associated genes based on their expression variance explained by SSc eQTLs (r² > 0.05). As a result, 233 candidates were identified, 134 (58%) of them associated with hallmarks of SSc and 105 (45%) of them differentially expressed in the blood cells, skin, or lung tissue of SSc patients. Transcription factor binding site analysis revealed enriched motifs of 24 transcription factors (5%) among SSc eQTLs, 5 of which were found to be differentially regulated in the blood cells (ELF1 and MGA), skin (KLF4 and ID4), and lungs (TBX4) of SSc patients. Ten candidate genes (4%) can be targeted by approved medications for immune-mediated diseases, of which only 3 have been tested in clinical trials in patients with SSc.

CONCLUSION

The findings of the present study indicate a new layer to the molecular complexity of SSc, contributing to a better understanding of the pathogenesis of the disease.

Novel classifications for systemic sclerosis: challenging historical subsets to unlock new doors

PURPOSE OF REVIEW

Systemic sclerosis (SSc) is a severe rheumatic disease characterized by a considerable heterogeneity in clinical presentations and pathophysiological mechanisms. This variability has a substantial impact on morbidity and mortality and limits the generalizability of clinical trial results. This review aims to highlight recent studies that have proposed new innovative approaches to decipher this heterogeneity, in particular, by attempting to optimize disease classification.

RECENT FINDINGS

The historical dichotomy limited/diffuse subsets based on cutaneous involvement has been challenged by studies highlighting an underestimated heterogeneity between these two subtypes and showing that presence of organ damage and autoantibody profiles markedly influenced survival beyond skin extension. Advanced computational methods using unsupervised machine learning analyses of clinical variables and/or high-throughput omics technologies, clinical variables trajectories modelling overtime or radiomics have provided significant insights on key pathogenic processes that could help defining new subgroups beyond the diffuse/limited subsets.

SUMMARY

We can anticipate that a future classification of SSc patients will integrate innovative approaches encompassing clinical phenotypes, variables trajectories, serological features and innovative omics molecular signatures. It nevertheless seems crucial to also pursue the implementation and standardization of readily available and easy to use tools that can be used in clinical practice.

Systemic sclerosis pathogenesis: contribution of recent advances in genetics

PURPOSE OF REVIEW

To review susceptibility genes and how they could integrate in systemic sclerosis (SSc) pathophysiology providing insight and perspectives for innovative therapies.

RECENT FINDINGS

SSc is a rare disease characterized by vasculopathy, dysregulated immunity and fibrosis. Genome-Wide association studies and ImmunoChip studies performed in recent years revealed associated genetic variants mainly localized in noncoding regions and mostly affecting the immune system of SSc patients. Gene variants were described in innate immunity (IRF5, IRF7 and TLR2), T and B cells activation (CD247, TNFAIP3, STAT4 and BLK) and NF-κB pathway (TNFAIP3 and TNIP1) confirming previous biological data. In addition to impacting immune response, CSK, DDX6, DNASE1L3 and GSDMA/B could also act in the vascular and fibrotic components of SSc.

SUMMARY

Although genetic studies highlighted the dysregulated immune response in SSc, future research must focus on a deeper characterization of these variants with determination of their functional effects. Moreover, the role of these genes or others on specific vasculopathy and fibrosis would provide insight. Establishment of polygenic score or integrated genome approaches could identify new targets specific of SSc clinical features. This will allow physicians to propose new therapies to SSc patients.

Scleroderma epidemiology update

PURPOSE OF REVIEW

Systemic sclerosis (scleroderma, SSc) is a rare multisystem autoimmune disease characterized by autoantibodies, vasculopathy, and fibrosis of the skin and internal organs. This review aims to provide an overview and summary of the recent epidemiological studies in systemic sclerosis.

RECENT FINDINGS

Global trends of scleroderma demonstrate greater prevalence of SSc in European, North, and South American patients compared with East Asian patients. However, the greatest prevalence (47 in 100 000), was found among the indigenous peoples in Canada. Phenotypical differences exist depending on the age of presentation with greater internal organ involvement and disease acceleration present in older patients. Sex differences include greater severity of disease expression, relative prevalence of diffuse cutaneous SSc, and organ involvement in males versus females. New studies conflict with previous data reporting greater proportion of pulmonary arterial hypertension in females. Furthermore, the effect of low median household income is demonstrated as a factor increasing risk of death in SSc patients.

SUMMARY

Understanding the epidemiological factors in SSc enables patient care through patient classification, prognostication, and monitoring. Future research may emphasize enrichment of SSc patients in randomized trials who are more likely to progress or be treatment responsive, focused screening, and personalized patient care through the creation and validation of new SSc criteria and subsets.

Classical Disease-Specific Autoantibodies in Systemic Sclerosis: Clinical Features, Gene Susceptibility, and Disease Stratification

Systemic sclerosis (SSc) is an autoimmune disease characterized by abnormalities in microcirculation, extracellular matrix accumulation, and immune activation. Autoantibodies are markers of immune abnormalities and provide diagnostic and predictive value in SSc. Anti-topoisomerase antibodies (ATAs), anticentromere antibodies (ACAs), and anti-RNA polymerase antibodies (ARAs) are the three classical specific antibodies with the highest availability and stability. In this review, we provide an overview of the recent progress in SSc research with respect to ATAs, ACAs, and ARAs, focusing on their application in distinguishing clinical phenotypes, such as malignancy and organ involvement, identifying genetic background in human leukocyte antigen (HLA) or non-HLA alleles, and their potential roles in disease pathogenesis based on the effects of antigen-antibody binding. We finally summarized the novel analysis using ATAs, ACAs, and ARAs on more detailed disease clusters. Considering these advantages, this review emphasizes that classical SSc-specific autoantibodies are still practical and have the potential for patient and risk stratification with applications in precise medicine for SSc.

Revisiting B cell tolerance and autoantibodies in seropositive and seronegative autoimmune rheumatic disease (AIRD)

Autoimmune rheumatic diseases (AIRD) are categorized seropositive or seronegative, dependent upon the presence or absence of specific autoreactive antibodies, including rheumatoid factor and anti-citrullinated protein antibodies. Autoantibody-based diagnostics have proved helpful in patient care, not only for diagnosis but also for monitoring of disease activity and prediction of therapy responsiveness. Recent work demonstrates that AIRD patients develop autoantibodies beyond those contained in the original categorization. In this study we discuss key mechanisms that underlie autoantibody development in AIRD: defects in early B cell development, genetic variants involved in regulating B cell and T cell tolerance, environmental triggers and antigen modification. We describe how autoantibodies can directly contribute to AIRD pathogenesis through innate and adaptive immune mechanisms, eventually culminating in systemic inflammation and localized tissue damage. We conclude by discussing recent insights that suggest distinct AIRD have incorrectly been denominated seronegative.

Exploratory Study of Autoantibody Profiling in Drug-Induced Liver Injury with an Autoimmune Phenotype

Drug-induced liver injury (DILI) sometimes presents with an autoimmune hepatitis-like phenotype (AI-DILI), and it is challenging to distinguish it from de novo autoimmune hepatitis (AIH). We conducted a study to identify autoantibodies unique to AI-DILI by profiling serum autoantibodies. Autoantibodies were quantified using an autoantigen array containing 94 autoantigens from four groups: AI-DILI (n = 65), DILI controls (n = 67), de novo AIH (n = 17), and healthy controls (HCs; n = 30). In 37 patients with AI-DILI, samples were also collected 6 months after presentation. AI-DILI and de novo AIH had similar anti-neutrophil antibody and anti-smooth muscle antibody prevalence. Compared to HCs, de novo AIH had an increase in many immunoglobulin G (IgG; 35 [46.1%]) and IgM (51 [70%]) autoantibodies, whereas AI-DILI had an increase of IgM (40 [54.8%]) but not IgG autoantibodies. DILI controls had a similar IgG and IgM profile compared to HCs. Comparing de novo AIH to AI-DILI identified 18 (23.7%) elevated IgG but only one (1.4%) IgM autoantibodies, indicating the unique IgG autoantibody profile in de novo AIH. Compared to DILI and HCs, increased IgM autoantibodies in AI-DILI and de novo AIH were common; however, AI-DILI induced by different drugs showed different frequencies of IgM autoantibodies, with nitrofurantoin-related AI-DILI showing a higher number of increased IgM autoantibodies. AI-DILI autoantibody levels at diagnosis and at 6 months showed a significant decline in 37 IgM autoantibodies. A model with highly correlated IgG and IgM was fitted into multivariate logistic regression and revealed an area under the curve of 0.87 (95% confidence interval, 0.79-0.95) to distinguish de novo AIH from AI-DILI. Conclusion: The unique IgG and IgM autoantibody signature appears to be a promising biomarker for distinguishing AI-DILI from de novo AIH.

The Contribution of Genetics and Epigenetics to Our Understanding of Health Disparities in Rheumatic Diseases

Socioeconomic determinants of health are associated with worse outcomes in the rheumatic diseases and contribute significantly to health disparities. However, genetic and epigenetic risk factors may affect different populations disproportionally and further exacerbate health disparities. We discuss the role of genetics and epigenetics to the health disparities observed in rheumatic diseases. We review concepts of population genetics and natural selection, current genome-wide genetic and epigenetic studies of several autoimmune diseases, and environmental exposures associated with disease risk in different populations. To understand how genomics influence health disparities in the rheumatic diseases, further studies in different populations worldwide are needed.

Patient ancestry significantly contributes to molecular heterogeneity of systemic lupus erythematosus

Gene expression signatures can stratify patients with heterogeneous diseases, such as systemic lupus erythematosus (SLE), yet understanding the contributions of ancestral background to this heterogeneity is not well understood. We hypothesized that ancestry would significantly influence gene expression signatures and measured 34 gene modules in 1566 SLE patients of African ancestry (AA), European ancestry (EA), or Native American ancestry (NAA). Healthy subject ancestry-specific gene expression provided the transcriptomic background upon which the SLE patient signatures were built. Although standard therapy affected every gene signature and significantly increased myeloid cell signatures, logistic regression analysis determined that ancestral background significantly changed 23 of 34 gene signatures. Additionally, the strongest association to gene expression changes was found with autoantibodies, and this also had etiology in ancestry: the AA predisposition to have both RNP and dsDNA autoantibodies compared with EA predisposition to have only anti-dsDNA. A machine learning approach was used to determine a gene signature characteristic to distinguish AA SLE and was most influenced by genes characteristic of the perturbed B cell axis in AA SLE patients.

Transcriptional profiling of lupus patients and healthy controls reveals ancestry-related differences and transcriptional heterogeneity among lupus patients.

Common genetic susceptibility loci link PFAPA syndrome, Behçet's disease, and recurrent aphthous stomatitis

Periodic fever, aphthous stomatitis, pharyngitis, and cervical adenitis (PFAPA) syndrome is the most common periodic fever syndrome in children. The disease appears to cluster in families, but the pathogenesis is unknown. We queried two European-American cohorts and one Turkish cohort (total n = 231) of individuals with PFAPA for common variants previously associated with two other oropharyngeal ulcerative disorders, Behçet's disease and recurrent aphthous stomatitis. In a metaanalysis, we found that a variant upstream of IL12A (rs17753641) is strongly associated with PFAPA (OR 2.13, P = 6 × 10-9). We demonstrated that monocytes from individuals who are heterozygous or homozygous for this risk allele produce significantly higher levels of IL-12p70 upon IFN-γ and LPS stimulation than those from individuals without the risk allele. We also found that variants near STAT4, IL10, and CCR1-CCR3 were significant susceptibility loci for PFAPA, suggesting that the pathogenesis of PFAPA involves abnormal antigen-presenting cell function and T cell activity and polarization, thereby implicating both innate and adaptive immune responses at the oropharyngeal mucosa. Our results illustrate genetic similarities among recurrent aphthous stomatitis, PFAPA, and Behçet's disease, placing these disorders on a common spectrum, with recurrent aphthous stomatitis on the mild end, Behçet's disease on the severe end, and PFAPA intermediate. We propose naming these disorders Behçet's spectrum disorders to highlight their relationship. HLA alleles may be factors that influence phenotypes along this spectrum as we found new class I and II HLA associations for PFAPA distinct from Behçet's disease and recurrent aphthous stomatitis.

A Bioinformatics Analysis Reveals Novel Pathogens as Molecular Mimicry Triggers of Systemic Sclerosis

A recent bioinformatic analysis revealing dominant B cell epitopes of systemic sclerosis-specific autoantibodies, including anti-centromere B, anti-topoisomerase I and anti-fibrillarin, has demonstrated the existence of several in silico antigenic mimics of pathogens that could act as triggers of the respective dominant autoepitopes. Based on those findings, the aim of the present study was to use a more comprehensive bioinformatic analysis. We demonstrated the presence of a plethora of novel microbial mimics, unnoticed by the studies so far conducted, which share remarkable amino acid similarities with the respective autoantigenic epitopes. This bioinformatic approach coupled by in vitro testing of the homologous self/non-self-mimics in serum samples from patients with systemic sclerosis may provide novel evidence of immunological cross-reactivity, implicating currently ignored or overlooked pathogens, which may indeed play a role in the induction of SSc-specific autoantibodies and assist efforts to understand the pathogenesis of this enigmatic disease.