Deciphering the role of cDC2s in Sjögren's syndrome: transcriptomic profile links altered antigen processes with IFN signature and autoimmunity.

OBJECTIVE: Type 2 conventional dendritic cells (cDC2s) are key orchestrators of inflammatory responses, linking innate and adaptative immunity. Here we explored the regulation of immunological pathways in cDC2s from patients with primary Sjögren's syndrome (pSS). METHODS: RNA sequencing of circulating cDC2s from patients with pSS, patients with non-Sjögren's sicca and healthy controls (HCs) was exploited to establish transcriptional signatures. Phenotypical and functional validation was performed in independent cohorts. RESULTS: Transcriptome of cDC2s from patients with pSS revealed alterations in type I interferon (IFN), toll-like receptor (TLR), antigen processing and presentation pathways. Phenotypical validation showed increased CX3CR1 expression and decreased integrin beta-2 and plexin-B2 on pSS cDC2s. Functional validation confirmed impaired capacity of pSS cDC2s to degrade antigens and increased antigen uptake, including self-antigens derived from salivary gland epithelial cells. These changes in antigen uptake and degradation were linked to anti-SSA/Ro (SSA) autoantibodies and the presence of type I IFNs. In line with this, in vitro IFN-α priming enhanced the uptake of antigens by HC cDC2s, reflecting the pSS cDC2 profile. Finally, pSS cDC2s compared with HC cDC2s increased the proliferation and the expression of CXCR3 and CXCR5 on proliferating CD4+ T cells. CONCLUSIONS: pSS cDC2s are transcriptionally altered, and the aberrant antigen uptake and processing, including (auto-)antigens, together with increased proliferation of tissue-homing CD4+ T cells, suggest altered antigen presentation by pSS cDC2s. These functional alterations were strongly linked to anti-SSA positivity and the presence of type I IFNs. Thus, we demonstrate novel molecular and functional pieces of evidence for the role of cDC2s in orchestrating immune response in pSS, which may yield novel avenues for treatment.

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.

Genomic Risk Score impact on susceptibility to systemic sclerosis.

OBJECTIVES: Genomic Risk Scores (GRS) successfully demonstrated the ability of genetics to identify those individuals at high risk for complex traits including immune-mediated inflammatory diseases (IMIDs). We aimed to test the performance of GRS in the prediction of risk for systemic sclerosis (SSc) for the first time. METHODS: Allelic effects were obtained from the largest SSc Genome-Wide Association Study (GWAS) to date (9 095 SSc and 17 584 healthy controls with European ancestry). The best-fitting GRS was identified under the additive model in an independent cohort that comprised 400 patients with SSc and 571 controls. Additionally, GRS for clinical subtypes (limited cutaneous SSc and diffuse cutaneous SSc) and serological subtypes (anti-topoisomerase positive (ATA+) and anti-centromere positive (ACA+)) were generated. We combined the estimated GRS with demographic and immunological parameters in a multivariate generalised linear model. RESULTS: The best-fitting SSc GRS included 33 single nucleotide polymorphisms (SNPs) and discriminated between patients with SSc and controls (area under the receiver operating characteristic (ROC) curve (AUC)=0.673). Moreover, the GRS differentiated between SSc and other IMIDs, such as rheumatoid arthritis and Sjögren's syndrome. Finally, the combination of GRS with age and immune cell counts significantly increased the performance of the model (AUC=0.787). While the SSc GRS was not able to discriminate between ATA+ and ACA+ patients (AUC<0.5), the serological subtype GRS, which was based on the allelic effects observed for the comparison between ACA+ and ATA+ patients, reached an AUC=0.693. CONCLUSIONS: GRS was successfully implemented in SSc. The model discriminated between patients with SSc and controls or other IMIDs, confirming the potential of GRS to support early and differential diagnosis for SSc.

Low RUNX3 expression alters dendritic cell function in patients with systemic sclerosis and contributes to enhanced fibrosis.

OBJECTIVES: Systemic sclerosis (SSc) is an autoimmune disease with unknown pathogenesis manifested by inflammation, vasculopathy and fibrosis in skin and internal organs. Type I interferon signature found in SSc propelled us to study plasmacytoid dendritic cells (pDCs) in this disease. We aimed to identify candidate pathways underlying pDC aberrancies in SSc and to validate its function on pDC biology. METHODS: In total, 1193 patients with SSc were compared with 1387 healthy donors and 8 patients with localised scleroderma. PCR-based transcription factor profiling and methylation status analyses, single nucleotide polymorphism genotyping by sequencing and flow cytometry analysis were performed in pDCs isolated from the circulation of healthy controls or patients with SSc. pDCs were also cultured under hypoxia, inhibitors of methylation and hypoxia-inducible factors and runt-related transcription factor 3 (RUNX3) levels were determined. To study Runx3 function, Itgax-Cre:Runx3f/f mice were used in in vitro functional assay and bleomycin-induced SSc skin inflammation and fibrosis model. RESULTS: Here, we show downregulation of transcription factor RUNX3 in SSc pDCs. A higher methylation status of the RUNX3 gene, which is associated with polymorphism rs6672420, correlates with lower RUNX3 expression and SSc susceptibility. Hypoxia is another factor that decreases RUNX3 level in pDC. Mouse pDCs deficient of Runx3 show enhanced maturation markers on CpG stimulation. In vivo, deletion of Runx3 in dendritic cell leads to spontaneous induction of skin fibrosis in untreated mice and increased severity of bleomycin-induced skin fibrosis. CONCLUSIONS: We show at least two pathways potentially causing low RUNX3 level in SSc pDCs, and we demonstrate the detrimental effect of loss of Runx3 in SSc model further underscoring the role of pDCs in this disease.

Influence of TYK2 in systemic sclerosis susceptibility: a new locus in the IL-12 pathway.

OBJECTIVES: TYK2 is a common genetic risk factor for several autoimmune diseases. This gene encodes a protein kinase involved in interleukin 12 (IL-12) pathway, which is a well-known player in the pathogenesis of systemic sclerosis (SSc). Therefore, we aimed to assess the possible role of this locus in SSc. METHODS: This study comprised a total of 7103 patients with SSc and 12 220 healthy controls of European ancestry from Spain, USA, Germany, the Netherlands, Italy and the UK. Four TYK2 single-nucleotide polymorphisms (V362F (rs2304256), P1104A (rs34536443), I684S (rs12720356) and A928V (rs35018800)) were selected for follow-up based on the results of an Immunochip screening phase of the locus. Association and dependence analyses were performed by the means of logistic regression and conditional logistic regression. Meta-analyses were performed using the inverse variance method. RESULTS: Genome-wide significance level was reached for TYK2 V362F common variant in our pooled analysis (p=3.08×10(-13), OR=0.83), while the association of P1104A, A928V and I684S rare and low-frequency missense variants remained significant with nominal signals (p=2.28×10(-3), OR=0.80; p=1.27×10(-3), OR=0.59; p=2.63×10(-5), OR=0.83, respectively). Interestingly, dependence and allelic combination analyses showed that the strong association observed for V362F with SSc, corresponded to a synthetic association dependent on the effect of the three previously mentioned TYK2 missense variants. CONCLUSIONS: We report for the first time the association of TYK2 with SSc and reinforce the relevance of the IL-12 pathway in SSc pathophysiology.

Leflunomide/hydroxychloroquine combination therapy targets type I IFN-associated proteins in patients with Sjögren's syndrome that show potential to predict and monitor clinical response.

OBJECTIVES: To assess to what extent leflunomide (LEF) and hydroxychloroquine (HCQ) therapy in patients with primary Sjögren's syndrome (RepurpSS-I) targets type I IFN-associated responses and to study the potential of several interferon associated RNA-based and protein-based biomarkers to predict and monitor treatment. METHODS: In 21 patients treated with LEF/HCQ and 8 patients treated with placebo, blood was drawn at baseline, 8, 16 and 24 weeks. IFN-signatures based on RNA expression of five IFN-associated genes were quantified in circulating mononuclear cells and in whole blood. MxA protein levels were measured in whole blood, and protein levels of CXCL10 and Galectin-9 were quantified in serum. Differences between responders and non-responders were assessed and receiver operating characteristic analysis was used to determine the capacity of baseline expression and early changes (after 8 weeks of treatment) in biomarkers to predict treatment response at the clinical endpoint. RESULTS: IFN-signatures in peripheral blood mononuclear cell and whole blood decreased after 24 weeks of LEF/HCQ treatment, however, changes in IFN signatures only poorly correlated with changes in disease activity. In contrast to baseline IFN signatures, baseline protein concentrations of galectin-9 and decreases in circulating MxA and Galectin-9 were robustly associated with clinical response. Early changes in serum Galectin-9 best predicted clinical response at 24 weeks (area under the curve 0.90). CONCLUSIONS: LEF/HCQ combination therapy targets type-I IFN-associated proteins that are associated with strongly decreased B cell hyperactivity and disease activity. IFN-associated Galectin-9 is a promising biomarker for treatment prediction and monitoring in pSS patients treated with LEF/HCQ.

Additive immunosuppressive effect of leflunomide and hydroxychloroquine supports rationale for combination therapy for Sjögren's syndrome.

Objective: Effective treatment for primary Sjögren's syndrome (pSS) is not available. pSS immunopathology involves a variety of immune-cells and dysregulated pathways; targeting several pathways instead of only one could therefore be effective. Treatment with leflunomide (LEF) and hydroxychloroquine (HCQ) might be successful given their unique immunosuppressive properties. We aimed to study the in vitro effects of LEF, HCQ and their combination on T- and B-cell proliferation, cytokine and immunoglobulin production by activated PBMCs. Methods: PBMCs of six healthy individuals and nine pSS patients were stimulated with superantigen and TLR9 agonist to mimic the hallmark features. LEF, HCQ and their combinations were tested at clinically observed concentrations and proliferation, cytokine and immunoglobulin production were measured. Results: TCR/TLR9 activation of PBMCs induced strong proliferation of T and B-cells and production of CXCL13, IFN-α, IFN-γ, IgG and IgM. LEF dose-dependently inhibited all measured parameters, where HCQ potently and dose-dependently decreased B cell proliferation, CXCL13, IFN-α, IgG and IgM production. At different concentration combinations, HCQ and LEF inhibited several immune hallmark features more potently than each single compound. Conclusion: A combination of LEF and HCQ at clinically applicable concentrations additively inhibits immune activation, supporting a potential implementation of this drug combination in pSS treatment.

A multicenter study confirms CD226 gene association with systemic sclerosis-related pulmonary fibrosis.

INTRODUCTION: CD226 genetic variants have been associated with a number of autoimmune diseases and recently with systemic sclerosis (SSc). The aim of this study was to test the influence of CD226 loci in SSc susceptibility, clinical phenotypes and autoantibody status in a large multicenter European population. METHODS: A total of seven European populations of Caucasian ancestry were included, comprising 2,131 patients with SSc and 3,966 healthy controls. Three CD226 single nucleotide polymorphisms (SNPs), rs763361, rs3479968 and rs727088, were genotyped using Taqman 5'allelic discrimination assays. RESULTS: Pooled analyses showed no evidence of association of the three SNPs, neither with the global disease nor with the analyzed subphenotypes. However, haplotype block analysis revealed a significant association for the TCG haplotype (SNP order: rs763361, rs34794968, rs727088) with lung fibrosis positive patients (PBonf = 3.18E-02 OR 1.27 (1.05 to 1.54)). CONCLUSION: Our data suggest that the tested genetic variants do not individually influence SSc susceptibility but a CD226 three-variant haplotype is related with genetic predisposition to SSc-related pulmonary fibrosis.