Risk loci involved in giant cell arteritis susceptibility: a genome-wide association study.

BACKGROUND: Giant cell arteritis is an age-related vasculitis that mainly affects the aorta and its branches in individuals aged 50 years and older. Current options for diagnosis and treatment are scarce, highlighting the need to better understand its underlying pathogenesis. Genome-wide association studies (GWAS) have emerged as a powerful tool for unravelling the pathogenic mechanisms involved in complex diseases. We aimed to characterise the genetic basis of giant cell arteritis by performing the largest GWAS of this vasculitis to date and to assess the functional consequences and clinical implications of identified risk loci. METHODS: We collected and meta-analysed genomic data from patients with giant cell arteritis and healthy controls of European ancestry from ten cohorts across Europe and North America. Eligible patients required confirmation of giant cell arteritis diagnosis by positive temporal artery biopsy, positive temporal artery doppler ultrasonography, or imaging techniques confirming large-vessel vasculitis. We assessed the functional consequences of loci associated with giant cell arteritis using cell enrichment analysis, fine-mapping, and causal gene prioritisation. We also performed a drug repurposing analysis and developed a polygenic risk score to explore the clinical implications of our findings. FINDINGS: We included a total of 3498 patients with giant cell arteritis and 15 550 controls. We identified three novel loci associated with risk of giant cell arteritis. Two loci, MFGE8 (rs8029053; p=4·96 × 10-8; OR 1·19 [95% CI 1·12-1·26]) and VTN (rs704; p=2·75 × 10-9; OR 0·84 [0·79-0·89]), were related to angiogenesis pathways and the third locus, CCDC25 (rs11782624; p=1·28 × 10-8; OR 1·18 [1·12-1·25]), was related to neutrophil extracellular traps (NETs). We also found an association between this vasculitis and HLA region and PLG. Variants associated with giant cell arteritis seemed to fulfil a specific regulatory role in crucial immune cell types. Furthermore, we identified several drugs that could represent promising candidates for treatment of this disease. The polygenic risk score model was able to identify individuals at increased risk of developing giant cell arteritis (90th percentile OR 2·87 [95% CI 2·15-3·82]; p=1·73 × 10-13). INTERPRETATION: We have found several additional loci associated with giant cell arteritis, highlighting the crucial role of angiogenesis in disease susceptibility. Our study represents a step forward in the translation of genomic findings to clinical practice in giant cell arteritis, proposing new treatments and a method to measure genetic predisposition to this vasculitis. FUNDING: Institute of Health Carlos III, Spanish Ministry of Science and Innovation, UK Medical Research Council, and National Institute for Health and Care Research.

Current evidence on the role of fibroblasts in large-vessel vasculitides: From pathogenesis to therapeutics.

Large-vessel vasculitides (LVV) comprise a group of chronic inflammatory diseases of the aorta and its major branches. The most common forms of LVV are giant cell arteritis (GCA) and Takayasu arteritis (TAK). Both GCA and TAK are characterized by granulomatous inflammation of the vessel wall accompanied by a maladaptive immune and vascular response that promotes vascular damage and remodeling. The inflammatory process in LVV starts in the adventitia where fibroblasts constitute the dominant cell population. Fibroblasts are traditionally recognized for synthesizing and renewing the extracellular matrix thereby being major players in maintenance of normal tissue architecture and in tissue repair. More recently, fibroblasts have emerged as a highly plastic cell population exerting various functions, including the regulation of local immune processes and organization of immune cells at the site of inflammation through production of cytokines, chemokines and growth factors as well as cell-cell interaction. In this review, we summarize and discuss the current knowledge on fibroblasts in LVV. Furthermore, we identify key questions that need to be addressed to fully understand the role of fibroblasts in the pathogenesis of LVV.

Impaired IL-6-induced JAK-STAT signaling in CD4+ T cells associates with longer treatment duration in giant cell arteritis.

INTRODUCTION: The IL-12-IFNγ-Th1 and the IL-6-IL-23-Th17 axes are considered the dominant pathogenic pathways in Giant Cell Arteritis (GCA). Both pathways signal via activation of the downstream JAK/STAT proteins. We hypothesized that phosphorylated STAT (pSTAT) signatures in circulating immune cells may aid to stratify GCA-patients for personalized treatment. METHODS: To investigate pSTAT expression, PBMCs from treatment-naive GCA-patients (n = 18), infection controls (INF, n = 11) and age-matched healthy controls (HC, n = 15) were stimulated in vitro with IL-6, IL-2, IL-10, IFN-γ, M-CSF or GM-CSF, and stained with CD3, CD4, CD19, CD45RO, pSTAT1, pSTAT3, pSTAT5 antibodies, and analyzed by flow cytometry. Serum IL-6, sIL-6-receptor and gp130 were measured by Luminex. The change in percentages of pSTAT3+CD4+T-cells was evaluated at diagnosis and at 3 months and 1-year of follow-up. Kaplan-Meier analyses was used to asses prognostic accuracy. RESULTS: Analysis of IL-6 stimulated immune cell subsets revealed a significant decrease in percentages of pSTAT3+CD4+T-cells of GCA-patients and INF-controls compared to HCs. Following patient stratification according to high (median>1.5 pg/mL) and low (median<1.5 pg/mL) IL-6 levels, we observed a reduction in the pSTAT3 response in GCA-patients with high serum IL-6. Percentages of pSTAT3+CD4+T-cells in patients with high serum IL-6 levels at diagnosis normalized after glucocorticoid (GC) treatment. Importantly, we found that patients with low percentages of pSTAT3+CD4+T-cells at baseline require longer GC-treatment. CONCLUSION: Overall, in GCA, the percentages of in vitro IL-6-induced pSTAT3+CD4+T-cells likely reflect prior in vivo exposure to high IL-6 and may serve as a prognostic marker for GC-treatment duration and may assist improving personalized treatment options in the future.

A direct comparison in diagnostic performance of CDUS, FDG-PET/CT and MRI in patients suspected of giant cell arteritis.

OBJECTIVES: This study directly compares diagnostic performance of Colour Duplex Ultrasound (CDUS), Fluor-18-deoxyglucose Positron Emission Tomography Computed Tomography (FDG-PET/CT) and Magnetic Resonance Imaging (MRI) in patients suspected of giant cell arteritis (GCA). METHODS: Patients with suspected GCA were included in a nested-case control pilot study. CDUS, whole body FDG-PET/CT and cranial MRI were performed within 5 working days after initial clinical evaluation. Clinical diagnosis after six months follow-up by experienced rheumatologists in the field of GCA, blinded for imaging, was used as reference standard. Diagnostic performance of the imaging modalities was determined. Stratification for GCA subtype was performed and imaging results were evaluated in different risk stratification groups. RESULTS: In total, 23 patients with GCA and 19 patients suspected of but not diagnosed with GCA were included. Sensitivity was 69.6% (95%CI 50.4%-88.8%) for CDUS, 52.2% (95%CI 31.4%-73.0%) for FDG-PET/CT and 56.5% (95%CI 35.8%-77.2%) for MRI. Specificity was 100% for CDUS, FDG-PET/CT and MRI. FDG-PET/CT was negative for GCA in all isolated cranial GCA patients (n = 8), while MRI was negative in all isolated extracranial GCA patients (n = 4). In 4 GCA patients with false-negative (n = 2; intermediate and high risk) or inconclusive (n = 2; low and intermediate risk) CDUS results, further imaging confirmed diagnosis. CONCLUSIONS: Sensitivity of CDUS was highest, while specificity was excellent in all imaging modalities. Nevertheless, confidence intervals of all imaging modalities were overlapping. Following EULAR recommendations, CDUS can be used as a first test to diagnose GCA. With insufficient evidence for GCA, further testing considering GCA subtype is warranted.

Large vessel giant cell arteritis.

Giant cell arteritis is the principal form of systemic vasculitis affecting people over 50. Large-vessel involvement, termed large vessel giant cell arteritis, mainly affects the aorta and its branches, often occurring alongside cranial giant cell arteritis, but large vessel giant cell arteritis without cranial giant cell arteritis can also occur. Patients mostly present with constitutional symptoms, with localising large vessel giant cell arteritis symptoms present in a minority of patients only. Large vessel giant cell arteritis is usually overlooked until clinicians seek to exclude it with imaging by ultrasonography, magnetic resonance angiography (MRA), computed tomography angiography (CTA), or [18F]fluorodeoxyglucose-PET-CT. Although the role of imaging in treatment monitoring remains uncertain, imaging by MRA or CTA is crucial for identifying aortic aneurysm formation during patient follow up. In this Series paper, we define the large vessel subset of giant cell arteritis and summarise its clinical challenges. Furthermore, we identify areas for future research regarding the management of large vessel giant cell arteritis.

Altered Plasma Levels and Tissue Expression of Fibroblast Activation Protein Alpha in Giant Cell Arteritis.

OBJECTIVE: Giant cell arteritis (GCA) is characterized by granulomatous inflammation of the medium- and large-sized arteries accompanied by remodeling of the vessel wall. Fibroblast activation protein alpha (FAP) is a serine protease that promotes both inflammation and fibrosis. Here, we investigated the plasma levels and vascular expression of FAP in GCA. METHODS: Plasma FAP levels were measured with enzyme-linked immunosorbent assay in treatment-naive patients with GCA (n = 60) and polymyalgia rheumatica (PMR) (n = 63) compared with age- and sex-matched healthy controls (HCs) (n = 42) and during follow-up, including treatment-free remission (TFR). Inflamed temporal artery biopsies (TABs) of patients with GCA (n = 9), noninflamed TABs (n = 14), and aorta samples from GCA-related (n = 9) and atherosclerosis-related aneurysm (n = 11) were stained for FAP using immunohistochemistry. Immunofluorescence staining was performed for fibroblasts (CD90), macrophages (CD68/CD206/folate receptor beta), vascular smooth muscle cells (desmin), myofibroblasts (α-smooth muscle actin), interleukin-6 (IL-6), and matrix metalloproteinase-9 (MMP-9). RESULTS: Baseline plasma FAP levels were significantly lower in patients with GCA compared with patients with PMR and HCs and inversely correlated with systemic markers of inflammation and angiogenesis. FAP levels decreased even further at 3 months on remission in patients with GCA and gradually increased to the level of HCs in TFR. FAP expression was increased in inflamed TABs and aorta of patients with GCA compared with control tissues. FAP was abundantly expressed in fibroblasts and macrophages. Some of the FAP+ fibroblasts expressed IL-6 and MMP-9. CONCLUSION: FAP expression in GCA is clearly modulated both in plasma and in vessels. FAP may be involved in the inflammatory and remodeling processes in GCA and have utility as a target for imaging and therapeutic intervention.

Development of a diagnostic prediction model for giant cell arteritis by sequential application of Southend Giant Cell Arteritis Probability Score and ultrasonography: a prospective multicentre study.

BACKGROUND: Giant cell arteritis is a critically ischaemic disease with protean manifestations that require urgent diagnosis and treatment. European Alliance of Associations for Rheumatology (EULAR) recommendations advocate ultrasonography as the first investigation for suspected giant cell arteritis. We developed a prediction tool that sequentially combines clinical assessment, as determined by the Southend Giant Cell Arteritis Probability Score (SGCAPS), with results of quantitative ultrasonography. METHODS: This prospective, multicentre, inception cohort study included consecutive patients with suspected new onset giant cell arteritis referred to fast-track clinics (seven centres in Italy, the Netherlands, Spain, and UK). Final clinical diagnosis was established at 6 months. SGCAPS and quantitative ultrasonography of temporal and axillary arteries with three scores (ie, halo count, halo score, and OMERACT GCA Score [OGUS]) were performed at diagnosis. We developed prediction models for diagnosis of giant cell arteritis by multivariable logistic regression analysis with SGCAPS and each of the three ultrasonographic scores as predicting variables. We obtained intraclass correlation coefficient for inter-rater and intra-rater reliability in a separate patient-based reliability exercise with five patients and five observers. FINDINGS: Between Oct 1, 2019, and June 30, 2022, we recruited and followed up 229 patients (150 [66%] women and 79 [34%] men; mean age 71 years [SD 10]), of whom 84 were diagnosed with giant cell arteritis and 145 with giant cell arteritis mimics (controls) at 6 months. SGCAPS and all three ultrasonographic scores discriminated well between patients with and without giant cell arteritis. A reliability exercise showed that the inter-rater and intra-rater reliability was high for all three ultrasonographic scores. The prediction model combining SGCAPS with the halo count, which was termed HAS-GCA score, was the most accurate model, with an optimism-adjusted C statistic of 0·969 (95% CI 0·952 to 0·990). The HAS-GCA score could classify 169 (74%) of 229 patients into either the low or high probability groups, with misclassification observed in two (2%) of 105 patients in the low probability group and two (3%) of 64 of patients in the high probability group. A nomogram for easy application of the score in daily practice was created. INTERPRETATION: A prediction tool for giant cell arteritis (the HAS-GCA score), combining SGCAPS and the halo count, reliably confirms and excludes giant cell arteritis from giant cell arteritis mimics in fast-track clinics. These findings require confirmation in an independent, multicentre study. FUNDING: Royal College of Physicians of Ireland, FOREUM.

Advances in PET Imaging of Large Vessel Vasculitis: An Update and Future Trends.

Systemic vasculitides are autoimmune diseases characterized by inflammation of blood vessels. They are categorized based on the size of the preferentially affected blood vessels: large-, medium-, and small-vessel vasculitides. The main forms of large-vessel vasculitis include giant cell arteritis (GCA) and Takayasu arteritis (TAK). Depending on the location of the affected vessels, various imaging modalities can be employed for diagnosis of large vessel vasculitis: ultrasonography (US), magnetic resonance angiography (MRA), computed tomography angiography (CTA), and [18F]-fluoro-2-deoxy-d-glucose positron emission tomography/computed tomography (FDG-PET/CT). These imaging tools offer complementary information about vascular changes occurring in vasculitis. Recent advances in PET imaging in large vessel vasculitis include the introduction of digital long axial field-of-view PET/CT, dedicated acquisition, quantitative methodologies, and the availability of novel radiopharmaceuticals. This review aims to provide an update on the current status of PET imaging in large vessel vasculitis and to share the latest developments on imaging vasculitides.

Immune checkpoint inhibitor-mediated polymyalgia rheumatica versus primary polymyalgia rheumatica: comparison of disease characteristics and treatment requirement.

OBJECTIVES: To compare clinical characteristics, imaging findings and treatment requirements of patients with immune checkpoint inhibitor-mediated polymyalgia rheumatica (ICI-PMR) and primary PMR. METHODS: This single centre, retrospective cohort study compared ICI-PMR in patients with cancer (n = 15) to patients with primary PMR (n = 37). A comparison was made between clinical symptoms, laboratory markers, ultrasonography,18F-FDG-PET/CT findings and treatment requirements related to PMR. RESULTS: Patients with ICI-PMR less frequently fulfilled the EULAR/ACR classification criteria for PMR (66.7%) than patients with primary PMR (97.3%). Morning stiffness, weight loss and elevation of the ESR were less frequently seen in patients with ICI-PMR. No differences were observed regarding the presence of inflammatory lesions on ultrasound of the shoulders and hips between the two groups. The Leuven and the Leuven/Groningen 18F-FDG-PET/CT scores were significantly lower in the ICI-PMR group. Finally, the ICI-PMR group could be managed with less glucocorticoids than the primary PMR group. CONCLUSION: Our findings indicate that ICI-PMR may have a milder course with less inflammation than primary PMR on 18F-FDG-PET/CT. ICI-mediated PMR patients can be managed with a relatively low glucocorticoid dose. Our study underscores that ICI-PMR should be regarded as PMR-like syndrome.

Diagnostic delay in patients with giant cell arteritis: results of a fast-track clinic.

Giant cell arteritis (GCA) can lead to severe complications if left untreated. The aim of this study was to describe time from onset of symptoms to diagnosis and treatment in GCA suspected patients in a fast-track clinic (FTC), and secondarily to assess the influence of GCA symptoms on this time. A retrospective cohort consisting of suspected GCA patients who visited the FTC between January 2017 and October 2019 was used. Time between symptom onset, first general practitioner visit, FTC referral, first FTC visit, and treatment initiation was analysed. Furthermore, this was stratified for subtypes of GCA and GCA symptoms. Of 205 patients referred with suspected GCA, 61 patients received a final diagnosis of GCA (GCA+) and 144 patients had no GCA (GCA-). Median time after onset of symptoms to first FTC visit was 31.0 days (IQR 13.0-108.8) in all referred patients. Time between onset of symptoms and first GP visit was 10.5 (4.0-36.3) days, and time between first GP visit and FTC referral was 10.0 (1.0-47.5) days. Patients were generally seen at the FTC within 1 day after referral. For patients with isolated cranial GCA (n = 41), median delay from onset of symptoms to treatment initiation was 21.0 days (11.0-73.5), while this was 57.0 days (33.0-105.0) in patients with extracranial large-vessel involvement (n = 20) (p = 0.02). Our results indicate considerable delay between symptom onset and FTC referral in patients suspected of GCA. Suspected patients were examined and GCA+ patients were treated instantly after referral. Key Points • GCA can cause severe complications with delayed treatment, but non-specific symptoms make diagnosis challenging. • Diagnostic delay still occurs despite introducing a successful fast-track clinic resulting from delay between start of symptoms and FTC referral. • Patients who presented with constitutional symptoms had longer delay than patients who presented with isolated cranial symptoms.

Humoral SARS-CoV-2 Vaccine Responses in Patients With Giant Cell Arteritis and Polymyalgia Rheumatica: Decay After Primary Vaccination and Effects of the Booster.

OBJECTIVE: Vaccination remains essential in preventing morbidity of SARS-CoV-2 infections. We previously showed that >10 mg/day of prednisolone and methotrexate was associated with reduced antibody concentrations after primary vaccination in patients with giant cell arteritis (GCA) and polymyalgia rheumatica (PMR). This follow-up study was undertaken to measure the decay of antibody concentrations and the immunogenicity of SARS-CoV-2 booster vaccination. METHODS: Patients with GCA/PMR included in the primary vaccination (BNT162b2 [Pfizer-BioNTech] or ChAdOx1 [Oxford/AstraZeneca]) study were asked again to donate blood samples 6 months after primary vaccination (n = 24) and 1 month after booster vaccination (n = 46, BNT162b2 or mRNA1273). Data were compared to those of age-, sex-, and vaccine-matched controls (n = 58 and n = 42, respectively). Multiple linear regression was performed with post-booster antibody concentrations as dependent variable and post-primary vaccination antibodies, prednisolone >10mg/day, and methotrexate use as predicting variables. RESULTS: Antibody concentrations decreased faster over time in GCA/PMR patients than in controls, which was associated with prednisolone treatment during primary vaccination. Post-booster antibody concentrations were comparable between patients and controls. Antibody concentrations post primary vaccination, but not treatment during booster vaccination, were predictive for antibody concentrations post booster vaccination. CONCLUSION: These results indicate that the decay of humoral immunity after primary vaccination is associated with prednisolone treatment, whereas the subsequent increase after booster vaccination, was not. Patients with low antibody concentrations following primary vaccination remained at an immunogenic disadvantage after a single booster vaccination. This longitudinal study in GCA/PMR patients stresses the importance of repeated booster vaccination for patients with poor responses to primary vaccination.

Increased Diagnostic Accuracy of the Labial Gland Biopsy in Primary Sjögren Syndrome When Multiple Histopathological Features Are Included.

OBJECTIVE: The aim of this study was to evaluate the diagnostic accuracy of the labial salivary gland biopsy based on multiple histopathological features in patients with suspected primary Sjögren syndrome (pSS). METHODS: Patients from a diagnostic sicca cohort with clinically suspected pSS who underwent a labial gland biopsy were included. Patients were categorized as having pSS or non-Sjögren syndrome sicca (non-SS sicca) based on vignettes scored by an expert panel. Labial gland biopsies were analyzed for the presence of four histopathological features: focus score (FS) ≥1, prelymphoepithelial and lymphoepithelial lesions, immunoglobulin G plasma cell shift, and germinal centers. Sensitivity and specificity of histologic features were calculated, and the optimal cutoff value for the number of histopathological features needed to diagnose pSS was determined with receiver operating curve analysis. RESULTS: A total of 38 patients were categorized as having pSS and 65 as having non-SS sicca. In labial gland biopsies of patients with pSS, the prevalence of FS ≥1 was 82%, followed by 68% for pre-lymphoepithelial and lymphoepithelial lesions, 63% for plasma cell shift, and 24% for germinal centers. Although FS ≥1 showed the highest sensitivity for patients with pSS (82%), specificity was higher for the other three features (98%-100%). The presence of two or more (of four) histopathological features had almost comparable sensitivity to FS alone, but specificity increased with 12% to 100%. For fulfillment of American College of Rheumatology/EULAR criteria, specificity increased from 84% to 95% when an abnormal biopsy was defined by the presence of two or more histopathological features instead of FS ≥1 only. CONCLUSION: The diagnostic accuracy of the labial gland biopsy increases when other histopathological features besides FS are taken into account, by reducing the number of false-positive biopsies.

Salivary gland 18F-FDG-PET/CT uptake patterns in Sjögren's syndrome and giant cell arteritis patients.

OBJECTIVES: Wide variety in salivary gland 18F-FDG-uptake is observed in the general population. A general consensus about the usefulness of 18F-FDG-PET/CT to detect salivary gland inflammatory conditions, such as in primary Sjögren's syndrome (pSS), is not yet clear. This study aimed to investigate whether there are differences in uptake of 18F-FDG in salivary glands among two autoimmune groups [pSS, giant cell arteritis (GCA)] and a non-autoimmune group (lung cancer). METHODS: PSS patients aged ≥50 years who underwent 18F-FDG-PET/CT were included and age-matched with GCA patients and a non-autoimmune control group (lung cancer patients). Scans were visually evaluated and quantitative analysis was performed by measuring standardised uptake values (SUV) within salivary glands and lacrimal glands. For GCA patients, arteries in the vicinity of the parotid and submandibular gland were assessed for positivity. RESULTS: PSS patients did not show increased 18F-FDG-uptake in the parotid or submandibular gland, compared to the other two groups. For the tubarial gland, significantly higher SUVmax was found in the pSS patient group. Interestingly, GCA patients had significantly higher SUVmax in the submandibular gland than the other two groups. Visual 18F-FDG-positivity of cranial arteries related to the parotid and submandibular glands was associated with significantly higher SUVmax in salivary glands of GCA patients. CONCLUSIONS: Although 18F-FDG-uptake was not increased in parotid and submandibular glands of pSS patients, increased 18F-FDG-uptake in tubarial glands of pSS patients might indicate a role for these glands in pSS. Furthermore, parotid and submandibular glands may be affected by local vasculitis in GCA.

Recommendations for early referral of individuals with suspected polymyalgia rheumatica: an initiative from the international giant cell arteritis and polymyalgia rheumatica study group.

OBJECTIVE: To develop international consensus-based recommendations for early referral of individuals with suspected polymyalgia rheumatica (PMR). METHODS: A task force including 29 rheumatologists/internists, 4 general practitioners, 4 patients and a healthcare professional emerged from the international giant cell arteritis and PMR study group. The task force supplied clinical questions, subsequently transformed into Population, Intervention, Comparator, Outcome format. A systematic literature review was conducted followed by online meetings to formulate and vote on final recommendations. Levels of evidence (LOE) (1-5 scale) and agreement (LOA) (0-10 scale) were evaluated. RESULTS: Two overarching principles and five recommendations were developed. LOE was 4-5 and LOA ranged between 8.5 and 9.7. The recommendations suggest that (1) each individual with suspected or recently diagnosed PMR should be considered for specialist evaluation, (2) before referring an individual with suspected PMR to specialist care, a thorough history and clinical examination should be performed and preferably complemented with urgent basic laboratory investigations, (3) individuals with suspected PMR with severe symptoms should be referred for specialist evaluation using rapid access strategies, (4) in individuals with suspected PMR who are referred via rapid access, the commencement of glucocorticoid therapy should be deferred until after specialist evaluation and (5) individuals diagnosed with PMR in specialist care with a good initial response to glucocorticoids and a low risk of glucocorticoid related adverse events can be managed in primary care. CONCLUSIONS: These are the first international recommendations for referral of individuals with suspected PMR, which complement the European Alliance of Associations for Rheumatology/American College of Rheumatology management guidelines for established PMR.

High BMI is associated with lower TNF-α inhibitor serum trough levels and higher disease activity in patients with axial spondyloarthritis.

BACKGROUND: TNF-α inhibitor (TNFi) serum trough levels have previously been found to be related to disease activity in axial spondyloarthritis (axSpA). However, most research regarding serum trough levels has been conducted in patients who only recently started TNFi therapy. Therefore, our objective was to explore TNFi serum trough level measurements in relation to disease activity and BMI in the total axSpA population in daily clinical practice, also including patients on long-term TNFi therapy. METHODS: Consecutive patients from the Groningen Leeuwarden Axial Spondyloarthritis (GLAS) cohort were approached for a TNFi serum trough level measurement during their regular outpatient visit at the UMCG. Spearman's correlation coefficient was used to analyse the relation of serum trough levels with disease activity and BMI. Logistic regression was performed to analyse the relation between therapeutic drug levels and disease activity, corrected for potential confounders, including BMI. RESULTS: Thirty-four patients on adalimumab and 21 patients on etanercept were included. Mean age was 45 ± 12 years, 47% were male, median BMI was 26.4 (IQR 23.9-32.5) and median treatment duration was 41 months (range 2-126). According to definitions of Sanquin, 47% of patients had therapeutic serum trough levels. No significant correlations were found between TNFi levels and disease activity (ASDAS-CRP: adalimumab: ρ = -0.16, p = 0.39; etanercept: ρ = -0.29, p = 0.20). TNFi levels were moderately correlated with BMI (adalimumab: ρ = -0.48, p = 0.004; etanercept: ρ = -0.50, p = 0.021). Patients with active disease (ASDAS ≥ 2.1) showed higher BMI than patients with inactive disease (median 29.7 vs. 24.6, p = 0.015). In multivariable regression analyses, BMI was identified as the only confounder for the relationship between therapeutic drug levels and ASDAS. CONCLUSION: In this cross-sectional, observational study of axSpA patients mainly on long-term treatment with TNFi, higher BMI was significantly associated with lower adalimumab and etanercept serum trough levels and higher disease activity.

Autoantibody Profiling and Anti-Kinesin Reactivity in ANCA-Associated Vasculitis.

ANCA-associated vasculitides (AAV) are rare autoimmune diseases causing inflammation and damage to small blood vessels. New autoantibody biomarkers are needed to improve the diagnosis and treatment of AAV patients. In this study, we aimed to profile the autoantibody repertoire of AAV patients using in-house developed antigen arrays to identify previously unreported antibodies linked to the disease per se, clinical subgroups, or clinical activity. A total of 1743 protein fragments representing 1561 unique proteins were screened in 229 serum samples collected from 137 AAV patients at presentation, remission, and relapse. Additionally, serum samples from healthy individuals and patients with other type of vasculitis and autoimmune-inflammatory conditions were included to evaluate the specificity of the autoantibodies identified in AAV. Autoreactivity against members of the kinesin protein family were identified in AAV patients, healthy volunteers, and disease controls. Anti-KIF4A antibodies were significantly more prevalent in AAV. We also observed possible associations between anti-kinesin antibodies and clinically relevant features within AAV patients. Further verification studies will be needed to confirm these findings.

Cytokine producing B-cells and their capability to polarize macrophages in giant cell arteritis.

OBJECTIVE: The lack of disease-specific autoantibodies in giant cell arteritis (GCA) suggests an alternative role for B-cells readily detected in the inflamed arteries. Here we study the cytokine profile of tissue infiltrated and peripheral blood B-cells of patients with GCA. Moreover, we investigate the macrophage skewing capability of B-cell-derived cytokines. METHODS: The presence of various cytokines in B-cell areas in temporal artery (n = 11) and aorta (n = 10) was identified by immunohistochemistry. PBMCs of patients with GCA (n = 11) and polymyalgia rheumatica (n = 10), and 14 age- and sex-matched healthy controls (HC) were stimulated, followed by flow cytometry for cytokine expression in B-cells. The skewing potential of B-cell-derived cytokines (n = 6 for GCA and HC) on macrophages was studied in vitro. RESULTS: The presence of IL-6, GM-CSF, TNFα, IFNγ, LTß and IL-10 was documented in B-cells and B-cell rich areas of GCA arteries. In vitro, B-cell-derived cytokines (from both GCA and HC) skewed macrophages towards a pro-inflammatory phenotype with enhanced expression of IL-6, IL-1ß, TNFα, IL-23, YKL-40 and MMP-9. In vitro stimulated peripheral blood B-cells from treatment-naïve GCA patients showed an enhanced frequency of IL-6+ and TNFα+IL-6+ B-cells compared to HCs. This difference was no longer detected in treatment-induced remission. Erythrocyte sedimentation rate positively correlated with IL-6+TNFα+ B-cells. CONCLUSION: B-cells are capable of producing cytokines and steering macrophages towards a pro-inflammatory phenotype. Although the capacity of B-cells in skewing macrophages is not GCA specific, these data support a cytokine-mediated role for B-cells in GCA and provide grounds for B-cell targeted therapy in GCA.

Aberrant phenotype of circulating antigen presenting cells in giant cell arteritis and polymyalgia rheumatica.

Background: Giant Cell Arteritis (GCA) and Polymyalgia Rheumatica (PMR) are overlapping inflammatory diseases. Antigen-presenting cells (APCs), including monocytes and dendritic cells (DCs), are main contributors to the immunopathology of GCA and PMR. However, little is known about APC phenotypes in the peripheral blood at the time of GCA/PMR diagnosis. Methods: APCs among peripheral blood mononuclear cells (PBMCs) of treatment-naive GCA and PMR patients were compared to those in age- and sex-matched healthy controls (HCs) using flow cytometry (n=15 in each group). We identified three monocyte subsets, and three DC subsets: plasmacytoid DCs (pDCs), CD141+ conventional DCs (cDC1) and CD1c+ conventional DCs (cDC2). Each of these subsets was analyzed for expression of pattern recognition receptors (TLR2, TLR4), immune checkpoints (CD86, PDL1, CD40) and activation markers (HLA-DR, CD11c). Results: t-SNE plots revealed a differential clustering of APCs between GCA/PMR and HCs. Further analyses showed shifts in monocyte subsets and a lower proportion of the small population of cDC1 cells in GCA/PMR, whereas cDC2 proportions correlated negatively with CRP (r=-0.52). Classical monocytes of GCA/PMR patients show reduced expression of TLR2, HLA-DR, CD11c, which was in contrast to non-classical monocytes that showed higher marker expression. Additionally, single cell RNA sequencing in GCA patients identified a number of differentially expressed genes related to inflammation and metabolism in APCs. Conclusion: Circulating non-classical monocytes display an activated phenotype in GCA/PMR patients at diagnosis, whereas classical monocytes show reduced expression of activation markers. Whether these findings reflect APC migration patterns or the effects of long-term inflammation remains to be investigated.