Proteomic mapping identifies serum marker signatures associated with MIS-C specific hyperinflammation and cardiovascular manifestation.

Multisystem inflammatory syndrome in children (MIS-C) shares several clinical and immunological features with Kawasaki Disease (KD) and pediatric hyperinflammation, but the immuno-phenotypic overlap among these clinical mimics is still incompletely understood. Here we analyzed serum samples from treatment-naïve patients with MIS-C (n = 31) and KD (n = 11), pediatric hyperinflammation (n = 13) and healthy controls (HC, n = 10) by proximity extension assay (PEA) to profile 184 blood biomarkers. Collectively, immunophenotypic overlap between MIS-C and hyperinflammation exceeds overlap with KD. Overexpression of IL-17A in MIS-C and KD could best separate these conditions from hyperinflammatory conditions, while those were hallmarked by overabundance of adenosin deaminase and IL-18. Depletion in serum TNF-related subfamily member 9 (TNFRSF9) and apoptosis inducing ligand (TRAIL) linked with cardiovascular manifestations and myocarditis in MIS-C. Altogether, our analysis highlights important differences in molecular marker signatures also across different MIS-C and KD cohorts and suggests several previously unidentified molecular associations in context of cardiovascular inflammation.

Autoantibody-Mediated Depletion of IL-1RA in Still's Disease and Potential Impact of IL-1 Targeting Therapies.

BACKGROUND: Adult-onset Still's disease (AOSD) and systemic juvenile idiopathic arthritis (sJIA) resemble a continuum of a rare, polygenic IL-1ß-driven disease of unknown etiology. OBJECTIVE: In the present study we sought to investigate a potential role of recently described autoantibodies neutralizing the interleukin-1(IL-1)-receptor antagonist (IL-1-Ra) in the pathogenesis of Still's disease. METHODS: Serum or plasma samples from Still's disease patients (AOSD, n = 23; sJIA, n = 40) and autoimmune and/or inflammatory disease controls (n = 478) were analyzed for autoantibodies against progranulin (PGRN), IL-1Ra, IL-18 binding protein (IL-18BP), and IL-36Ra, as well as circulating IL-1Ra and IL-36Ra levels by ELISA. Biochemical analyses of plasma IL-1Ra were performed by native Western blots and isoelectric focusing. Functional activity of the autoantibodies was examined by an in vitro IL-1ß-signaling reporter assay. RESULTS: Anti-IL-1-Ra IgG were identified in 7 (27%) out of 29 Still's disease patients, including 4/23 with AOSD and 3/6 with sJIA and coincided with a hyperphosphorylated isoform of endogenous IL-1Ra. Anti-IL-36Ra antibodies were found in 2 AOSD patients. No anti-PGRN or anti-IL-18BP antibodies were detected. Selective testing for anti-IL-1Ra antibodies in an independent cohort (sJIA, n = 34) identified 5 of 34 (14.7%) as seropositive. Collectively, 8/12 antibody-positive Still's disease patients were either new-onset active disease or unresponsive to IL-1 blocking drugs. Autoantibody-seropositivity associated with decreased IL-1Ra plasma/serum levels. Seropositive plasma impaired in vitro IL-1Ra bioactivity, which could be reversed by anakinra or canakinumab treatment. CONCLUSION: Autoantibodies neutralizing IL-1Ra may represent a novel patho-mechanism in a subgroup of Still's disease patients, which is sensitive to high-dose IL-1 blocking therapy.

Patients with Systemic Juvenile Idiopathic Arthritis (SJIA) Show Differences in Autoantibody Signatures Based on Disease Activity.

Systemic juvenile idiopathic arthritis (SJIA) is a severe rheumatic disease in children. It is a subgroup of juvenile idiopathic arthritis (JIA; MIM #604302), which is the most common rheumatic disease in children. The diagnosis of SJIA often comes with a significant delay, and the classification between autoinflammatory and autoimmune disease is still discussed. In this study, we analyzed the immunological responses of patients with SJIA, using human proteome arrays presenting immobilized recombinantly expressed human proteins, to analyze the involvement of autoantibodies in SJIA. Results from group comparisons show several differentially reactive antigens involved in inflammatory processes. Intriguingly, many of the identified antigens had a high reactivity against proteins involved in the NF-κB pathway, and it is also notable that many of the detected DIRAGs are described as dysregulated in rheumatoid arthritis. Our data highlight novel proteins and pathways potentially dysregulated in SJIA and offer a unique approach to unraveling the underlying disease pathogenesis in this chronic arthropathy.

Aberrant Naive CD4-Positive T Cell Differentiation in Systemic Juvenile Idiopathic Arthritis Committed to B Cell Help.

OBJECTIVE: Systemic juvenile idiopathic arthritis (JIA) features characteristics of autoinflammation and autoimmunity, culminating in chronic arthritis. In this study, we hypothesized that aberrant or incomplete polarization of T helper cells contributes to disease pathology. METHODS: Cells or serum samples were obtained from healthy controls (n = 72) and systemic JIA patients (n = 171). Isolated naive T helper cells were cultured under Th1, Th17, and T follicular helper (Tfh) or T peripheral helper (Tph)-polarizing conditions and were partly cocultured with allogenic memory B cells. Cell samples were then analyzed for surface marker, transcription factor, and cytokine expression, as well as plasmablast generation. Serum samples were subjected to multiplexed bead and self-antigen arrays and enzyme-linked immunosorbent assays, and all data were compared to retrospective RNA profiling analyses. RESULTS: Differentiation of systemic JIA-naive T helper cells toward Th1 cells resulted in low expression levels of interferon-γ (IFNγ) and eomesodermin, which was associated in part with disease duration. In contrast, developing Th1 cells in patients with systemic JIA were found to produce elevated levels of interleukin-21 (IL-21), which negatively correlated with cellular expression of IFNγ and eomesodermin. In both in vitro and ex vivo analyses, IL-21 together with programmed cell death 1 (PD-1), inducible T cell costimulator (ICOS), and CXCR5 expression induced naive T helper cells from systemic JIA patients to polarize toward a Tfh/Tph cell phenotype. Retrospective analysis of whole-blood RNA-sequencing data demonstrated that Bcl-6, a master transcription factor in Tfh/Tph cell differentiation, was overexpressed specifically in patients with systemic JIA. Naive T helper cells from systemic JIA patients which were stimulated in vitro promoted B cellular plasmablast generation, and self-antigen array data indicated that IgG reactivity profiles of patients with systemic JIA differed from those of healthy controls. CONCLUSION: In the pathogenesis of systemic JIA, skewing of naive T helper cell differentiation toward a Tfh/Tph cell phenotype may represent an echo of autoimmunity, which may indicate the mechanisms driving progression toward chronic destructive arthritis.

An Immunological Axis Involving Interleukin 1ß and Leucine-Rich-α2-Glycoprotein Reflects Therapeutic Response of Children with Kawasaki Disease: Implications from the KAWAKINRA Trial.

PURPOSE: A recent phase II open-label study of the interleukin 1 (IL-1) receptor antagonist (IL-1Ra) anakinra in treating IVIG-resistant Kawasaki disease (KD) patients reported promising results. Here, we aimed to characterize the immunological impact of IL-1 blockade in this unique study population. METHODS: Patients' and control sera and supernatants of cells (whole blood, neutrophils, coronary artery endothelial cells) stimulated with recombinant IL-1ß were analyzed for single or multiple marker (n = 22) expression by ELISA or multiplexed bead array assay. Data were analyzed using unsupervised hierarchical clustering, multiple correlation, and multi-comparison statistics and were compared to retrospective analyses of KD transcriptomics. RESULTS: Inflammation in IVIG-resistant KD (n = 16) is hallmarked by over-expression of innate immune mediators (particularly IL-6 > CXCL10 > S100A12 > IL-1Ra). Those as well as levels of immune or endothelial cell activation markers (sICAM-1, sVCAM-1) declined most significantly in course of anakinra treatment. Prior as well as following IL-1R blockade, over-expression of leucine-rich-α2-glycoprotein 1 (LRG1) associated best with remnant inflammatory activity and the necessity to escalate anakinra dosage and separated inflammatory KD patients from sJIA-MAS (n = 13) and MIS-C (n = 4). Protein as well as retrospective gene expression analyses indicated tight association of LRG1 with IL-1ß signaling and neutrophilia, while particularly neutrophil stimulation with recombinant IL-1ß resulted in concentration-dependent LRG1 release. CONCLUSION: Our study identifies LRG1 as known trigger of endothelial activation and cardiac re-modeling to associate with IL-1ß signaling in KD. Besides a potential patho-mechanistic implication of these findings, our data suggest blood leukocyte and neutrophil counts to best predict response to IL-1Ra treatment in IVIG-resistant KD.

Soluble interleukin-2 receptor serum levels facilitate prediction of relapses in subgroups of patients with juvenile idiopathic arthritis.

OBJECTIVES: JIA is characterised by a chronic disease course. Once patients achieve a state of inactive disease, there are no established biomarkers to predict the further course of inflammation for these patients. Therefore, the purpose of this study was to quantify serum biomarkers during quiescent disease to evaluate their use in identifying JIA patients at risk for future disease flare. METHODS: Patients with non-systemic JIA reaching inactive disease status were divided into two groups: 92 patients with future active disease after a median period of 6 months (range 3-9) and 80 patients with persistent inactive disease for the following period (median 11 months, range 7-16) according to the juvenile arthritis DAS (JADAS). Clinical parameters and serum levels of various biomarkers were measured in the state of inactive disease using immunoassays in both groups and were analysed for their potential to predict the further course of disease. RESULTS: Soluble interleukin-2 receptor (sIL-2R) serum levels were significantly higher in patients with future active disease (P = 0.021), which especially applied to patients with RF-negative polyarticular and extended oligoarticular JIA (P < 0.001). Higher sIL-2R serum levels during inactive disease were associated with a greater number of active joints at future active disease. CONCLUSION: Patients without clinical signs of disease activity already presented with increased sIL-2R serum levels several months before disease relapses, whereas conventional inflammation parameters were not elevated. Determination of sIL-2R serum levels during inactive disease may facilitate identifying patients with subclinical disease activity at risk for future active disease.

Prevalence of autoantibodies in patients with juvenile idiopathic arthritis: results from the German inception cohort ICON-JIA.

BACKGROUND: An association of different autoimmune diseases is suspected. In juvenile idiopathic arthritis (JIA), only few and partially conflicting data on the co-existence of other autoimmune disorders are available. The prevalence of autoantibodies in patients with JIA in Germany is not known. METHODS: Samples from 499 patients (median age at time of blood collection 11 years, median disease duration 4.4 years) in the prospective, multicenter inception cohort of children newly diagnosed with JIA (ICON-JIA) were analysed for the presence of anti-thyroid antibodies, celiac disease-specific antibodies (anti-tTG IgA, anti-tTG IgG), and connective tissue disease-associated antibodies (CTD-screen). RESULTS: A total of 76 (15.2%) patients had either clinically diagnosed autoimmune comorbidity or elevated autoantibodies. Of 21 patients with clinical autoimmune comorbidity, only 8 were also serologically positive at the time of testing, while 55 patients had autoantibodies without clinical diagnosis. Thus, 63 patients (12.6%) had at least one elevated autoantibody. Antibodies against thyroglobulin were found in 3% and against thyreoperoxidase in 4% of the samples. TSH receptor antibodies could not be detected in any of the 499 patients. Tissue transglutaminase antibodies were elevated in 0.4% of the patients. A positive screen for CTD-specific antinuclear antibodies was found in 7%, but only rarely specific antibodies (anti-dsDNA 1.4%, anti-SS-A and -SS-B 0.2% each, anti-CENP-B 0.4%) were confirmed. CONCLUSIONS: In our study, a specific correlation between JIA and other autoimmune phenomena could not be confirmed. The lack of well-matched control groups makes interpretation challenging. Further data need to corroborate the suspected increased risk of developing other autoimmune phenomena in JIA patients.

Trajectories of disease courses in the inception cohort of newly diagnosed patients with JIA (ICON-JIA): the potential of serum biomarkers at baseline.

OBJECTIVE: Juvenile idiopathic arthritis (JIA) is a heterogeneous group of inflammatory joint disorders with a chronic-remitting disease course. Treat-to-target approaches have been proposed but monitoring disease activity and predicting the response to treatment remains challenging. METHODS: We analyzed biomarkers and their relationship to outcome within the first year after JIA diagnosis in the German Inception Cohort of Newly diagnosed patients with JIA (ICON-JIA). CRP, CXCL9, CXCL10, CXCL11, erythrocyte sedimentation rate, G-CSF, IL-6, IL-17A, IL-18, MCP-1, MIP-1α, MMP-3, S100A8/A9, S100A12, TNFα, and TWEAK were measured at baseline and 3 months later. RESULTS: Two-hundred-sixty-six JIA patients with active disease at baseline were included, with oligoarthritis and rheumatoid factor-negative polyarthritis representing the most frequent categories (72.9%). Most biomarkers were elevated in JIA compared to healthy pediatric controls. Patients with systemic JIA had higher CRP, S100A8/A9 and S100A12 levels compared to other JIA categories. Baseline levels of TWEAK, G-CSF and IL-18 were lower in oligoarthritis patients with disease extension within 1 year. Increased baseline levels of CRP, S100A8/A9, S100A12 and ESR were associated with the subsequent addition of biologic disease-modifying antirheumatic drugs (DMARDs). Higher baseline ESR, G-CSF, IL-6, IL-17A and TNF levels indicated an increased risk for ongoing disease activity after 12 months. CONCLUSION: Our data demonstrate that elevated baseline levels of CRP, S100A8/A9 and S100A12 as well as increased ESR are associated with the necessity to escalate therapy during the first 12 month of follow-up. Furthermore, biomarkers related to Th17 activation may inform on future disease course in previously treatment-naïve JIA patients.

Impact of IL1RN Variants on Response to Interleukin-1 Blocking Therapy in Systemic Juvenile Idiopathic Arthritis.

OBJECTIVE: To analyze the reported association of IL1RN polymorphisms with response to interleukin-1 (IL-1) blockade in a German cohort of patients with systemic juvenile idiopathic arthritis (JIA), and to assess the impact of other factors on treatment response. METHODS: Sixty-one patients with systemic JIA who had received IL-1 blockade were identified within the German Autoinflammatory Disease registry DNA biobank. Response to IL-1 blockade was assessed according to 1) the clinical response (initially at least a transient response or good response compared to a poor response), 2) switch (or no switch) to anti-IL-6 receptor therapy following IL-1 blockade, 3) achievement of clinically inactive disease within 6 months of IL-1 blockade, 4) improvement in disease activity measured using the modified Juvenile Arthritis Disease Activity Score, and 5) achievement of a glucocorticoid-free state. In addition, basic demographic data, key features of the disease course, laboratory data, and IL1RN single-nucleotide polymorphisms (SNPs) were assessed. RESULTS: Six of 7 IL1RN SNPs reported to be associated with response to anakinra therapy were analyzed. These 6 IL1RN SNPs were inherited as haplotypes. An association of IL1RN haplotypes and SNPs with response to IL-1 blockade could not be confirmed in this cohort of patients with systemic JIA. Patients who received tocilizumab following IL-1 blockade had a longer duration from disease onset to diagnosis than those who did not receive tocilizumab (median 0.27 years versus 0.08 years). CONCLUSION: The results of this study could not confirm an impact of IL1RN SNPs on response to IL-1 blockade therapy with either anakinra or canakinumab in a cohort of patients with systemic JIA. However, a longer time frame from disease onset to diagnosis was associated with poorer long-term treatment response, thereby supporting the "window of opportunity" hypothesis that suggests improved long-term treatment response with shorter time from disease onset to diagnosis (and treatment).

Purification of Human S100A12 and Its Ion-induced Oligomers for Immune Cell Stimulation.

In this protocol, we describe a method to purify human calcium-binding protein S100A12 and its ion-induced oligomers from Escherichia coli culture for immune cell stimulations. This protocol is based on a two-step chromatography strategy, which comprises protein pre-purification on an anion-exchange chromatography column and a subsequent polishing step on a hydrophobic-interaction column. This strategy produces S100A12 protein of high purity and yield at manageable costs. For functional assays on immune cells eventual remnant endotoxin contamination requires careful monitoring and further cleaning steps to obtain endotoxin-free protein. The majority of endotoxin contaminations can be excluded by anion-exchange chromatography. To deplete residual contaminations, this protocol describes a removal step with centrifugal filters. Depending on the available ion-strength S100A12 can arrange into different homomultimers. To investigate the relationship between structure and function, this protocol further describes ion-treatment of S100A12 protein followed by chemical crosslinking to stabilize S100A12 oligomers and their subsequent separation by size-exclusion chromatography. Finally, we describe a cell-based assay that confirms the biological activity of the purified protein and confirms LPS-free preparation.