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Over the past few years, new-generation cell-based assays have demonstrated a robust association of autoantibodies to full-length human myelin oligodendrocyte glycoprotein (MOG-IgG) with (mostly recurrent) optic neuritis, myelitis and brainstem encephalitis, as well as with acute disseminated encephalomyelitis (ADEM)-like presentations. Most experts now consider MOG-IgG-associated encephalomyelitis (MOG-EM) a disease entity in its own right, immunopathogenetically distinct from both classic multiple sclerosis (MS) and aquaporin-4 (AQP4)-IgG-positive neuromyelitis optica spectrum disorders (NMOSD). Owing to a substantial overlap in clinicoradiological presentation, MOG-EM was often unwittingly misdiagnosed as MS in the past. Accordingly, increasing numbers of patients with suspected or established MS are currently being tested for MOG-IgG. However, screening of large unselected cohorts for rare biomarkers can significantly reduce the positive predictive value of a test. To lessen the hazard of overdiagnosing MOG-EM, which may lead to inappropriate treatment, more selective criteria for MOG-IgG testing are urgently needed. In this paper, we propose indications for MOG-IgG testing based on expert consensus. In addition, we give a list of conditions atypical for MOG-EM (“red flags”) that should prompt physicians to challenge a positive MOG-IgG test result. Finally, we provide recommendations regarding assay methodology, specimen sampling and data interpretation.

In this study, interferon-γ was found to play a large role in the pathogenesis of APS-1. Results were confirmed in studies in animals and led to a trial of ruxolitinib in five patients, who had dramatic responses.

Objective The detection of autoantibodies is essential to diagnose autoimmune hepatitis (AIH). Particularly in children, specificity of autoantibodies decreases due to lower titers being diagnostic and being present not only in AIH but also in other liver diseases. Recently, quantification of polyreactive IgG (pIgG) for detection of adult AIH showed the highest overall accuracy compared to antinuclear antibodies (ANA), anti-smooth muscle antibodies (anti-SMA), anti-liver kidney microsomal antibodies (anti-LKM) and anti-soluble liver antigen/liver pancreas antibodies (anti-SLA/LP). We aimed to evaluate the diagnostic value of pIgG for pediatric AIH. Design pIgG, quantified using HIP1R/BSA coated ELISA, and immunofluorescence on rodent tissue sections were performed centrally. The diagnostic fidelity to diagnose AIH was compared to conventional autoantibodies of AIH in training and validation cohorts from a retrospective, European multi-center cohort from nine centers from eight European countries composed of existing biorepositories from expert centers ( n  = 285). Results IgG from pediatric AIH patients exhibited increased polyreactivity to multiple protein and non-protein substrates compared to non-AIH liver diseases and healthy children. pIgG had an AUC of 0.900 to distinguish AIH from non-AIH liver diseases. pIgG had a 31–73% higher specificity than ANA and anti-SMA and comparable sensitivity that was 6–20 times higher than of anti-SLA/LP, anti-LC1 and anti-LKM. pIgG had a 21–34% higher accuracy than conventional autoantibodies, was positive in 43–75% of children with AIH and normal IgG and independent from treatment response. Conclusion Detecting pIgG improves the diagnostic evaluation of pediatric AIH compared to conventional autoantibodies, primarily owing to higher accuracy and specificity. Graphical Abstract

This study aimed to test whether injections of alum-formulated glutamic acid decarboxylase 65 (GAD), a major autoantigen in type 1 diabetes mellitus, would reverse recent-onset disease. C-peptide levels declined in both the treatment group and the control group, without significant between-group differences at month 15 (the primary end point), but they had declined significantly more slowly with treatment by month 30. The authors conclude that alum-formulated GAD may help preserve residual insulin secretion in patients with recent-onset type 1 diabetes. Study patients received injections of alum-formulated glutamic acid decarboxylase 65 (GAD). C-peptide levels declined in both the treatment group and the control group, but they had declined significantly more slowly with treatment by month 30. Type 1 diabetes mellitus is an autoimmune disease 1 that causes substantial morbidity and mortality. 2 , 3 Even modest residual insulin secretion, with stimulated C-peptide levels above 0.2 nmol per liter (0.6 ng per milliliter), has been reported to provide clinically meaningful benefits in terms of reducing long-term complications. 4 However, most attempts to preserve residual beta-cell function have achieved minimal benefits or have been associated with adverse effects. 5 – 14 Treatment with anti-CD3 monoclonal antibodies appears promising, although many patients in whom this approach has been used have had therapy-related adverse events. 15 , 16 As an alternative to immunosuppression, autoantigens may be used to . . .

Introduction Recently, arrays have become available that allow the simultaneous analysis of several anti-citrullinated protein antibody (ACPA) reactivities using distinct citrullinated peptides. Such assays are designed for exploratory studies. The interpretation of positive antibody reactivities can best be made if the diagnostic and prognostic value of a multiplex array in an early arthritis setting is known and if the multiplex-positive patients who are negative according to three commonly used commercial ACPA assays are characterized. Methods Using Thermo Scientific’s ImmunoCap ISAC (Immuno Solid-phase Allergen Chip) system, a multiplexed array that determines reactivities to 11 citrullinated peptides, we analysed serum/plasma of 195 healthy controls and 1282 early arthritis patients from two independent cohorts: the Leiden Early Arthritis Clinic (n = 1013) and the IMPROVED (n = 269) cohort. Findings were compared with results primarily of the anti-citrullinated cyclic peptide 2 (anti-CCP-2) assay but also with anti- CCP-3 and anti-mutated citrullinated vimentin (anti-MCV) assays. The associations between ACPA reactivities and patient characteristics, risk factors (shared epitope, smoking) and disease outcomes (progression of undifferentiated arthritis to rheumatoid arthritis (RA) and severity of joint destruction) were assessed. Results Thirty-one percent of anti-CCP-2-negative RA patients displayed reactivity toward citrullinated peptides in the multiplex assay. These patients had a positive signal toward a more restricted peptide repertoire than anti-CCP-2-positive RA patients (median of 1 versus 5). Within anti-CCP-2-negative patients, ACPA reactivity as detected by multiplex array was not significantly associated with known risk factors or clinical or prognostic parameters. The frequency of sera from anti-CCP-2-negative RA patients who were positive for the multiplexed peptides was comparable to the frequency in non-RA arthritic patients (27 %). Conclusions Additive citrulline peptide reactivities detected by the current multiplex system did not reach significant power to be RA-specific. The presence of residual citrulline reactivities detected by this multiplex system in arthritis patients who are negative in commercial ACPA assays needs to be interpreted with caution.

Objective: To study serum levels of citrullinated protein/peptide antibodies (anti-CP) during up to 5 years’ follow up of patients with early rheumatoid arthritis (RA), and to relate serum levels to disease course and to treatments in clinical practice. Methods: 279 patients with early RA were followed up with clinical investigations, radiographs, and measurement of anti-CP at baseline and after 3 months, 1, 2, 3, and 5 years. Results: 160/279 (57.3%) patients were anti-CP positive at the first visit (mean 5 months after first symptoms). During follow up only 11/279 (3.9%) of the patients changed their anti-CP status. Anti-CP levels fell significantly during the first year, and this drop correlated with the extent of sulfasalazine treatment but not with other drugs or clinical indices. Anti-CP positive and negative patients had similar disease activities at baseline, but during follow up the anti-CP positive patients had worse clinical disease and greater radiological progression, despite at least equally intensive antirheumatic treatment. Conclusions: Anti-CP are stable during the first 5 years of RA, suggesting that events before rather than after onset of clinical manifestations of disease determine this phenotype. The presence of anti-CP at diagnosis predicts a less favourable disease course and greater radiological progression despite antirheumatic treatment, but subsequent changes in antibody levels do not reflect changes in disease activity. Taken together, these observations suggest that anti-CP positive RA is a distinct clinical and pathophysiological entity.

The autoimmune polyendocrine syndrome type 1 (APS-1) is a multiorgan autoimmune disorder caused by mutations in AIRE, the autoimmune-regulator gene. The authors identified reactivity to the NACHT leucine-rich-repeat protein 5 (NALP5) by immunoscreening a human parathyroid complementary DNA library, using serum samples from patients with APS-1 and hypoparathyroidism. The findings suggest that NALP5 is a tissue-specific autoantigen involved in hypoparathyroidism in patients with APS-1. The authors identified reactivity to the NACHT leucine-rich-repeat protein 5 (NALP5) using serum samples from patients with autoimmune polyendocrine syndrome type 1 and hypoparathyroidism. The findings suggest that NALP5 is a tissue-specific autoantigen in these patients. Autoimmune polyendocrine syndrome type 1 (APS-1) (Online Mendelian Inheritance in Man number 240300) is a rare autosomal recessive disorder that develops in early childhood and results in tissue-specific multiorgan autoimmunity, leading to the hypofunction of multiple glands. 1 Endocrine organs such as the adrenal cortex, ovaries, and parathyroid glands are typically affected, resulting in a variety of clinical diseases, including hypocortisolism, hypoaldosteronism, delayed puberty, premature ovarian failure, and hypoparathyroidism with life-threatening hypocalcemia. 2 APS-1 is clinically defined as the presence of at least two components of the classic triad of hypoparathyroidism, adrenal insufficiency, and mucocutaneous candidiasis. APS-1 is caused by mutations in . . .

ObjectivesAnti-Ro52 autoantibodies are associated with more severe interstitial lung disease (ILD) in adult myositis patients with antiaminoacyl transfer (t)RNA synthetase autoantibodies. However, few studies have examined anti-Ro52 autoantibodies in juvenile myositis. The purpose of this study was to define the prevalence and clinical features associated with anti-Ro52 autoantibodies in a large cohort of patients with juvenile myositis.MethodsWe screened sera from 302 patients with juvenile dermatomyositis (JDM), 25 patients with juvenile polymyositis (JPM) and 44 patients with juvenile connective tissue disease–myositis overlap (JCTM) for anti-Ro52 autoantibodies by ELISA. Clinical characteristics were compared between myositis patients with and without anti-Ro52 autoantibodies.ResultsAnti-Ro52 autoantibodies were found in 14% patients with JDM, 12% with JPM and 18% with JCTM. Anti-Ro52 autoantibodies were more frequent in patients with antiaminoacyl tRNA synthetase (64%, p<0.001) and anti-MDA5 (31%, p<0.05) autoantibodies. After controlling for the presence of myositis-specific autoantibodies, anti-Ro52 autoantibodies were associated with the presence of ILD (36% vs 4%, p<0.001). Disease course was more frequently chronic, remission was less common, and an increased number of medications was received in anti-Ro52 positive patients.ConclusionsAnti-Ro52 autoantibodies are present in 14% of patients with juvenile myositis and are strongly associated with anti-MDA5 and antiaminoacyl tRNA synthetase autoantibodies. In all patients with juvenile myositis, those with anti-Ro52 autoantibodies were more likely to have ILD. Furthermore, patients with anti-Ro52 autoantibodies have more severe disease and a poorer prognosis.

Activation of the immune system is implicated in the Post-Acute Sequelae after SARS-CoV-2 infection (PASC) but the mechanisms remain unknown. Angiotensin-converting enzyme 2 (ACE2) cleaves angiotensin II (Ang II) resulting in decreased activation of the AT1 receptor and decreased immune system activation. We hypothesized that autoantibodies against ACE2 may develop after SARS-CoV-2 infection, as anti-idiotypic antibodies to anti-spike protein antibodies. We tested plasma or serum for ACE2 antibodies in 67 patients with known SARS-CoV-2 infection and 13 with no history of infection. None of the 13 patients without history of SARS-CoV-2 infection and 1 of the 20 outpatients that had a positive PCR test for SARS-CoV-2 had levels of ACE2 antibodies above the cutoff threshold. In contrast, 26/32 (81%) in the convalescent group and 14/15 (93%) of patients acutely hospitalized had detectable ACE2 antibodies. Plasma from patients with antibodies against ACE2 had less soluble ACE2 activity in plasma but similar amounts of ACE2 protein compared to patients without ACE2 antibodies. We measured the capacity of the samples to inhibit ACE2 enzyme activity. Addition of plasma from patients with ACE2 antibodies led to decreased activity of an exogenous preparation of ACE2 compared to patients that did not have antibodies. Many patients with a history of SARS-CoV-2 infection have antibodies specific for ACE2. Patients with ACE2 antibodies have lower activity of soluble ACE2 in plasma. Plasma from these patients also inhibits exogenous ACE2 activity. These findings are consistent with the hypothesis that ACE2 antibodies develop after SARS-CoV-2 infection and decrease ACE2 activity. This could lead to an increase in the abundance of Ang II, which causes a proinflammatory state that triggers symptoms of PASC.

Antinephrin autoantibodies occur in adults with minimal change disease and children with idiopathic nephrotic syndrome and appear to be disease activity markers. Their binding at slit diaphragms may induce podocyte dysfunction.