Autoantibodies against CD74 in spondyloarthritis

Serum biomarkers and their relationship to axial spondyloarthritis associated with inflammatory bowel diseases

Spondyloarthritis (SpA) constitute a group of chronic inflammatory immune-mediated rheumatic diseases characterized by genetic, clinical, and radiological features. Recent efforts have concentrated on identifying biomarkers linked to axial SpA associated with inflammatory bowel disease (IBD), offering predictive insights into disease onset, activity, and progression. Genetically, the significance of the HLA-B27 antigen is notably diminished in ankylosing spondylitis (AS) associated with IBD, but is heightened in concurrent sacroiliitis. Similarly, certain polymorphisms of endoplasmic reticulum aminopeptidase (ERAP-1) appear to be involved. Carriage of variant NOD2/CARD15 polymorphisms has been demonstrated to correlate with the risk of subclinical intestinal inflammation in AS. Biomarkers indicative of pro-inflammatory activity, including C-reactive protein (CRP) along with erythrocyte sedimentation rate (ESR), are among the consistent predictive biomarkers of disease progression. Nevertheless, these markers are not without limitations and exhibit relatively low sensitivity. Other promising markers encompass IL-6, serum calprotectin (s-CLP), serum amyloid (SAA), as well as biomarkers regulating bone formation such as metalloproteinase-3 (MMP-3) and Dickkopf-related protein 1 (DKK-1). Additional candidate indicators of structural changes in SpA patients include matrix metalloproteinase-3 (MMP-3), vascular endothelial growth factor (VEGF), tenascin C (TNC), and CD74 IgG. Fecal caprotein (f-CLP) levels over long-term follow-up of AS patients have demonstrated predictive value in anticipating the development of IBD. Serologic antibodies characteristic of IBD (ASCA, ANCA) have also been compared; however, results exhibit variability. In this review, we will focus on biomarkers associated with both axial SpA and idiopathic intestinal inflammation, notably enteropathic spondyloarthritis.

[Autoimmune diagnostics in nephrology and rheumatology]

Autoimmune diagnostics plays a central role in the detection of various acute and/or chronic diseases in both nephrology and rheumatology, which are associated with high morbidity and mortality if left untreated or not detected in time. Patients are threatened with significant limitations in everyday skills and quality of life due to loss of kidney function and dialysis, immobilizing and destructive joint processes or also significant damage of organ systems. In all of these autoimmune diseases, early diagnosis and treatment is of central importance for the further course and prognosis of disease.Antibodies play an essential role in the pathogenesis of autoimmune diseases. Antibodies are either directed against organ or tissue-specific antigens, such as in primary membranous glomerulonephritis or Goodpasture's syndrome, or they lead to a systemic disease such as systemic lupus erythematosus (SLE) or rheumatoid arthritis.Knowledge of the sensitivity and specificity of antibodies is crucial for the interpretation of antibody diagnostics results. Antibody detection can precede the clinical onset of the disease, and antibody titers often reflect disease activity. However, there are also false positive results. Detection of antibodies in the absence of disease symptoms often leads to uncertainty and unnecessary further diagnostics. Therefore, an unfounded "antibody screening" is not recommended.A rational antibody diagnostics is an integral part of the diagnostics and during treatment of nephrological and rheumatological diseases like glomerulonephrititis, pulmorenal syndrome, SLE and other collagenosis, thrombotic microangiopathy (HUS/TTP) and rheumatoid arthritis.

Antibodies of the immunoglobulin a isotype to novel antigens in early axial spondyloarthritis

Introduction

There is an unmet need for biomarkers to identify patients with axial spondyloarthritis (axSpA). Increasing evidence suggest the presence of autoantibodies in a subset of axSpA patients. The aim of this study was to identify novel IgA antibodies in early axSpA patients and to determine their diagnostic potential in combination with previously determined IgG antibodies against UH (Hasselt University)-axSpA-IgG antigens.

Methods

An axSpA cDNA phage display library constructed from axSpA hip synovium, was used to screen for novel IgA antibodies in plasma from early axSpA patients. The presence of these antibodies against novel UH-axSpA-IgA antigens was determined in two independent axSpA cohorts, in healthy controls and in patients with chronic low back pain.

Results

We identified antibodies to 7 novel UH-axSpA-IgA antigens, of which 6 correspond to non-physiological peptides and 1 to the human histone deacetylase 3 (HDAC3) protein. IgA antibodies against 2 of these 7 novel UH-axSpA-IgA antigens and IgG antibodies against 2 of the previously identified antigens were significantly more present in early axSpA patients from the UH cohort (18/70, 25.7%) and the (Bio)SPAR cohort (26/164, 15.9%), compared to controls with chronic low back pain (2/66, 3%). Antibodies to this panel of 4 antigens were present in 21.1% (30/142) of patients with early axSpA from the UH and (Bio)SPAR cohorts. The positive likelihood ratio for confirming early axSpA using antibodies to these 4 UH-axSpA antigens was 7.0. So far, no clinical correlation between the novel identified IgA antibodies and inflammatory bowel disease could be identified.

Discussion

In conclusion, screening an axSpA cDNA phage display library for IgA reactivity resulted in the identification of 7 novel UH-axSpA-IgA antigens, of which 2 show promising biomarker potential for the diagnosis of a subset of axSpA patients, in combination with previously identified UH-axSpA-IgG antigens.

Anti-CD74 IgA antibodies show diagnostic potential for axial spondyloarthritis but are not associated with microscopic gut inflammation

OBJECTIVES

Gut inflammation commonly occurs in axial SpA (axSpA), and is linked to disease activity and outcome. Given the role of IgA in mucosal immunity, we explored the association between anti-CD74 IgA antibodies, gut inflammation and axSpA.

METHODS

Anti-CD74 IgA was measured by ELISA in serum samples of axSpA patients, fulfilling the 2009 Assessment of SpondyloArthritis international Society classification criteria. A group of fibromyalgia (FM) and RA patients served as non-inflammatory and inflammatory controls. Newly diagnosed axSpA patients underwent ileocolonoscopy; mucosal biopsies were histopathologically assessed as normal, acute or chronically inflamed. Optimal anti-CD74 IgA cut-off values were determined with a receiver operating characteristics curve.

RESULTS

axSpA patients (n = 281) showed higher anti-CD74 IgA levels [mean (s.d.) 18.8 (12.4) U/ml] compared with 100 FM patients [10.9 (5.0) U/ml, P < 0.001] and 34 RA patients [13.7 (9.6) U/ml, P = 0.02]. The area under the receiver operating characteristics curve for diagnosis (axSpA vs FM) was 0.70, providing a sensitivity of 60% and specificity of 87% (cut-off 15 U/ml). Antibody concentrations were not significantly different between axSpA patients with (n = 40) and without (n = 69) gut inflammation (P = 0.83), yielding an area under the receiver operating characteristics curve of 0.51. Anti-CD74 IgA levels were not associated with degree of bone marrow oedema on MRI of the sacroiliac joints, CRP or any other disease-specific feature such as the use of NSAIDs or biological treatment.

CONCLUSION

Serum anti-CD74 IgA is a potentially useful diagnostic biomarker for axSpA. However, antibody levels do not correlate with any phenotypical feature, including microscopic gut inflammation, suggesting this to be a disease-specific rather than an inflammatory marker.

Macrophage migration inhibitory factor (MIF) and IgA anti CD74 antibodies in Indian patients with enthesitis-related arthritis category of Juvenile idiopathic arthritis

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine and has been implicated in pathogenesis of ankylosing spondylitis (AS). CD 74 is the receptor for MIF and IgA antiCD74 autoantibodies have been described from different parts of the world in patients with AS. As enthesitis-related arthritis (ERA) is a form of juvenile spondyloarthropathy, we studied the serum and synovial fluid levels of MIF in ERA and looked for the IgA antiCD74 antibodies in patients with ERA in our population. Patients with JIA (ILAR classification) were studied. Serum MIF levels were measured by ELISA in 101 patients of ERA (synovial fluid also where available) and compared to 28 patients of other categories of JIA, 25 patients each of ankylosing spondylitis and rheumatoid arthritis, and 38 healthy controls. In addition, association of MIF with disease activity was assessed. Ig A antiCD74 antibodies were measured in sera of ERA, AS and healthy controls. Median serum MIF levels were higher in ERA [2.50 (1.20-4.85) ng/ml] than in healthy controls [0.28 (0.16-0.48); p < 0.0001] and patients with RA [1.13 (0.44-2.45); p < 0.01] MIF levels in ERA were comparable to other categories of JIA [2.63 (1.70-4.05)] and patients with AS [3.62 (0.52-6.51)]. Synovial fluid MIF levels were higher than serum levels (p < 0.01). Serum MIF level had an association with the JSpADA score (r = 0.29, p < 0.01). Serum MIF levels had no association with presence of inflammatory markers, enthesitis, inflammatory back pain or sacroiliitis. IgA AntiCD74 antibody was positive only in 3/88 (3.41%) of ERA patients and was not detected in any patients of AS or healthy controls. Patients with ERA have high MIF levels that show modest correlation with disease activity. Higher synovial fluid MIF levels suggest that it may play a role in synovitis seen in ERA. IgA antiCD74 antibodies are rarely seen in ERA.

How Has Molecular Biology Enhanced Our Undertaking of axSpA and Its Management

PURPOSE

This review aims at investigating pathophysiological mechanisms in spondyloarthritis (SpA). Analysis of genetic factors, immunological pathways, and abnormalities of bone metabolism lay the foundations for a better understanding of development of the axial clinical manifestations in patients, allowing physician to choose the most appropriate therapeutic strategy in a more targeted manner.

RECENT FINDINGS

In addition to the contribution of MHC system, findings emerged about the role of non-HLA genes (as ERAP1 and 2, whose inhibition could represent a new therapeutic approach) and of epigenetic mechanisms that regulate the expression of genes involved in SpA pathogenesis. Increasing evidence of bone metabolism abnormalities secondary to the activation of immunological pathways suggests the development of various bone anomalies that are present in axSpA patients. SpA are a group of inflammatory diseases with a multifactorial origin, whose pathogenesis is linked to the genetic predisposition, the action of environmental risk factors, and the activation of immune response. It is now well known how bone metabolism leads to long-term structural damage via increased bone turnover, bone loss and osteoporosis, osteitis, erosions, osteosclerosis, and osteoproliferation. These effects can exist in the same patient over time or even simultaneously. Evidence suggests a cross relationship among innate immunity, autoimmunity, and bone remodeling in SpA, making treatment approach a challenge for rheumatologists. Specifically, treatment targets are consistently increasing as new drugs are upcoming. Both biological and targeted synthetic drugs are promising in terms of their efficacy and safety profile in patients affected by SpA.

Diagnostic value of anti-Kaiso autoantibody in axial spondyloarthritis

Objective

Axial spondyloarthritis (axSpA) is a chronic rheumatic disease predominantly characterized by inflammation and progressive structural damage. Patients are often diagnosed very late, which delays the optimal treatment period. Early diagnosis of axSpA, especially non-radiographic axSpA (nr-axSpA), remains a major challenge. This study aimed to investigate the diagnostic value of anti-Kaiso autoantibodies in axSpA and their correlation with clinical disease indicators.

Methods

Two pooled serum samples (seven patients with nr-axSpA and seven healthy controls) were profiled using HuProt arrays to investigate the diagnostic value of autoantibodies in nr-axSpA. Levels of anti-Kaiso autoantibodies in patients with axSpA and controls were determined using the Meso Scale Discovery assay system. Receiver operating characteristic curve analysis was performed to evaluate the diagnostic performance of anti-Kaiso autoantibodies in axSpA. Pearson's correlation was used to assess the correlation between anti-Kaiso autoantibodies and clinical parameters.

Results

Seven candidate autoantibodies were present in the serum of patients with nr-axSpA. The levels of anti-Kaiso autoantibodies were significantly higher in the nr-axSpA group than in the other groups. It can differentiate nr-axSpA from ankylosing spondylitis (AS), healthy controls, and rheumatoid arthritis. The level of early-stage AS among patients with nr-axSpA decreased when they progressed to the late stage. Of all patients with axSpA, serum anti-Kaiso autoantibody levels were positively correlated with the C-reactive protein level and the Bath Ankylosing Spondylitis Disease Activity Index score and negatively correlated with disease duration.

Conclusion

Anti-Kaiso autoantibody may be a valuable diagnostic biomarker for early-stage AS in the nr-axSpA period and may be a potential therapeutic target.

Deep Insight into the Role of MIF in Spondyloarthritis

PURPOSE OF REVIEW

Pathological roles of macrophage migration inhibitory factor (MIF) have recently been demonstrated in spondyloarthritis (SpA) preclinical models, identifying MIF as a new treatment target for SpA. However, the specific contribution of MIF and therapeutic potential of MIF-targeted therapies to various tissue types affected by SpA are not well delineated.

RECENT FINDINGS

MIF and its cognate receptor CD74 are extensively involved in the pathogenesis of SpA including inflammation in the spine, joint, eyes, skin, and gut. The majority of the current evidence has consistently shown that MIF drives the inflammation in these distinct anatomical sites. In preclinical models, genetic deletion or blockade of MIF reduces the severity of inflammation. Although MIF is generally an upstream cytokine which regulates downstream effector cytokines, MIF also intensifies type 3 immunity by promoting helper T 17 (Th17) plasticity. MIF- or CD74-targeted therapies have also reported to be well tolerated in clinical trials for other diseases. Recent findings suggest that MIF-CD74 axis is a new therapeutic target for SpA to improve various clinical features. Clinical trials for MIF- or CD74-targeted therapies for SpA patients are warranted.

Quantification of polyreactive immunoglobulin G facilitates the diagnosis of autoimmune hepatitis

BACKGROUND AND AIMS

Detection of autoantibodies is a mainstay of diagnosing autoimmune hepatitis (AIH). However, conventional autoantibodies for the workup of AIH lack either sensitivity or specificity, leading to substantial diagnostic uncertainty. We aimed to identify more accurate serological markers of AIH with a protein macroarray.

APPROACH AND RESULTS

During the search for more-precise autoantibodies to distinguish AIH from non-AIH liver diseases (non-AIH-LD), IgG antibodies with binding capacities to many human and foreign proteins were identified with a protein macroarray and confirmed with solid-phase ELISAs in AIH patients. Subsequently, polyreactive IgG (pIgG) was exemplarily quantified by reactivity against human huntingtin-interacting protein 1-related protein in bovine serum albumin blocked ELISA (HIP1R/BSA). The diagnostic fidelity of HIP1R/BSA binding pIgG to diagnose AIH was assessed in a retrospective training, a retrospective multicenter validation, and a prospective validation cohort in cryoconserved samples from 1,568 adults from 10 centers from eight countries. Reactivity against HIP1R/BSA had a 25% and 14% higher specificity to diagnose AIH than conventional antinuclear and antismooth muscle antibodies, a significantly higher sensitivity than liver kidney microsomal antibodies and antisoluble liver antigen/liver pancreas antigen, and a 12%-20% higher accuracy than conventional autoantibodies. Importantly, HIP1R/BSA reactivity was present in up to 88% of patients with seronegative AIH and in up to 71% of AIH patients with normal IgG levels. Under therapy, pIgG returns to background levels of non-AIH-LD.

CONCLUSIONS

pIgG could be used as a promising marker to improve the diagnostic workup of liver diseases with a higher specificity for AIH compared to conventional autoantibodies and a utility in autoantibody-negative AIH. Likewise, pIgG could be a major source of assay interference in untreated AIH.

B Cell Involvement in the Pathogenesis of Ankylosing Spondylitis

Extensive research into ankylosing spondylitis (AS) has suggested the major role of genetics, immune reactions, and the joint-gut axis in its etiology, although an ultimate consensus does not yet exist. The available evidence indicates that both autoinflammation and T-cell-mediated autoimmune processes are actively involved in the disease process of AS. So far, B cells have received relatively little attention in AS pathogenesis; this is largely due to a lack of conventional disease-defining autoantibodies. However, against prevailing dogma, there is a growing body of evidence suggestive of B cell involvement. This is illustrated by disturbances in circulating B cell populations and the formation of auto-reactive and non-autoreactive antibodies, along with B cell infiltrates within the axial skeleton of AS patients. Furthermore, the depletion of B cells, using rituximab, displayed beneficial results in a subgroup of patients with AS. This review provides an overview of our current knowledge of B cells in AS, and discusses their potential role in its pathogenesis. An overarching picture portrays increased B cell activation in AS, although it is unclear whether B cells directly affect pathogenesis, or are merely bystanders in the disease process.

Cellular and molecular diversity in spondyloarthritis

The spondyloarthritides are a cluster of inflammatory rheumatic diseases characterized by different diagnostic entities with heterogeneous phenotypes. The current classification system groups spondyloarthritis patients in two main categories, axial and peripheral spondyloarthritis, providing a framework wherein the clinical picture guides the treatment. However, the heterogeneity of the clinical manifestations of the pathologies, even when residing in the same group, highlights the importance of analyzing the smallest features of each entity to understand how different cellular subsets evolve, what the underlying mechanisms are and what biological markers can be identified and validated to evaluate the stage of disease and the corresponding efficacy of treatments. In this review, we will focus mostly on axial spondyloarthritis, report current knowledge concerning the cellular populations involved in its pathophysiology, and their molecular diversity. We will discuss the implications of such a diversity, and their meaning in terms of patients' stratification.

Anti-CD74 IgA autoantibodies in radiographic axial spondyloarthritis: a longitudinal Swedish study

Objectives

Antibodies against anti-CD74 are related to axial spondyloarthritis (axSpA). The objectives were (i) to study IgA anti-CD74 in radiographic (r)-axSpA patients in the Backbone cohort and to calculate the sensitivity and specificity of anti-CD74, (ii) to study the fluctuation of IgA anti-CD74 levels in prospectively collected samples, and (iii) to explore the relation between IgA anti-CD74 and radiographic spinal changes.

Methods

IgA anti-CD74 was analysed by ELISA in 155 patients with r-axSpA and age- and sex-matched controls. BASDAI, ASDAS, BASFI and BASMI were assessed and spinal radiographs were scored for r-axSpA-related changes with mSASSS. Previously donated samples, before inclusion in the Backbone study, were identified in the Medical Biobank of Northern Sweden.

Results

A total of 155 patients comprising 69% men and 31% women, age [mean (s.d.)] 55.5 (11.4) years and 152 (98.1%) HLA-B27 positive, were included. The plasma level of IgA anti-CD74 was significantly higher in the patients [median (interquartile range), 12.9 (7.9–17.9) U/ml] compared with controls [10.9 (7.2–14.6) U/ml, P = 0.003]. IgA anti-CD74 was above the cut-off level of 20 U/ml in 36/155 (23.2%) patients and in 15/151 (9.9%) controls (P = 0.002). Multivariable logistic regression analyses revealed ≥1 syndesmophyte associated with IgA anti-CD74 (odds ratio 5.64; 95% CI: 1.02, 35.58; P = 0.048) adjusted for hsCRP, smoking, BMI, sex and age. No distinct pattern of IgA anti-CD74 over time was revealed.

Conclusion

Plasma levels of IgA anti-CD74 were increased in r-axSpA and independently associated with radiographic spinal changes, which suggests that IgA anti-CD74 could play a role in the pathogenies of r-axSpA.

Ankylosing spondylitis: an autoimmune or autoinflammatory disease?

Ankylosing spondylitis (AS) is a chronic inflammatory disorder of unknown aetiology. Unlike other systemic autoimmune diseases, in AS, the innate immune system has a dominant role characterized by aberrant activity of innate and innate-like immune cells, including γδ T cells, group 3 innate lymphoid cells, neutrophils, mucosal-associated invariant T cells and mast cells, at sites predisposed to the disease. The intestine is involved in disease manifestations, as it is at the forefront of the interaction between the mucosal-associated immune cells and the intestinal microbiota. Similarly, biomechanical factors, such as entheseal micro-trauma, might also be involved in the pathogenesis of the articular manifestation of AS, and sentinel immune cells located in the entheses could provide links between local damage, genetic predisposition and the development of chronic inflammation. Although these elements might support the autoinflammatory nature of AS, studies demonstrating the presence of autoantibodies (such as anti-CD74, anti-sclerostin and anti-noggin antibodies) and evidence of activation and clonal expansion of T cell populations support an autoimmune component to the disease. This Review presents the evidence for autoinflammation and the evidence for autoimmunity in AS and, by discussing the pathophysiological factors associated with each, aims to reconcile the two hypotheses.

Exploring IL-17 in spondyloarthritis for development of novel treatments and biomarkers

Spondyloarthritis (SpA) is an umbrella term describing a family of chronic inflammatory rheumatic diseases. These diseases are characterised by inflammation of the axial skeleton, peripheral joints, and entheseal insertion sites throughout the body which can lead to structural joint damage including formation of axial syndesmophytes and peripheral osteophytes. Genetic evidence, preclinical and clinical studies indicate a clear role of interleukin (IL)- 23 and IL-17 as mediators in SpA pathogenesis. Targeting the IL-23/-17 pathways seems an efficient strategy for treatment of SpA patients, and despite the remaining challenges the pathway holds great promise for further advances and improved therapeutic opportunities. Much research is focusing on serological markers and imaging strategies to correctly diagnose patients in the early stages of SpA. Biomarkers may facilitate personalised medicine tailored to each patient's specific disease to optimise treatment efficacy and to monitor therapeutic response. This narrative review focuses on the IL-17 pathway in SpA-related diseases with emphasis on its role in pathogenesis, current approved IL-17 inhibitors, and the need for biomarkers reflecting core disease pathways for early diagnosis and measurement of disease activity, prognosis, and response to therapy.

Diagnostic value of anti-CD74 antibodies in early and late axial spondyloarthritis and its relationship to disease activity

OBJECTIVES

This study was designed to evaluate the role of anti-CD74 antibodies in diagnosis of axial spondyloarthritis (axSpA) and their relationship to disease duration and disease activity.

METHODS

Fifty patients with axSpA, 15 patients with RA and 15 healthy subjects were included in the study. Clinical examination and laboratory tests were done. The ESR, CRP level and ASDAS were measured as markers of the disease activity. Quantitative determination of human CD74 IgG antibodies was done.

RESULTS

The mean age of the patients was 38.22 (S.D.12.20) years. The level of CD74 autoantibodies was significantly higher in axSpA in comparison to control groups. Most patients with positive articular and extra-articular manifestations were positive for CD74 autoantibodies. In patients with inactive disease, 33.3% were positive for CD74 autoantibodies, as were 83% with active disease. High percentages of patients with early and late axSPA were CD74 autoantibody positive. The majority of patients with positive disease activity in early and late axSpA were CD74 autoantibody positive. CD74 autoantibodies had 80% sensitivity vs both control groups with 87% specificity vs the healthy control group and 80% vs the RA control group in the diagnosis of axSpA.

CONCLUSIONS

The frequency of positive anti-CD74 IgG antibodies was as high in patients with early axSpA as in those with late axSpA, with no significant differences. There was a significant difference in the frequency of positive anti-CD74 IgG antibodies between patients with positive and negative disease activity. Based on the sensitivity and specificity of anti-CD74 IgG, this is a promising diagnostic tool to support the clinical diagnosis of axSpA.

Molecular mechanisms and clinical studies of iguratimod for the treatment of ankylosing spondylitis

Iguratimod (IGU) is a novel small molecule anti-rheumatic drug with the effect of non-steroidal anti-inflammatory drug and disease-modifying anti-rheumatic drug. IGU has various mechanisms of action, including inhibition of prostaglandin E2, tumor necrosis factor-α (TNF-α), interleukin-17 (IL-17) production, inhibition of macrophage migration inhibitory factor (MIF)-induced proinflammatory effects, inhibition of osteoclastogenesis, and promotion of osteoblastic differentiation. Ankylosing spondylitis (AS) is the major subtype of spondyloarthritis that affects the axial skeleton, causing inflammatory back pain, which can lead to impairments in structure and function and a decrease in quality of life. Theories on pathogenesis of AS include misfolding of human leukocyte antigen-B27 during its assembly leading to endoplasmic reticulum stress and unfolded protein response (UPR). Activation of UPR genes results in release of TNF-α and IL-17, which have been shown to be important in the development of AS. In addition, current evidence suggests the importance of cyclooxygenase-2/prostaglandin E2 pathway and MIF in the pathogenesis of AS. Current drugs for the treatment of AS are limited and exploration of effective drugs is needed. IGU may be effective for the treatment of AS given that its mechanisms of action are closely related to the pathogenesis of AS. In fact, several small-scale clinical trials have shown the efficacy of IGU for the treatment of AS. This article reviews the molecular mechanisms of IGU that are related to the pathogenesis of AS and clinical trials of IGU for the treatment of AS, providing a reference for future clinical application of IGU for AS.

CD74 auto-antibodies display little clinical value in Chinese Han population with axial spondyloarthritis

The European cohort study has indicated about CD74 IgG-autoantibodies as potential marker for axial spondyloarthritis (axSpA) diagnosis. However, multiple studies have questioned the diagnostic value of various disease-specific autoantibodies in different ethnic groups. Here, we have tried to assess the diagnostic value of anti-CD74 IgG and IgA autoantibodies in axSpA patients from Chinese Han population.The anti-CD74 IgG and IgA autoantibodies were analyzed using ELISA assay in a cohort of 97 axSpA patients, including 47 treatment-naïve axSpA patients never treated with steroids or immunosuppressants and 50 treated axSpA patients. The rheumatic disease control (RDC) group consisted of 40 rheumatoid arthritis, 25 systemic lupus erythematosus, 18 psoriatic arthritis patients, and 60 healthy controls (HC).Our data demonstrated the presence of anti-CD74 IgA auto-antibodies in 25.8% of the axSpA patients, 30.1% of the RDC group patients and none in HC. Similarly, anti-CD74 IgG autoantibodies were observed in 23.7% of the axSpA patients, 18.1% of the RDC patients and 18.3% of the HC. The sensitivity, specificity, and accuracy of IgA autoantibodies were 21.3%, 82.5%, & 67.4%, respectively, while for IgG, it was 27.7%, 81.8%, and 68.4%, in treatment-naïve axSpA patients. Furthermore, weak positive relationship between anti-CD74 IgA autoantibodies and bath ankylosing spondylitis disease activity index ( r = 0.253, P = .012) and functional index (bath ankylosing spondylitis functional index; r = 0.257, P = .011) was observed.Overall, our study demonstrated little clinical and predictive value of CD74 autoantibodies in the diagnosis of axSpA and its related manifestations, among Chinese Han population.

Anti-CD74 antibodies in spondyloarthritis: A systematic review and meta-analysis

OBJECTIVE

There is still an unmet need for a simple and reliable biomarker for the diagnosis of spondyloarthritis. Recent studies indicated that anti-CD74 antibody could act as a biomarker for spondyloarthritis. Therefore, this review aims to evaluate the levels of anti-CD74 IgG and IgA antibodies in spondyloarthritis and the diagnostic value of anti-CD74 antibodies.

METHODS

PubMed, Web of Science and Medline were comprehensively searched from inception to August 7th, 2019. The pooled standard mean difference (SMD) with 95% confidence interval (CI) was used to estimate the differences of the levels of anti-CD74 IgG and IgA antibodies between spondyloarthritis patients and controls. Sensitivity, specificity and summary receiver operating characteristics (SROC) curve were used for evaluating the diagnostic value of anti-CD74 antibodies. The use of fixed-effect or random-effects model depended on heterogeneity.

RESULTS

Among 55 searched studies, 9 studies were finally included for analysis. Anti-CD74 IgG and IgA antibodies were both significantly increased in spondyloarthritis patients compared with matched controls (IgG: SMD = 0.88, 95% CI = 0.55 to 1.21; IgA: SMD = 0.98, 95% CI = 0.68 to 1.28). The pooled sensitivity, specificity and area under the SROC curve of anti-CD74 IgG antibodies were 0.61, 0.90 and 0.8881, while these indicators of anti-CD74 IgA antibodies were 0.59, 0.95 and 0.8671, respectively.

CONCLUSION

Anti-CD74 IgG and IgA antibodies were significantly increased in spondyloarthritis patients and suggest a high diagnostic specificity of spondyloarthritis. Anti-CD74 antibody could potentially be a biomarker for the diagnosis of spondyloarthritis, but many open questions remain.

An update on serum biomarkers to assess axial spondyloarthritis and to guide treatment decision

Axial spondyloarthritis (axSpA) is a group of debilitating, chronic, rheumatic conditions characterized by inflammation and new bone formation, mainly involving the spine and the sacroiliac joints. The lack of biomarkers in axSpA is well known. Despite significant treatment advances in recent years thanks to the introduction of drugs with a new mode of action, such as new biologic and targeted synthetic disease-modifying antirheumatic drugs, no relevant improvement in the identification of disease biomarkers has been achieved. Common parameters, such as erythrocyte sedimentation rate and C-reactive protein, which are routinely used to measure systemic inflammation, are the sole markers available to date and are not adequate to assess disease activity in all patients. The aim of this study is to review the most promising serum biomarkers that may help treatment decision in axSpA via a proper assessment of disease activity and identification of negative prognostic factors.

MHC class II invariant chain-adjuvanted viral vectored vaccines enhances T cell responses in humans

Strategies to enhance the induction of high magnitude T cell responses through vaccination are urgently needed. Major histocompatibility complex (MHC) class II-associated invariant chain (Ii) plays a critical role in antigen presentation, forming MHC class II peptide complexes for the generation of CD4⁺ T cell responses. Preclinical studies evaluating the fusion of Ii to antigens encoded in vector delivery systems have shown that this strategy may enhance T cell immune responses to the encoded antigen. We now assess this strategy in humans, using chimpanzee adenovirus 3 and modified vaccinia Ankara vectors encoding human Ii fused to the nonstructural (NS) antigens of hepatitis C virus (HCV) in a heterologous prime/boost regimen. Vaccination was well tolerated and enhanced the peak magnitude, breadth, and proliferative capacity of anti-HCV T cell responses compared to non-Ii vaccines in humans. Very high frequencies of HCV-specific T cells were elicited in humans. Polyfunctional HCV-specific CD8⁺ and CD4⁺ responses were induced with up to 30% of CD3⁺CD8⁺ cells targeting single HCV epitopes; these were mostly effector memory cells with a high proportion expressing T cell activation and cytolytic markers. No volunteers developed anti-Ii T cell or antibody responses. Using a mouse model and in vitro experiments, we show that Ii fused to NS increases HCV immune responses through enhanced ubiquitination and proteasomal degradation. This strategy could be used to develop more potent HCV vaccines that may contribute to the HCV elimination targets and paves the way for developing class II Ii vaccines against cancer and other infections.

Immunoglobulin A antibodies to oxidized collagen type II as a potential biomarker for the stratification of spondyloarthritis from rheumatoid arthritis

OBJECTIVES

The discovery of diseased tissue-specific neoantigens offers the opportunity to develop important disease tissue-specific biomarkers that can help in the prediction, diagnosis, and stratification of diseases. This opportunity is specifically significant for autoimmune diseases where diagnostic biomarkers are not available. Inflammatory autoimmune diseases are commonly associated with local generation of large amounts of reactive oxidants. We have previously identified oxidative post-translationally modified (oxPTM) tissue-specific neoantigens in rheumatoid arthritis (RA) and type 1 diabetes that elicit an immune response. In the current study, we studied the presence and clinical significance of antibodies to oxPTM collagen type II (CII) in patients with spondyloarthritis (SpA).

METHOD

Levels of antibodies specific to native CII and oxPTM-CII were assessed by enzyme-linked immunosorbent assay.

RESULTS

Immunoglobulin G (IgG) binding to oxPTM-CII was observed in 52%, 83%, and 28% of serum samples from patients with axial spondyloarthritis (axSpA), RA, and psoriatic arthritis (PsA), respectively. Importantly, while strong IgA anti-oxPTM-CII responses were detected in axSpA and PsA patients, with 47% and 84% respective binders, no IgA anti-oxPTM-CII was detected in RA patients. IgA anti-oxPTM-CII reactivity in axSpA patients treated with biologics was higher and more frequent, with 85% binders compared to 9% binders in patients treated with synthetic disease-modifying anti-rheumatic drugs.

CONCLUSION

Our data imply that SpA and PsA are associated with the presence of antibodies to oxPTM-CII, suggesting that there may be a humoral component that may distinguish patients with SpA from RA. Our approach could be adapted to other diseases, particularly to inflammatory autoimmune diseases.

Impaired proteolysis by SPPL2a causes CD74 fragment accumulation that can be recognized by anti-CD74 autoantibodies in human ankylosing spondylitis

Ankylosing spondylitis (AS) is associated with autoantibody production to class II MHC‐associated invariant chain peptide, CD74/CLIP. In this study, we considered that anti‐CD74/CLIP autoantibodies present in sera from AS might recognize CD74 degradation products that accumulate upon deficiency of the enzyme signal peptide peptidase‐like 2A (SPPL2a). We analyzed monocytes from healthy controls (n = 42), psoriatic arthritis (n = 25), rheumatoid arthritis (n = 16), and AS patients (n = 15) for SPPL2a enzyme activity and complemented the experiments using SPPL2a‐sufficient and ‐deficient THP‐1 cells. We found defects in SPPL2a function and CD74 processing in a subset of AS patients, which culminated in CD74 and HLA class II display at the cell surface. These findings were verified in SPPL2a‐deficient THP‐1 cells, which showed expedited expression of MHC class II, total CD74 and CD74 N‐terminal degradation products at the plasma membrane upon receipt of an inflammatory trigger. Furthermore, we observed that IgG anti‐CD74/CLIP autoantibodies recognize CD74 N‐terminal degradation products that accumulate upon SPPL2a defect. In conclusion, reduced activity of SPPL2a protease in monocytes from AS predisposes to endosomal accumulation of CD74 and CD74 N‐terminal fragments, which, upon IFN‐γ‐exposure, is deposited at the plasma membrane and can be recognized by anti‐CD74/CLIP autoantibodies.

Immune checkpoint inhibitor-induced inflammatory arthritis as a model of autoimmune arthritis

The development of inflammatory arthritis in patients receiving immune checkpoint inhibitor therapy is increasingly recognized due to the growing use of these drugs for the treatment of cancer. This represents an important opportunity not only to define the mechanisms responsible for the development of this immune-related adverse event and to ultimately predict or prevent its development, but also to provide a unique window into early events in the development of inflammatory arthritis. Knowledge gained through the study of this patient population, for which the inciting event is known, could shed light into the pathogenesis of autoimmune arthritis. This review will highlight the clinical and immunologic features of these entities to define common elements for future study.

Autoantibodies against P29ING4 are associated with complex regional pain syndrome

INTRODUCTION

Complex regional pain syndrome (CRPS) is a complication following trauma or surgery and may be difficult to diagnose since biomarkers are lacking. Using protein array technology, we found antibodies binding to p29ING4, which we further characterized using ELISA.

METHODS

Thirty-six sera of early-stage type 1 CRPS, 66 sera of rheumatoid arthritis (RA), 53 sera of axial spondyloarthritis (axSpA), 29 sera of psoriatic arthritis (PsA), 22 sera of patients after radial fractures (trauma control), and 100 sera of blood donors (BD) were analyzed for anti-p29ING4. We established ELISAs with 7 different antigens and using different secondary antibodies binding to IgG, IgG1, IgG2, IgG3, IgG4, IgA, and IgM, and 2 different tests to detect immune complexes (IC) of p29ING4 and IgG or IgG1.

RESULTS

The highest likelihood ratios versus CRPS and trauma control were observed considering the A1-23 (sensitivity 19%, specificity 100%, LR > 19) using IgG as a secondary antibody, the A120-165 (sensitivity 17%, specificity 100%, LR = 17) using IgG as a secondary antibody and the A120-165 (sensitivity 31%, specificity 95%, LR = 6.2) using IgA as a secondary antibody. IC of p29ING4 and IgG were present in 11/36 (31%) CRPS sera, 17/64 (27%) RA sera, 13/53 (25%) SpA sera, 5/29 (17%) PsA sera, 1/22 (5%) trauma control sera, and 4/100 (4%) sera of BD. IC of p29ING4 and IgG1 were present in 14/36 (39%) CRPS sera, 19/64 (30%) RA sera, 13/53 (25%) SpA, 1/29 (3%) PsA, 2/22 (9%) trauma control, and 4/100 (4%) of the BD sera.

CONCLUSION

Due to the lack of other biomarkers of type 1 CRPS, P29ING4 autoantibodies could be helpful in its diagnostic work-up.

The potential of adenoviral vaccine vectors with altered antigen presentation capabilities

Introduction: Despite their appeal as vaccine vectors, adenoviral vectors are yet unable to induce protective immune responses against some weakly immunogenic antigens. Additionally, the maximum doses of adenovirus-based vaccines are limited by vector-induced toxicity, causing vector elimination and diminished immune responses against the target antigen. In order to increase immune responses to the transgene, while maintaining a moderate vector dose, new technologies for improved transgene presentation have been developed for adenoviral vaccine vectors.Areas covered: This review provides an overview of different genetic-fusion adjuvants that aim to improve antigen presentation in the context of adenoviral vector-based vaccines. The influence on both T cell and B cell responses are discussed, with a main focus on two technologies: MHC class II-associated invariant chain and virus-like-vaccines.Expert opinion: Different strategies have been tested to improve adenovirus-based vaccinations with varying degrees of success. The reviewed genetic adjuvants were designed to increase antigen processing and MHC presentation, or promote humoral immune responses with an improved conformational antigen display. While none of the introduced technologies is universally applicable, this review shall give an overview to identify potential improvements for future vaccination approaches.

The Probiotic BB12 Induces MicroRNAs Involved in Antigen Processing and Presentation in Porcine Monocyte-Derived Dendritic Cells

MicroRNAs (miRNAs) mediate the regulation of gene expression. Several reports indicate that probiotics induce miRNA-mediated immunomodulation at different levels, such as cytokine production and the up-regulation of several markers related to antigen presentation in antigen-presenting cells. The objective of this work was to identify target genes of miRNAs that are involved in the processing and presentation of antigens in monocyte-derived dendritic cells (moDCs) stimulated with the probiotic Bifidobacterium animalis ssp. lactis BB12 (BB12). First, an in silico prediction analysis for a putative miRNA binding site within a given mRNA target was performed using RNAHybrid software with mature sequences of differentially expressed miRNAs retrieved from a Genbank data set that included BB12-stimulated and unstimulated porcine monocytes. From them, 23 genes resulted in targets of 19 miRNAs, highlighting miR-30b-3p, miR-671-5p, and miR-9858-5p, whose targets were costimulatory molecules, and were overexpressed (p < 0.05) in BB12-stimulated moDCs. The analysis of moDCs showed that the percentage of cells expressing SLA-DR⁺CD80⁺ decreased significantly (p = 0.0081) in BB12-stimulated moDCs; interleukin (IL)-10 production was unchanged at 6 h but increased after 24 h of culture in the presence of BB12 (p < 0.001). In summary, our results suggest that SLA-DR and CD80 can be down-regulated by miRNAs miR-30b-3p, miR-671-5p, and miR-9858-5p, while miR-671-5p targets IL-10.

[Rheumatoid arthritis-mimics : When appearances are deceptive]

Rheumatology represents a discipline full of differential diagnoses. Even for classical diseases, such as rheumatoid arthritis as the most frequent chronic inflammatory joint disease and described so clearly in many textbooks, it is not uncommon that it can be a diagnostic challenge in daily practice. This applies to arthritic joint involvement and also to frequently associated extra-articular manifestations. The patient history and results of the clinical examination are essential; however, laboratory and imaging findings often make a significant contribution to confirming the diagnosis, especially in early phases of the disease. This article, which makes no claims to completeness, focuses on diseases that in the opinion of the authors can imitate rheumatoid arthritis due to similar joint and other organ manifestations. These include metabolic, inflammatory infective and non-infective as well as tumorous diseases. A misinterpretation as rheumatoid arthritis as a rule leads to long-term and severe consequences for affected patients. Thus, the diagnosis of rheumatoid arthritis should be questioned and re-evaluated in cases of unusual accompanying symptoms, atypical course of disease and a lack of response to standard treatment approaches.

Biomarkers in Inflammatory Bowel Disease-Associated Spondyloarthritis: State of the Art and Unmet Needs

Inflammatory bowel disease-associated spondyloarthritis is a systemic disease characterized by the chronic inflammation of both the gastrointestinal tract and the musculoskeletal system. Since inflammatory bowel disease-associated spondyloarthritis has been associated with a significant diagnostic delay, which may lead to poor quality of life and progression of joint damage, efforts to discover new reliable and noninvasive diagnostic biomarkers have been made. We reviewed the state of the art of biomarker research in inflammatory bowel disease-associated spondyloarthritis, showing that to date it has been largely unsatisfactory. Only a few of the biomarkers that have been investigated are likely to enter the clinical practice upon further validation in independent cohorts. The research of new and innovative biomarkers for inflammatory bowel disease-associated spondyloarthritis is warranted.

Added Value of Anti-CD74 Autoantibodies in Axial SpondyloArthritis in a Population With Low HLA-B27 Prevalence

Axial spondyloarthritis (axSpA) is often diagnosed late due to the non-specific nature of its main symptom [chronic back pain (CBP)] and to the paucity of diagnostic markers, particularly in regions with low HLA-B27 prevalence, such as the Middle-East. We tested the performance of IgG4 and IgA anti-CD74 antibodies as an early diagnostic marker for axSpA, compared with the performance of HLA-B27, in Lebanon. Sera of axSpA patients diagnosed by the rheumatologist and also fulfilling the imaging arm of the ASAS criteria (patients) and of blood donors (BD) (controls) were analyzed for HLA-B27, IgG4 and IgA anti-CD74, blinded to clinical characteristics. Receiver Operating Characteristic curves were constructed to identify an optimal cut-off point for anti-CD74 antibodies. Diagnostic properties were calculated (sensitivity, specificity, positive, and positive predictive values (PPV, NPV), Likelihood ratios) for each marker. Forty-nine axSpA patients and 102 BD were included in the final analysis. IgA anti-CD74 correlated poorly with axSpA (Area Under the Curve (AUC) 0.657), whereas IgG4 anti-CD74 had a good discriminative value (AUC 0.837). Respectively, for HLA-B27, IgG4 anti-CD74, and the combination of both, we found a sensitivity of 33-92-33%, specificity of 96-79-98%, PPV 80-68-89%, NPV 75-95-75%, and LR+ 8.2-4.4-16.5. IgG4 anti-CD 74 were positive in 88% of HLA-B27 negative axSpA patients, and correlated with BASDAI. In this first study in a population with low HLA-B27 prevalence, IgG4 anti-CD74 antibodies combined with HLA-B27 showed higher diagnostic value than HLA-B27 alone for early axSpA. IgG4 anti-CD74 should be considered for further evaluation as an early axSpA diagnostic marker in future dedicated research, particularly in patients with CBP.

Sensitivity and Specificity of Autoantibodies Against CD74 in Nonradiographic Axial Spondyloarthritis

OBJECTIVE

Autoantibodies against CD74 (anti-CD74) are associated with ankylosing spondylitis (AS). The present multicenter study, the International Spondyloarthritis Autoantibody (InterSpA) trial, was undertaken to compare the sensitivity and specificity of anti-CD74 and HLA-B27 in identifying patients with nonradiographic axial spondyloarthritis (axSpA).

METHODS

Patients ages 18-45 years with inflammatory back pain of ≤2 years' duration and a clinical suspicion of axSpA were recruited. HLA-B27 genotyping and magnetic resonance imaging of sacroiliac joints were performed in all patients. One hundred forty-nine patients with chronic inflammatory back pain (IBP) not caused by axSpA served as controls, and additional controls included 50 AS patients and 100 blood donors whose specimens were analyzed.

RESULTS

One hundred patients with inflammatory back pain received a diagnosis of nonradiographic axSpA from the investigators and fulfilled the Assessment of SpondyloArthritis international Society (ASAS) criteria. The mean age was 29 years, and the mean symptom duration was 12.5 months. The sensitivity of IgA anti-CD74 and IgG anti-CD74 for identifying the 100 axSpA patients was 47% and 17%, respectively. The specificity of both IgA anti-CD74 and IgG anti-CD74 was 95.3%. The sensitivity of HLA-B27 was 81%. The positive likelihood ratios were 10.0 (IgA anti-CD74), 3.6 (IgG anti-CD74), and 8.1 (HLA-B27). Assuming a 5% pretest probability of axSpA in chronic back pain patients, the posttest probability, after consideration of the respective positive test results, was 33.3% for IgA anti-CD74, 15.3% for IgG anti-CD74, and 28.8% for HLA-B27. A combination of IgA anti-CD74 and HLA-B27 results in a posttest probability of 80.2%.

CONCLUSION

IgA anti-CD74 may be a useful tool for identifying axSpA. The diagnostic value of the test in daily practice requires further confirmation.

[Spondyloarthritides]

Spondyloarthritides (SpA) are inflammatory rheumatic diseases affecting the axial skeleton, peripheral joints and entheses, and also manifest at extraskeletal sites. According to the more recently introduced nomenclature, predominant axial SpA is distinguished from predominant peripheral SpA. Axial SpA is further divided into radiographic and nonradiographic axial SpA. Genetic factors are relevant, with HLA-B27 being most important. The interleukin 23/17 pathway seems to be relevant and points towards new therapeutic targets. Inflammatory back pain is the leading symptom in axial SpA and has certain characteristics. In addition, HLA-B27 and sacroiliitis on imaging are important for diagnosis. Therapy consists of physiotherapy, nonsteroidal anti-inflammatory drugs (first line) and biologicals (second line). Conventional disease-modifying antirheumatic drugs are effective only in peripheral arthritis.

Biomarkers for Diagnosis of Axial Spondyloarthritis, Disease Activity, Prognosis, and Prediction of Response to Therapy

There exists a major unmet need for biomarkers that can identify axial spondyloarthritis (axSpA) early after disease onset because of the availability of highly effective therapies. Several recent reports have examined the autoantibody response in patients with axSpA through the use of protein microarrays and protein-protein interactions although diagnostic performance of biomarkers identified to date has been inadequate. An example of such a biomarker is protein phosphatase magnesium-dependent 1A. Antibodies to the human leukocyte antigen class II-associated invariant chain peptide (anti-CD74) are candidate diagnostic biomarkers but sensitivity declines with increasing duration of disease. Metabolomic studies have employed nuclear magnetic resonance (NMR) spectrometry to identify disease-specific metabolites related to fat metabolism and intestinal microbial metabolism. A second major unmet need exists for biomarkers of disease activity that have superiority over standard C-reactive protein assessment and reflect MRI inflammation in the axial spine. Several biomarkers reflecting inflammation (calprotectin), angiogenesis (vasoactive endothelial growth factor), and connective tissue turnover (C2M, C3M, and citrullinated metalloproteinase degraded fragment of vimentin) have recently been shown to reflect disease activity when compared with clinical outcomes but comparisons with MRI inflammation are very limited. With increasing availability of highly effective but costly therapies, a third unmet need is biomarkers that can predict response to therapies with different mechanisms of action and are superior to C-reactive protein. Calprotectin is currently the only candidate. Although there are as yet no proven therapies for preventing progression of disease there is an unmet need for biomarkers of prognosis that are more responsive than radiography. Aside from CRP no consistent candidates have emerged. Future studies will need to be prospective, include consecutive patients presenting with undiagnosed back pain, and use more reliable and objective endpoints such as MRI inflammation. Moreover, it has become evident that targeted biomarker studies have not been successful in identifying clinically useful biomarkers and technologies that can simultaneously assess “multiomic” markers will need to be analyzed for future advances. These include more sophisticated metabolomic profiling and universal metabolome-standard (UMS) methodology, next generation RNA sequencing, and affinity-based quantitative proteomics based on the use of nucleic acid binders such as the aptamer-based SOMAscan assay.

Enthesitis-related arthritis: current perspectives

In this narrative review, we overview the recent literature on enthesitis-related arthritis (ERA). For the purpose of our review, we searched Scopus for recent articles on this subject from 2013 onward, including some classic older articles for perspective. ERA is a juvenile idiopathic arthritis (JIA) subtype more common in males, associated in a majority with human leucocyte antigen B27. Such children generally present with asymmetric oligoarthritis or polyarthritis, predominantly of lower limb joints, associated with enthesitis or sacroiliitis. While diagnosis remains clinical, ultrasound is being increasingly used to detect subclinical enthesitis and for guiding entheseal site injections. Spine MRI can help detect sacroiliitis, inflammatory spinal changes, and pelvic sites of enthesitis in such patients. The recent juvenile spondyloarthropathy disease activity index recognizes the key clinical features of ERA, viz enthesitis and inflammatory back pain, which other disease activity indices used in JIA did not include. Management includes NSAIDs with physical therapy. Conventional disease-modifying agents like sulfasalazine and methotrexate may be used to minimize duration of NSAID use and in those with high inflammatory burden. In patients refractory to these drugs, biologics such as antitumor necrosis factor alpha agents have proven useful, based on evidences from randomized controlled trials and retrospective registry analyses. Factors predicting a poorer outcome in such children include hip or ankle involvement or restricted spinal mobility. Considering that children with ERA have overall poorer long-term outcomes than other subtypes of JIA, there is a need to further optimize therapeutic strategies for such patients.

Autoantibodies in Spondyloarthritis, Focusing on Anti-CD74 Antibodies

Spondyloarthritis (SpA) is an inflammatory rheumatic disease with diverse clinical presentation. The diagnosis of SpA remains a big challenge in daily clinical practice because of the limitation in specific biomarkers of SpA, more biomarkers are still needed for SpA diagnosis and disease activity monitoring. In the past, SpA was considered predominantly as auto-inflammatory disease vs. autoimmune disease. However, in recent years several researches demonstrated a broad autoantibody response in SpA patients. Study also indicated that mice lack of ZAP70 in T cell develop SpA featured inflammation. These studies indicated the autoimmune features of SpA and gave rise to the potential use of autoantibody in SpA management. In this article, we reviewed recent reports of autoantibodies associated with SpA patients, revealing the autoimmune features of SpA, suggesting the hypothesis that SpA was also an autoimmune disease, studies about the autoimmune features might provide more insights in the pathogenesis of SpA. In addition, as there are two opposite conclusions in the role of anti-CD74 autoantibody in the diagnosis of SpA, we also gave our own data on the diagnostic value of anti-CD74 in Chinese SpA patients. Though our data indicated that anti-CD74 might not be a good biomarker for SpA diagnosis in Asian people, CD74 was still a good molecule target in the research of SpA pathogenesis.

Anti-SIRT1 autoantibody is elevated in ankylosing spondylitis: a potential disease biomarker

Background

Little is known about the presence of specific autoantibodies in ankylosing spondylitis (AS), an immune-mediated inflammatory disease. The object of this study was to explore potential autoantibody profiles in AS patients.

Results

Levels of anti-SIRT1 autoantibodies were significantly higher in AS (P < 0.001) and psoriatic arthritis (PsA) (P < 0.01) patients but not rheumatoid arthritis (RA) patients compared with healthy controls. Additionally, titers of anti-NAD-dependent protein deacetylase sirtuin-1(SIRT1) antibodies were significantly higher in AS patients than in RA (P < 0.05) and PsA (P < 0.05) patients. Moreover, levels of anti-SIRT1 (P < 0.001) antibodies were significantly higher during the first year in patients with hip joint involvement. The anti-SIRT1 antibody positivity rate was 18.9% in AS patients.

Conclusions

Our findings indicate that anti-SIRT1 autoantibodies may serve as a marker for diagnosing AS and predicting hip joint involvement at an early stage.

Electronic supplementary material

The online version of this article (10.1186/s12865-018-0280-x) contains supplementary material, which is available to authorized users.

Development of a Molecular Adjuvant to Enhance Antigen-Specific CD8+ T Cell Responses

Despite promising progress in malaria vaccine development, an efficacious subunit vaccine against P. falciparum remains to be licensed and deployed. This study aimed to improve on the immunogenicity of the leading liver-stage vaccine candidate (ChAd63-MVA ME-TRAP), known to confer protection by eliciting high levels of antigen-specific CD8⁺ T cells. We previously showed fusion of ME-TRAP to the human MHC class II invariant chain (Ii) could enhance CD8⁺ T cell responses in non-human primates, but did not progress to clinical testing due to potential risk of auto-immunity by vaccination of humans with a self-antigen. Initial immunogenicity analyses of ME-TRAP fused to subdomains of the Ii showed that the Ii transmembrane domain alone can enhance CD8⁺ T cell responses. Subsequently, truncated Ii sequences with low homology to human Ii were developed and shown to enhance CD8⁺ T cell responses. By systematically mutating the TM domain sequence, multimerization of the Ii chain was shown to be important for immune enhancement. We subsequently identified several proteins from a variety of microbial pathogens with similar characteristics, that also enhance the CD8⁺ T cell response and could therefore be used in viral vector vaccines when potent cell mediated immunity is required.

Stress proteins in the pathogenesis of spondyloarthritis

Spondyloarthritis is an autoinflammatory rheumatic disease in which arthritis and osteoproliferation lead the patients who suffer from it to chronic disability. This disease is associated with the expression of class I MHC molecule HLA-B27, which tends to be misfolded in the endoplasmic reticulum and, therefore, expressed in aberrant forms. This phenomena lead to endoplasmic reticulum stress, which in time, evokes a whole response to cellular injury. Under these conditions, the molecules involved in restoring cell homeostasis play a key role. Such is the case of the "heat-shock proteins", which usually regulate protein folding, but also have important immunomodulatory functions, as well as some roles in tissue modeling. In this review, we attempt to summarize the involvement of cell stress and heat-shock proteins in the homeostatic disturbances and pathological conditions associated with this disease.

The Role of Autoantibodies in Bone Metabolism and Bone Loss

Many autoimmune diseases are associated with deranged bone metabolism. The resulting localized or systemic bone loss can compromise the quality of life of patients by causing local bone deformities or fragility fractures. There is emerging evidence that antibodies have a direct impact on key players of bone homeostasis, in particular osteoclasts. Clinical and pre-clinical studies provide insight into the function of autoantibodies related to Rheumatoid Arthritis (rheumatoid factor, anti-citrullinated protein antibodies, and anti-carbamylated protein antibodies) and their inflammation-independent interaction with bone cells. Furthermore, we summarize the current knowledge about neutralizing antibodies to the antiresorptive protein osteoprotegerin, which have been described in patients with Coeliac Disease, Rheumatoid Arthritis, and Spondyloarthritis.

Anti-CD74 antibodies have no diagnostic value in early axial spondyloarthritis: data from the spondyloarthritis caught early (SPACE) cohort

BACKGROUND

Anti-CD74 IgG antibodies are reported to be elevated in patients with axial spondyloarthritis (axSpA). This study assessed the diagnostic value of anti-CD74 antibodies in patients with early axSpA.

METHODS

Anti-CD74 IgG and IgA antibodies were first measured in an exploratory cohort of patients with radiographic axSpA (138 patients with ankylosing spondyloarthritis (AS)) and 57 healthy controls and then were measured in patients with early axSpA (n = 274) and with non-SpA chronic back pain (CBP) (n = 319), participating in the spondyloarthritis caught early (SPACE) prospective cohort study of patients under 45 years old with early back pain (for ≥ 3 months, but ≤ 2 years).

RESULTS

In the exploratory cohort, anti-CD74 IgG antibodies were present in 79.7% of patients with AS vs. 43.9% of healthy controls (p < 0.001). Anti-CD74 IgA antibodies were present in 28.5% of patients with AS vs. 5.3% of healthy controls (p < 0.001). In the SPACE cohort, anti-CD74 IgG antibody levels were present in 46.4% of the patients with axSpA vs. 47.9% of the patients with CBP (p = 0.71). Anti-CD74 IgA antibodies were present in 54.7% of the patients with axSpA and 37.0% of the patients with CBP (p < 0.001). This resulted in a positive predictive value of 58.8% (compared to a prior probability of 46.2%) and a negative predictive value of 59.1% (compared to a prior probability of 53.8%). In a regression model, total serum IgA was associated with axSpA odds ratio (OR) 1.19, p < 0.001) whereas anti-CD74 IgA was not (OR) 1.01, p = 0.33). Furthermore, anti-CD74 IgA was associated with sacroiliitis on magnetic resonance imaging (MRI) (OR) = 2.50, p = 0.005) and heel enthesitis (OR) = 2.56, p = 0.002).

CONCLUSIONS

Albeit anti-CD74 IgA is elevated in patients with early axSpA, this elevation is not sufficiently specific to yield significant diagnostic value in patients under 45 years old presenting with early back pain.

Macrophage Migration Inhibitory Factor Induces Inflammation and Predicts Spinal Progression in Ankylosing Spondylitis

OBJECTIVE

To investigate the role of macrophage migration inhibitory factor (MIF) in the pathogenesis of ankylosing spondylitis (AS).

METHODS

Patients who met the modified New York criteria for AS were recruited for the study. Healthy volunteers, rheumatoid arthritis patients, and osteoarthritis patients were included as controls. Based on the annual rate of increase in modified Stoke AS Spine Score (mSASSS), AS patients were classified as progressors or nonprogressors. MIF levels in serum and synovial fluid were quantitated by enzyme-linked immunosorbent assay. Predictors of AS progression were evaluated using logistic regression analysis. Immunohistochemical analysis of ileal tissue was performed to identify MIF-producing cells. Flow cytometry was used to identify MIF-producing subsets, expression patterns of the MIF receptor (CD74), and MIF-induced tumor necrosis factor (TNF) production in the peripheral blood. MIF-induced mineralization of osteoblast cells (SaOS-2) was analyzed by alizarin red S staining, and Western blotting was used to quantify active β-catenin levels.

RESULTS

Baseline serum MIF levels were significantly elevated in AS patients compared to healthy controls and were found to independently predict AS progression. MIF levels were higher in the synovial fluid of AS patients, and MIF-producing macrophages and Paneth cells were enriched in their gut. MIF induced TNF production in monocytes, activated β-catenin in osteoblasts, and promoted the mineralization of osteoblasts.

CONCLUSION

Our findings indicate an unexplored pathogenic role of MIF in AS and a link between inflammation and new bone formation.

Axial spondyloarthritis

The term axial spondyloarthritis covers both patients with non-radiographic and radiographic axial spondyloarthritis, which is also termed ankylosing spondylitis. The disease usually starts in the third decade of life with a male to female ratio of two to one for radiographic axial spondyloarthritis and of one to one for non-radiographic axial spondyloarthritis. More than 90% heritabilty has been estimated, the highest genetic association being with HLA-B27. The pathogenic role of HLA-B27 is still not clear although various hypotheses are available. On the basis of evidence from trials the cytokines tumour necrosis factor (TNF)-α and interleukin-17 appear to have a relevant role in pathogenesis. The mechanisms of interaction between inflammation and new bone formation is still not completely understood but clarification will be important for the prevention of long-term structural damage of the bone. The development of new criteria for classification and for screening of patients with axial spondyloarthritis have been crucial for the early indentification and treatment of such patients, with MRI being the most important existing imaging method. Non-steroidal anti-inflammatory drugs and TNF blockers are effective therapies. Blockade of interleukin-17 is a new and relevant treatment option.

[Spondyloarthritides]

Spondyloarthritides (SpA) are inflammatory rheumatic diseases affecting the axial skeleton, peripheral joints and entheses, and also manifest at extraskeletal sites. According to the more recently introduced nomenclature, predominant axial SpA is distinguished from predominant peripheral SpA. Axial SpA is further divided into radiographic and nonradiographic axial SpA. Genetic factors are relevant, with HLA-B27 being most important. The interleukin 23/17 pathway seems to be relevant and points towards new therapeutic targets. Inflammatory back pain is the leading symptom in axial SpA and has certain characteristics. In addition, HLA-B27 and sacroiliitis on imaging are important for diagnosis. Therapy consists of physiotherapy, nonsteroidal anti-inflammatory drugs (first line) and biologicals (second line). Conventional disease-modifying antirheumatic drugs are effective only in peripheral arthritis.

New insights toward the pathogenesis of ankylosing spondylitis; genetic variations and epigenetic modifications

Ankylosing spondylitis (AS) is a chronic inflammatory autoimmune disease, characterized by typically an axial arthritis. AS is the prototype of a group of disorders called spondyloarthropathies, which is believed to have common clinical manifestations and genetic predisposition. To date, the exact etiology of AS remains unclear. Over the past few years, however, the role of genetic susceptibility and epigenetic modifications caused through environmental factors have been extensively surveyed with respect to the pathogenesis of AS, resulted in important advances. This review article focuses on the recent advances in the field of AS research, including HLA and non-HLA susceptibility genes identified in genome-wide association studies (GWAS), and aberrant epigenetic modifications of gene loci associated with AS. HLA genes most significantly linked with AS susceptibility include HLA-B27 and its subtypes. Numerous non-HLA genes such as those in ubiquitination, aminopeptidases and MHC class I presentation molecules like ERAP-1 were also reported. Moreover, epigenetic modifications occurred in AS has been summarized. Taken together, the findings presented in this review attempt to explain the circumstance by which both genetic variations and epigenetic modifications are involved in triggering and development of AS. Nonetheless, several unanswered dark sides continue to clog our exhaustive understanding of AS. Future researches in the field of epigenetics should be carried out to extend our vision of AS etiopathogenesis.

Detection of novel diagnostic antibodies in ankylosing spondylitis: An overview

Ankylosing spondylitis (AS) is a debilitating, chronic, rheumatic disease characterized by inflammation and new bone formation resulting in fusion of the spine and sacroiliac joints. Since early treatment is impeded by a delayed diagnosis, it is highly important to find new biomarkers that improve early diagnosis and may also contribute to a better assessment of disease activity, prognosis and therapy response in AS. Because of the absence of rheumatoid factor, AS was long assumed to have a seronegative character and antibodies are thus not considered a hallmark of the disease. However, emerging evidence suggests plasma cells and autoantibodies to be involved in the disease course. In this review, the role of B cells and antibodies in AS is discussed. Furthermore, an overview is provided of antibodies identified in AS up till now, and their diagnostic potential. Many of these antibody responses were based on small study populations and further validation is lacking. Moreover, most were identified by a hypothesis-driven approach and thus limited to antibodies against targets that are already known to be involved in AS pathogenesis. Hence, we propose an unbiased approach to identify novel diagnostic antibodies. The already successfully applied techniques cDNA phage display and serological antigen selection will be used to identify antibodies against both known and new antigen targets in AS plasma. These newly identified antibodies will enhance early diagnosis of AS and provide more insight into the underlying disease pathology, resulting in a more effective treatment strategy and eventually an improved disease outcome.