A Shared Epitope of Collagen Type XI and Type II Is Recognized by Pathogenic Antibodies in Mice and Humans with Arthritis

Antigen-presenting autoreactive B cells activate regulatory T cells and suppress autoimmune arthritis in mice

B cells undergo several rounds of selection to eliminate potentially pathogenic autoreactive clones, but in contrast to T cells, evidence of positive selection of autoreactive B cells remains moot. Using unique tetramers, we traced natural autoreactive B cells (C1-B) specific for a defined triple-helical epitope on collagen type-II (COL2), constituting a sizeable fraction of the physiological B cell repertoire in mice, rats, and humans. Adoptive transfer of C1-B suppressed arthritis independently of IL10, separating them from IL10-secreting regulatory B cells. Single-cell sequencing revealed an antigen processing and presentation signature, including induced expression of CD72 and CCR7 as surface markers. C1-B presented COL2 to T cells and induced the expansion of regulatory T cells in a contact-dependent manner. CD72 blockade impeded this effect suggesting a new downstream suppressor mechanism that regulates antigen-specific T cell tolerization. Thus, our results indicate that autoreactive antigen-specific naïve B cells tolerize infiltrating T cells against self-antigens to impede the development of tissue-specific autoimmune inflammation.

Proteomics Landscape Mapping of Organ-Resolved Behçet's Disease Using In-Depth Plasma Proteomics for Identifying Hyaluronic Binding Protein 2 Expression Associated With Vascular Involvement

OBJECTIVE

This study was undertaken to elucidate the pathogenesis and heterogeneity of Behçet's disease (BD) involving different organs using in-depth proteomics to identify the biomarkers for clinical assessment and treatment of patients with BD.

METHODS

We measured the expression levels of proteins in plasma samples from 98 patients with BD and from 31 healthy controls using our in-depth proteomics platform with a data-independent acquisition mass spectrometer and antibody microarray. We performed bioinformatics analyses of the biologic processes and signaling pathways that were changed in the BD group and constructed a proteomics landscape of organ-resolved BD pathogenesis. We then validated the biomarkers of disease severity and the vascular subset in an independent cohort of 108 BD patients and 29 healthy controls using an enzyme-linked immunosorbent assay.

RESULTS

The BD group had 220 differentially expressed proteins, which discriminated between BD patients (88.6%) and healthy controls (95.5%). The bioinformatics analyses revealed different biologic processes associated with BD pathogeneses, including complement activation, wound healing, angiogenesis, and leukocyte-mediated immunity. Furthermore, the constructed proteomics landscape of organ-resolved BD identified proteomics features of BD associated with different organs and protein targets that could be used for the development of therapeutic treatment. Hyaluronic binding protein 2, tenascin, and serpin A3 were validated as potential biomarkers for the clinical assessment of vascular BD and treatment targets.

CONCLUSION

Our results provide valuable insight into the pathogenesis of organ-resolved BD in terms of proteomics characteristics and potential biomarkers for clinical assessment and potential therapies for vascular BD.

Characterization of chronic relapsing antibody mediated arthritis in mice with a mutation in Ncf1 causing reduced oxidative burst

Rheumatoid arthritis (RA) is a chronic autoimmune disorder affecting joints with a hallmark of autoantibody production. Mannan-enhanced collagen type II (COL2) antibody induced arthritis (mCAIA) in neutrophil cytosolic factor 1(Ncf1) mutation mouse is a chronic disease model imitating RA in mice. In this study, we characterize the chronic phase of mCAIA in Ncf1 mutated (BQ.Ncf1^m1j/m1j) mice. Arthritis was induced by an intravenous injection of anti-COL2 monoclonal antibodies on day 0 followed by intra-peritoneal injections of mannan (from Saccharomyces cerevisiae) on days 3 and 65 in BQ.Ncf1^m1j/m1j and BQ mice. Bone erosion was analysed by computed tomography (CT) and blood cell phenotypes by flow cytometry. Cytokines and anti-COL2 antibodies were analyzed with multiplex bead-based assays. The arthritis in the Ncf1^m1j/m1j mice developed with a chronic and relapsing disease course, which was followed for 200 days and bone erosions of articular joints were evaluated. An increased number of circulating CD11b⁺ Ly6G⁺ neutrophils were observed during the chronic phase, together with a higher level of G-CSF (granulocyte colony-stimulating factor) and TNF-α. In conclusion, the chronic relapsing arthritis of mCAIA in the Ncf1^m1j/m1j mice develop bone erosions associated with a sustained neutrophil type of inflammatory responses.

Main and Minor Types of Collagens in the Articular Cartilage: The Role of Collagens in Repair Tissue Evaluation in Chondral Defects

Several collagen subtypes have been identified in hyaline articular cartilage. The main and most abundant collagens are type II, IX and XI collagens. The minor and less abundant collagens are type III, IV, V, VI, X, XII, XIV, XVI, XXII, and XXVII collagens. All these collagens have been found to play a key role in healthy cartilage, regardless of whether they are more or less abundant. Additionally, an exhaustive evaluation of collagen fibrils in a repaired cartilage tissue after a chondral lesion is necessary to determine the quality of the repaired tissue and even whether or not this repaired tissue is considered hyaline cartilage. Therefore, this review aims to describe in depth all the collagen types found in the normal articular cartilage structure, and based on this, establish the parameters that allow one to consider a repaired cartilage tissue as a hyaline cartilage.

Preclinical models of arthritis for studying immunotherapy and immune tolerance

Increasingly earlier identification of individuals at high risk of rheumatoid arthritis (RA) (eg, with autoantibodies and mild symptoms) improves the feasibility of preventing or curing disease. The use of antigen-specific immunotherapies to reinstate immunological self-tolerance represent a highly attractive strategy due to their potential to induce disease resolution, in contrast to existing approaches that require long-term treatment of underlying symptoms.

Preclinical animal models have been used to understand disease mechanisms and to evaluate novel immunotherapeutic approaches. However, models are required to understand critical processes supporting disease development such as the breach of self-tolerance that triggers autoimmunity and the progression from asymptomatic autoimmunity to joint pain and bone loss. These models would also be useful in evaluating the response to treatment in the pre-RA period.

This review proposes that focusing on immune processes contributing to initial disease induction rather than end-stage pathological consequences is essential to allow development and evaluation of novel immunotherapies for early intervention. We will describe and critique existing models in arthritis and the broader field of autoimmunity that may fulfil these criteria. We will also identify key gaps in our ability to study these processes in animal models, to highlight where further research should be targeted.

Lymphocyte modulation by tofacitinib in patients with rheumatoid arthritis

Tofacitinib is an oral small molecule targeting the intracellular Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathways approved for the treatment of active rheumatoid arthritis (RA). We investigated the effects of tofacitinib on the response of RA lymphocytes to B and T cell collagen epitopes in their native and post-translationally modified forms. In particular, peripheral blood mononuclear cells (PBMCs) from patients with RA and healthy subjects were cultured with type II collagen peptides (T261-273, B359-369, carT261-273, citB359-369) or with phorbol myristate acetate (PMA)/ionomycin/CD40L in the presence or absence of 100 nM tofacitinib for 20 h and analyzed by fluorescence activated cell sorter (FACS). Cultures without brefeldin A were used for cytokine supernatant enzyme-linked immunosorbent assay (ELISA) analysis. Tofacitinib down-regulated inflammatory cytokines by stimulated B [interleukin (IL)-6 and tumor necrosis factor (TNF)-α] and T [interferon (IFN)-γ, IL-17 or TNF-α] cells in the short term, while a significant reduction of IL-17 and IL-6 levels in peripheral blood mononuclear cell (PBMC) supernatant was also observed. IL-10 was significantly reduced in collagen-stimulated B cells from patients with RA and increased in controls, thus mirroring an altered response to collagen self-epitopes in RA. Tofacitinib partially prevented the IL-10 down-modulation in RA B cells stimulated with collagen epitopes. In conclusion, the use of tofacitinib exerts a rapid regulatory effect on B cells from patients with RA following stimulation with collagen epitopes while not reducing inflammatory cytokine production by lymphocytes.

Synthesis of an Array of Triple-Helical Peptides from Type II Collagen for Multiplex Analysis of Autoantibodies in Rheumatoid Arthritis

Type II collagen (CII) is the most abundant protein in joint cartilage. Antibodies to CII appear around the clinical onset of the autoimmune disease rheumatoid arthritis (RA) in a subset of patients. They target specific epitopes on CII and can be pathogenic or protective. Assays for early detection of such autoantibodies may provide new opportunities for selecting effective treatment strategies of RA. We report the efficient and reproducible assembly of an array of covalently branched native and citrullinated triple helical peptides (THPs) from CII that contain defined autoantibody epitopes. Both monoclonal antibodies and sera from experimental mouse models show a unique reactivity toward the THPs, compared to cyclic peptides containing the epitopes, revealing the importance that the epitopes are displayed in a triple-helical conformation. Importantly, antibodies against three of the THPs that contain major CII epitopes were found to be increased in sera from patients with RA, compared to control persons. These results indicate that such synthetic THPs should be included in multiplex analysis of autoantibodies that are uniquely occurring in individuals with early RA, to provide valuable information on disease prognosis and on what type of therapy should be chosen for individual patients.

Cartilage-binding antibodies initiate joint inflammation and promote chronic erosive arthritis

BACKGROUND

Antibodies binding to cartilage proteins are present in the blood and synovial fluid of early rheumatoid arthritis patients. In order to develop animal models mimicking the human disease, we have characterized the arthritogenic capacity of monoclonal antibodies directed towards different joint proteins in the cartilage.

METHODS

Purified antibodies specific to unmodified or citrullinated collagen type II (CII), collagen type XI (CXI), and cartilage oligomeric matrix protein (COMP) were produced as culture supernatant, affinity purified, pooled as antibody cocktails (Cab3 and Cab4), and injected intravenously into mice to induce arthritis. An adjuvant (lipopolysaccharide or mannan) was subsequently injected intraperitoneally on either day 5 or day 60 to enhance arthritis. Antibody binding and complement activation on the cartilage surface were analyzed by immunohistochemical methods. Bone erosions and joint deformations were analyzed by histological assessments, enzyme-linked immunosorbent assays, and micro-CT. Luminex was used to detect CII-triple helical epitope-specific antibody responses.

RESULTS

The new cartilage antibody cocktails induced an earlier and more severe disease than anti-CII antibody cocktail. Many of the mouse strains used developed severe arthritis with 3 antibodies, binding to collagen II, collagen XI, and cartilage oligomeric matrix protein (the Cab3 cocktail). Two new models of arthritis including Cab3-induced LPS-enhanced arthritis (lpsCAIA) and Cab3-induced mannan-enhanced arthritis (mCAIA) were established, causing severe bone erosions and bone loss, as well as epitope spreading of the B cell response. Cab4, with addition of an antibody to citrullinated collagen II, induced arthritis more efficiently in moderately susceptible C57BL/6 J mice.

CONCLUSIONS

The new mouse model for RA induced with cartilage antibodies allows studies of chronic development of arthritis and epitope spreading of the autoimmune response and bone erosion.

Proteomics in Chronic Arthritis-Will We Finally Have Useful Biomarkers?

PURPOSE OF REVIEW

Current technical advances enable the assessment of the complex changes in body fluid proteomes and thus allow for the discovery of biomarker signatures rather than just following differences of a single marker. In this review, we aim to summarize current approaches to discover and evaluate multi-biomarker panels for improved monitoring of chronic arthritis disease activity.

RECENT FINDINGS

Mass spectrometry and affinity proteomic methodologies have been used to identify biomarker panels in synovial fluid, serum, plasma, or urine of pediatric and adult chronic arthritis patients. Notably, despite the numerous efforts to develop new and better biomarker panels, very few have undergone extensive analytical and clinical validation and been adopted into routine use for patient benefit. There remains a significant gap between discovery of chronic arthritis biomarker signatures and their validation for clinical use.