Dataset Information

Citrullinated Aggrecan Epitopes as Targets of Autoreactive CD4+ T Cells in Patients With Rheumatoid Arthritis.

ABSTRACT: OBJECTIVE:Recognition of citrullinated antigens such as vimentin, fibrinogen, and ?-enolase is associated with rheumatoid arthritis (RA). Emerging data suggest that the matrix protein aggrecan is also recognized as a citrullinated antigen. This study was undertaken to directly visualize Cit-aggrecan-specific T cells and characterize them in patients with RA. METHODS:Citrullinated aggrecan peptides with likely DRB1*04:01 binding motifs were predicted using a previously published scanning algorithm. Peptides with detectable binding were assessed for immunogenicity by HLA tetramer staining, followed by single cell cloning. Selectivity for citrullinated peptide was assessed by tetramer staining and proliferation assays. Ex vivo tetramer staining was then performed to assess frequencies of aggrecan-specific T cells in peripheral blood. Finally, disease association was assessed by comparing T cell frequencies in RA patients and controls and correlating aggrecan-specific T cells with levels of aggrecan-specific antibodies. RESULTS:We identified 6 immunogenic peptides, 2 of which were the predominant T cell targets in peripheral blood. These 2 epitopes were citrullinated at HLA binding residues and shared homologous sequences. RA patients had significantly higher frequencies of Cit-aggrecan-specific T cells than healthy subjects. Furthermore, T cell frequencies were significantly correlated with antibodies against citrullinated aggrecan. CONCLUSION:Our findings indicate that T cells that recognize citrullinated aggrecan are present in patients with RA and correlate with antibodies that target this same antigen. Consequently, aggrecan-specific T cells and antibodies are potentially relevant markers that could be used to monitor patients with RA or at-risk subjects.

SUBMITTER: Rims C

PROVIDER: S-EPMC6438725 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature

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Citrullinated Aggrecan Epitopes as Targets of Autoreactive CD4+ T Cells in Patients With Rheumatoid Arthritis.

Rims Cliff C Uchtenhagen Hannes H Kaplan Mariana J MJ Carmona-Rivera Carmelo C Carlucci Philip P Mikecz Katalin K Markovics Adrienn A Carlin Jeffrey J Buckner Jane H JH James Eddie A EA

Arthritis & rheumatology (Hoboken, N.J.) 20190308 4

<h4>Objective</h4>Recognition of citrullinated antigens such as vimentin, fibrinogen, and α-enolase is associated with rheumatoid arthritis (RA). Emerging data suggest that the matrix protein aggrecan is also recognized as a citrullinated antigen. This study was undertaken to directly visualize Cit-aggrecan-specific T cells and characterize them in patients with RA.<h4>Methods</h4>Citrullinated aggrecan peptides with likely DRB1*04:01 binding motifs were predicted using a previously published sc ...[more]

PMID: 30390384

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Project description:BackgroundRheumatoid arthritis (RA) is an autoimmune inflammatory disease affecting the joints. Anti-citrullinated protein antibodies (ACPA) are frequently found in RA. Previous studies identified a citrullinated epitope in cartilage proteoglycan (PG) aggrecan that elicited pro-inflammatory cytokine production by RA T cells. We recently reported the presence of ACPA-reactive (citrullinated) PG in RA cartilage. Herein, we sought to identify additional citrullinated epitopes in human PG that are recognized by T cells or antibodies from RA patients.MethodsWe used mice with PG-induced arthritis (PGIA) as a screening tool to select citrulline (Cit)-containing PG peptides that were more immunogenic than the arginine (R)-containing counterparts. The selected peptide pairs were tested for induction of pro-inflammatory T-cell cytokine production in RA and healthy control peripheral blood mononuclear cell (PBMC) cultures using ELISA and flow cytometry. Anti-Cit and anti-R peptide antibodies were detected by ELISA.ResultsSplenocytes from mice with PGIA exhibited greater T-cell cytokine secretion in response to the Cit than the R version of PG peptide 49 (P49) and anti-P49 antibodies were found in PGIA serum. PBMC from ACPA+ and ACPA- RA patients, but not from healthy controls, responded to Cit49 with robust cytokine production. High levels of anti-Cit49 antibodies were found in the plasma of a subset of ACPA+ RA patients. Another PG peptide (Cit13) similar to the previously described T-cell epitope induced greater cytokine responses than R13 by control (but not RA) PBMC, however, anti-Cit13 antibodies were rarely detected in human plasma.ConclusionsWe identified a novel citrullinated PG epitope (Cit49) that is highly immunogenic in mice with PGIA and in RA patients. We also describe T-cell and antibody reactivity with Cit49 in ACPA+ RA. As citrullinated PG might be present in RA articular cartilage, Cit PG epitope-induced T-cell activation or antibody deposition may occur in the joints of RA patients.

Project description:BackgroundThe pre-symptomatic stage of Rheumatoid arthritis (RA) is associated with pro-inflammatory cytokines and autoantibodies. High levels and epitope spread by Rheumatoid factors (RhF) and autoantibodies to citrullinated proteins signify progression towards disease expression. In established RA, the persistence of high autoantibody levels reflects production by both long-lived plasma cells and short-lived plasmablasts. Neither the relative contributions to pathogenesis by autoantibodies from either source, nor the factors responsible for deciding the fate of autoantigen specific 'parent' B-cells, is understood. Phenotypic markers identifying subsets of autoreactive B-cells are therefore of interest in understanding the origin and perpetuation of the autoimmune response in RA. One such phenotypic marker is the rat monoclonal antibody, 9G4, which recognises an idiotope on immunoglobuins derived from the inherently autoreactive VH-gene, VH4-34. We therefore investigated whether the 9G4 idiotope was expressed on autoantibodies in patients with RA.Methodology/principal findingsSera from 19 patients with established RA and those with <1year history of untreated polyarthritis either resolving into RA (n?=?42) or non-RA diagnosis (n?=?31) were included. Autoantibodies to cyclic citrullinated peptides (CCP), RhF and co-expression of the 9G4 idiotope were measured by ELISA. 9G4 recognised a population of anti-CCP antibodies in the majority of sera from patients with established disease and also in samples from patients with early disaese. 9G4+RhF levels were generally lower and not associated with positivity for, or levels of 9G4+CCP.Conclusions/significanceThe persistence of 9G4+ immunoglobulins, of any isotype, in serum is rare. We describe here the novel finding of 9G4 expression on anti-CCP antibodies in patients from the earliest symptoms of RA through to established disease. Our results suggest that 9G4 expression on anti-CCP autoantibodies was not due to polyclonal expansion of VH4-34-encoded immunoglobulins. These studies may therefore provide a new focus for investigation into the evolution of the autoimmune response in RA patients.

Project description:OBJECTIVE:Because of its association with joint destruction, anti-citrullinated protein antibody (ACPA)-positive rheumatoid arthritis (RA) is considered to be more severe than ACPA-negative RA. Clinically relevant joint destruction is now infrequent thanks to adequate disease suppression. According to patients, important outcomes are pain, fatigue, and independence. We evaluated whether ACPA-positive RA patients diagnosed during or after 2000 have more severe self-reported limitations and impairments, including restrictions at work, than ACPA-negative RA patients. METHODS:A total of 492 ACPA-positive and 450 ACPA-negative RA patients who fulfilled the 2010 criteria and were included in the Leiden Early Arthritis Clinic cohort during or after 2000 were compared for self-reported pain, fatigue, disease activity, general well-being (measured by numerical rating scales), physical function (measured by the Health Assessment Questionnaire), and work restrictions, including absenteeism at baseline and during the 4-year followup. Linear mixed models were used. RESULTS:At disease presentation, ACPA-negative patients had more severe pain, fatigue, self-reported disease activity scores, and functional disability (P < 0.05), although absolute differences were small. During followup, ACPA-negative patients remained somewhat more fatigued (P = 0.002), whereas other patient-reported impairments and limitations were similar. Thirty-eight percent of ACPA-negative and 48% of ACPA-positive patients reported absenteeism (P = 0.30), with median 4 days missed in both groups in the last 3 months. Also, restrictions at work among employed patients and restrictions with household work were not statistically different at baseline and during followup. CONCLUSION:In current rheumatology practice, ACPA-positive RA is not more severe than ACPA-negative RA in terms of patients' relevant outcomes, including physical functioning and restrictions at work. This implies that efforts to further improve the disease course should be proportional to both disease subsets.

Project description:INTRODUCTION: Anti-citrullinated protein/peptide antibodies (ACPAs) are highly specific to rheumatoid arthritis (RA) patients and are thought to have a close relationship with the pathogenesis of arthritis. Several proteins, including fibrinogen, vimentin, and alpha-enolase, were reported as ACPA-target antigens, and their importance in RA pathogenesis was widely proposed. We identified citrullinated immunoglobulin binding protein (citBiP) as another ACPA target in RA patients and examined its pro-inflammatory role in arthritis. METHODS: We measured the levels of anti-citBiP, anti-BiP, and anti-cyclic citrullinated peptide (CCP) antibodies in the serum of RA patients (n = 100), systemic lupus erythematosus (SLE) patients (n = 60), and healthy controls (n = 30) using ELISA and immunoblotting. Epitope mapping was performed using 27 citBiP-derived peptides. In the mouse study, after DBA/1J mice were immunized with BiP or citBiP, serum titers of ACPAs were measured by ELISA and immunohistochemistry. The development of collagen-induced arthritis (CIA) was observed in BiP- or citBiP-pre-immunized mice. RESULTS: The serum levels of anti-BiP and anti-citBiP antibodies were significantly increased in RA patients, although only anti-BiP antibodies were slightly increased in SLE patients. Interestingly, anti-citBiP antibody levels were higher than anti-BiP antibody levels in 72% of RA patients, whereas no significant increase in anti-citBiP antibody levels was detected in SLE patients and healthy controls. The serum levels of anti-CCP antibodies were correlated with those of anti-citBiP antibodies in RA patients (R2 = 0.41). Several citrulline residues of citBiP were determined to be major epitopes of anti-citBiP antibodies, one of which showed cross-reactivity with CCP. Immunization of DBA/1J mice with citBiP induced several kinds of ACPAs, including anti-CCP and anti-citrullinated fibrinogen antibodies. Pre-immunization with citBiP exacerbated CIA, and anti-CCP antibody levels were increased in citBiP-pre-immunized CIA mice. CONCLUSIONS: CitBiP is a newly described ACPA target that may play a pro-inflammatory role in arthritis.

Dataset Information

Citrullinated Aggrecan Epitopes as Targets of Autoreactive CD4+ T Cells in Patients With Rheumatoid Arthritis.

Publications

Citrullinated Aggrecan Epitopes as Targets of Autoreactive CD4+ T Cells in Patients With Rheumatoid Arthritis.

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