Immune Recognition of Citrullinated Cartilage PG Aggrecan in Autoimmune Arthritis

自身免疫性关节炎中瓜氨酸软骨 PG 聚集蛋白聚糖的免疫识别

• 批准号: 8636402
• 负责人: KATALIN MIKECZ
• 金额: $ 32.51万
• 依托单位: RUSH UNIVERSITY MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-05-01 至 2018-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8636402
• 关键词: Adult; Affect; Animal Model; Anti-citrullinated peptide antibody; Antibodies; Arginine; Arthritis; Autoantibodies; Autoantigens; Autoimmune Diseases; Autoimmune Responses; Autoimmunity; B-Lymphocyte Epitopes; B-Lymphocytes; Binding; Cartilage; Citrulline; Clinical; Collagen Type II; Core Protein; Data; Deposition; Development; Disease; Epitope Mapping; Epitopes; Evolution; Extracellular Matrix; Goals; Human; Immune; Immune Tolerance; Immune response; Immunity; Immunization; Immunoglobulin G; Immunoglobulin M; Immunoglobulins; In Vitro; Inbred BALB C Mice; Individual; Inflammatory; Joints; Laboratories; Lead; Maps; Modeling; Monitor; Mus; Onset of illness; Pain; Pathogenesis; Pathogenicity; Patients; Peptides; Peripheral; Population; Post-Translational Protein Processing; Predisposition; Production; Proteins; Proteoglycan; Reaction; Recombinants; Relative (related person); Research; Resistance; Rheumatoid Arthritis; Rheumatoid Factor; Role; Serum; Severities; Severity of illness; T cell response; T-Cell Immunologic Specificity; T-Lymphocyte; Testing; Transgenes; aggrecan; articular cartilage; autoimmune arthritis; base; clinically relevant; genetic risk factor; genome wide association study; in vivo; insight; joint destruction; joint function; joint injury; macromolecule; peripheral blood; public health relevance; tool

DESCRIPTION (provided by applicant): Proteoglycan (PG) aggrecan is a major macromolecular component of articular cartilage. PG has been considered a T-cell autoantigen in patients with rheumatoid arthritis (RA), an autoimmune disease of the peripheral joints that results in inflammatory destruction of cartilage and loss of joint function. The "arthritogenic" potential of PG is underscored by the observation that immunization of BALB/c mice with human PG induces arthritis with clinical and immunological features similar to those in RA. We have recently found that PG extracted from adult human cartilage is citrullinated. While citrullination (enzymatic conversion of arginine residues to citrulline) is a post-translational protein modification that may occur in healthy individuals, the majority of patients with RA, unlike healthy subjects, recognize citrullinated self proteins as "foreign" and produce anti-citrullinated protein autoantibodies (ACPA). Importantly, we have found that ACPA+ RA sera react with in vivo or in vitro citrullinated human PG, predominantly with the first globular (G1) domain of the molecule. Citrullinated PG present in the joint cartilage of RA patients has the potential to initite autoimmune responses and/or serve as a target for ACPA with serious consequences. However, very limited data is available about T-cell recognition of citrullinated PG epitopes, and nothing is known about the epitope repertoire, cartilage-specific deposition, and pathogenicity of PG-specific ACPA in RA. The studies described in Aim 1 will (i) explore the citrullinated PG (G1 domain)-specific T-cell and ACPA epitope repertoire using peripheral blood from RA patients, and (ii) identify PG-specific ACPA deposited in cartilage of damaged RA joints. Since mice with human PG-induced or PG G1-domain induced arthritis (GIA) also produce ACPA, this animal model provides a unique research tool for investigating the mechanistic aspects of citrullinated PG-specific autoimmunity that cannot be studied in patients with RA. Therefore, in Aims 2 and 3, we will (i) map the full repertoire of citrullinated epitopes within the G1 domain of human PG in BALB/c mice immunized with in vitro citrullinated G1, (ii) monitor the evolution of citrullinate G1-specific immunity, (iii) correlate the magnitude and epitope repertoire of anti-G1 ACPA with the severity of arthritis, and (iv) determine whether selective loss of citrullinated G1-specific immune tolerance can lead to arthritis development. The results of our studies should provide clinically relevant insights into the role of citrullinated PG in the pathogenesis of ACPA+ RA.

描述(申请人提供)：蛋白多糖(PG)聚集素是关节软骨的主要大分子成分。PG一直被认为是类风湿性关节炎(RA)患者的T细胞自身抗原，RA是一种周围关节的自身免疫性疾病，导致软骨炎性破坏和关节功能丧失。用人PG免疫BALB/c小鼠可引起与RA相似的临床和免疫学特征的关节炎，这突显了PG的“关节致炎”潜力。我们最近发现从成人软骨中提取的PG是瓜氨酸化的。虽然瓜氨酸化(精氨酸残基的酶转化为瓜氨酸)是一种翻译后蛋白质修饰，可能发生在健康人身上，但与健康人不同的是，大多数类风湿关节炎患者认为瓜氨酸化的自身蛋白是“外来的”，并产生抗瓜氨酸化的蛋白质 蛋白自身抗体(ACPA)。重要的是，我们发现ACPA+RA血清在体内或体外与瓜氨酸化的人PG反应，主要与分子的第一个球状(G1)结构域反应。存在于RA患者关节软骨中的瓜氨酸PG有可能启动自身免疫反应和/或成为ACPA的靶点，导致严重后果。然而，关于T细胞识别瓜氨酸PG表位的数据非常有限，对于PG特异性ACPA在RA中的表位谱系、软骨特异性沉积和致病性还知之甚少。目标1中描述的研究将(I)利用RA患者的外周血探索瓜氨酸PG(G1结构域)特异性T细胞和ACPA表位谱，以及(Ii)鉴定沉积在受损RA关节软骨中的PG特异性ACPA。由于人PG诱导的或PG G1结构域诱导的关节炎(GIA)小鼠也产生ACPA，该动物模型为研究瓜氨酸PG特异性自身免疫的机制提供了一个独特的研究工具，而在RA患者中无法进行研究。因此，在目标2和3中，我们将(I)在体外用瓜氨酸G1免疫的BALB/c小鼠中绘制人PG G1区的全部瓜氨酸表位图谱，(Ii)监测瓜氨酸G1特异性免疫的进化，(Iii)将抗G1ACPA的大小和表位图谱与关节炎的严重程度相关联，以及(Iv)确定选择性丧失瓜氨酸G1特异性免疫耐受是否会导致关节炎的发生。我们的研究结果应该为瓜氨酸PG在ACPA+RA发病机制中的作用提供临床相关的见解。