Disconnecting CR2/CD21 from Its C3d Ligand to Ameliorate Lupus

断开 CR2/CD21 与其 C3d 配体的连接以改善狼疮

• 批准号: 8492301
• 负责人: Vernon Michael Holers
• 金额: $ 23.14万
• 依托单位: UNIVERSITY OF COLORADO DENVER
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-02-01 至 2015-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8492301
• 关键词: Address; Affect; Affinity; Alternative Splicing; Antibodies; Antibody Affinity; Antigens; Autoantibodies; Autoantigens; Autoimmune Diseases; Autoimmune Process; Autoimmune Responses; Autoimmunity; B-Cell Activation; B-Lymphocytes; Binding; Binding Sites; CD19 gene; Cells; Chronic; Clinical; Complement; Complement 3b; Complement 3b Receptors; Complement 3d; Complement 3d Receptors; Complement 4b; Complement Inactivators; Complement Receptor; Complement Receptor Type 1; Complex; Defect; Development; Disease; Evolution; Follicular Dendritic Cells; Functional disorder; Gene Targeting; Genes; Goals; Histologic; Human; Immune; Immune response; Immunologic Deficiency Syndromes; Impairment; Inbred MRL lpr Mice; Individual; Injury; Kidney; Lead; Ligands; Light; Longevity; Lupus; Mediating; Memory B-Lymphocyte; Modeling; Monoclonal Antibodies; Mouse Protein; Mus; National Institute of Allergy and Infectious Disease; Onset of illness; Outcome; Phenotype; Play; Prevention; Proteins; Proteinuria; Public Health; Receptors, Antigen, B-Cell; Reporting; Research; Role; Site; Specificity; Structure of germinal center of lymph node; Suggestion; System; Systemic Lupus Erythematosus; Testing; Time; Work; antibody inhibitor; antigen binding; base; complement system; early onset; improved; novel; public health relevance; receptor; receptor binding; receptor function; response; tool; treatment effect

DESCRIPTION (provided by applicant): Complement receptor type 2 (CR2/CD21) and its primary C3 activation fragment-derived ligand designated C3d play a central role in the development of high affinity antibodies to foreign antigens. The primary B cell receptors for antigen-bound C3 fragments in mice are CR2 and complement receptor type 1 (CR1/CD35). As opposed to humans, where unique genes encode these proteins, mouse CR2 and CR1 are derived through alternative splicing from a common gene designated Cr2. The larger CR1 protein is the primary receptor for the C3b form of C3 as well as antigen-bound C4b, while the smaller CR2 protein only binds C3d with a high affinity. High affinity autoantibodies and B lymphocytes play central roles in the immunopathogenesis of human systemic lupus erythematosus (SLE). In principle, given our current understanding of the immune basis for the development of SLE through subversion of normal tolerance checkpoints and development of autoreactive responses, one might expect a similar enhancing role as found with foreign antigens to be played by CR2 interactions with C3d-bound self-antigens in SLE. However, prior studies using gene-targeted Cr2-/- mice, which lack both CR2 and CR1, in murine models of SLE have not supported this presumption and have suggested that CR2, in addition to CR1, expression is necessary to maintain tolerance to lupus-related self- antigens. It is straightforward to understand how CR1 could play this role as a high affinity receptor for C4b, which is itself necessary to maintain tolerance to self-antigen in mice and humans. However, no similar experimentally supported role exists for CR2, and thus how expression of this particular receptor could be needed to protect from autoimmune disease development in SLE remains enigmatic. To address this question, we have overcome the technical challenges that exist in the murine CR2/CR1 receptor system by developing new highly specific mouse anti-mouse monoclonal antibodies (mAbs). The first is a non-B cell depleting mAb that recognizes and blocks only CR2/CD21 function without directly affecting CR1 interactions with C4b or C3b. The second mAb recognizes the C3d fragment at its receptor binding site and blocks its interaction with CR2 without affecting C3b or C4b interactions with CR1. With these newly developed tools and pursuing the following specific aims, we will for the first time be able to test the hypothesis that disruption of the critical C3d- CR2 ligand-receptor binding step alone will ameliorate, rather than enhance, autoimmunity and clinical disease in SLE: Specific Aim #1. Evaluate the effects of specific monoclonal antibody-mediated blockade of CR2/CD21 function on the evolution of autoimmunity and clinical outcomes in the MRL/lpr model of human lupus; and Specific Aim #2. Using a novel C3d-specific monoclonal antibody to interrupt the interaction by C3d-bearing autoantigen complexes with CR2/CD21, characterize the ameliorative effects of this strategy on the evolution of autoimmunity and clinical outcomes in the MRL/lpr model.

描述（由申请人提供）：2 型补体受体 (CR2/CD21) 及其主要 C3 激活片段衍生配体（称为 C3d）在针对外源抗原的高亲和力抗体的开发中发挥着核心作用。小鼠中抗原结合 C3 片段的主要 B 细胞受体是 CR2 和补体受体 1 型 (CR1/CD35)。与人类不同的是，人类的独特基因编码这些蛋白质，小鼠 CR2 和 CR1 是通过选择性剪接自称为 Cr2 的常见基因衍生而来。较大的 CR1 蛋白是 C3 的 C3b 形式以及抗原结合的 C4b 的主要受体，而较小的 CR2 蛋白仅以高亲和力结合 C3d。高亲和力自身抗体和 B 淋巴细胞在人类系统性红斑狼疮 (SLE) 的免疫发病机制中发挥着核心作用。原则上，鉴于我们目前对通过破坏正常耐受检查点和发展自身反应性反应来发展 SLE 的免疫基础的理解，人们可能期望在 SLE 中 CR2 与 C3d 结合的自身抗原相互作用，可以发挥与外来抗原类似的增强作用。然而，之前在 SLE 小鼠模型中使用基因靶向 Cr2-/- 小鼠（缺乏 CR2 和 CR1）的研究并不支持这一假设，并表明除了 CR1 之外，CR2 的表达对于维持对狼疮相关自身抗原的耐受性也是必要的。很容易理解 CR1 作为 C4b 的高亲和力受体如何发挥这一作用，C4b 本身对于维持小鼠和人类对自身抗原的耐受性是必需的。然而，CR2 不存在类似的实验支持作用，因此如何需要表达这种特定受体来防止 SLE 中自身免疫性疾病的发展仍然是个谜。为了解决这个问题，我们通过开发新的高度特异性的小鼠抗小鼠单克隆抗体（mAb），克服了小鼠 CR2/CR1 受体系统中存在的技术挑战。第一种是非 B 细胞消耗型 mAb，仅识别和阻断 CR2/CD21 功能，而不直接影响 CR1 与 C4b 或 C3b 的相互作用。第二种 mAb 识别其受体结合位点的 C3d 片段并阻断其与 CR2 的相互作用，而不影响 C3b 或 C4b 与 CR1 的相互作用。借助这些新开发的工具并追求以下具体目标，我们将首次能够检验该假设 单独破坏关键的 C3d-CR2 配体-受体结合步骤就会改善，而不是 而非增强系统性红斑狼疮的自身免疫和临床疾病：具体目标#1。评估人类狼疮 MRL/lpr 模型中特异性单克隆抗体介导的 CR2/CD21 功能阻断对自身免疫进化和临床结果的影响；和具体目标#2。使用新型 C3d 特异性单克隆抗体来中断带有 C3d 的自身抗原复合物与 CR2/CD21 的相互作用，表征该策略对 MRL/lpr 模型中自身免疫进化和临床结果的改善作用。