Antibody Mediated Autoimmunity in Neuromyelitis Optica

描述（由申请人提供）：越来越多的人认识到B细胞和抗体在中枢神经系统（CNS）自身免疫性脱髓鞘疾病(如视神经脊髓炎（NMO）和多发性硬化症（MS）的免疫发病机制中起着重要作用。NMO是一种严重的炎性脱髓鞘疾病，影响视神经和脊髓。水通道蛋白-4 （AQP4）已被确定为NMO致病性自身抗体反应的靶标。因此，NMO可以被认为是中枢神经系统定向B细胞和抗体自身免疫的模型疾病。AQP4是一种水通道蛋白，在中枢神经系统星形胶质细胞中表达。抗AQP4抗体在NMO中通过多种不同的机制发挥神经病理作用，包括补体激活、抗体依赖细胞介导的细胞毒性、AQP4及相关蛋白的下调。然而，致病性抗aqp4抗体的确切表位特异性尚不清楚。目前尚不清楚AQP4以外的抗原是否也是病理相关自身抗体的靶点，也没有关于抗AQP4血清阴性患者致病性自身抗体表位靶点的信息。然而，有证据表明NMO中存在广泛的B细胞依赖性自身免疫，这可能转化为多种致病性cns导向的自身抗体库。我们假设AQP4特异性抗体库是多种多样的，无论是在AQP4表位识别方面，还是在中枢神经系统组织的病理作用方面。为了解决这一假设，我们将首先描述由a.)从脑脊液浆细胞产生的重组单克隆抗体（rAbs）和b.)从抗AQP4血清阳性NMO患者的血清和脑脊液中纯化的可溶性免疫球蛋白识别的AQP4表位库。随后，代表单个AQP4表位的单克隆抗AQP4抗体将进一步表征其对表达AQP4的细胞的损伤潜力。为了建立尽可能接近体内的体外实验体系，我们还将研究抗aqp4抗体对NMO患者诱导多能干细胞（iPSC）衍生星形胶质细胞的病理影响。我们还假设，抗体介导的针对AQP4以外靶点的免疫可能在AQP4血清阴性甚至可能是AQP4血清阳性的NMO患者中发挥作用。为了解决这一假设，我们建议从AQP4血清阴性和-血清阳性的NMO患者中确定AQP4非反应性抗体的靶点。为了实现这一目标，我们将确定AQP4非反应性抗体与ipsc来源的中枢神经系统细胞（如星形胶质细胞、少突胶质细胞或神经元）的反应性，并研究这种自身抗体结合引起的病理效应。这些研究将阐明病理相关的抗体-抗原相互作用，并有望为疾病特异性治疗和新型生物标志物的发展奠定重要基础。

DESCRIPTION (provided by applicant): There is increasing appreciation that B cells and antibodies are important players in the immunopathogenesis of autoimmune demyelinating disorders of the central nervous system (CNS) such as neuromyelitis optica (NMO) and multiple sclerosis (MS). NMO is a severe inflammatory demyelinating disease affecting the optic nerves and spinal cord. Aquaporin-4 (AQP4) has been identified as a target of pathogenic autoantibody responses in NMO. Thus, NMO can be considered a model disease for CNS directed B cell and antibody autoimmunity. AQP4 is a water channel protein, which is expressed in astrocytes of the CNS. Anti- AQP4 antibodies have been proposed to exert neuropathological effects by a number of different mechanisms in NMO, including complement activation, antibody-dependent cell-mediated cytotoxicity, and downregulation of AQP4 and associated proteins. However, the exact epitope specificities of pathogenic anti-AQP4 antibodies remain unknown. It is unclear whether antigens other than AQP4 are also targets of pathologically relevant autoantibodies and no information is available regarding epitope targets of pathogenic autoantibodies in anti- AQP4 seronegative patients. However, there is evidence for extensive B cell-dependent autoimmunity in NMO, which likely translates into a diverse, pathogenic, CNS-directed autoantibody repertoire. We hypothesize that the AQP4-specific antibody repertoire is diverse, both in regards to AQP4 epitope recognition and with respect to pathological effects on CNS tissue. To address this hypothesis, we will first delineate the repertoire of AQP4 epitopes recognized by a.) recombinant monoclonal antibodies (rAbs) generated from CSF plasma cells, and by b.) purified soluble immunoglobulins from serum and CSF from anti- AQP4 seropositive NMO patients. Subsequently, monoclonal anti-AQP4 antibodies representative of individual AQP4-epitopes will be further characterized regarding their potential to damage AQP4 expressing cells. To establish an in vitro experimental system as close to in vivo as possible, we will also study pathological effects of anti-AQP4 antibodies on astrocytes derived from induced pluripotent stem cells (iPSC) from NMO patients. We also hypothesize, that antibody mediated immunity against targets other than AQP4 may play a role in AQP4-seronegative and possibly even AQP4-seropositive NMO patients. To address this hypothesis, we propose to identify targets of AQP4 non-reactive antibodies from AQP4-seronegative and -seropositive NMO patients. To achieve this goal, we will determine the reactivity of AQP4 non-reactive antibodies with iPSC-derived CNS cells (e.g. astrocytes, oligodendrocytes or neurons) and study pathological effects resulting from this autoantibody binding. These studies will elucidate pathologically relevant antibody-antigen interactions and are expected to serve as an important foundation for the development of disease-specific therapies and novel biomarkers.