Antibody Mediated Autoimmunity in Neuromyelitis Optica

描述(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))的免疫病理机制中发挥重要作用。NMO是一种严重的炎症性脱髓鞘疾病，影响视神经和脊髓。水通道蛋白-4(AQP4)已被认为是NMO致病自身抗体反应的靶点。因此，NMO可以被认为是CNS导向的B细胞和抗体自身免疫的模型疾病。AQP4是一种水通道蛋白，表达于中枢神经系统的星形胶质细胞。抗AQP4抗体通过多种不同的机制在NMO中发挥神经病理作用，包括补体激活、抗体依赖的细胞介导的细胞毒作用以及AQP4及其相关蛋白的下调。然而，致病性抗AQP4抗体的确切表位特异性仍不清楚。目前尚不清楚AQP4以外的抗原是否也是与病理相关的自身抗体的靶标，也没有关于抗AQP4血清阴性患者病理性自身抗体的表位靶标的信息。然而，有证据表明在NMO中存在广泛的B细胞依赖性自身免疫，这可能转化为一种多样化的、致病的、中枢神经系统定向的自身抗体谱系。我们假设，AQP4特异性抗体谱系是多样化的，无论是关于AQP4表位的识别，还是关于对中枢神经系统组织的病理影响。为了解决这一假设，我们将首先描述由A识别的AQP4表位的谱系。)由脑脊液浆细胞产生的重组单抗(RAB)，由b.从抗AQP4血清阳性NMO患者的血清和脑脊液中提纯可溶性免疫球蛋白。随后，代表单个AQP4表位的抗AQP4单抗将进一步鉴定它们对表达AQP4的细胞的潜在损伤。为了建立一个尽可能接近体内的体外实验系统，我们还将研究抗AQP4抗体对NMO患者诱导多能干细胞(IPSC)来源的星形胶质细胞的病理影响。我们还假设，针对AQP4以外的靶点的抗体介导的免疫可能在AQP4血清阴性甚至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患者中识别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(例如星形胶质细胞、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所产生的病理效应。这些研究将阐明与病理相关的抗体-抗原相互作用，并有望成为开发疾病特异性治疗和新的生物标记物的重要基础。

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.