Epitopic targets of the monoclonal auto-antibody repertoire in autoimmune encephalitis

仅在几年前发现的抗NMDA受体（NMDAR）脑炎已成为脑炎最常见的病因之一，也是新发精神病的重要鉴别诊断，其特征与幻觉、紧张症、意识水平改变、癫痫发作、通气不足、运动障碍和自主神经功能障碍有关。针对NMDAR的自身抗体通过引起受体内化和突触功能障碍而直接致病。我们最近可以通过单细胞扩增、测序和克隆来自记忆B细胞和浆细胞的全长免疫球蛋白重链和轻链基因，从这种脑炎患者的脑脊液中产生单克隆人NMDAR自身抗体。单克隆NMDAR自身抗体已迅速成为组织学和电生理学测定以及高分辨率显微镜的宝贵工具。令人惊讶的是，这些患者脑中的大多数抗体分泌细胞产生针对其他表位的抗体，尽管这些表位是脑限制性的，如星形胶质细胞、轴突纤维束、海马神经元或颗粒细胞、内皮细胞或脉络丛。对靶蛋白的首次鉴定表明，它们与神经元功能、神经变性和自身免疫的关键参与者结合。以这种方式，这些额外的自身抗体可能具有类似的致病性，并且可能通过干扰离子通道或受体功能而导致疾病的可变临床症状。因此，目前的建议，目的是在鉴定的人脑脊液自身抗体库脑炎患者使用免疫沉淀和质谱的靶蛋白。此外，研究结果将与相关形式的脑部炎症和健康对照进行比较。这项研究的数据将有助于了解自身免疫和神经精神疾病之间的因果关系，并可能确定治疗此类疾病的新靶点。

Discovered only a few years ago, anti-NMDA receptor (NMDAR) encephalitis has become one of the most commonly identified causes of encephalitis and an important differential diagnosis for new-onset psychosis, characteristically associated with hallucinations, catatonia, altered levels of consciousness, seizures, hypoventilation, dyskinesia, and autonomic dysfunction. Auto-antibodies against the NMDAR are directly pathogenic by causing receptor internalization and synaptic dysfunction. We could recently generate monoclonal human NMDAR auto-antibodies from the cerebrospinal fluid of patients with this encephalitis by single-cell amplification, sequencing and cloning of full-length immunoglobulin heavy and light chain genes from memory B cells and plasma cells. The monoclonal NMDAR autoantibodies have quickly become invaluable tools for histological and electrophysiological assays and for high-resolution microscopy. Surprisingly, the majority of antibody-secreting cells in the brain of these patients produced antibodies against other, although brain-restricted, epitopes, such as astrocytes, axonal fiber tracts, hippocampal neuropil or granule cells, endothelium or choroid plexus. First identifications of target proteins suggest that they bind to key players of neuronal function, neurodegeneration and autoimmunity. In this way these additional auto-antibodies might be similarly pathogenic and can contribute to the variable clinical symptoms of the disease, potentially by interfering with ion channel or receptor function. Thus, the current proposal aims at the identification of the target proteins of the human cerebrospinal fluid auto-antibody repertoire in patients with encephalitis using immunoprecipitation and mass spectrometry. In addition, the findings will be compared to related forms of brain inflammation and to healthy controls. Data from this study will help to understand the causal relationship between autoimmunity and neuropsychiatric disorders, and potentially identify novel targets for the treatment of such conditions.