Molecular approaches for understanding and advancing tau immunotherapies

项目总结/摘要 使用单克隆抗体（mAb）的免疫疗法已被证明在治疗许多疾病和糖尿病方面是成功的。 目前正在调查痴呆症最常见的原因，阿尔茨海默病（AD）。 细胞外斑块，含有淀粉样蛋白β（Aβ），和神经元内神经元缠结，由 过度磷酸化tau，表征AD病理学。Aβ蓄积在显著tau之前开始 病理学、脑萎缩和痴呆发作，但降低淀粉样蛋白的治疗，包括抗A β 抗体，并没有导致认知的好处，轻度至中度痴呆症患者由于AD。而 在AD的早期“临床前”阶段，在广泛的Aβ病理学之前， 在认知症状中，tau正在成为另一个有希望的治疗靶点。Tau沉积物的存在， 特定的大脑区域与AD和其他神经退行性疾病中的认知下降相关， tau蛋白病，其中单独的tau内含物足以引起变性。霍尔茨曼实验室和其他 已经显示用抗tau单克隆抗体被动免疫减少鼠模型中tau相关的病理学 tau蛋白病因此，本提案的总体目标是研究tau的理想方法 免疫疗法被动免疫的一个主要限制是需要长期高剂量的mAb， 在脑中达到治疗水平，因为只有一小部分穿过血脑屏障。该提案使用 重组腺相关病毒在tau蛋白病的脑中表达嵌合全长抗tau mAb 小鼠模型我们假设通过基因转移将抗tau单克隆抗体直接递送到大脑将刺激长时间的 术语在宿主细胞中的表达将减少tau相关的病理。此外，我们还设计了抗- Tau片段抗原结合（Fab）结构域和全长嵌合mAb，其中Tau片段抗原结合（Fab）结构域的恒定区是恒定的。 重链被免疫球蛋白G（IgG）片段可结晶（Fc）变体取代， 与Fcγ受体结合。IgG Fc结构域结合主要在微胶质细胞中表达的Fcγ受体。 可能介导细胞外tau清除，但也可能导致促炎反应， 加剧了退化过程。我们将检验消除IgG结构域和Fc 抗tau单克隆抗体的效应子功能避免了不利的促炎作用，同时仍然提供神经保护 通过将抗Tau Fab或全长IgG Fc变体直接施用到细胞内， tau蛋白病小鼠模型的大脑。因此，该建议使用分子方法来研究 抗tau免疫疗法的机制，并提高mAb递送到大脑的效率， 推进脑源性抗原（如tau）的被动免疫，并可能带来治疗选择 数百万人患有AD和相关的Tau蛋白病。

Project Summary/Abstract Immunotherapy using monoclonal antibodies (mAbs) has proven successful in treating numerous diseases and is currently under investigation for the most common cause of dementia, Alzheimer's disease (AD). Extracellular plaques, containing amyloid beta (Aβ), and intraneuronal neurofibrillary tangles, composed of hyperphosphorylated tau, characterize AD pathology. Aβ accumulation begins prior to significant tau pathology, cerebral atrophy and the onset of dementia, yet amyloid-lowering treatments, including anti-Aβ antibodies, have not resulted in cognitive benefits for patients with mild to moderate dementia due to AD. While these treatments are re-evaluated in the earlier “pre-clinical” stage of AD, before extensive Aβ pathology and cognitive symptoms, tau is emerging as another promising therapeutic target. The presence of tau deposits in specific brain regions correlates with cognitive decline in AD and in other neurodegenerative diseases, termed tauopathies, where tau inclusions alone are sufficient to cause degeneration. The Holtzman lab and others have shown that passive immunization with anti-tau mAbs reduces tau-associated pathology in murine models of tauopathy. Therefore, the overall objective of this proposal is to investigate ideal approaches to tau immunotherapy. A major limitation of passive immunization is the chronic high doses of mAbs required to reach therapeutic levels in the brain as only a small fraction cross the blood brain barrier. This proposal uses recombinant adeno-associated virus to express a chimeric full-length anti-tau mAb in the brain of a tauopathy mouse model. We hypothesize direct delivery of anti-tau mAbs to the brain by gene transfer will stimulate long- term expression in host cells that will reduce tau-associated pathology. Additionally, we have engineered anti- tau fragment antigen binding (Fab) domains and full-length chimeric mAbs in which the constant region of the heavy chain is replaced with immunoglobulin G (IgG) fragment crystallible (Fc) variants that exhibit differential binding to Fcγ receptors. The IgG Fc domain binds to Fcγ receptors primarily expressed on microglia in the brain and may mediate extracellular tau clearance, but can also lead to pro-inflammatory responses that may exacerbate the degenerative process. We will test the hypothesis that eliminating the IgG domain and Fc effector function of anti-tau mAbs avoids adverse pro-inflammatory effects while still providing neuroprotection by sequestering extracellular tau through direct administration of anti-tau Fab or full-length IgG Fc variants into the brain of a tauopathy mouse model. Thus, this proposal uses molecular approaches to investigate mechanisms of anti-tau immunotherapy and improve the efficiency of mAb delivery to the brain in order to advance passive immunization for brain derived antigens, like tau, and potentially lead to treatment options for the millions of people suffering from AD and related tauopathies.