特异性tau单克隆抗体77G阻断tau病理及其传播的分子机制研究

Alzheimer's disease (AD) is the most common cause of dementia in adults and characterized by the presence of extracellular -amyloid plaques and intraneuronal neurofibrillary tangles made up of paired helical filaments of hyperphosphorylated tau. The number of neurofibrillary tangles directly correlates with the degree of dementia in AD patients. The exact cause of the sporadic form of AD, which accounts for >99% of AD cases, is at present not understood. Neurofibrillary pathology is initiated in the locus coeruleus and transentorhinal area from where it progresses to the limbic system and further to the neocortex—the Braak stages. Tau pathology can be induced by intracerebral injection of brain extract containing pathological tau from either AD brain or end-stage transgenic mouse brain with tauopathy or even by peripheral administration of tau from diseased tissue in transgenic human tau mice and wild type tau mice. Furthermore, aggregates produced from recombinant tau in vitro with heparin also show capability of inducing tau pathology in cultured cells and in vivo. Thus, diseased tau gains a prion-like property and is transmitted from one area of the brain to another. In the preliminary study, we treated SH-SY5Y cells and FVB mice with monoclonal anti-tau antibody 77G and found that 77G significantly reduced tau level in cultured cells and in mouse brains. Intravenous injection of 77G suppressed pathological changes of tau in Tg/htau mice, in which six tau isoforms are expressed, induced by abnormally hyperphosphorylated and oligomeric tau from AD brain. Thus, we hypothesize that monoclonal tau antibody 77G may suppress tau aggregation and the propagation of tau pathology and may have potential therapeutic effect. To test this hypotheses, we proposed to 1) study inhibition of aggregation and sequestration of tau pathology seeded by AD P-tau by 77G in vitro, 2) study the role of 77G in tau aggregation templated by AD P-tau in cultured cells, 3) study the role of 77G in tau pathology in 3XTg-AD mice and the propagation of tau pathology templated by AD P-tau in Tg/htau mice, and 4) study whether Fab fragment of 77G cleaved by papain has a similar role in tau aggregation and the propagation of tau pathology seeded by AD P-tau in vitro and in vivo. This pre-clinical study will help us to understand the role and mechanism of this monoclonal tau antibody in tau pathogenesis and the propagation of tau pathology. Base on this pilot study, we will be able to develop a passive immunization therapeutics for AD and related tauopathies.

阿尔茨海默病（AD）严重影响老年人的健康，迄今尚无有效治疗手段。异常过度磷酸化的tau蛋白聚集因其形成的神经原纤维缠结与AD痴呆程度呈正相关，被认为是致病关键。近年来的研究显示tau病理呈朊样传播，而tau抗体能有效抑制tau病理形成并改善AD模型小鼠的学习记忆功能，因此针对tau的免疫治疗是当前AD研究的热点，被业界认为是治疗的希望所在。在前期工作中我们发现特异性单克隆tau抗体77G减低细胞和小鼠脑内tau的水平，并抑制AD P-tau诱导的Tg/htau小鼠tau的病理改变，提示77G可能具有潜在的治疗价值。本项目拟在分子、细胞和整体动物(AD模型小鼠)水平，从tau的聚集、tau被AD P-tau猎获和诱导的朊样聚集、tau病理形成及其朊样传播等方面，研究77G特别是其Fab段对tau病理发生发展和传播的作用和分子机制，为基于特异性tau被动免疫治疗药物开发奠定科学基础。

阿尔茨海默病(Alzheimer’s disease, AD)是最常见的神经退行性疾病，严重影响老年人的健康，迄今尚无有效治疗手段。异常过度磷酸化的tau蛋白聚集形成的神经原纤维缠结(NFTs)的数量和在脑区中分布与AD痴呆程度和疾病的进展呈正相关，被认为是AD致病关键因素。近年来的研究显示tau病理呈朊样传播，而tau抗体能有效抑制tau病理形成并改善AD模型小鼠的学习记忆功能，因此针对tau的免疫治疗是当前AD研究的热点，被认为是治疗AD的希望所在。本课题在体外、培养的细胞中和动物体内探讨了特异性tau单克隆抗体77G阻断tau病理及其传播的分子机制研究，取得了满意的进展。发现77G对AD患者脑中聚集的tau呈现更强的亲和力。77G在体外抑制病理性AD O-tau对正常tau的猎获和诱导其聚集；在培养的细胞中，77G抑制病理性AD O-tau诱导正常tau的聚集；在转基因动物体内，77G对AD O-tau诱导的tau的异常过度磷酸化和病理也呈现一定的抑制作用。这些结果提示77G能抑制病理性tau的朊样活性，抑制tau病理的朊样传播，展现极其重要的开发前景。