Water-soluble Abeta and its role in Alzheimer's disease

描述(申请人提供)：阿尔茨海默病(AD)是一种个人和社会悲剧，需要加快努力开发有效的治疗方法。强有力的遗传证据将淀粉样前体蛋白(APP)及其蛋白分解衍生物与AD联系在一起。一个主要的假说提出，APP的一个小的两亲性片段，淀粉样b蛋白(AB)，自结合形成被松散地称为“寡聚体”的组件，这些组件触发了一系列复杂的事件，最终导致痴呆症。然而，抗体在人脑中的毒性形式及其与疾病的关系尚未得到严格的研究。鉴于AD正在给世界各地的医疗保健系统带来不可持续的负担，至关重要的是，必须直接和迅速地处理对抗体作用及其最佳靶向的科学疑虑。十多年前，我们和其他人提出，某些非单体、非纤维形式的抗体是有效的神经毒素，可能是AD的沉淀剂。然而，这些“有毒低聚物”的确切生化特征仍不清楚。此外，虽然大量关于抗体结构和活性的研究都使用了合成的抗体多肽，但现在明显的是，脑源性抗体制剂比体外形成的抗体集合体对神经元的损害更大，对淀粉样蛋白的形成也更好。我们假设，脑源性低聚物毒性活性的增强与不同抗体序列混合物的存在、翻译后修饰和/或共价交联链的形成有关，所有这些都有助于增加毒性组件的稳定性。S在普恩病毒病中似乎是正确的，我们预测抗体集合体的大小、构象和稳定性强烈地影响其毒活性。使用AD脑的水提取物，并基于大量的初步数据，我们建议严格调查：(I)组装大小，(Ii)构象和(Iii)有毒抗体物种的动态性质。然后，我们建议将它们提纯到均一，并阐明它们的组成。在我们的整个实验中，我们将不断地将我们的物理分析与与AD直接相关的神经生物学活动的测量联系起来。此后，我们将分析死后组织，以比较痴呆症受试者和认知正常的高斑块负荷人群大脑中有毒低聚物的数量和质量。使用相同的人体组织，我们还将测量其他APP片段的水平，看看其中是否有比抗体更好地与疾病相关的片段。然后，我们将检查接受AN1792疫苗接种的AD患者的脑组织和血浆。这项特殊实验的目的是确定疫苗接种如何影响人脑中抗体的水平和形式，以及一些免疫患者是否会产生能够针对有毒寡聚体的抗体。最后，从手头的20种候选抗体中，我们将确定一种 优先识别有毒低聚物。然后，我们希望了解它是否能在AD小鼠模型中更好地保护抗体物种，而不是目前的先导治疗性抗体mAb266。

DESCRIPTION (provided by applicant): Alzheimer's disease (AD) represents a personal and societal tragedy that demands an accelerated effort to develop effective therapies. Strong genetic evidence links the amyloid precursor protein (APP) and its proteolytic derivatives to AD. A leading hypothesis proposes that a small amphipathic fragment of APP, amyloid b-protein (Ab), self-associates to form assemblies loosely referred to as "oligomers", and that these trigger a complex pathogenic sequence of events that culminate in dementia. However, the toxic forms of Ab in human brain, and their relationship to disease have not been rigorously studied. Given the unsustainable burden that AD is placing on healthcare systems worldwide, it is essential that scientific doubts about the role of Ab and how it is best targeted are dealt with directly and swiftly. More than a decade ago, we and others proposed that certain non-monomeric, non-fibrillar forms of Ab are potent neurotoxins and may be the precipitating agent in AD. Yet the precise biochemical identity of these "toxic oligomers" remains unclear. Moreover, while the vast bulk of studies of Ab structure and activity have used synthetic Ab peptides, it is now apparent that brain-derived Ab preparations are much more damaging to neurons and much better seeds for amyloidogenesis than are Ab assemblies formed in vitro. We hypothesize that the enhanced toxic activity of brain-derived oligomers is related to the presence of mixtures of different Ab sequences, post-translational modifications and/or formation of covalent cross-links, all of which act to increase the stability of toxic assemblies. s appears to be true in prion diseases, we predict that the size, conformation and stability of Ab assemblies strongly influence their toxic activity. Using aqueous extracts of AD brains, and based on substantial preliminary data, we propose to investigate rigorously: (i) the assembly size, (ii) conformations and (iii) dynamic nature of toxic Ab species. Then we propose to purify them to homogeneity and to elucidate their composition. Throughout our experiments, we will constantly link our physical analyses with measures of neurobiological activity directly relevant to AD. Thereafter, we will analyze postmortem tissue to compare the quantity and quality of toxic oligomers in brains of demented subjects vs. cognitively normal humans with high plaque burdens. Using the same human tissues, we will also measure the levels of other APP fragments to see if any of these better relate to disease than does Ab. Then we will examine brain tissue and plasma from AD patients that received the AN1792 vaccination. The goal of this particular experiment is to ascertain how vaccination affects the levels and forms of Ab in the human brain and whether some immunized patients develop antibodies capable of targeting the toxic oligomers. Finally, from a selection of 20 candidate antibodies in hand, we will identify one that preferentially recognizes toxic oligomers. Then we expect to learn whether it can protect against Ab species in AD mouse models better than does the current lead therapeutic antibody, mAb266.