A new look at mechanism-based Alzheimer's Disease biomarkers in blood

一项血液测试，以确定认知未受损的个人在阿尔茨海默氏病（AD）的风险和 唐氏综合征（Down syndrome，DS）中AD的出现是迫切需要的。在这里，我们提出实验来解决 这种未满足的需求。具体来说，我们将测量（血浆中）与这些疾病有关的蛋白质（tau和Aβ）水平。 AD的病因学和针对这些蛋白质的天然存在的自身抗体（NAb）。在血液中，tau和Aβ是 存在于不同的池中，例如自由漂浮，与其他蛋白质结合，以及在外来体内部。许多现有 研究测量了血浆中的Aβ，但很少考虑到不同的池，许多研究受到以下因素的混淆： 不完善的测定和/或患者样本。只有少数研究观察了血液中的tau蛋白， 解释了tau的分子异质性或其在不同库中的出现。相比之下， 小心地使用能够检测不同形式的tau的测定并评估不同形式的tau的贡献。 以及它们如何随着疾病而变化。由于tau蛋白在血液中的含量很低， 血浆中Aβ的测量需要稀释以克服基质效应，我们将使用最先进的内部 使用Simoa（tau）和Erenna（Aβ）平台开发的超灵敏测定。NAbs结合的tau和Aβ 将从抗原-抗体复合物中释放出来，然后进行测量，并通过 定量与板固定的抗原的结合。将非常小心地纳入内部标准，以便 监控我们检测的灵敏度和重现性。大多数先前的研究仅在单一浓度下评价分析物。 时间点，很少有纵向研究。考虑到临床前和临床试验的持续时间较长， AD的临床阶段，以及不同形式的tau，Aβ和NAb在这些长期的 在这一时期，横截面研究迄今为止产生了相互矛盾和不同的结果，这并不奇怪。 考虑到这些缺陷，我们首次提出测量抗tau和抗A β NAb及其同源物。 使用来自仔细表征的研究受试者的标本，在相同的血浆样品中检测抗原。获得 深入了解tau，Aβ和NAb在整个疾病过程中的变化，我们将运用我们的良好- 对来自3个不同队列的血浆样品进行表征分析。这些将包括已被 在临床发作前和临床发作后即刻前瞻性地收集个体， 存在遗传和组织病理学数据，以及0-65岁DS受试者的血浆。DS是最常见的 早发型AD的遗传原因，大多数DS成人在60岁之前变得痴呆。因此，学习 来自不同年龄DS受试者的样本为AD的不同阶段提供了一个窗口， DS治疗AD的最佳治疗间隔。将这种系统方法与仔细的统计方法相结合， 分析我们期望识别一种或可能选择的分析物，其可以：（i）准确地检测受试者， 发展AD的风险，和（ii）确定在DS中治疗AD的适当年龄范围。

A blood test to identify cognitively unimpaired individuals at risk for Alzheimer's disease (AD) and the emergence of AD in Down syndrome (DS) is desperately needed. Here, we propose experiments to address this unmet need. Specifically, we will measure (in plasma) levels of proteins (tau and Aβ) implicated in the etiology of AD, and naturally occurring autoantibodies (NAbs) against these proteins. In blood tau and Aβ are present in distinct pools, e.g. free floating, bound to other proteins, and inside exosomes. Numerous prior studies have measured Aβ in plasma, but few took account of the distinct pools and many were confounded by imperfect assays and/or patient specimens. Only a handful of studies have looked at tau in blood, none accounted for the molecular heterogeneity of tau or its occurrence in different pools. In contrast, we will be careful to use assays capable of detecting distinct forms of tau and to assess the contributions of different pools and how they may change with disease. Since tau is present in blood at very low levels and measurement of Aβ in plasma requires dilution to overcome matrix effects, we will use state-of-the-art in-house ultra-sensitive assays developed using the Simoa (tau) and Erenna (Aβ) platforms. NAbs-bound tau and Aβ will be liberated from antigen-antibody complexes and then measured, and free NAbs will be detected by quantifying binding to plate-immobilized antigen. Great care will be taken to include internal standards so as to monitor the sensitivity and reproducibility of our assays. Most prior studies evaluated analytes at only a single time point and there have been few longitudinal studies. Considering the long duration of both the pre-clinical and clinical phases of AD, and how distinct forms of tau, Aβ and NAbs may change during these protracted periods, it is not surprising that cross-sectional studies have, thus far, yielded conflicting and variable results. Mindful of these pitfalls, we propose for the first time to measure anti-tau and anti-Aβ NAbs and their cognate antigens in the same plasma samples using specimens from carefully characterized study subjects. To gain insight on how tau, Aβ and NAbs change throughout the course of the disease, we will apply our well- characterized assays to plasma samples from 3 distinct cohorts. These will include samples that have been collected prospectively before and just after clinical onset from individuals of whom a detailed set of clinical, genetic, and histopathology data exist, and plasma from 0-65 years old DS subjects. DS is the most common genetic cause of early-onset AD and most DS adults become demented before the age of 60. Thus, studying samples from different-aged DS subjects provides a window on different stages of AD, and should also identify the optimal therapeutic interval to treat AD in DS. Combining this systematic approach with careful statistical analysis we expect to identify one, or possibly a selection of analytes, that can: (i) accurately detect subjects at risk of developing AD, and (ii) determine an appropriate age range in which to treat AD in DS.