Targeting cross-linked amyloid protein species as a therapy for AD.

描述(由申请人提供)：抗体蛋白在b-淀粉样蛋白沉积中过度积累是阿尔茨海默病(AD)的一个标志性事件。近年来，一些最有前景的增强β-淀粉样蛋白清除的治疗策略涉及到抗抗体的使用。在转基因阿尔茨海默病动物模型中，外周注射外源性抗抗体抗体(被动)或合成抗体免疫诱导自身免疫(主动)均可抑制淀粉样蛋白沉积。不幸的是，后一种方法与潜在的致命并发症有关，涉及人类中枢神经系统的炎症。虽然到目前为止的实验使用了未经修饰的单体抗体来测试自身免疫，但AD大脑中高达40%的抗体池由低分子量低聚交联型b-淀粉样蛋白物种(CAPS)组成。此外，大量证据表明，可溶性CAPS是AD的主要神经毒剂。我们最近报道，虽然抗单体抗体的自身抗体水平在AD和非痴呆对照组的血浆中相似，但抗CAPS的自身抗体在AD患者中显著降低。此外，阿尔茨海默病的发病年龄与血浆对CAPS的免疫反应有关。基于这些发现，我们假设针对CAPS的抗体亚库正常情况下可能提供对AD发病的自然防御，但在AD患者中被耗尽。因此，补充抗CAPS抗体的水平可能会为AD提供治疗益处。在拟议的研究中，我们计划a)确定具有最高神经毒性潜力的CAPS，b)使用重组噬菌体展示系统选择针对神经毒性最强的CAPS的单链片段可变抗体(ScFv)，以从超过10^12个人源性抗体的载体库中鉴定CAPS特异的免疫活性scFv，以及c)测试抗CAPS scFv抗体在减轻CAPS神经毒性的皮层神经元原代培养中的活性。我们假设，使用人源性抗体靶向可溶性CAPS可能比以前基于疫苗的AD治疗策略具有明显的优势，后者使用了更多的通用抗抗体。最后，关于被动免疫疗法，通过专门针对与AD病理最相关的抗体种类，可能会开出较低的抗抗体效价，从而减轻与炎症相关的潜在副作用。

DESCRIPTION (provided by applicant): Excessive accumulation of Ab protein in b-amyloid deposits is a hallmark event in Alzheimer's disease (AD). In recent years, some of the most promising therapeutic strategies for potentiating b-amyloid clearance has involved the use of anti-Ab antibodies. In transgenic animal models of AD b-amyloid deposition can be inhibited by either peripheral infusion of exogenous anti-Ab antibodies (passive) or autoimmunity induced by immunization with synthetic Ab peptide (active). Unfortunately, the latter approach has been associated with potentially fatal complications involving inflammation of the CNS vasculature in humans. While experiments to date have employed unmodified monomeric Ab to test for autoimmunity, up to 40 % of the Ab pool in AD brain consists of low molecular weight oligomeric cross-linked b-amyloid protein species (CAPS). Moreover, numerous lines of evidence have implicated soluble CAPS as the primary neurotoxic agent in AD. We have recently reported that while levels of autoantibodies to monomeric Ab are similar in the plasma of AD and non-demented control subjects, autoantibodies to CAPS are significantly reduced in AD patients. In addition, age-at-onset for AD correlates with plasma immunoreactivity to CAPS. Based on these findings, we hypothesize that the sub-pool of Ab autoantibodies targeted at CAPS may normally provide a natural defense against AD pathogenesis, but are depleted in AD patients. Accordingly, replenishing the level of anti-CAPS antibodies could potentially provide therapeutic benefit for AD. In the proposed study we plan to a) identify CAPS with the highest neurotoxic potential, b) select single-chain fragment variable antibodies (scFvs) specific for the most neurotoxic CAPS using recombinant phage display system to identify CAPS-specific immunoreactive scFvs from a vector library of over 10^12 human derived antibodies, and, c) test anti-CAPS scFv antibodies for activity in attenuating CAPS neurotoxicity in primary cultures of cortical neurons. We posit that targeting soluble CAPS with human derived antibodies may have distinct advantages over previous vaccine-based AD treatment strategies that have employed more generic anti-Ab antibodies. Finally, with regard to passive immunization therapies, by specifically targeting the Ab species that are most relevant to AD pathology, lower anti-Ab antibody titers might be prescribed, thereby attenuating potential side-effects associated with inflammation.