Receptor Decoy Inhibitor of Anthrax Toxin

炭疽芽胞形成菌引起炭疽病，被归类为六类A之一 像生物武器一样被视为主要威胁的毒剂。由于其在疾病发病机制中的关键作用， 目前正在开发一些抑制炭疽毒素的策略，包括基于单抗的 治疗。然而，人们对细菌的易感性有很大的担忧 被设计成避免疫苗保护或抗毒素治疗，例如通过从 保护性抗原(PA)毒素亚基。下一代抗毒素开发战略，旨在解决 这一限制涉及使用可溶性受体诱骗抑制物(RDI)；推测PA不能 被设计成逃避细胞受体识别，因此RDI应该是有效的，即使是针对形式 被故意改变以抵抗抗体中和的PA。我们最近开发了一个RDI 它具有广泛作用的炭疽疗法所需的许多特性：它与受体结合 PA的结合部位，其亲和力与一些主要的治疗性抗体(Kd=0.2 nM)相当；它 通过两种已知的炭疽毒素细胞受体阻断中毒；它与PA的解离率非常高 缓慢(T1/2复合体=15小时)；它是非免疫原性的；它的生产很容易使用细菌进行缩放 表达系统；它能在化学计量浓度下中和PA，并保护老鼠免受毒素杀死。 这项研究计划代表了推进RDI作为候选疗法的综合战略 炭疽热。我们将通过破坏其与其相互作用来表征和优化其药代动力学特性 生理配体(IV型胶原和层粘连蛋白)，并利用聚乙二醇化和免疫球蛋白融合蛋白的方法。 我们还将确定这类抑制剂在中和抗体抵抗形式的PA方面是否有效，如 预期中。此外，我们将确定这种类型的抑制剂是否可以预防由Sterne引起的小鼠疾病 表达野生型或抗抗体PA的孢子。这些实验将为未来奠定基础 旨在确定RDI在预防由高毒力病毒引起的疾病方面的有效性的研究 炭疽杆菌菌株。我们预计，RDI将是一种有用的辅助炭疽热疗法，可能 与单抗协同治疗野生型细菌引起的感染，同时 时间为处理工程化、武器化的细菌菌株提供了一种直接的策略。

The spore-forming bacterium Bacillus anthracis causes anthrax, and is classified as one of six Category A agents considered as major threats as a bioweapon. Because of its pivotal role in disease pathogenesis, a number of strategies to inhibit anthrax toxin are currently under development, including monoclonal antibodybased therapies. However, there is significant concern about the ease with which the bacterium may be engineered to avoid vaccine protection or antitoxin therapy, e.g. by removing antibody-binding sites from the protective antigen (PA) toxin subunit. A next-generation strategy for antitoxin development, one that addresses this limitation, involves the use of a soluble receptor decoy inhibitor (RDI); Presumably PA cannot be engineered to evade cellular receptor recognition and therefore the RDI should be effective even against forms of PA that have been deliberately altered to resist antibody neutralization. We have recently developed an RDI which has many properties desirable in a broadly acting anthrax therapeutic: it binds to the receptor-binding site of PA with an affinity that is on a par with some of the leading therapeutic antibodies (Kd = 0.2nM); it blocks intoxication via both known cellular receptors for anthrax toxin; its dissociation rate from PA is extremely slow (t1/2 complex = 15 hours); it is non-immunogenic; its production is easily scaleable using a bacterial expression system; it can neutralize PA at stoichiometric concentrations and protects rats against toxin killing. This research plan represents a comprehensive strategy for advancing the RDI as a candidate therapy for anthrax. We will characterize and optimize its pharmacokinetic properties by disrupting its interaction with its physiological ligands (collagen IV and laminin), and by exploiting PEGylation and Ig fusion protein approaches. We will also establish if this class of inhibitor is effective at neutralizing antibody-resistant forms of PA, as expected. Moreover, we will establish if this class of inhibitor can prevent disease in mice caused by Sterne spores that express either wild-type or antibody-resistant PA. These experiments will set the stage for future studies aimed at establishing the effectiveness of the RDI in preventing disease caused by highly virulent strains of B. anthracis. We anticipate that the RDI will be a useful adjunct anthrax therapy that could potentially synergize with monoclonal antibodies to treat infections caused by wild-type bacterial strains while at the same time providing a straightforward strategy for dealing with engineered, weaponized bacterial strains.