Development of a novel antibody therapy for clostridium difficile infection

描述（由申请人提供）：艰难梭菌是医院和社区获得性胃肠道感染的常见原因，可能发生在患者用各种抗菌药物治疗其他感染后。虽然主要引起抗生素相关性腹泻，但艰难梭菌感染可能导致更严重的疾病，并且可能对目前的标准治疗形式难以治愈。近年来，出现了一种毒性更强的艰难梭菌菌株，在一些患者中引起了严重的疾病。艰难梭菌感染的发病机制尚不完全清楚，但它涉及有机体产生的毒素a （TcdA）和毒素b （TcdB）两种毒素对肠道上皮的作用。有很好的证据表明，针对TcdA和TcdB的抗体对人类和艰难梭菌结肠炎动物模型具有保护作用。本研究的目的是通过克隆艰难梭菌感染个体的人单克隆抗体（mab）来开发一种基于抗体的艰难梭菌感染免疫疗法，并利用仓鼠感染模型确定这些抗体是否可以预防疾病。这些抗体将在体外通过噬菌体展示系统克隆患者的抗体来生产，这项研究的联合研究员唐纳德·西格尔博士是这项技术的先驱之一。毒素特异性抗体将在体外产生，并将测试这些抗体保护动物免受艰难梭菌结肠炎的能力。在过去的15年里，利用这项技术已经生产出了针对大量人类自身抗原和异体抗原以及人类感染因子具有特异性的人类单克隆抗体。因此，噬菌体展示技术是一种理想的生产完全人类蛋白质的方法，这种方法利用人类免疫系统的能力，产生大量高亲和力、抗原选择、对疾病相关表位具有不同特异性的抗体。鉴于将在本提案中开发的大量抗体，该策略将提供足够的试剂进行表征，并允许我们选择最佳抗体（或抗体组合）作为治疗用途的先导化合物。

DESCRIPTION (provided by applicant): Clostridium difficile is a common cause of both hospital- and community acquired gastrointestinal infection that may occur after patients have been treated for other infections with a variety of antimicrobial agents. While mostly causing antibiotic-associated diarrhea, C. difficile infection may cause more severe disease and may be refractory to current standard forms of therapy. In recent years, a more virulent strain of C. difficile has emerged that has caused serious disease in some patients. The pathogenesis of C. difficile infection, while not completely understood, involves the action of two toxins, toxin-A (TcdA) and toxin-B (TcdB), produced by the organism, on the gut epithelium. There is very good evidence showing that antibodies against TcdA and TcdB have protective effects against disease in humans and in animal models of C. difficile colitis. The purpose of the current study is to develop an antibody-based immunotherapy for C. difficile infection by cloning human monoclonal antibodies (mAbs) from individuals with C. difficile and determine whether these antibodies can protect against disease using a hamster model of infection. The antibodies will be produced in vitro by cloning patients' antibodies using a phage display system, a technique for which Dr. Donald Siegel, Co- Investigator of the study, is among the pioneers. Toxin specific antibodies will be produced in vitro and will be tested for the ability of these antibodies to protect animals from developing C. difficile colitis. Use of this technology over the past 15 years has produced human monoclonal antibodies with specificities against a large number of human auto- and alloantigens, and human infectious agents. Thus, phage display technology is an ideal approach for producing completely human proteins in a way that exploits the human immune system's ability to generate large repertoires of high affinity, antigen selected, antibodies with varying specificities for disease- associated epitopes. Given the multitude of antibodies that will be developed in this proposal, the strategy will provide enough reagents for characterization and allow us to choose optimal antibodies (or combinations of antibodies) as lead compounds for therapeutic use. PUBLIC HEALTH RELEVANCE: C difficile is one of the most common causes of antibiotic associated diarrhea in healthcare settings as is being increasingly recognized as a community acquired infection. Patients with nosocomially acquired C. difficile disease incur significantly higher hospital costs and length of stay and has been estimated to exceed 1 billion dollars in the US. Thus, C. difficile disease is of considerable public health concern.