RELATIONSHIP OF IMMUNITY AND DISEASE DUE TO C DIFFICILE

本申请是为了响应第25号试点研究课题（疫苗和免疫反应）。首席研究员是一位新研究员。本项目将研究血清和结肠抗体对艰难梭菌的反应与疾病表达之间的关系。这是一项初步临床研究，旨在为开发和测试用于老年人的艰难梭菌疫苗提供重要信息。艰难梭菌相关疾病（CDAD）是一种重要的医源性医院疾病，主要影响老年患者。这种疾病的常规抗生素治疗与高复发率和微生物中抗菌素耐药性的出现有关。目前正在研究用抗体产品进行免疫治疗，作为一种替代疗法，并正在开发预防CDAD的人用疫苗。了解免疫反应的动力学，特别是与衰老的关系，以及预防疾病所需的抗原特异性和抗体水平，对疫苗开发至关重要。我们的初步研究表明，定殖后血清和结肠抗体反应与疾病表达之间存在关联。然而，这些初步研究的解释受到样本量小、回顾性研究设计和未能控制潜在混杂因素（如年龄）的限制。我们将确定并前瞻性随访300名有艰难梭菌感染危险因素的住院患者。将获得一系列粪便和血清样本，以确定患者的难辨梭菌定植，并检查定植的免疫反应动力学。ELISA检测艰难梭菌毒素和非毒素抗原血清IgG、IgM和IgA、粪便IgA和IgG。抗毒素中和活性将通过组织培养细胞毒性试验进行评估。将对所有年龄的成年患者进行研究，以确定年龄对抗体反应的影响。将区分不同结局的患者（无定植、无症状定植、有症状定植、病情严重、病情复发），并比较其血清和结肠anti-C。艰难梭菌抗体反应。通过这个过程，我们希望确定抗原特异性抗体和水平，如果有的话，保护患者免受定植，疾病表达，严重和复发的疾病。这些数据将用于建立替代保护标记物，用于即将进行的人类艰难梭菌疫苗试验。

This application is in response to the pilot research topic number 25 (Vaccines and immune response). The principal investigator is a new investigator. This project will examine the relationship between serum and colonic antibody responses to Clostridium difficile and disease expression. It is a preliminary clinical study designed to provide essential information for the development and testing of a vaccine against C. difficile for use in elderly populations. C. difficile-associated disease (CDAD) is an important iatrogenic, nosocomial condition which affects predominantly older patients. Conventional antibiotic therapy of this condition is associated with a high relapse rate and the emergence of antimicrobial resistance among micro-organisms. Immunotherapy with antibody products is being investigated as an alternative form of therapy and work is underway to develop a human vaccine for the prevention of CDAD. Knowledge of the kinetics of the immune response, particularly in relationship to aging, and the antigen specificity and level of antibody needed to protect against disease would be vital for vaccine development. Our preliminary studies suggest an association between serum and colonic antibody response and disease expression following colonization. However, interpretation of these preliminary studies is limited by their small sample sizes, retrospective study design, and failure to control for potential confounders, such as age. We will identify and prospectively follow a cohort of 300 hospitalized patients with risk factors for C. difficile. Serial stool and serum samples will be obtained to identify patients colonized with C. difficile and to examine the kinetics of the immune response to colonization. Serum IgG, IgM and IgA, fecal IgA and IgG against C. difficile toxins and non-toxin antigens will be measured by ELISA. Anti-toxin neutralizing activity will be assessed by tissue culture cytotoxicity assay. Adult patients of all ages will be studied, to determine the effect of age on antibody response. Patients with different outcomes will be identified (no colonization, asymptomatic colonization, symptomatic colonization, severe disease, relapsing disease) and compared in terms of their serum and colonic anti-C. difficile antibody responses. By this process, we hope to determine the antigen-specific antibody and level, if any, which protects patients against colonization, disease expression, severe and relapsing disease. These data will be used to establish surrogate markers of protection for use in upcoming human C. difficile vaccine trials.