Immune Response to Clostridium difficile

描述（由申请方提供）：艰难梭菌是医院患者感染性腹泻的最常见原因，与大量发病率、死亡率和经济成本相关。本项目的长期目标是协助开发和临床应用新型非抗生素药物来预防和治疗C。艰难梭菌相关腹泻和结肠炎。该提议的中心假设是宿主因素，尤其是对C.艰难梭菌抗原在决定C.艰难感染我们将对150例C.艰难梭菌相关性腹泻（CDAD），以检查以下三个假设中的每一个：假设1：艰难梭菌毒素A和毒素B有助于防止复发性CDAD。我们最近的研究表明，血清IgG对C。艰难梭菌毒素A在受保护免于症状性或复发性CDAD的受试者中是明显的。在这个目标中，我们将确定是否体液和细胞介导的免疫反应毒素B，免疫反应毒素A重组肽和/或毒素中和活性也与保护。假设2：复发性CDAD的风险可以根据临床参数和/或抗毒素抗体测量进行预测。基于我们先前对CDAD患者的研究（衍生队列），我们开发了预测复发准确率>80%的预测规则。在这个目标中，我们将在为特定目标1招募的150名受试者（验证队列）中前瞻性地测试这些规则。一旦得到验证，这些工具就可以用于临床实践和研究，以确定最有可能从预防复发性丙型肝炎的措施中受益的高危患者。艰难感染假设3：免疫反应C。艰难梭菌表面层蛋白（SLP）可以防止定植和/或CDAD。以往对C. difficile几乎完全集中在抗毒素抗体上。C.艰难梭菌表面层蛋白（SLP）是C.艰难梭菌，最近已经在分子水平上被表征，并且似乎充当细菌粘附素。我们的初步数据表明，对C。difficile表面层蛋白可能是保护性的。在这个目标中，我们将比较体液和细胞介导的免疫反应纯化和重组C。在CDAD单次发作受试者、复发性疾病受试者以及疾病和健康对照者中，我们还将确定是否接种抗C。difficile SLP可防止C. difficile和/或C.仓鼠艰难梭菌相关性回肠-盲肠炎。这些特定的目的是为了进一步推进我们对C.艰难梭菌毒素诱导的腹泻和人体免疫保护机制。

DESCRIPTION (provided by applicant): Clostridium difficile is the most common cause of infectious diarrhea in hospital patients and is associated with substantial morbidity, mortality and financial cost. The longterm goal of this project is to assist in the development and clinical application of novel non-antibiotic agents to prevent and treat C. difficile-associated diarrhea and colitis. The central hypothesis of this proposal is that host factors, especially the immune response to C. difficile antigens, play a major role in determining the clinical outcome of C. difficile infection. We will perform a prospective cohort study of 150 subjects with C. difficile-associated diarrhea (CDAD) to examine each of the following three hypotheses: Hypothesis 1: lmmune responses to both C. difficile toxin A and toxin B are instrumental in protecting against recurrent CDAD. Our recent studies have shown that a serum IgG response to C. difficile toxin A is evident in subjects that are protected against symptomatic or recurrent CDAD. In this aim we will determine whether humoral and cell-mediated immune responses to toxin B, immune responses to toxin A recombinant peptides and/or toxin neutralizing activity are also associated with protection. Hypothesis 2: Risk for recurrent CDAD can be predicted based on clinical parameters and or anti-toxin antibody measurement. Based on our previous study of patients with CDAD (derivation cohort) we have developed prediction rules with >80% accuracy in predicting recurrence. In this aim we will prospectively test these rules in the 150 subjects recruited for Specific Aim 1 (validation cohort). Once validated these tools can be used in clinical practice and in research studies to identify high-risk patients that are most likely to benefit from measures to prevent recurrent C. difficile infection. Hypothesis 3: lmmune responses to C. difficile Surface Layer Protein (SLP) can protect against colonization and/or CDAD. Previous studies of the immune response to C. difficile have focused almost exclusively on anti-toxin antibodies. C. difficile surface layer protein (SLP) is the predominant surface protein in C. difficile, has been characterized recently at the molecular level and appear to act as a bacterial adhesin. Our preliminary data indicate that an immune response to C. difficile surface layer protein may be protective. In this aim we will compare humoral and cell-mediated immune responses to purified and recombinant C. difficile SLP in subjects with a single episode of CDAD, those with recurrent disease and in disease and healthy controls. We will also determine whether vaccination against C. difficile SLP can prevent colonization by C. difficile and/or C. difficile associated ileo-cecitis in hamsters. These specific aims are designed to advance further our knowledge of the immunobiology of C. difficile toxin-induced diarrhea and the mechanisms of immune protection in humans.