Long Polar Fimbriae of Attaching and Effacing Escherichia coli

描述（由申请方提供）：附着和去除大肠杆菌（AEEC）毒力因子的表达是一个严格调控的过程，在某些情况下，由于这些因子在体外受到抑制或表达条件未知，因此难以鉴定这些因子。虽然很明显，某些毒力因子的表达与人类疾病密切相关，但AEEC菌株中存在的与其致病过程相关的其他因子仍不清楚。缺乏对编码这些额外毒力因子的基因如何被控制的充分理解是重要的，因为没有这些知识，我们不可能了解AEEC菌株的总体致病特性。因此，我们的目标是确定如何在AEEC菌株的长极性（LP）菌毛的发病机制，并使用这些菌毛编码基因作为标记，以检测强毒株。核心假设是，除了已经表征的定殖因素（例如，尽管编码这些菌毛的基因在致病性大肠杆菌中广泛分布，但AEEC菌株具有高度调节的LP菌毛，其在定殖过程中起作用。大肠杆菌菌株中，一些LP菌毛类型仅在特定的AEEC菌株中发现。我们将通过三个具体的目标来验证这一假设，即：1）确定Ler和H-NS是否作为一种选择性沉默/抗沉默防御系统来控制AEEC菌株中LP菌毛的表达; 2）鉴定控制非典型EPEC中LP菌毛表达的调节蛋白，并在兔模型中确定LP菌毛在定殖过程中的功能;（3）确定LP菌毛基因簇在AEEC菌株中的分布，并确定某些LP菌毛亚基类型是否是不同致病性AEEC菌株的可靠标记。为了实现我们的目标，我们将充分表征Ler，H-NS和非典型肠致病性E。大肠杆菌编码的调节剂在体外和体内（幼兔定植模型）条件下，并进行致病性AEEC菌株的特定子集中的lpf基因的流行率的详细研究。我们的研究工作是创新的，因为它利用了我们关于AEEC菌株中新型定植因子及其在治疗和诊断中的潜在应用的发现。控制LP菌毛表达的调控网络的研究结果具有重要意义，因为我们将能够确定根本的差异来解释不同AEEC菌株的组织向性，并确定LP菌毛沉默是否是AEEC菌株对水平获得基因的防御系统的一个例子。此外，兔模型的使用将使我们对AEEC菌株的发病机制和定植特性有新的认识。了解AEEC定植到胃肠道的机制不仅将进一步加深我们对这些微生物发病机制的了解，而且还将为降低感染率和改善针对这些生物制剂的治疗方案提供机会，这些生物制剂被归类为B类病原体，因为它们可能用作食品安全威胁。公共卫生相关性：附着和消失大肠杆菌（AEEC）代表了一组与几个国家的人类腹泻有关的分离株。大多数AEEC菌株具有高度调节的长极性（LP）菌毛，这有助于一些AEEC分离株的肠道定植过程。它们的完整表征将为AEEC定殖过程提供新的和更深入的见解，并更好地理解其控制表达的调控机制，这将成为开发新疗法和简化诊断测试的基础。

DESCRIPTION (provided by applicant): The expression of Attaching and Effacing Escherichia coli (AEEC) virulence factors is a tightly regulated process, and, in some cases, the identification of these factors has been difficult because they are either repressed in vitro or the conditions of expression are unknown. While it is evident that expression of certain virulence factors is strictly associated with human disease, the additional factors present in AEEC strains that are linked to their pathogenic process remain unclear. Lack of a full understanding of how the genes encoding these additional virulence factors are controlled is important, because, without this knowledge, we are unlikely to understand the overall pathogenic properties of AEEC strains. Thus, our objective is to determine how the Long Polar (LP) fimbriae in AEEC strains contribute to pathogenesis and to use these fimbrial-encoding genes as markers to detect virulent strains. The central hypothesis is that, in addition to the already characterized colonization factors (e.g., intimin-mediated adhesion), AEEC strains possess a highly regulated LP fimbriae, that plays a role in the colonization process, and although the genes encoding these fimbriae are widely distributed in pathogenic E. coli strains, some LP fimbriae types are found exclusively in specific AEEC strains. We will test this hypothesis through three specific aims, which are to: 1) Define whether Ler and H-NS act as a selective silencing/anti-silencing defense system that controls LP fimbriae expression in AEEC strains; 2) Identify the regulatory protein(s) controlling LP fimbriae expression in atypical EPEC and determine in a rabbit model the function of LP fimbriae during colonization; and 3) Characterize the distribution of the LP fimbrial gene clusters among AEEC strains and determine whether certain LP fimbrial subunit types are reliable markers of different pathogenic AEEC strains. To accomplish our aims, we will fully characterize the functions of Ler, H-NS, and atypical enteropathogenic E. coli-encoded regulators under in vitro and in vivo (infant rabbit colonization model) conditions and perform a detailed study of prevalence of the lpf genes in specific subsets of pathogenic AEEC strains. Our research work is innovative because it capitalizes on our findings regarding novel colonization factors in AEEC strains and their potential application in therapeutics and diagnostics. The results from studies of the regulatory networks controlling LP fimbriae expression have significance, because we will be able to identify fundamental differences to explain the tissue tropism of different AEEC strains and to determine whether silencing of LP fimbriae is an example of a defense system that AEEC strains have against horizontally acquired genes. In addition, the use of the rabbit model will give us new insight into the pathogenesis and colonization properties of AEEC strains. An understanding of the mechanisms underlying AEEC colonization to the gastrointestinal tract will not only further our knowledge of the pathogenesis of these organisms but also provide opportunities for reducing infection rates and improving treatment options against these biological agents classified as category B pathogens due t their potential use as a food safety threat. PUBLIC HEALTH RELEVANCE: Attaching and effacing Escherichia coli (AEEC) represent a diverse group of isolates implicated in diarrhea in humans in several countries. Most AEEC strains possess highly regulated Long Polar (LP) fimbriae, which contribute to the intestinal colonization process of some of the AEEC isolates. Their full characterization will provide new and deeper insights into the process of AEEC colonization, and a better understanding of their regulatory mechanisms controlling expression, which will be a basis for developing novel therapeutics and simplified diagnostic tests