The regulation of the intestinal epithelium and host-pathogen interactions by the constitutive androstane receptor

约翰氏病是反刍动物的一种消瘦病症，是由鸟分枝杆菌亚种副结核（MAP）感染引起的，这种疾病通过受污染的牛奶和粪口途径传播。由于约翰氏病的体征和症状往往需要数年才能形成（在此期间MAP可随粪便排出），因此很难实施传统的监测方法来减少其传播。为了限制家畜和天然反刍动物的传染病负担，我们必须了解导致病原体传播、入侵和宿主炎症反应的步骤。***使用的实验动物模型不能反映其自然传播的重要方面，阻碍了目前了解MAP侵袭和感染关键方面的努力。在这笔拨款中，我们建议开发新的实验模型来研究约翰氏病的发病机制。在我们节目的第一部分，我们将在老鼠身上建立一个模型，该模型使用反映反刍动物自然感染的条件。由于反刍动物在患约翰氏病之前，通过低剂量MAP的长期口服途径感染，我们将使用相同的参数来感染小鼠。在我们计划的第二部分，我们将开发一个模型，通过从小鼠和牛的肠道干细胞中分离出培养的“迷你肠道”或“类肠道”，使我们能够评估MAP入侵宿主的各个方面。这些肠样体将使我们能够实时观察MAP在微注射进入管腔后进入宿主细胞的情况。通过开发这些模型，将使我们能够根据宿主的反应检查MAP进入和感染的各个方面。我们计划的最后一个方面将是使用我们的新模型来检查环境刺激在调节宿主对MAP的反应中所起的作用。由于家畜和天然反刍动物暴露于各种环境来源的化合物，我们假设这些物质与宿主中的特定受体相互作用，最终影响其对约翰氏病的易感性。*** ***我们预计，从我们的项目中产生的新知识将为约翰氏病的发病机制提供重要的见解。我们将开发和验证的模型将产生广泛的影响，并可被加拿大各地及其他地区的研究人员用于研究MAP并评估新疗法治疗家畜和天然反刍动物约翰氏病的疗效

Johne's disease, a wasting condition in ruminants, is caused by infection with Mycobacterium avium subspecies paratuberculosis (MAP), which is transmitted via contaminated milk and through the fecal-oral route. Since signs and symptoms of Johne's disease often take years to develop (during which MAP can be shed in the feces), it is difficult to implement traditional surveillance methods to reduce its spread. To limit the burden of infectious disease in livestock and natural ruminants we must understand the steps that lead to pathogen transmission, invasion and the host inflammatory response.***Current efforts to understand key aspects of MAP invasion and infection are hindered by the use of experimental animal models that do not reflect important aspects of its natural transmission. In this grant, we propose to develop new experimental models to study the pathogenesis of Johne's disease. In the first portion of our program, we will develop a model in mice that uses conditions that reflect the natural infection in ruminants. Since ruminants are infected via the oral route with low doses of MAP over extended periods of time, prior to developing Johne's disease, we will use the same parameters to infect mice. In the second part of our program, we will develop a model that will allow us to assess aspects of MAP invasion into the host, by generating cultured “mini-guts” or “enteroids” from intestinal stem cells isolated from mice and cattle. These enteroids will allow us to visualize, in real-time, the entry of MAP into host cells following its micro-injection into the lumen. ***By developing these models, it will allow us to examine aspects of MAP entry and infection, in concert with the host's response. The final aspect of our program will be to use our new models to examine the role that environmental stimuli play in regulating the host's response to MAP. Since livestock and natural ruminants are exposed to a variety of compounds of environmental origin, we posit that these agents interact with specific receptors in the host, which ultimately affect its susceptibility to developing Johne's disease. *** ***We anticipate that the new knowledge generated from our program will provide significant insight into the pathogenesis of Johne's disease. The models that we will develop and validate will have broad-reaching impact, and could be used by investigators across Canada and beyond, to study MAP and evaluate the efficacy of new therapeutics to treat Johne's disease in livestock and natural ruminants.**