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耗性疾病，由鸟分枝杆菌副结核亚种（MAP）感染引起，通过污染的牛奶和粪-口途径传播。 由于约翰氏病的体征和症状通常需要数年才能发展（在此期间MAP可以在粪便中脱落），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。目前的努力，以了解MAP入侵和感染的关键方面受到阻碍的实验动物模型的使用，不反映其自然传播的重要方面。 在这项资助中，我们建议开发新的实验模型来研究约翰氏病的发病机制。 在我们计划的第一部分，我们将在小鼠中建立一个模型，该模型使用反映反刍动物自然感染的条件。 由于反刍动物在发生约翰氏病之前通过口服途径长时间感染低剂量MAP，我们将使用相同的参数感染小鼠。 在我们计划的第二部分，我们将开发一个模型，使我们能够评估MAP入侵宿主的各个方面，通过从小鼠和牛的肠道干细胞中分离培养“迷你肠”或“肠样细胞”。 这些肠状结构将使我们能够实时观察MAP在其微注射到管腔中后进入宿主细胞的过程。* 通过开发这些模型，它将使我们能够检查MAP进入和感染的各个方面，与宿主的反应相一致。 我们计划的最后一个方面将是使用我们的新模型来研究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，我们认为这些药物与宿主中的特定受体相互作用，最终影响其对发生约翰氏病的易感性。** 我们预计，从我们的计划产生的新知识将提供显着深入了解约翰氏病的发病机制。 我们将开发和验证的模型将产生广泛的影响，并可供加拿大及其他地区的研究人员使用，以研究MAP并评估新疗法治疗牲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.**