The developing intestinal immune system in Yersinia enterocolitica infection

描述（由申请方提供）：绝大多数感染原发生在粘膜表面。了解这些部位的免疫细胞和感染性微生物的动态界面是微生物学和免疫学领域的最大挑战之一。这些相互作用在新生儿生命中第一次遇到微生物抗原时尤为重要。为了研究免疫细胞/细菌的相互作用，在新生儿期，我们已经开发了一种新的小鼠模型的口胃感染的细胞外细菌小肠结肠炎耶尔森氏菌。引人注目的是，新生儿比成年人对这种肠道病原体的抵抗力明显更强，这是所有其他研究的病原体相互作用中唯一的观察结果。该系统为了解新生儿肠道中如何实现完全保护性免疫提供了前所未有的机会。因此，本申请的一个主要目标是鉴定导致新生儿对肠道暴露于Y的抗性的真核免疫机制。小肠结肠炎本申请的第二个主要目标是应用Y。小肠结肠炎产品对调节新生儿肠道免疫力的健康和疾病。这些明确的目标将为我们的长期目标提供重要的新的构建模块，这些长期目标是：（a）了解个体发育期间肠道免疫如何发展，（B）获得高效的儿科粘膜疫苗，以及（c）开发治疗早期病理性肠道炎症的新策略。具体目标1将定义保护新生儿免受口服Y的适应性免疫机制。小肠结肠炎中和的效果？将检查IFN和/或IL-17对炎性细胞浸润、菌血症和与死亡率相关的相对体重减轻的应答。将通过遗传和急性B细胞消融以及在无法产生细菌特异性抗体应答的B细胞充足新生儿中检测B细胞应答的重要性。最后，将通过将成人Treg过继转移至感染的新生儿和通过体内耗尽Treg区室来分析天然Treg（CD 4 + CD 25+）的贡献。具体目标2将利用Y。在一些实施方案中，本发明涉及小肠结肠炎菌效应蛋白YopP（其存在或不存在）来操纵新生儿免疫应答并在体内鉴定关键靶免疫细胞类型。自从？YopP突变株诱导新生儿肠道严重炎症，我们将测试一个修改的能力？YopP突变株作为粘膜免疫的有效佐剂。卵清蛋白表达？将产生YopP菌株，并监测卵清蛋白特异性抗体和Th应答，以及卵清蛋白特异性TCR转基因T细胞的体内活化。第二，将测试YopP本身是否可以下调新生儿致病性肠道炎症。细菌（Y.小肠结肠炎菌和沙门氏菌）将被应用于调节新生儿DSS诱导的结肠炎中的炎症。此外，Y.小肠结肠炎的发病机制将确定评估NF？B激活肠细胞感染后？YopP菌株。儿童对通过受污染食物传播的微生物非常敏感。本申请有两个主要目的。首先，我们将发现生命早期的肠道免疫系统如何对微生物产生保护性反应;其次，我们将了解微生物本身的产物如何用于增强儿童疫苗反应和治疗肠道炎症，如小儿克罗恩病。

DESCRIPTION (provided by applicant): The vast majority of infectious agents are encountered at mucosal surfaces. Understanding the dynamic interface of immune cells and infectious microbes at these sites is one of the greatest challenges in the fields of microbiology and immunology. These interactions are especially important in neonatal life when microbial antigens are encountered for the first time. To study immune cell/bacterial interactions during the neonatal period, we have developed a novel murine model of orogastric infection with the extracellular bacterium Yersinia enterocolitica. Strikingly, neonates are markedly more resistant than adults to this enteropathogen, an observation unique among all other studied neonate-pathogen interactions. This system provides an unprecedented opportunity for learning how fully protective immunity is achieved in the neonatal intestine. Thus, a major goal of this application is to identify the eukaryotic immune mechanisms leading to resistance of neonates to intestinal exposure to Y. enterocolitica. A second major goal of this application is to apply Y. enterocolitica products to the regulation of neonatal intestinal immunity in health and disease. These defined goals will provide major new building blocks for our long term goals of (a) understanding how intestinal immunity develops during ontogeny, (b) achieving highly effective pediatric mucosal vaccines, and (c) developing novel strategies for the treatment of pathological intestinal inflammation in early life. Specific Aim 1 will define adaptive immune mechanisms underlying protection of neonates from oral Y. enterocolitica infection. The effects of neutralization of ?IFN and/or IL-17 responses on inflammatory cell infiltration, bacteremia, and relative weight loss associated with mortality will be examined. The importance of B cell responses will be tested by genetic and acute B cell ablation and in B cell-sufficient neonates unable to mount bacterial-specific antibody responses. Lastly, the contribution of natural Treg (CD4+CD25+) will be analyzed by adoptive transfer of adult Treg to infected neonates and by the in vivo depletion of the Treg compartment. Specific Aim 2 will exploit the Y. enterocolitica effector protein YopP (its presence or its absence) to manipulate neonatal immune responses and identify key target immune cell types in vivo. Since the ?YopP mutant strain induces profound inflammation in the neonatal intestine, we will test the capacity of a modified ?YopP mutant strain to act as a potent adjuvant for mucosal immunization. An ovalbumin - expressing ?YopP strain will be created and ovalbumin-specific antibody and Th responses will be monitored, as well as the in vivo activation of ova-specific TCR transgenic T cells. Second, the possibility that YopP, by itself, can downregulate pathogenic intestinal inflammation in neonates will be tested. Bacteria (Y. enterocolitica and Salmonella) engineered to express only YopP will be applied to modulate inflammation in DSS-induced colitis in neonates. In addition, cell types critical for Y. enterocolitica pathogenesis will be identified by assessing NF?B activation in intestinal cells following infection with the ?YopP strain. Children are highly susceptible to microbes transmitted through contaminated food. This application has two main objectives. First, we will discover how the intestinal immune system in early life develops protective responses against microbes; second, we will learn how products of the microbes themselves can be used to enhance childhood vaccine responses and treat intestinal inflammation, such as pediatric Crohn's disease.