EptB pseudogene formation as a novel mechanism of typhoidal Salmonella virulence

项目总结 肠沙门氏菌是一种高度多样化的革兰氏阴性细菌，可以 分为伤寒和非伤寒血清型。非伤寒血清型，如S. 鼠伤寒沙门氏菌可引起胃肠炎和炎症性腹泻，而伤寒血清型， 如伤寒沙门氏菌引起伤寒，伤寒是一种系统性疾病，其发病率相对较低。 炎症反应。然而，设置伤寒沙门氏菌的毒力策略 除非伤寒沙门氏菌外的其他血清型仍未得到充分研究。实验 在本申请中提出的建议旨在解决知识方面的这一重要差距。我们的长- Range的目标是阐明伤寒沙门氏菌血清型的分子机制 在感染期间操纵宿主的反应。此前，沙门氏菌的比较分析 基因组显示伤寒血清型比非伤寒血清型含有更多的假基因 伤寒血清型，表明假基因积累可能是造成差异的原因 在这些血清型引起的疾病表现中。伤寒沙门氏菌中的一个这样的假基因是EPTB， 它编码一种磷酸乙醇胺转移酶，该酶能特异性地修饰外层酮基- 脂多糖(LPS)的脱氧辛硫酸钠(KDO)残留物。我们的中心假设是 伤寒沙门氏菌EPTB假基因的形成代表了一种新的毒力机制 具有伤寒沙门氏菌特有的隐形和免疫逃避特性 血型。本申请的目标是确定EPTB通过的机制 假基因的形成缓和宿主的免疫反应，并确定如何获得 EPTB假基因与额外的假基因的积累协同促进 伤寒沙门氏菌血清型的毒力。为了检验我们的假设并实现这些 目的，我们将研究EPTB假基因的形成如何影响宿主蛋白的结合， 内毒素，调节宿主对内毒素的反应(特定目标1)，并确定如何 EPTB假基因建造抵消了对其他伤寒假基因的获取，以增强 Peyer‘s斑块定植(特指2)。我们对这一新的毒力机制的分析 伤寒沙门氏菌血清型将是有用和必要的，以了解如何相互作用 病原体和先天免疫系统之间的反应 由胃肠炎引起的伤寒，从而带来了一项重大的概念进步。

PROJECT SUMMARY Salmonella enterica is a highly diverse species of Gram-negative bacteria that can be grouped into typhoidal and non-typhoidal serovars. Non-typhoidal serovars, such as S. Typhimurium, cause gastroenteritis and inflammatory diarrhea, whereas typhoidal serovars, such as S. Typhi, cause typhoid fever, a systemic disease with a comparatively decreased inflammatory response. However, the virulence strategies that set typhoidal Salmonella serovars apart from non-typhoidal Salmonella serovars remain understudied. Experiments proposed in this application are aimed at addressing this important gap in knowledge. Our long- range goal is to elucidate the molecular mechanisms by which typhoidal Salmonella serotypes manipulate host responses during infection. Previously, comparative analysis of Salmonella genomes revealed that typhoidal serovars contain a higher number of pseudogenes than non- typhoidal serovars, suggesting that pseudogene accumulation may contribute to the differences in disease manifestation caused by these serovars. One such pseudogene in S. Typhi is eptB, which encodes a phosphoethanolamine transferase that specifically modifies the outer keto- deoxyoctulosonate (KDO) residue of lipopolysaccharide (LPS). Our central hypothesis is that eptB pseudogene formation in S. Typhi represents a novel virulence mechanism that contributes to the stealth and immune evasion properties that characterize typhoidal Salmonella serovars. The objectives of this application are to identify the mechanism by which eptB pseudogene formation moderates the host immune response and to determine how acquisition of the eptB pseudogene synergizes with accumulation of additional pseudogenes to promote the virulence of typhoidal Salmonella serovars. To test our hypothesis and accomplish these objectives, we will examine how eptB pseudogene formation impacts binding of the host protein, intelectin, to LPS to regulate host responses to LPS (specific aim 1) and also determine how eptB pseudogene formation offsets the acquisition of other typhoidal pseudogenes to enhance Peyer's patch colonization (specific aim 2). Our analysis of this novel virulence mechanism in typhoidal Salmonella serovars will be useful and necessary to understand how the interplay between pathogen and the innate immune system gives rise to responses that distinguish typhoid fever from gastroenteritis, thereby ushering in a significant conceptual advance.