Bacterial effector inhibition of type I interferon

描述（由申请人提供）：我们发现一种名为NleB的大肠杆菌蛋白是宿主干扰素（IFN）产生的有效抑制剂，该蛋白是高度保守的，并由对人类健康有重要意义的附着/清除（A/E）细菌病原体表达。IFN最初被发现是一种由病毒感染细胞分泌的因子，能够介导保护其他细胞免受随后的病毒感染。令人信服的是，I型IFN不仅对抗病毒防御很重要，而且对宿主防御细菌感染也很重要。 由肠道细菌引起的腹泻病是一种主要的地方性健康威胁，也是食源性疾病日益频繁的来源。在这些肠道致病菌中，肠致病性E.大肠埃希菌（EPEC）和肠出血性大肠杆菌（E.大肠埃希菌（EHEC）分别是引起婴幼儿腹泻和出血性结肠炎的常见原因。肠出血性大肠杆菌尤其重要，因为它是小儿肾衰竭的主要原因。 虽然已知细菌和病毒病原体已经进化出干扰哺乳动物I型IFN信号传导的策略，但是之前尚未观察到通过III型分泌系统（T3 SS）（革兰氏阴性病原体的重要毒力策略）易位的细菌效应蛋白能够抑制I型IFN产生的程度。这些研究将阐明，第一次，T3 SS效应器抑制IFN-？在受感染的细胞中生产。 具体目标是：1）表征NleB结合导致IFN-γ降低的宿主蛋白？在被附着/去除病原体感染的细胞中产生。2)通过附着/清除病原体确定NleB和感染对TBK 1的差异活化与降解相关泛素化的影响，TBK 1是激活I型IFN应答所必需的宿主蛋白激酶。 拟议的实验将对人类健康产生重大的积极影响，因为它们将使我们能够阐明肠道病原体通过抑制宿主先天免疫反应促进其生存的新机制。首先，确定宿主靶点和分子机制，NleB抑制IFN-？生产将提供一个重要的进展，我们的理解T3 SS效应靶点和机制在感染。值得注意的是，T3 SS效应子和I型干扰素通路之间的相互作用以前没有报道。其次，阐明NleB功能可能会提出新的治疗策略，以打击细菌性牙周病。此外，我们的研究可能会提高对病毒-细菌合并感染的理解，并最终改善对病毒-细菌合并感染的治疗，因为NleB介导的I型IFN抑制有可能加重由胃肠道嗜性病毒介导的肠道疾病。

DESCRIPTION (provided by applicant): We have discovered that an Escherichia coli protein named NleB, which is highly conserved and expressed by the attaching/effacing (A/E) bacterial pathogens of significance to human health, is a potent inhibitor of host interferon (IFN) production. IFN was originally discovered as a factor secreted by virally infected cells able to mediate protection of other cells from subsequent viral infection. It has become convincingly clear that type I IFNs are important not only to anti-viral defense but also to host defense against bacterial infection. Diarrheal disease caused by enteric bacteria is a major endemic health threat and an increasingly frequent source of foodborne illness. Among these enteric pathogens, enteropathogenic E. coli (EPEC) and enterohemorrhagic E. coli (EHEC) are frequent causes of infantile diarhea and hemorhagic colitis, respectively. EHEC is especially significant because it is a leading cause of pediatric renal failure. While it is known that bacterial and viral pathogens have evolved strategies to interfere with mammalian type I IFN signaling, the extent to which bacterial effector proteins translocated by type III secretion systems (T3SS), an important virulence strategy of Gram-negative pathogens, are able to inhibit type I IFN production, has not been observed previously. These studies will elucidate, for the first time, the mechanism by which a T3SS effector inhibits IFN-? production in infected cells. The specific aims are to: 1) Characterize the host protein(s) to which NleB binds that results in decreased IFN-? production in cells infected by attaching/effacing pathogens. 2) Determine the impact of NleB and infection by attaching/effacing pathogens on the differential activation vs. degradation-associated ubiquitination of TBK1, a host protein kinase essential to activation of type I IFN responses. The proposed experiments will have a significant positive impact on human health because they will allow us to elucidate a novel mechanism by which enteric pathogens promote their survival by suppressing the host innate immune response. First, determining the host target of and molecular mechanism by which NleB inhibits IFN-? production will provide an important advance in our understanding of T3SS effector targets and mechanisms during infection. Notably, interplay between T3SS effectors and the type I interferon pathway has not been previously reported. Second, elucidating NleB function may suggest novel therapeutic strategies to combat bacterial diarrheal diseases. Additionally, our studies may improve the understanding of and eventually improve the treatment for viral-bacterial co-infections, as NleB-mediated suppression of type I IFN has the potential to exacerbate diarrheal illness mediated by viruses with gastrointestinal tropism.