Synergistic extra and intracellular recognition of F. tularensis

描述(申请人提供)：表面表达的Toll样受体(TLRs)和一类新描述的胞质模式识别受体(PRRs)，属于Nod样受体(NLR)家族成员，在对抗A类生物制剂--细胞内病原体Francisella tularensis的天然宿主防御中发挥重要作用。最近有研究表明，图拉氏疟原虫在免疫细胞中触发TLR2信号，这种PRR的突变与感染的易感性增加有关。同样，通过含有半胱氨酸天冬氨酸氨基转移酶招募结构域(ASC)的凋亡相关斑点样蛋白(ASC)、NLR接头分子和随后的caspase-1激活信号对于诱导对图拉氏丝虫病的保护性免疫是必不可少的。一个有趣的问题仍然没有答案是TLR和NLR信号通路之间的确切关系，以及响应F.tularensis的NLR的激活是发生在TLRs下游还是独立于TLR信号。此外，触发下游信号事件的图拉氏丝虫特异性成分(S)和NLR途径的受体(S)尚不清楚。本研究试图通过以下具体目的来解决这些问题：1)鉴定激活NLR途径的土拉氏杆菌SchuS4组分(S)，并评价部分NLRs在介导对土拉F杆菌的促炎反应中的作用。2)建立了TLR2和NLR信号通路整合的关键部位。这项提议将研究先天免疫关键组成部分之间信号整合的细胞生物学，以及这些在细胞水平上的过程如何有助于宿主抵抗微生物挑战的能力。确定先天免疫的分子机制(S)将是发展免疫治疗以及有效的疫苗策略以对抗各种细胞内细菌病原体的必要的第一步。这一建议是创新的，因为它提供了一种综合的方法来探索在我们CDC批准的ABSL3/BSL3设施中感染图拉氏杆菌SchuS4后细胞外和细胞内天然免疫机制之间相对未知的信号整合。这项研究将确定负责触发胞液机制的图拉氏杆菌组分(S)和受体(S)，并阐明整合细胞外和细胞内信号以诱导最佳先天免疫反应的分子机制。公共卫生相关性：这项提案旨在调查图拉热症的免疫病理机制，图拉热症是一种由A类生物制剂图拉氏菌引起的人畜共患病。这些研究将集中于探索先天免疫关键组成部分之间信号整合的细胞生物学，以及这些细胞水平上的过程如何有助于宿主抵抗微生物挑战的能力。确定先天免疫的分子机制(S)将是发展免疫治疗以及有效的疫苗策略对抗这种致命疾病的必要的第一步。

DESCRIPTION (provided by applicant): Surface-expressed Toll-like receptors (TLRs) and a newly described class of cytosolic pattern recognition receptors (PRRs), members of the Nod-like receptor (NLR) family, play a major role in innate host defense against the intracellular pathogen Francisella tularensis, a category A biothreat agent. Recently it was shown that F.tularensis triggers TLR2 signaling in immune cells and that mutation of this PRR is associated with greater susceptibility to infection. Similarly, signaling through apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC), an NLR adaptor molecule, and subsequent caspase-1 activation were shown to be essential for eliciting protective immunity to F. tularensis infection. One intriguing question which remains unanswered is the precise relationship between the TLR and NLR signaling pathways and whether activation of NLRs in response to F. tularensis occurs downstream of TLRs or proceeds independent of TLR signaling. Furthermore, the specific component(s) of F. tularensis that triggers the downstream signaling events and the receptor(s) of the NLR pathways are not known. This proposal seeks to address these issues by testing the hypothesis that integration of signals transduced via the TLR2 and NLR pathway is required for the optimal development of innate immune responses to F. tularensis infection via the following Specific Aims: 1) Identify the F. tularensis SchuS4 component(s) activating the NLR pathway and evaluate the role of select NLRs in mediating the pro-inflammatory responses to F. tularensis. 2) Establish the key sites of integration between the TLR2 and NLR signaling pathways in response to F. tularensis SchuS4. This proposal will study the cell biology of signal integration between key components of innate immunity and how these processes at the cellular level contribute to the host's ability to resist microbial challenge. Defining the molecular mechanism(s) of innate immunity will be an essential first step towards development of immunotherapeutic, as well as effective vaccine strategies to combat a variety of intracellular bacterial pathogens. This proposal is innovative because it provides a comprehensive approach to explore the relatively unknown signal integration between extra- and intracellular innate immune mechanisms following F. tularensis SchuS4 infection in our CDC-approved ABSL3/BSL3 facility. This study will identify the F. tularensis component(s) and the receptor(s) responsible for triggering the cytosolic machinery and elucidate the molecular mechanisms by which extra- and intracellular signals are integrated to elicit an optimal innate immune response. PUBLIC HEALTH RELEVANCE: This proposal aims to investigate the immunopathologic mechanisms underlying tularemia, a zoonotic disease caused by Francisella tularensis, a Category A biothreat agent. The studies will focus on exploring the cell biology of signal integration between key components of innate immunity and how these processes at the cellular level contribute to the host's ability to resist microbial challenge. Defining the molecular mechanism(s) of innate immunity will be an essential first step towards development of immunotherapeutic, as well as effective vaccine strategies to combat this fatal disease.