Toll-Like Receptors and Immunity to F. tularensis

项目3说明(申请人提供)：图拉氏方济氏菌为革兰氏阴性杆菌 是图拉热症的病原体的细菌，图拉热症是一种高度传染性的疾病，在 人类，特别是肺炎的形式。土拉藻是一种理想的生物武器，因为它具有 极低的LD50，易于气雾剂传播。如果及早诊断，这种疾病是可以用抗生素治疗的，但目前没有获得许可的疫苗，因此，如果大规模接触，人群面临相当大的风险。许多研究都集中在对图拉氏亚种减毒活疫苗株(LVS)的免疫上。但对由高毒力的图拉氏杆菌亚种引起的肺炎性图拉热症期间的免疫反应几乎一无所知。图拉尔人。Toll样受体是关键的先天免疫反应元件，通过识别许多病原体表达的分子中保守的、重复的模式，作为第一道防线。TLRs通过诱导趋化因子、促炎细胞因子和共刺激分子的表达，向细胞发出先天反应的信号，并形成随后的获得性免疫，因此是新型佐剂和疫苗的重要靶点。我们的初步研究表明，MyD88小鼠的原代肺泡巨噬细胞在感染图拉氏原虫LVS时分泌肿瘤坏死因子-α的能力存在缺陷，并且MyD88-/-和TLR2-/-小鼠对LVS感染的易感性增加。近期 已发表的研究表明，图拉氏丝虫可能逃避宿主的先天免疫反应。这项工作的中心假设是，TLR信号的激活/抑制在确定肺部对图拉氏福氏杆菌强毒力气溶胶感染的先天反应的性质中起着关键作用。拟议的研究将在小鼠肺炎图拉热症的气雾剂感染模型中检验这一假设。我们将1)确定TLR信号在宿主对图拉氏丝虫亚种肺部感染反应中的作用。图拉氏菌(Schu4)利用KO小鼠和siRNA进行免疫调节；2)识别和表征TLR调节的免疫效应机制，涉及肺图拉热症的先天反应；以及3)确定图拉氏菌逃避宿主先天免疫反应的TLR信号调节机制。我们期望，这些研究将为我们理解图拉氏杆菌强毒力的整体免疫发病机制提供重要的进展，并将为了解Toll样受体在宿主对肺炎图拉热症的先天反应中的作用提供重要的见解。

PROJECT 3 DESCRIPTION (provided by applicant): Francisella tularensis is a gram-negative bacterium that is the causative agent of tularemia, a highly infectious disease that can be fatal in humans, particularly in the pneumonic form. F. tularensis is an ideal bioweapon because of its extremely low LD50 and ease of aerosol dissemination. The disease is treatable with antibiotics if diagnosed early, but there is no licensed vaccine currently available and, therefore the population is at considerable risk in case of mass exposure. Many studies have focused on immunity to an attenuated live vaccine strain (LVS) derived from F. tularensis subsp. holoarctica, but virtually nothing is known about the immune response during pneumonic tularemia caused by the highly virulent F. tularensis subsp. tularensis. Toll-like receptors (TLRs) are critical innate immunity response elements that serve as a first line of defense by recognizing conserved, repeated patterns in molecules expressed by many pathogens. TLRs signal cells of the innate response and shape subsequent adaptive immunity by inducing expression of chemokines, pro-inflammatory cytokines and co-stimulatory molecules and thus are important targets for new adjuvants and vaccines. Our preliminary studies demonstrate a defect in the ability of primary alveolar macrophages from MyD88 mice to secrete TNF-a upon infection with F. tularensis LVS and increased susceptibility of MyD88-/- and TLR2-/- mice to LVS infection. Recent published studies suggest that F. tularensis may evade host innate immune responses. The central hypothesis for the proposed work is that activation/inhibition of TLR signaling plays a critical role in determining the nature of the innate response in the lung to aerosol infection by virulent F. tularensis. The proposed studies will test this hypothesis in an aerosol infection model of pneumonic tularemia in the mouse. We will 1) determine the role of TLR signaling in the host response to pulmonary infection with F. tularensis subsp. tularensis (Schu4) using KO mice and SiRNA; 2) identify and characterize TLR-regulated immune effector mechanisms that are involved in the innate response to pulmonary tularemia; and 3) define TLR signal-modulating mechanisms by which F. tularensis evades the host innate immune response. We expect that these studies will provide significant advances in our understanding of the overall immunopathogenesis of virulent F. tularensis and will provide critical insight into the role of Toll-like receptors in the host innate response to pneumonic tularemia.