Phagosomal Signals Shape Inflammatory Responses to B. Burgdorferi

吞噬体信号塑造对伯氏疏螺旋体的炎症反应

基本信息

批准号：
8186600
负责人：
Juan C Salazar
金额：
$ 43.7万
依托单位：
UNIVERSITY OF CONNECTICUT SCH OF MED/DNT
依托单位国家：
美国
项目类别：
财政年份：
2011
资助国家：
美国
起止时间：
2011-07-15 至 2016-06-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8186600
关键词：
Adult Anti-Inflammatory Agents Anti-inflammatory Area Bacteria Binding Bone Marrow Borrelia Borrelia burgdorferi CD14 gene Castor Bean Tick Cell surface Cells Child Clinical Communicable Diseases Complex Deer Disease Elements Event Exotoxins Generations Genes Genetic Transcription Goals Growth Human IRAK1 gene Immune Immune response In Vitro Inflammatory Inflammatory Response Interferon Type I Interferons Knockout Mice Laboratories Life Ligands Lipoproteins Lyme Disease Mediating Membrane Modeling Mus Nature Order Spirochaetales Orthologous Gene Patients Phagocytosis Phagolysosome Phagosomes Population Process Production Progress Reports Reporting Research Research Personnel Role Shapes Signal Pathway Signal Transduction Signs and Symptoms Staging Structure Surface System TLR1 gene TLR2 gene TLR8 gene Tail Techniques Ticks Tissues Toll-Like Receptor 1 United States Validation base cytokine extracellular in vivo insight macrophage monocyte novel pathogen receptor research study response vector

项目摘要

DESCRIPTION (provided by applicant): Lyme disease (LD) is a tick-borne, multi-system, infectious disorder caused by the extracellular spirochetal bacterium Borrelia burgdorferi (Bb). Since Bb lacks exotoxins or known bacterial secretory system, it is widely believed that the inflammatory manifestations of the disease result from the host's innate and co-evolving adaptive immune responses to the bacterium. Monocytes and macrophages are considered to be critical cellular elements of the innate immune response to the spirochete. For more than a decade, Bb-mediated cell activation was thought to occur chiefly as a result of the interactions of the spirochete's abundant outer membrane-associated lipoproteins with CD14 and Toll-like receptors (TLR) 1/2 on the surface of these cells. We now have extensive evidence that phagocytosis of live spirochetes by human monocytes and murine macrophages generates a more intense and far broader inflammatory response than can be attributed to lipoprotein-mediated, cell surface TLR1/2 activation. Phagocytosis of intact Bb also induced transcription of interferon-2 (IFN-2) and type I interferon-stimulated genes (ISGs), independently of TLR2. Recent evidence from the investigator's laboratory provides substantial evidence the TLR2-independent signaling events elicited by Bb in human monocytes are MyD88-dependent and occur via TLR8. On the basis of our collective findings we now propose a new model of Bb-induced monocyte activation, which emphasizes the importance of phagocytosis and the cooperative role of TLR2 and TLR8 signaling. In this model, binding of Bb to the monocyte/macrophage cell surface, through a yet to be characterized phagocytic receptor, is followed by a broad sequence of immune signaling events which mechanistically can only be integrated following internalization of the bacterium and formation of the phagolysosome. The validation of the phagosomal signaling model, the centerpiece of our research strategy, will significantly enhance our understanding for how the bacterium triggers the inflammatory processes that under actual disease conditions cause tissue damage and/or that promote bacterial clearance. To accomplish our goals and examine mechanistic aspects of the proposed model, we have formulated the following Specific aims. In Aim 1 we will use a ex vivo stimulation technique to characterize in detail the mechanisms by which phagocytosis of Bb elicits activation and TLR1/2 and TLR8 dependent inflammatory signals in human monocytes. In Aim 2, we will examine key elements of the phagosomal signaling model in Bb-infected human and murine macrophages. The use a large repertoire of available knockout mice will allow us to define mechanistically how Bb is sensed and triggers immune responses in these cells. In Aim 3 we will characterize MyD88 dependent and independent responses to Borrelia burgdorferi both in vitro and in vivo using human monocytes and macrophages obtained from children and adults with known congenital deficiencies in components of the MyD88 signaling pathway (IRAK-4 and MyD88 deficient). PUBLIC HEALTH RELEVANCE: Lyme disease (LD) is a tick-borne infectious disorder caused by the spirochetal bacteria Borrelia burgdorferi (Bb), which has continued to increase in endemic areas and has spread geographically, paralleling the distribution of its primary vector, Ixodes ricinus complex, and the explosive growth in the white-tailed deer population. To study the inflammatory responses to the LD spirochete, the investigator will use a powerful stimulation model that allows a very complete characterization for how the bacterium activates human immune cells and in parallel experiments takes advantage of the large repertoire of available knockout mice to study these responses. Using this combined translational-experimental approach, in this application the investigator will validate key elements of a proposed new model of spirochetal recognition, where the phagosome is a central platform for recognition of diverse borrelial ligands and which involves a cooperative interaction between TLR2 and TLR8 in pro- and anti-inflammatory cytokine responses, and TLR8 in IRF-7 mediated induction of IFN-2.

描述（由申请人提供）：莱姆病（LD）是一种由蜱传的多系统感染性疾病，由细胞外螺旋体细菌伯氏疏螺旋体（Bb）引起。由于Bb缺乏外毒素或已知的细菌分泌系统，人们普遍认为该疾病的炎症表现是宿主对细菌的先天和共同进化的适应性免疫反应造成的。单核细胞和巨噬细胞被认为是对螺旋体的先天免疫反应的关键细胞元件。十多年来，Bb 介导的细胞激活被认为主要是螺旋体丰富的外膜相关脂蛋白与这些细胞表面的 CD14 和 Toll 样受体 (TLR) 1/2 相互作用的结果。我们现在有大量证据表明，人类单核细胞和鼠巨噬细胞对活螺旋体的吞噬作用产生比脂蛋白介导的细胞表面 TLR1/2 激活更强烈、更广泛的炎症反应。完整 Bb 的吞噬作用还诱导干扰素 2 (IFN-2) 和 I 型干扰素刺激基因 (ISG) 的转录，与 TLR2 无关。研究人员实验室的最新证据提供了充分的证据，证明人类单核细胞中 Bb 引发的不依赖于 TLR2 的信号传导事件是 MyD88 依赖性的，并且通过 TLR8 发生。基于我们的集体发现，我们现在提出了一种 Bb 诱导的单核细胞激活的新模型，该模型强调了吞噬作用的重要性以及 TLR2 和 TLR8 信号传导的协同作用。在该模型中，Bb 通过尚未表征的吞噬细胞受体与单核细胞/巨噬细胞表面结合，随后发生一系列广泛的免疫信号事件，从机制上讲，这些事件只能在细菌内化和吞噬溶酶体形成后整合。吞噬体信号模型的验证是我们研究策略的核心，将显着增强我们对细菌如何触发炎症过程的理解，而炎症过程在实际疾病条件下会导致组织损伤和/或促进细菌清除。为了实现我们的目标并检查所提出模型的机制方面，我们制定了以下具体目标。在目标 1 中，我们将使用离体刺激技术来详细描述 Bb 吞噬作用在人单核细胞中引发激活以及 TLR1/2 和 TLR8 依赖性炎症信号的机制。在目标 2 中，我们将检查 Bb 感染的人类和小鼠巨噬细胞中吞噬体信号传导模型的关键要素。使用大量可用的基因敲除小鼠将使我们能够从机制上定义 Bb 是如何被感知并触发这些细胞中的免疫反应的。在目标 3 中，我们将使用从已知先天性 MyD88 信号通路成分缺陷（IRAK-4 和 MyD88 缺陷）的儿童和成人获得的人类单核细胞和巨噬细胞，在体外和体内表征对伯氏疏螺旋体的 MyD88 依赖和独立反应。公共卫生相关性：莱姆病 (LD) 是一种由螺旋体细菌伯氏疏螺旋体 (Bb) 引起的蜱传传染病，该病在流行地区持续增加，并在地理上蔓延，与其主要媒介蓖麻硬蜱的分布平行复杂的情况，以及白尾鹿数量的爆炸性增长。为了研究 LD 螺旋体的炎症反应，研究人员将使用强大的刺激模型，该模型可以非常完整地表征细菌如何激活人类免疫细胞，并在平行实验中利用现有的大量敲除小鼠来研究这些反应。使用这种组合的翻译实验方法，在本申请中，研究人员将验证所提出的螺旋体识别新模型的关键要素，其中吞噬体是识别不同疏螺旋体配体的中心平台，并且涉及 TLR2 和 TLR8 之间的协作相互作用。促炎和抗炎细胞因子反应，IRF-7 中的 TLR8 介导 IFN-2 的诱导。