Innate Immune Recognition and Type I IFN Response to Cytosolic Pathogens

描述（由申请人提供）：I型IFN是由宿主细胞响应病原体产生的分泌性细胞因子家族，其产生受到严格调控。I型IFN控制在抵抗感染中重要的一大组基因的转录，并且也是激活先天性和适应性免疫系统的应答所需的，所述应答包括抗原呈递和参与T细胞、B细胞和自然杀伤细胞的激活的细胞因子的产生。虽然I型IFN信号传导越来越被理解为针对入侵病原体的重要宿主防御机制，但对触发I型IFN诱导的细菌配体和相应的宿主受体知之甚少。我们的长期目标是了解如何操纵I型IFN的产生来预防和治疗自身炎症和感染性疾病。本提案的目的，这是我们追求这一目标的下一步，是确定在细菌感染过程中有助于I型IFN生产的宿主因素，使用模型胞质病原体弗朗西斯菌。我们假设，多个I型IFN刺激胞质受体激活不同的配体从胞质病原体弗朗西斯。最近的研究已经证明，免疫细胞表达几种胞质传感器，其响应于核酸配体（包括DNA、RNA和环状二核苷酸（CDN））诱导I型IFN。到目前为止，已经描述了两种一般的激活机制。首先，活细菌可以通过专门的分泌系统分泌刺激性配体到胞质溶胶中。其次，可以从裂解或降解的细菌中检测配体。从初步实验，我们认为，这两种激活机制发生在弗朗西斯感染。在这个建议中概述的实验将可能导致识别参与I型IFN信号传导的新因子，并提供对分子生物学的深入了解。 宿主抵御病原体的机制。我们建议通过以下三个目标来研究弗朗西斯菌感染过程中导致I型IFN产生的机制。目的1：确定在弗朗西斯菌感染期间，CDNs是否对I型IFN的激活重要。目的2：确定弗朗西斯菌因子，调节胞质先天免疫反应。目的3：确定胞质传感器，调节I型干扰素诱导响应弗朗西斯。我们将采取有针对性的遗传和无偏见的遗传筛查方法，以确定弗朗西斯因子，调节I型IFN的生产。此外，我们将采取遗传和生物化学的方法来确定胞质传感器，有助于I型IFN信号。这项工作将增加我们对胞质检测，先天免疫和宿主-病原体相互作用的理解。

DESCRIPTION (provided by applicant): Type-I IFNs are a family of secreted cytokines made by host cells in response to pathogens and whose production is strictly regulated. Type I IFNs control the transcription of a large group of genes important in resisting infection and are also required to activate responses of the innate and adaptive immune systems including antigen presentation and production of cytokines involved in activation of T cells, B cells and natural killer cells. While type I IFN signaling is increasingly appreciated as an important host defense mechanism against invading pathogens, little is known about the bacterial ligands and respective host receptors that trigger type I IFN induction. Our long-term goal is to understand how type I IFN production can be manipulated to prevent and treat auto-inflammatory and infectious diseases. The objective of this proposal, which is our next step in pursuit of that goal is to determine the host factors that contribute to type I IFN production during bacterial infections, using the model cytosolic pathogen Francisella. We hypothesize that multiple type I IFN-stimulating cytosolic receptors are activated by diverse ligands from the cytosolic pathogen Francisella. Recent studies have demonstrated that immune cells express several cytosolic sensors that induce type I IFNs in response to nucleic acid ligands, including DNA, RNA and cyclic-di-nucleotides (CDNs). Thus far, two general mechanisms of activation have been described. First, viable bacteria can secrete stimulatory ligands into the cytosol through specialized secretion systems. Second, ligands can be detected from bacteria that are lysed or degraded. From preliminary experiments, we believe that both mechanisms of activation occur during a Francisella infection. The experiments outlined in this proposal will likely lead to the identification of new factors involved in type I IFN signaling and provide insight on the molecular mechanisms employed by the host to protect against pathogens. We propose to study the mechanisms that lead to type I IFN production during infections with Francisella by pursuing the following three aims. Aim 1: Determine if CDNs are important for activation of type-I IFNs during Francisella infection. Aim 2: Identify Francisella factors that modulate the cytosolic innate immune response. Aim 3: Identify cytosolic sensors that regulate type-I IFN induction in response to Francisella. We will take targeted genetic and unbiased forward genetic screen approaches to identify Francisella factors that modulate type I IFN production. Additionally, we will take genetic and biochemical approaches to identify cytosolic sensors that contribute to type I IFN signaling. This work will increase our understanding of cytosolic detection, innate immunity and host-pathogen interactions.