Innate Immune Recognition and Type I IFN Response to Cytosolic Pathogens

描述（由申请人提供）：i型干扰素是宿主细胞对病原体反应产生的一种分泌型细胞因子家族，其产生受到严格调控。I型ifn控制着一组对抵抗感染很重要的基因的转录，也需要激活先天和适应性免疫系统的反应，包括抗原呈递和细胞因子的产生，这些细胞因子参与T细胞、B细胞和自然杀伤细胞的激活。虽然I型IFN信号越来越被认为是一种重要的宿主防御病原体入侵的机制，但人们对触发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控制I型IFN的产生，以预防和治疗自身炎症和感染性疾病。该提案的目标是，我们追求这一目标的下一步是确定在细菌感染期间促进I型IFN产生的宿主因素，使用模型胞质病原体Francisella。我们假设多种I型ifn刺激胞质受体被来自胞质病原体Francisella的不同配体激活。最近的研究表明，免疫细胞表达几种细胞质传感器，诱导I型ifn响应核酸配体，包括DNA、RNA和环二核苷酸（cdn）。到目前为止，已经描述了两种一般的激活机制。首先，活菌可以通过专门的分泌系统将刺激配体分泌到细胞质中。其次，可以从被裂解或降解的细菌中检测到配体。从初步实验来看，我们认为这两种激活机制都发生在弗朗西斯菌感染期间。本提案中概述的实验可能会导致识别参与I型IFN信号传导的新因子，并提供对分子的见解

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.