Exploiting a cyclic dinucleotide-mediated immune response to reduce the burden of Coxiella burnetii infection

项目概要/摘要： 环状二核苷酸（Cyclic dinucleotides，CDN）在革兰氏阴性菌中发挥重要的第二信使作用， 调节许多不同类型的细菌过程，例如运动性、生物膜形成、宿主 定植、细菌生长和代谢。CDN水平由细菌编码的 二鸟苷酸/二腺苷酸环化酶和磷酸二酯酶。除了调节细菌的生命周期 在感染过程中，CDN可以提醒先天免疫反应。一种主要的细胞溶质传感器， 在动物宿主中的胞内CDN是STING，其在其激活时触发先天免疫应答 通过诱导I型干扰素和促炎细胞因子。因此，合成CDN已经被 在感染前外源性应用，以刺激炎性体活性并减少衣原体负荷 沙眼衣原体，一种革兰氏阴性专性细胞内细菌。因此，CDN可用于启动免疫 除了标准的两周抗生素治疗外，治疗衣原体感染的反应。 另一种革兰氏阴性、专性细胞内嗜巨噬细胞细菌是贝氏柯克斯体， 是人畜共患病Q热的病原体。柯克斯体传播的主要途径是通过 气溶胶然而，柯克斯体也在蜱虫中发现，它们被认为是媒介。急性期 这种疾病在人类中的主要特征是流感样症状， 慢性感染必须接受18-24个月的抗生素治疗。我们认为，替代方法， 需要开发目前的抗生素治疗以减少感染动物中的柯克斯体负荷。我们的初步 数据表明，CDN在Coxiella感染期间产生，并且Coxiella基因组含有 编码二鸟苷酸/二腺苷酸环化酶和磷酸二酯酶的推定基因。然而， 关于CDN如何在Coxiella感染期间引发STING介导的宿主反应。因此，我们建议 确定CDN如何控制对贝氏柯克斯体感染的先天免疫反应。在目标1中，我们 在脊椎动物和无脊椎动物模型中表征STING介导的宿主对柯克斯体感染的反应。在 目的2，我们将从caspase激活的角度来剖析STING在柯克斯体感染中的作用机制 和程序性细胞死亡在目标3中，我们将用CDN刺激宿主的先天免疫应答， 脊椎动物和无脊椎动物模型，以减少柯克斯体感染的程度。 总之，拟议的工作将表征CDN介导的先天免疫反应，以柯克斯体 感染和我们如何利用CDN来减少整体Coxiella负担。使用无脊椎动物模型 柯克斯体感染可能适用于其他媒介传播疾病。本研究中获得的信息将 对先天免疫有广泛的影响，有助于开发治疗柯克斯体的新疗法 感染，我们将确定潜在的新的CDN/STING介导的免疫机制， 适用于其他病原性感染。

Project Summary/Abstract: Cyclic dinucleotides (CDNs) play important second messenger roles in Gram-negative bacteria, regulating a number of different types of bacterial processes such as motility, biofilm formation, host colonization, bacterial growth, and metabolism. CDNs levels are tightly controlled by bacterial encoded diguanylate/diadenylate cyclases and phosphodiesterases. In addition to regulating bacterial life cycle processes, CDNs can alert the innate immune response during infection. A major cytosolic sensor for intracellular CDNs in animal hosts is STING, which upon its activation, triggers an innate immune response through the induction of type I interferon and pro-inflammatory cytokines. As such, synthetic CDNs have been applied exogenously prior to infection to stimulate inflammasome activity and reduce the load of Chlamydia trachomatis, a Gram-negative, obligate intracellular bacterium. Thus CDNs can be used to initiate an immune response to therapeutically treat Chlamydia infection, in addition to standard two-week antibiotic therapy. Another Gram-negative, obligate intracellular, macrophage-tropic bacterium is Coxiella burnetii, which is the causative agent of the zoonotic disease Q fever. The primary route of Coxiella transmission is through aerosols. However, Coxiella is also found in ticks, and they have been implicated as vectors. Acute phase of the disease in humans is characterized primarily by influenza-like symptoms, and individuals that develop chronic infection must undergo 18-24 months of antibiotic therapy. We contend that alternative methods to current antibiotic treatments need to be developed to reduce Coxiella load in infected animals. Our preliminary data suggests that CDNs are produced during Coxiella infection and that the Coxiella genome contains putative genes that encode diguanylate/diadenylate cyclases and phosphodiesterases. However, little is known about how CDNs elicit a STING-mediated host response during Coxiella infection. Thus, we propose to determine how CDNs control the innate immune response to Coxiella burnetii infection. In Aim 1, we will characterize the STING-mediated host response to Coxiella infection in vertebrate and invertebrate models. In Aim 2, we will dissect STING's mechanism of action during Coxiella infection with regard to caspase activation and programmed cell death. In Aim 3, we will stimulate the host innate immune response with CDNs in vertebrate and invertebrate models to reduce the magnitude of Coxiella infection. Together, the proposed work will characterize the CDN-mediated innate immune response to Coxiella infection and how we can exploit CDNs to reduce overall Coxiella burden. The use of invertebrate models of Coxiella infection may be applicable to other vector-borne diseases. The information gained in this study will have broad-ranging impacts in innate immunity towards to the development of new therapies to treat Coxiella infection, and we will identify potentially novel CDN/STING-mediated mechanisms of immunity that will be applicable to other pathogenic infections.