Dysregulated type-1 and Vascular Responses in Scrub typhus Pathogenesis

 描述（由申请人提供）： 恙虫病是一种由恙虫病东方体引起的危及生命的疾病，东方体是一种LPS阴性细菌，优先在内皮细胞（EC）和单核细胞中复制。每年约有100万人受到感染;约三分之一的世界人口面临感染风险。目前尚无有效的疫苗用于该感染，关于疾病发病机制的信息有限。为了应对这些挑战，我们开发了可以模仿人类恙虫病病理特征的小鼠模型。我们发现致命感染与过度的1型免疫反应有关，但与缺乏2型免疫反应有关，这与多个器官的血管损伤有关。然而，基本机制的定义很差。本研究的目的是利用O.恙虫病Karp株（OtK）感染，是人类感染的最流行株。我们的中心假设是，1型偏斜的炎症反应和血管生成素（Ang）表达失调是致命的OtK感染的主要原因。目的1将研究IFN-γ的细胞来源和IFN-γ相关反应在东方体感染中的细菌清除和免疫发病机制中的双重功能。通过使用IFN-γ报告小鼠以及RAG 2、IFN-γ或CXCR 3表达缺陷的小鼠来检查感染的肝、肺和脾中IFN-γ及其相关CXCR 3趋化因子的先天性与适应性细胞来源.在疾病的不同阶段接受抗IFN-γ治疗的小鼠将有助于确定IFN-γ在细菌清除与免疫发病机制中的体内功能。单细胞和分子水平的免疫学结果将与组织细菌载量和病理学评价结果相结合。目的2将验证由细菌感染引起的内皮细胞活化/失调可被IFN-γ相关的细胞因子/趋化因子改善的假设。在疾病的早期和晚期，将用重组Ang 1单独或与血管内皮生长因子（VEGF）或抗IFN-γ一起治疗致死性感染的小鼠。在IFN-γ-/-或CXCR 3-/-小鼠中的类似治疗，以及以EC为重点的体外研究，将有助于剖析细胞因子和血管反应之间复杂的相互作用。这项以机制为重点的研究支持研究团队之间的协同作用（每个团队都有独特的专业知识）;它利用了UTMB最先进的ABSL 3/BSL 3设施。本研究的长期目标是确定与东方体感染相关的致病机制，并利用这些信息设计控制策略。发现网络和初始功能障碍的性质将揭示免疫干预的关键窗口，以及疾病预后的标志性免疫特征。这项及时的研究将对其他细胞内病原体产生广泛的影响。

 DESCRIPTION (provided by applicant): Scrub typhus is a life-threatening disease caused Orientia tsutsugamushi, a LPS-negative bacterium that replicates preferentially in endothelial cells (EC) and monocytes. Approximately one million people are infected every year; about one third of world population is at risk of infection. There is no effective vaccine for this infection information on disease pathogenesis is limited. To address these challenges, we have developed mouse models that can mimic pathological features of human scrub typhus. We found that lethal infection was linked to excessive type 1, but deficient type 2, immune responses, which correlated with vascular damage in multiple organs. However, the underlying mechanisms are poorly defined. The goal of this study is to examine the molecular basis of such dysregulation by utilizing the EC-targeting model of O. tsutsugamushi Karp strain (OtK) infection, the most prevalent strain for human infections. Our central hypothesis is that type 1-skewed inflammatory responses and dysregulated angiopoietin (Ang) expression are leading causes for lethal OtK infection. Aim 1 will examine the cellular sources of IFN- and dual functions of IFN--related responses in bacterial clearance versus immunopathogenesis during Orientia infection. The innate vs. adaptive cell sources of IFN- and its related CXCR3 chemokines in infected liver, lungs and spleen will be examined by using IFN- reporter mice, as well as mice deficient in RAG2, IFN- or CXCR3 expression. Mice receiving anti-IFN- treatment at different stages of disease will help define in vivo function of IFN- in bacterial clearance vs. immunopathogenesis. Immunological findings from the single-cell and molecular levels will be integrated with those from tissue bacterial load and pathology evaluations. Aim 2 will test the hypothesis that endothelial activation/dysregulation initiated by bacterial infectionis ameliorated by IFN--related cytokines/chemokines. Lethally infected mice will be treated with recombinant Ang 1, alone or together with vascular endothelial growth factor (VEGF) or anti-IFN-, at early and late stages of disease. Similar treatment in IFN--/- or CXCR3-/- mice, as well as EC-focused in vitro studies, will help dissect complex interplays between cytokines and vascular responses. This mechanism-focused study endorses synergy among research teams (each with unique expertise); it utilizes the state-of-art ABSL3/BSL3 facilities at UTMB. The long-term goal of this study is to define the pathogenic mechanisms associated with Orientia infection and to utilize this information for the design of control strategies. Discovery of the onet and nature of initial dysfunction will reveal the critical window for immune intervention, as well s for signature immune profiles for disease prognosis. This timely study will have a broad implication for other intracellular pathogens.