Pathogenic Mechanisms of Vascular Dysfunction in Scrub Typhus

恙虫病是一种由恙虫病东方体引起的危及生命的疾病， 优先在内皮细胞（EC）和吞噬细胞中复制。虽然每年有100万人感染， 世界人口约有三分之一面临感染风险，因此缺乏有效的感染控制战略。 关于疾病发病机制和免疫失调的信息有限。为了应对这些挑战，我们 已经开发出了模仿人类恙虫病某些关键病理特征的小鼠模型。我们发现 内源性损伤相关分子模式（DAMP）分子如HMGB 1和 髓过氧化物酶（MPO）是负责血管生成素2分子功能障碍的关键调节因子 （Ang 2）、Tie 2和CD 41+血小板。我们还发现了持续的中性粒细胞激活的有害影响， 以及Ang 2和miR-200 b作为血小板减少症和血管损伤的独特生物标志物的潜力。 血管功能障碍本研究的目的是明确血管功能障碍的发病机制 以及利用O.恙虫 感染我们的中心假设是感染引发的DAMP释放加剧了O。 恙虫病通过改变中性粒细胞/血小板活化引起的血管损伤; 保持血管完整性或吞噬细胞功能有助于引起针对急性组织的平衡免疫 以及严重的丛林斑疹伤寒这一假设将在三个有凝聚力的具体目标中得到检验。目标1将 研究HMGB 1和TNF α介导的致敏和加重人类免疫缺陷的机制。 东方体感染中的内皮细胞。我们将使用人类微血管内皮细胞（HMEC）来测试是否 Orientia触发HMGB 1、TNF α、Ang 2和miR-200 b及其靶基因/蛋白的释放，如果 靶向这些机制的治疗减轻EC损伤。目标2将审查各种机制， 嗜中性粒细胞和HMGB 1在小鼠感染期间导致血管和血小板功能障碍。我们将成立 CXCR 2-/-或MPO-/-小鼠在不同感染阶段的致死和亚致死感染。同样，删除 HMGB 1受体（HMGB 1受体，HMGB 1-/-小鼠）或抗HMGB 1抗体将揭示HMGB 1/HMGB 1的特定作用。 在组织浸润的白细胞、血小板和血管功能中的信号传导。目标3将测试抗Ang 2和 基于他汀治疗剂通过调节血管功能和吞噬细胞活化促进宿主存活， 小鼠小鼠将接受抗Ang 2抗体、重组Ang 1或他汀类药物（单独或联合）治疗 在致死和亚致死感染之前或期间。我们将检查细菌播散、中性粒细胞/血小板 活化，以及Tie 2和标志性细胞因子/DAMP的水平。这项以机制为重点的研究利用了 几个研究团队的协同作用血管特异性生物标志物的发现，新的调节 途径，其对免疫反应的影响东方是及时的，创新的和非常重要的。

Scrub typhus is a life-threatening disease caused by Orientia tsutsugamushi, a LPS-negative bacterium that replicates preferentially in endothelial cells (EC) and phagocytes. While one million people are infected yearly, with about one-third of world population at risk of infection, effective strategies for infection control are lacking. Information on disease pathogenesis and immune dysregulation is limited. To address these challenges, we have developed mouse models that mimic certain key pathological features of human scrub typhus. We found that endogenous damage-associated molecular pattern (DAMP) molecules such as HMGB1 and myeloperoxidase (MPO) are key regulators responsible for molecular dysfunctions involving angiopoietin 2 (Ang2), Tie2, and CD41+ platelets. We also discovered the detrimental effect of sustained neutrophil activation in thrombocytopenia and vascular injury, and the potential of Ang2 and miR-200b as unique biomarkers for vascular dysfunction. The objective of this study is to define pathogenic mechanisms of vascular dysfunction and therapeutic modalities for severe scrub typhus by utilizing the EC-targeting model of O. tsutsugamushi infection. Our central hypothesis is that the infection-triggered release of DAMPs exacerbates O. tsutsugamushi-induced vascular damage by altering neutrophil/platelet activation; interventions aimed at preserving vascular integrity or phagocyte function help to elicit a balanced immunity against acute tissue damage and severe scrub typhus. This hypothesis will be tested in three cohesive Specific Aims. Aim 1 will examine the mechanisms of HMGB1- and TNF-mediated sensitization and exacerbation of human endothelium in Orientia infection. We will use human microvascular endothelial cells (HMEC) to test whether Orientia triggers the release of HMGB1, TNF, Ang2, and miR-200b and their target genes/proteins, and if therapeutics targeting these mechanisms mitigate EC injury. Aim 2 will examine mechanisms by which neutrophils and HMGB1 contribute to vascular and platelet dysfunction during infection in mice. We will set up lethal and sublethal infections in CXCR2-/- or MPO-/- mice at different infection stages. Likewise, the deletion of RAGE (a HMGB1 receptor, RAGE-/- mice) or anti-RAGE antibody will reveal specific roles of HMGB1/RAGE signaling in tissue-infiltrated leukocytes, platelet and vascular function. Aim 3 will test whether anti-Ang2 and statin-based therapeutics promote host survival via modulating vascular function and phagocyte activation in mice. Mice will be treated with anti-Ang2 antibody, recombinant Ang1, or statins (alone or in combination) before or during lethal and sublethal infection. We will examine bacterial dissemination, neutrophil/platelet activation, and the levels of Tie2 and signature cytokines/DAMPs. This mechanism-focused study capitalizes on the synergism among several research teams. Discovery of vascular-specific biomarkers, novel regulatory pathways, and their impact on immune responses to Orientia is timely, innovative and highly significant.