Rickettsia-host interface and multiple paths to invasion

项目摘要 立克次氏体属中的物种是革兰氏阴性专性细胞内细菌，具有共生和 致病生命周期立克次体感染的全球影响表现在感染的重新抬头 人与R。立克次氏体（落基山斑疹热的病原体）在南美洲和中美洲， 或R. conorii（Boutonneuse热）在欧洲，中东和非洲。引人注目的是，蜱虫和跳蚤传播 立克次体病在美国也呈上升趋势，最近爆发的立克次体病就是例证。立克次体 在亚利桑那州和R.在加州和德克萨斯州的伤寒（鼠伤寒的病原体），进一步强调了 立克次体疾病的威胁。目前还没有预防立克次体病的疫苗， 对立克次体细胞内生活方式的理解阻碍了有效治疗的进展 针对这些日益被认识到的细菌病原体的治疗剂。在过去的四年里，我们发现 致病性立克次氏体利用分泌的效应子通过 操纵ER结构或通过调节细胞内运输来破坏宿主防御途径。 然而，致病性立克次体物种利用这种效应子武器库破坏 支持内皮细胞或巨噬细胞（MΦ）细胞内生活方式的宿主先天防御途径 仍然不明确。为了解决这些知识差距，本更新申请建议：i）破译如何 强毒立克次体利用其效应子库操纵自噬反应以定殖宿主 细胞，和ii）确定毒性，但不是无毒力，立克次体物种的效应物的机制 抑制炎性小体激活和操纵MΦ极化以促进宿主播散。我们 总体目标是检验来自立克次体毒性种的效应子（如Risk 1）诱导 自噬负性调节炎性小体激活并使MΦ极化从M1偏向M2 来促进宿主的定居为了验证我们的假设，在目标1中，我们将定义 致病性立克次体破坏自噬体成熟以促进宿主定殖。在目标2中，我们将 阐明炎症体反应的颠覆和MΦ操纵的潜在机制 致病性立克次体物种的两极分化。这些目标旨在揭示一种联系， 致病性立克次体物种操纵自噬以破坏炎性体依赖性促炎作用 细胞因子信号传导和MΦ从杀微生物环境（M1-MΦ）向更有利的亲- 微生物环境（M2-MΦ）。这些研究将导致确定可以利用的联系 抗病毒策略。

PROJECT SUMMARY Species in the genus Rickettsia are Gram-negative obligate intracellular bacteria with both symbiotic and pathogenic lifecycles. The global impact of rickettsial infections is illustrated by the resurgence of infections of humans with R. rickettsia (etiologic agent of Rocky Mountain Spotted Fever) in South and Central America, or R. conorii (Boutonneuse fever) in Europe, the Middle East, and Africa. Strikingly, tick- and flea-borne rickettsial diseases are also on the rise in the United States, as exemplified by recent outbreaks of R. rickettsii in Arizona and R. typhi (etiologic agent of murine typhus) in California and Texas, further highlighting the threats of rickettsial diseases. There are currently no vaccines to prevent rickettsioses and our insufficient understanding of rickettsial intracellular lifestyle hinders the progression towards the development of effective therapeutics against these increasingly recognized bacterial pathogens. Over the past four years, we identified a complex mechanism by which pathogenic rickettsiae utilize secreted effectors to facilitate colonization by manipulating ER structures or by modulating intracellular trafficking to subvert host defense pathways. However, the precise mechanisms by which virulent Rickettsia species utilize this effector arsenal to subvert host innate defense pathways to support intracellular lifestyle in endothelial cells or macrophages (MΦ) remains ill-defined. To address these knowledge gaps, this renewal application proposes to: i) decipher how virulent Rickettsia species utilize their effector repertoire to manipulate autophagic responses to colonize host cells, and ii) determine the mechanism(s) by which effectors of virulent, but not avirulent, Rickettsia species suppress inflammasome activation and manipulate MΦ polarization to promote host dissemination. Our overall goal is to test the hypothesis that effectors from virulent species of Rickettsia, like Risk1, induce autophagy to negatively regulate inflammasome activation and skews MΦ polarization from a M1 to M2 bias to facilitate host colonization. To test our hypothesis, in Aim 1, we will define the mechanism(s) by which pathogenic Rickettsia subvert autophagosomal maturation to promote host colonization. In Aim 2, we will decipher the mechanism(s) underlying subversion of inflammasome responses and manipulation of MΦ polarization by pathogenic Rickettsia species. These Aims are intended to unveil a link by which effectors of pathogenic Rickettsia species manipulate autophagy to subvert inflammasome-dependent proinflammatory cytokine signaling and skew MΦ polarization from a microbicidal milieu (M1-MΦ) to a more favorable pro- microbial environment (M2-MΦ). These studies will lead to the identification of a link that could be exploited for anti-virulence strategy.