The role of aberrant gene expression in chlamydial persistence and reactivation

项目概要/摘要： 衣原体目中的细菌是真核细胞的细胞内寄生物。他们依赖于一种... 生殖周期由三种细胞形式组成，称为网状体（RB）、中间体（IB）和 基本体（EB）。EB病毒具有传染性，但不会复制。RB在宿主细胞中复制， 非传染性，而IB是过渡到EB形式的中间形式。完成这一发展- 心理周期是衣原体发病机制的核心。在该目中，衣原体属包含 许多重要的人类病原体的病原体。C.鹦鹉热导致人畜共患传染病， 在肺炎中，C.肺炎是一种引起呼吸道疾病的人类病原体， 动脉粥样硬化Biovars of C.沙眼是沙眼的病原体， 世界范围内的致盲症，以及性传播疾病衣原体。不管结果如何- 在疾病中，所有衣原体物种共享相同的专性细胞内生活周期和发育周期。 衣原体发育周期通过退出发育周期对环境压力作出反应， 形成“异常”细胞形式并延迟感染性EB的产生。这些细胞形式可以重新进入 环境压力解除后的生产发展周期。据推测，这一重新- 对应激条件的反应有助于临床观察，即衣原体感染通常是慢性的， 在大量确诊病例中复发。我们开发了一个活细胞报告系统 细胞类型转换在真实的时间在单一的包含水平，并确定衣原体的反应，以压力 条件如肽聚糖抑制剂或营养胁迫在处理之间和随着时间的推移而不同。治疗- 用肽聚糖抑制剂处理导致RB向IB发育的阻断，产生异常多倍体RB。 这些异常细胞在表达IB报告基因之前表达RB报告基因约10小时，但从未表达。 向EB记者施压或获得感染力。营养胁迫如色氨酸和铁饥饿也有报道 导致衣原体退出生殖发育周期并形成“异常”RB。我们的活细胞数据 表明这些细胞不表现出与用肽聚糖抑制剂处理的那些细胞相同的表型。 因此，目标1将确定与细胞增殖反应的异常RB的表型和基因表达谱。 容易产生传染性EB。IB到EB的发展是一个缓慢的过程，需要约10小时，直到最大EB 报告基因表达。因此，我们假设，IB可能会通过停止去- 直到营养素压力得到解决。然后，IB可以重新进入发育状态， 传染性后代因此，目标2将确定持续中IB向EB过渡的贡献。 tence.

Project Summary/Abstract: The bacteria in the Chlamydiales order are intracellular parasites of eukaryotic cells. They are reliant on a de- velopmental cycle consisting of three cell forms termed the reticulate body (RB), the intermediate body (IB) and the elementary body (EB). The EB is infectious but does not replicate. The RB replicates in the host cell but is non-infectious, while the IB is an intermediate form that transitions to the EB form. Completion of this develop- mental cycle is central to chlamydial pathogenesis. Within this order, the genus Chlamydia contains the causative agents of a number of important pathogens of humans. C. psittaci causes zoonotic infections result- ing in pneumonia, while C. pneumoniae is a human pathogen that causes respiratory disease and is linked to atherosclerosis. Biovars of C. trachomatis are the causative agents of trachoma, the leading cause of pre- ventable blindness worldwide, as well as the sexually transmitted disease Chlamydia. Irrespective of the result- ing disease, all chlamydial species share the same obligate intracellular life cycle and developmental cycle. The chlamydial developmental cycle reacts to environmental stresses by exiting the developmental cycle and forming “aberrant” cell forms and delaying the production of infectious EBs. These cell forms can then reenter the productive developmental cycle when the environmental stress is lifted. It is hypothesized that this re- sponse to stress conditions contributes to the clinical observation that chlamydial infections are often chronic or reoccur in a significant number of diagnosed cases. We have developed a live-cell reporter system to follow cell-type switching in real time at the single inclusion level and determined that Chlamydia’s response to stress conditions such as peptidoglycan inhibitors or nutrient stress differs between treatments and over time. Treat- ment with peptidoglycan inhibitors results in a block in RB to IB development creating aberrant polyploid RBs. These aberrant cells express the RB reporter for ~ 10 hours prior to expressing the IB reporter but never ex- press EB reporters or gain infectivity. Nutrient stress such as tryptophan and iron starvation are also reported to cause Chlamydia to exit the productive developmental cycle and form “aberrant” RBs. Our live cell data suggests that these cells do not exhibit the same phenotype as those treated with peptidoglycan inhibitors. Therefore Aim 1 will Determine the phenotype and gene expression profile of aberrant RBs that reacti- vate to produce infectious EBs. IB to EB development is a slow process taking ~10 hours until maximal EB reporter gene expression. We therefore hypothesize that the IB may respond to nutrient stress by halting de- velopment until the nutrient stress is resolved. The IB then could reenter the developmental state producing infectious progeny. Therefore Aim 2 will Determine the contribution of the IB to EB transition in persis- tence.