Determining the Mechanism of TNF in Defense Against Intracellular Bacterial Infection

项目摘要 细胞内的细菌病原体，如军团病的病原体嗜肺军团菌， 每年在美国造成巨大的疾病负担。成功地控制了这些 病原体依赖于炎性细胞因子肿瘤坏死因子(TNF)。肿瘤坏死因子负责 上调先天免疫活性，并引导炎症反应。靶向肿瘤坏死因子的治疗药物 信号在类风湿性关节炎或溃疡性结肠炎等炎症性疾病的治疗中很常见； 然而，这些治疗药物增加了对细胞内细菌感染的敏感性。肿瘤坏死因子 已经证明是防御军团菌和其他细胞内病原体的关键因素，而分子 对肿瘤坏死因子信号的细节进行了很好的描述。然而，肿瘤坏死因子的下游影响是多种多样的。 从促进细胞存活到触发细胞程序性死亡--从而通过 目前尚不清楚哪种肿瘤坏死因子介导了抗菌防御。 我们的新的初步数据表明，在军团菌感染时，需要肿瘤坏死因子才能达到最佳效果 骨髓源性巨噬细胞培养中炎性细胞因子的产生。这个机制是通过 在军团菌感染过程中，哪种肿瘤坏死因子促进了细胞因子的产生尚不清楚。此外，我们还推出了新的 更多数据显示，缺乏凋亡caspase-8的小鼠和细胞在 外源性rTNF治疗无法挽救的军团菌感染的控制 其下游机制可能与诱导感染宿主细胞凋亡有关。 因此，目标1试图测试促生存和炎症信号有助于上调妊娠的假设。 受感染的细胞产生保护性的细胞因子。目标2试图检验这一假设，即肿瘤坏死因子依赖 感染细胞中的凋亡信号作用于限制细菌的复制生态位，从而限制细菌的生长和 散开。这项研究将对肿瘤坏死因子如何介导细胞内免疫控制提供基本的见解。 细菌感染，并可能为开发改进的治疗方法提供基础 没有增加感染风险的病理性炎症。

Project Summary Intracellular bacterial pathogens such as Legionella pneumophila, the causative agent of Legionnaires’ Disease, are responsible for significant disease burden in the United States every year. Successful control of these pathogens is reliant on the inflammatory cytokine Tumor Necrosis Factor (TNF). TNF is responsible for the upregulation of innate immune activity, and directs the inflammatory response. Therapeutics targeting TNF signaling are common in treatment of inflammatory disorders such as rheumatoid arthritis or ulcerative colitis; however, these therapeutics carry with them an increased susceptibility to intracellular bacterial infection. TNF has proven a critical factor in defense against Legionella and other intracellular pathogens, and the molecular details of TNF signaling are well characterized. The downstream effects of TNF, however, are diverse – ranging from promoting cell survival to triggering programmed cell death – and thus the precise mechanisms through which TNF mediates anti-bacterial defense are still unclear. Our new preliminary data indicate that, upon Legionella infection, TNF is required for optimal inflammatory cytokine production in bone marrow-derived macrophage (BMDM) culture. The mechanism by which TNF promotes cytokine production during Legionella infection is unknown. Furthermore, we present new additional data showing that mice and cells deficient for the apoptotic caspase, Caspase-8, possess a defect in control of Legionella infection that cannot be rescued by exogenous rTNF treatment, suggesting that TNF’s downstream mechanism may be related to the induction of apoptosis of infected host cells. Thus, Aim 1 seeks to test the hypothesis that pro-survival and inflammatory signaling serves to upregulate the production of protective cytokines by infected cells. Aim 2 seeks to test the hypothesis that TNF-dependent apoptotic signaling in infected cells acts to restrict the replicative niche of the bacteria and thus limit growth and spread. This research will provide fundamental insight into how TNF mediates immune control of intracellular bacterial infection, and may provide a basis for the development of improved therapeutics that dampen pathological inflammation without increased risk of infection.