肺内共生菌柯林斯菌属通过调节肺内γδT-17细胞功能影响铜绿假单胞菌肺炎预后的作用机制研究

Pseudomonas aeruginosa is a common conditional pathogen in the hospital acquired infections. The clinical prognosis of Pseudomonas aeruginosa pneumonia mainly depends on patient immune status. The human body contains approximately ten times as many bacterial cells as human cells. Known as commensal bacteria, they exist in a mutually beneficial, symbiotic relationship with their human hosts.Previous studies have focused on how bacteria shape and protect the immune system within the intestines, it is becoming clear that pulmonary also benefit from commensal bacteria.Our previous studies showed that interleukin17-producing γδT cells (γδT-17 cells) have a protective effect on both innate immunity and humoral immunity via IL-17 during acute pulmonary Pseudomonas aeruginosa infection. We also found that the IL-17 protein level from low respiratory tract in the death Pseudomonas aeruginosa pneumonia patients was significantly decreased than the survival patients. Meanwhile, the relatively abundance of Collinsella in the lung microbiome was obviously lower in the death patients. Our animal experiments suggested that LGG inhalation which may rescue the relatively abundance of Collinsella, increased the IL-17 protein level in the lung and improved the clinical prognosis in the acute pulmonary Pseudomonas aeruginosa infection mice. To explore the role of the lung microbiome play on the pulmonary resident γδT-17 cells homeostasis during Pseudomonas aeruginosa pneumonia. We plan to ①design a clinical trial to validate the level of IL-17 produced by γδT-17 cells and the number of γδT-17 cells are significantly decreased in the Pseudomonas aeruginosa pneumonia patients with poor prognosis and it has a powerful relationship with the relatively abundance of Collinsella in the lung microbiome. ②identificate decreased the relatively abundance of Collinsella in the lung microbiome could impair the function γδ-T17 cells and the lower level of IL-17 in lung may worse the clinical prognosis in the infection mice model. After rescued the relatively abundance of Collinsella in the lung may maintain the homeostasis of pulmonary resident γδT-17 cells and may improve the prognosis. ③investigate whether the role of the lung microbiome play on the pulmonary resident γδT-17 cells homeostasis during Pseudomonas aeruginosa pneumonia is in a lipid antigen/CD1d dependent manner. Our project is based on host immunoregulation and try to explore a new strategy to improve the prognosis of Pseudomonas aeruginosa pneumonia patients.

铜绿假单胞菌是院内常见的条件致病菌，该类肺炎患者的临床预后与其免疫状态密切相关。研究表明宿主细胞的功能与体内共生菌密切相关，也证实肺内存在共生菌影响着免疫细胞的功能。我们的研究证实γδT-17细胞通过产IL-17在该类肺炎中发挥保护作用，也发现死亡患者肺内IL-17表达不足且肺内正常共生菌柯林斯菌属的比例显著下降。我们的小鼠实验发现吸入促柯林斯菌生长的鼠李糖乳杆菌能恢复肺内IL-17表达，改善预后，提示了柯林斯菌属可能对γδT-17细胞具有影响，但机制不明确。因此，本课题拟①确认肺内菌群变化与细胞功能相关的临床现象；②在该类感染模型中正反调节肺内柯林斯菌属比例，阐明该菌属的下降可导致肺内γδT-17 细胞产IL-17功能受损，恶化预后；上调该菌属比例可维护该细胞功能，改善预后。③调控CD1d/微生物脂质，探索该菌群影响免疫细胞功能的机制。本课题立足于免疫调节，探究改善该类感染预后的新策略。

铜绿假单胞菌肺炎是当前国内外常见的医院内获得性肺炎和呼吸机相关性肺炎。本课题主要探讨了肺部柯林斯菌在调节宿主肺部免疫细胞功能和肺部微生态，改善急性铜绿假单胞菌肺炎预后中的作用。在临床研究部分，我们初步发现急性铜绿假单胞菌肺炎患者外周血γδT-17 细胞的数量与患者疾病严重程度呈负相关。在动物实验部分，使用抗生素清除肺部菌群，明确破坏肺部菌群可导致肺炎严重程度呈现加重趋势；通过气管内滴入乳酸杆菌或柯林斯菌，确认增加肺部柯林斯菌丰度可以改善肺炎小鼠预后。我们检测了柯林斯菌干预后的小鼠肺部菌群分布，发现柯林斯菌可以调节肺部菌群构成，改善肺炎小鼠肺部微生态失衡现象。与此同时，我们评估了柯林斯菌干预后小鼠肺部免疫微环境的变化，发现气管内滴入乳酸杆菌间接增加肺内柯林斯菌丰度可通过CCL2/CCR2信号通路趋化单核来源巨噬细胞至肺部。此群单核来源巨噬细胞是改善肺炎预后的效应细胞，具有更强的清除病原体能力，TLR2信号通路激活可能与该群巨噬细胞的募集有关。综上所述，本课题立足于免疫、菌群调节，阐明了肺部柯林斯菌在改善急性铜绿假单胞菌肺炎预后中相关作用及机制，为临床抗感染治疗提供了新思路。