Inhibition of Th2 responses by secreted components of a common farm bacterium

项目总结/摘要 哮喘是一种慢性炎症性疾病，影响全球约3.39亿人， 其特征在于喘息、呼吸短促和气体交换效率低下。哮喘的发病率 在过去的半个世纪里，工业化国家的微生物暴露急剧增加;然而， 这些国家似乎对哮喘的发展有保护作用。多项研究发现， 在生命早期暴露于农场环境的儿童， 3-6的非农业伙伴。这种“农场效应”已经在几十年来的国家和地区得到了验证， 种族7-10;然而，微生物暴露导致抗哮喘表型的方式 仍然不清楚。目前对小鼠和人类的研究表明，阿米什人的房屋灰尘9，11以及 农场灰尘中的微生物产物可以防止哮喘的发展。内毒素10、12-16和农场棚 相关细菌鲁氏不动杆菌17可以使新生儿免疫系统对过敏性疾病难以耐受。 刺激。然而，这些药物的治疗能力受到潜在的脱靶炎症反应的限制。 结果如内毒素引起的急性肺损伤和A. lwoffii。因此 需要分离农场相关的微生物产物，其抑制过敏性炎症， 其他有害的炎症事件。我们的合作者已经发现，来自酵母的胞外多糖（EPS） 普通干草杆菌B。枯草芽孢杆菌可以限制包括肠道感染在内的几种小鼠模型中的炎症18，19 全身性金黄色葡萄球菌感染20例。我现在提出的数据，治疗屋尘螨（HDM）- 用EPS致敏的小鼠预防过敏性后遗症，例如气道杯状细胞增生，肺嗜酸性粒细胞增多， 和肺Th 2积聚。EPS还抑制了表达GATA 3的TcR的产生， 最近参与加剧过敏性炎症21，22.值得注意的是，单独的EPS不会引起炎症 或在没有炎症信号（如HDM）的情况下发生肺损伤， 抑制过敏性炎症。我还发现，EPS早在24岁时就改变了DC肺的组成， 在与HDM共暴露后24小时。这些数据清楚地证明了EPS对先天免疫细胞的作用， 然而，EPS抑制过敏性炎症的机制尚不清楚。整体 该项目的假设是EPS通过干扰先天性细胞活化来抑制过敏性炎症， 致病性前2型适应性细胞的产生。为了解决我的假设，我建议1）确定 EPS如何影响肺先天细胞库和2）确定EPS在抑制促过敏性 T细胞。了解微生物产物如EPS如何抑制炎症的产生将提供 对2型反应的发病机制有价值的见解。此外，本提案中的工作将揭示 作为预防或治疗过敏性哮喘的替代靶点，因此具有潜在的治疗效果。

PROJECT SUMMARY/ABSTRACT Asthma is a chronic inflammatory disease affecting an estimated 339 million people worldwide and is characterized by wheezing, shortness of breath, and inefficient gas exchange 2. The prevalence of asthma has increased dramatically in industrialized nations over the past half-century; however, microbial exposures within these nations appear to be protective against asthma development. Multiple studies have found that children exposed to a farm environment early in life have a reduced prevalence of asthma at school age as compared to their non-farming counterparts 3-6. This “farm effect” has been validated across decades, countries, and ethnic groups 7-10; however, the means by which microbial exposure leads to an anti-asthmatic phenotype remain unclear. Current studies from both mice and humans suggest that Amish house dust 9, 11 as well as microbial products in farm dust can protect from development of asthma. Endotoxin 10, 12-16 and the farm shed associated-bacterium Acinetobacter lwoffii 17 can render the neonatal immune system refractory to allergic stimuli. However, the therapeutic capacity of these agents is limited by potential off-target inflammatory consequences such as acute lung injury for endotoxin and opportunistic infection for A. lwoffii. Therefore, there is a need to isolate farm-associated microbial products that inhibit allergic inflammation while not inducing other, deleterious inflammatory events. Our collaborator has that found that exopolysaccharide (EPS) from the common hay bacillus B. subtilis can limit inflammation in several mouse models including enteric infection 18, 19 and systemic Staphylococcus aureus infection 20. I now present data that treatment of house dust mite (HDM)- sensitized mice with EPS prevents allergic sequelae such as airway goblet cell hyperplasia, lung eosinophilia, and lung Th2 accumulation. EPS also inhibited generation of GATA3-expressing Tregs, which have been recently implicated in exacerbating allergic inflammation 21, 22. Notably, EPS alone does not cause inflammation or lung injury in the absence of an inflammatory signal such as HDM, making is a much safer alternative for suppression of allergic inflammation. I have also found that EPS changes DC lung composition as early as 24 hours after co-exposure with HDM. These data clearly demonstrate an effect of EPS on innate immune cells, yet the mechanisms by which EPS acts to suppress allergic inflammation are unknown. The overall hypothesis of this project is that EPS inhibits allergic inflammation by interfering with innate cell activation and the generation of pathogenic pro-type 2 adaptive cells. To address my hypothesis, I propose to 1) determine how EPS impacts the lung innate cell repertoire and 2) determine the role of EPS in suppressing pro-allergenic T cells. Understanding how microbial products such as EPS inhibit the generation of inflammation will provide valuable insight into the pathogenesis of type 2 responses. Furthermore, the work in this proposal will uncover alternative targets for preventing or treating allergic asthma, and thus has potential therapeutic impact.