Immunopathogenesis in fungal asthma

本次竞争性更新R01的目标是继续揭示导致严重程度的机制 在对真菌敏感的近40%的重症哮喘患者中，疾病的发病率很高。甲壳素，一种发现于 室内尘螨和蟑螂的真菌细胞壁和外骨骼作为一种 潜在的免疫反应性过敏原。哺乳动物已经进化到表达降解几丁质的几丁质酶(酸性 哺乳动物几丁质酶和几丁三糖苷酶)和几丁质结合几丁质酶样蛋白(YKL-40在人类中，BRP-39 在小鼠中)，这可能调节对甲壳素的免疫反应。我们最近公布的数据表明，慢性 酸性哺乳动物几丁质酶(AMCase)缺陷小鼠暴露于真菌可降低AHR 较低类型17的应答(感染免疫86：e0094,2018)。这些观察结果引发了这样一个问题：如何 在没有AMCase的情况下，缺少几丁质的降解会导致更好的肺功能和更少的炎症吗？放 另一方面，在真菌性哮喘期间，肺中假定较高的几丁质含量如何才能有益呢？基于 有研究报道，不同的甲壳素颗粒大小会引起不同的免疫反应，我们假设 在体内产生一些甲壳素颗粒会导致调节而不是促进炎症的反应。 初步数据显示，几丁质颗粒大小(通过FITC标记的几丁质结合域在肺中检测 灌洗液)在哮喘WT和AMCase缺陷小鼠中不同，一些大小增加和 有些减少了。Aim 1中的研究将进一步检测正常、缺失和 AMCase的过度表达及其与正向或负向调节型免疫反应的相关性 17个回复。在其他数据中，YKL-40(BRP-39，CHI3L1-/-)小鼠缺乏小鼠同源基因 尽管2型反应较低，但真菌性哮喘期间的AHR更差。骨髓嵌合体研究证实 这些发现并证明了BRP-39在免疫或非免疫间隔中的表达 与在两个隔室都不表达BRP-39相比，AHR更好。研究项目： 目的2将进一步确定由BRP-39几丁质结合调节的免疫和非免疫反应。我们进一步 结果表明，长期接触纯烟曲霉甲壳素会导致1型和17型的诱导，但不会 2、回应。总体而言，我们的假设是，在慢性肺部暴露于活真菌期间，AMCase降解 甲壳素的大小各不相同，其中一些可能会驱动增强AHR的反应。相比之下，BRP-39 结合甲壳素的功能，导致调节/降低AHR的反应(S)。《公约》的具体目标 建议：(1)明确AMCase在真菌性哮喘中的免疫致病机制；(2)确定AMCase在真菌性哮喘中的免疫发病机制 确定BRP-39介导的真菌哮喘严重程度的调节机制和(3)检测几丁质酶和 真菌致敏的人哮喘患者肺标本中几丁质酶样蛋白的水平。

The objective of this competitive renewal R01 is to continue to uncover mechanisms that contribute to the severity of disease in the nearly 40% of severe asthmatics who are sensitized to fungi. Chitin, a polysaccharide found in the fungal cell wall and the exoskeletons of house dust mites and cockroaches, has garnered attention as a potential immunoreactive allergen. Mammals have evolved to express chitin-degrading chitinases (acidic mammalian chitinase and chitotriosidase) and chitin-binding chitinase-like proteins (YKL-40 in humans, BRP-39 in mice) that may modulate immune responses to chitin. Our recently published data demonstrated that chronic fungal exposure in acidic mammalian chitinase (AMCase) deficient mice resulted in lower AHR in the presence of lower type 17 responses (Infect Immun 86:e0094, 2018). These observations prompted the question how can lack of chitin degradation in the absence of AMCase result in better lung function and less inflammation? Put another way, how can putatively higher chitin content in the lung during fungal asthma be beneficial? Based on studies reporting that different chitin particle sizes induced different immune responses, we posited that the generation of some chitin particles in vivo results in responses that regulate rather than promote inflammation. Preliminary data demonstrates that chitin particle sizes (detected by a FITC-labeled chitin binding domain in lung lavage fluid) are different between asthmatic WT and AMCase deficient mice, with some sizes increased and some decreased. Studies in Aim 1 will further examine chitin particle sizes in mice with normal, absent and overexpressed AMCase and correlate these with immune responses that positively or negatively regulate type 17 responses. In other data, mice deficient in the murine homologue of YKL-40 (BRP-39, Chi3l1-/-) demonstrated worse AHR during fungal asthma, despite lower type 2 responses. Bone marrow chimera studies confirmed these findings and demonstrated that BRP-39 expression in either the immune or non-immune compartment resulted in better AHR compared to the dual absence of BRP-39 expression in both compartments. Studies in Aim 2 will further determine immune and non-immune responses modulated by BRP-39 chitin binding. We further show that chronic exposure to pure A. fumigatus chitin results in the induction of type 1 and type 17, but not type 2, responses. Overall, our hypothesis is that during chronic lung exposure to live fungi, AMCase degrades chitin into various sizes, some of which may drive responses that enhance AHR. In contrast, BRP-39 functions to bind chitin, resulting in a response(s) that regulate/reduce AHR. The specific aims of the proposal are: (1) to define mechanisms of AMCase-mediated immunopathogenesis during fungal asthma, (2) to define mechanisms of BRP-39-mediated modulation of fungal asthma severity and (3) to examine chitinase and chitinase-like protein levels in lung samples from human asthmatics sensitized to fungi.