Eosinophils and lung immunity to Pneumocystis

描述（由申请人提供）：尽管预防和HAART治疗的出现，但HIV/AIDS患者中与肺孢子虫肺炎相关的死亡率与开始这些治疗前报告的死亡率相似。从与HIV/AIDS的密切关系中，我们知道CD 4 + T细胞是抗肺孢子虫免疫所需的中心效应细胞。然而，尽管经过30年的研究，保护性CD 4 + T细胞表型及其诱导的反应仍然难以捉摸。我们最近发表的工作表明，骨髓Src酪氨酸激酶缺陷的小鼠（Src TKO小鼠）比对照小鼠更有效地清除肺孢子虫，这是由于增强的替代巨噬细胞激活（M2 a）签名。我们的研究现在表明，在鼠疟原虫暴露后，M2 a极化迅速发展，但在肺中维持M2 a极化需要CD 4 + T细胞。我们进一步证明了M2 a诱导和嗜酸性粒细胞募集到肺部之间的相关性。在Src TKO小鼠中观察到更高的Epx（嗜酸性粒细胞过氧化物酶）mRNA表达，其具有更高的M2 a特征和更有效地清除鼠疟原虫。然而，Epx在CD 4耗尽的小鼠中显著较低，其具有较低的M2 a特征和受损的鼠肺疟原虫肺清除率。这些数据暗示了在鼠疟原虫肺部感染期间M2 a介导的嗜酸性粒细胞募集的宿主防御作用。反过来，我们在初步研究中证明，缺乏嗜酸性粒细胞的小鼠（dbl GATA 1缺陷小鼠）具有受损的鼠肺吸虫肺清除。此外，我们提供了新的人类数据，显示在来自肺孢子虫定殖的HIV+患者的诱导痰中CCL 22水平较高，这也与较高的嗜酸性粒细胞数量相关。最后，我们证明了强诱导的“真正的”几丁质酶，酸性哺乳动物几丁质酶（AMCase; Chia），在肺后P. murina感染。此外，AMCase/Chia的诱导在具有更好的鼠疟原虫清除的小鼠中升高，而在鼠疟原虫清除受损的小鼠中降低，表明AMCase/Chia的抗真菌作用。因此，这项R21探索性/发展性研究资助的目标是确定两个M2 a宿主防御成分的作用，嗜酸性粒细胞招募和AMCase/Chia诱导，在肺免疫反应中。我们的工作假设是，早期的CD 4 + T细胞反应维持肺泡巨噬细胞的交替激活，导致嗜酸性粒细胞的招募和肺孢子虫从肺部的成功消除。为了验证这一假设，我们提出：（1）确定嗜酸性粒细胞在肺孢子虫肺部感染的保护能力和（2）建立酸性哺乳动物几丁质酶有助于宿主防御肺孢子虫肺部感染。 公共卫生相关性：我们的数据发现了一种新的机制，肺泡巨噬细胞在肺孢子虫（称为M2 a）的反应中被激活，这是HIV/AIDS肺炎的最重要原因之一。M2 a应答的一个作用是嗜酸性粒细胞的募集，嗜酸性粒细胞可能是宿主对肺孢子虫应答中不受重视的效应细胞。本研究将确定嗜酸性粒细胞在肺孢子虫肺部感染和免疫重建相关炎症中的具体作用。

DESCRIPTION (provided by applicant): Despite the advent of prophylaxis and HAART therapy, the mortality rate associated with Pneumocystis pneumonia in HIV/AIDS remains similar to that reported prior to the initiation of these therapies. From the close association wit HIV/AIDS, we know that CD4+ T cells are the central effector cell required for immunity against Pneumocystis. Yet the protective CD4+ T cell phenotype and the responses it induces remain elusive, despite 30 years of research. Our recent published work has shown that mice deficient in myeloid Src tyrosine kinases (Src TKO mice) clear Pneumocystis murina more efficiently than control mice as a result of an enhanced alternative macrophage activation (M2a) signature. Our studies now show that M2a polarization develops rapidly after P. murina exposure, yet CD4+ T cells are required for maintaining M2a polarization in the lungs. We further demonstrate a correlation between M2a induction and eosinophil recruitment to the lungs. Higher Epx (eosinophil peroxidase) mRNA expression was observed in Src TKO mice, which have a higher M2a signature and clear P. murina more efficiently. However, Epx was significantly lower in CD4- depleted mice, which have a lower M2a signature and impaired P. murina lung clearance. These data imply a host defense role for M2a-mediated eosinophil recruitment during P. murina lung infection. In turn, we demonstrate in a pilot study that mice lacking eosinophils (dbl GATA1 deficient mice) have impaired P. murina lung clearance. Moreover, we provide new human data showing that CCL22 levels are higher in induced sputum from HIV+ patients colonized with Pneumocystis, which also correlated with higher eosinophil numbers. Finally, we demonstrate strong induction of a "true" chitinase, acidic mammalian chitinase (AMCase; Chia), in the lungs after P. murina infection. Moreover, induction of AMCase/Chia was elevated in mice with better P. murina clearance and reduced in mice with impaired clearance of P. murina, suggesting an anti- fungal role for AMCase/Chia. Therefore, the goal of this R21 Exploratory/Developmental Research Grant is to define the roles of two M2a host defense components, eosinophil recruitment and AMCase/Chia induction, during the lung immune response P. murina. Our working hypothesis is that early CD4+ T cell responses maintain alternative activation of alveolar macrophages leading to the recruitment of eosinophils and successful elimination of Pneumocystis from the lungs. To test this hypothesis, we propose: (1) to determine the protective capacity of eosinophils during Pneumocystis lung infection and (2) to establish that acidic mammalian chitinase contributes to host defense during Pneumocystis lung infection. PUBLIC HEALTH RELEVANCE: Our data has discovered a new mechanism by which alveolar macrophages are activated in response to Pneumocystis (termed M2a), one of the most significant causes of pneumonia in HIV/AIDS. An effect of the M2a response is the recruitment of eosinophils, which may be an unappreciated effector cell in the host responses to Pneumocystis. Studies in this proposal will determine the specific roles of eosinophils in Pneumocystis lung infection and immune reconstitution associated inflammation.