Eosinophils and lung immunity to Pneumocystis

描述（由申请人提供）：尽管出现了预防和HAART治疗，但与艾滋病毒/艾滋病肺囊虫肺炎相关的死亡率仍然与开始这些治疗之前的报告相似。从与艾滋病毒/艾滋病的密切联系中，我们知道CD4+ T细胞是对肺囊虫免疫所需的中枢效应细胞。然而，尽管经过了30年的研究，保护性CD4+ T细胞表型及其诱导的反应仍然难以捉摸。我们最近发表的研究表明，由于选择性巨噬细胞激活（M2a）特征增强，髓系Src酪氨酸激酶缺乏的小鼠（Src TKO小鼠）比对照小鼠更有效地清除鼠肺囊虫。我们现在的研究表明，暴露于P. murina后，M2a极化迅速发展，但维持肺中M2a极化需要CD4+ T细胞。我们进一步证明了M2a诱导与肺嗜酸性粒细胞募集之间的相关性。在Src TKO小鼠中观察到较高的Epx（嗜酸性过氧化物酶）mRNA表达，具有较高的M2a特征，更有效地清除鼠弓形虫。然而，Epx在CD4-贫小鼠中显著降低，这使得小鼠的M2a信号降低，肺清除率受损。这些数据表明，在鼠肺感染期间，m2a介导的嗜酸性粒细胞募集具有宿主防御作用。反过来，我们在一项初步研究中证明，缺乏嗜酸性粒细胞的小鼠（dbl GATA1缺陷小鼠）会损害鼠假体肺清除率。此外，我们提供的新的人类数据显示，感染肺囊虫的HIV+患者的诱导痰中CCL22水平较高，这也与较高的嗜酸性粒细胞数量相关。最后，我们证明了一种“真正的”几丁质酶，酸性哺乳动物几丁质酶（AMCase; Chia），在P. murina感染后在肺部被强烈诱导。此外，AMCase/Chia在小鼠P. murina清除能力较强的小鼠中诱导率升高，而在小鼠P. murina清除能力受损的小鼠中诱导率降低，表明AMCase/Chia具有抗真菌作用。因此，本R21探索性/发展研究基金的目标是确定两种M2a宿主防御成分，嗜酸性粒细胞招募和AMCase/Chia诱导在肺免疫反应中的作用。我们的工作假设是，早期CD4+ T细胞反应维持肺泡巨噬细胞的选择性激活，导致嗜酸性粒细胞的募集和肺囊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囊虫感染期间的保护能力；(2)确定酸性哺乳动物几丁质酶在肺囊虫感染期间参与宿主防御。

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.