Eosinophils and lung immunity to Pneumocystis

描述(申请人提供)：尽管出现了预防和HAART疗法，但艾滋病毒/艾滋病中与肺孢子虫肺炎相关的死亡率仍与这些疗法开始之前报告的死亡率相似。从与HIV/AIDS的密切联系中，我们知道CD4+T细胞是抗肺孢子虫免疫所必需的中枢效应细胞。然而，尽管进行了30年的研究，但保护性的CD4+T细胞表型及其诱导的反应仍然难以捉摸。我们最近发表的工作表明，缺乏髓系Src酪氨酸激酶的小鼠(Src TKO小鼠)比对照小鼠更有效地清除肺孢子虫，这是由于增强了替代巨噬细胞激活(M2a)的信号。我们现在的研究表明，在P.Murina暴露后，M2a极化发展迅速，但在肺中维持M2a极化需要CD4+T细胞。我们进一步证明了M2a诱导和嗜酸性粒细胞向肺内募集之间的相关性。在Src TKO小鼠中观察到EPX(嗜酸性粒细胞过氧化物酶)的高表达，其具有更高的M2a签名和更有效的清除P.Murina。然而，EPX在CD4耗竭的小鼠中显著降低，这些小鼠的M2a签名较低，并损害了P.Murina的肺清除。这些数据表明，在P.Murina肺部感染期间，M2a介导的嗜酸性粒细胞募集具有宿主防御作用。反过来，我们在一项先导性研究中证明，缺乏嗜酸性粒细胞的小鼠(DBL GATA1缺陷小鼠)损害了P.Murina的肺清除。此外，我们提供了新的人类数据显示，来自感染肺孢子虫的HIV+患者的诱导痰中CCL22水平更高，这也与更高的嗜酸性粒细胞数量相关。最后，我们证明了在感染P.Murina后，在肺中强烈诱导了一种“真正的”几丁质酶，即酸性哺乳动物几丁质酶(AMCase；CHIA)。此外，AMCase/Chia的诱导在P.Murina清除较好的小鼠中增加，在P.Murina清除受损的小鼠中减少，这表明AMCase/Chia具有抗真菌作用。因此，R21探索/发展研究基金的目标是确定两个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，早期的CD4+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，并成功地从肺中消除了肺孢子虫。为了验证这一假设，我们建议：(1)确定嗜酸性粒细胞在肺孢子虫肺部感染过程中的保护能力；(2)建立酸性哺乳动物几丁质酶在肺孢子虫肺部感染过程中对宿主防御的作用。 公共卫生相关性：我们的数据发现了一种新的机制，通过这种机制，肺泡巨噬细胞被激活，以应对肺孢子虫(称为M2a)，这是艾滋病毒/艾滋病中最重要的肺炎原因之一。M2a反应的一个影响是嗜酸性粒细胞的招募，这可能是宿主对肺孢子虫的反应中一个未被认识的效应细胞。这项建议中的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.