Interaction of histamine-releasing factor with immunoglobulins in asthma

描述（申请人提供）：哮喘和过敏性疾病的患病率在过去几十年中急剧增加，在工业化国家已达到流行病的程度。目前的疗法既不是预防性的，也不是治疗性的。因此，迫切需要新的治疗策略。组胺释放因子（HRF）可以IgE依赖性方式激活肥大细胞和嗜碱性粒细胞。由于在后期过敏反应期间在体液中发现其分泌物，因此HRF已被暗示在包括哮喘在内的过敏性疾病中。20年来，HRF如何参与过敏反应一直是个谜。然而，我们2012年的研究通过鉴定IgE和IgG分子的子集作为HRF受体改变了这种情况; HRF分子内免疫球蛋白（IG）Fab结合位点的定位导致发现基于HRF序列的抑制剂N19和H3肽，其竞争性阻断HRF-IG相互作用;在肥大细胞和IgE依赖性哮喘模型中，给予这些抑制剂显著降低了气道炎症; RI（=高亲和力IgE受体）和肥大细胞依赖性方式。在这个项目中，为了获得更多关于HRF-Ig相互作用的结构见解，（i）我们将鉴定HRF反应性IgE和IgG分子的分子特征，（ii）通过X射线晶体学和NMR光谱分析原子和亚分子水平上HRF-Ig相互作用的结构和动力学特征。如果HRF抑制剂应该在临床环境中使用，它们最初将在具有丰富HRF-Ig相互作用的患者中进行测试。为了模拟这种情况，（iii）我们将测试HRF抑制剂是否以及何种HRF抑制剂可有效治疗肺中过表达HRF或HRF反应性IgE的转基因小鼠的气道炎症。在人类和其他哺乳动物基因组中存在几种与HRF相关的假基因。因此，（iv）我们将测试它们的基因产物是否影响HRF功能。通过本项目获得的知识将丰富我们对HRF-Ig相互作用以及HRF-Ig相互作用在哮喘模型中的致病作用的理解，这将对我们未来的临床研究至关重要。

DESCRIPTION (provided by applicant): The prevalence of asthma and allergic diseases has been dramatically increasing for the last few decades and has reached epidemic proportions in industrialized countries. Current therapy is not preventive or curative. Thus, novel therapeutic strategies are urgently needed. Histamine-releasing factor (HRF) can activate mast cells and basophils in an IgE-dependent manner. As its secretion was found in bodily fluids during late-phase allergic reactions, HRF has been implied in allergic diseases including asthma. How HRF is involved in allergic reactions had remained enigmatic for two decades. However, our 2012 study changed this situation by identifying a subset of IgE and IgG molecules as HRF receptors; mapping of the immunoglobulin (Ig) Fab-binding sites within the HRF molecule led to the discovery of HRF sequence-based inhibitors, N19 and H3 peptides, which competitively blocked HRF-Ig interactions; administration of these inhibitors drastically reduced airway inflammation in mast cell- and IgE-dependent models of asthma; intranasal administration of na¿ve mice with HRF caused airway inflammation in an Fc¿RI (= high-affinity IgE receptor) and mast cell-dependent manner. In this project, to gain more structural insights into HRF-Ig interactions, (i) we will identify the molecular signature of HRF-reactive IgE and IgG molecules, and (ii) analyze structural and dynamic features for HRF-Ig interactions at atomic and submolecular levels by X-ray crystallography and NMR spectroscopy. If HRF inhibitors should ever be used in a clinical setting, they would initially be tested on patients with abundant HRF-Ig interactions. To mimic such conditions, (iii) we will test whether and what HRF inhibitors are effective to treat airway inflammation in transgenic mice overexpressing HRF in the lung or HRF-reactive IgE. Several HRF-related pseudogenes are present in human and other mammalian genomes. Therefore, (iv) we will test whether their gene products affect HRF functions. Knowledge to be gained through this project will enrich our understanding of HRF-Ig interactions and the pathogenic roles of HRF-Ig interactions in asthma models, which will be crucial for our future clinical study.