Functional impact of IL33 polymorphisms on asthma & other Th2-mediated diseases

描述（由申请人提供）：哮喘是一种复杂的性状，具有既定的遗传基础，是一个主要的公共卫生负担。哮喘的下呼吸道炎症特征的通常来源是由常见的环境过敏原引发的Th 2介导的反应，其涉及抗原特异性IgE抗体的产生。过敏性疾病和蠕虫感染之间的反向关系，也以IgE升高为特征，长期以来一直被观察到，并且具有哮喘史的个体似乎被“保护”免受蠕虫寄生虫的侵害（即，曼氏血吸虫）。许多基因与哮喘有关，但迄今为止很少有复制。最近，代表超过40，000个DNA样本的三个独立的全基因组关联研究（GWAS）已经确定了白细胞介素-33（IL-33）基因中和侧翼的多态性与哮喘之间的显著关联，使得IL-33成为迄今为止最强的哮喘候选基因之一。我们在巴西巴伊亚血吸虫病流行区的村民中观察到相同的IL 33“哮喘风险”变异与血吸虫病相关结果之间的显著关联。IL-33是IL-1家族中诱导Th 2细胞因子的新成员。其受体白细胞介素1样（或ST 2）以膜和循环可溶性蛋白的形式存在，ST 2多态性也与哮喘GWAS中的一个哮喘相关。IL-33在粘膜水平上使Th 2应答偏斜从而导致哮喘和对寄生虫的免疫的机制尚不清楚。我们正在进行的以哮喘风险和血吸虫病抗性为特征的大型队列遗传流行病学研究提供了一个独特的机会来检验IL-33多态性通过改变IL-33的功能而导致这两种疾病的假设。为了实现我们的目标，我们聚集了来自6个机构的多学科研究人员团队：（i）使用称为“多反应监测”（MRM）的基于质谱（MS）的方法定量来自500名哮喘病例和对照的血清中的循环IL-33及其受体sST 2，所述方法提供蛋白质的绝对定量，并测试IL-33和sST 2浓度与IL-33基因型/单倍型之间的关联;（ii）表征IL-33遗传变异对响应于Th 2促进抗原的IL-33和sST 2产生的影响（尘螨，嗜酸性粒细胞）;（iii）测试在哮喘中偏斜Th 2应答的IL 33变体/单倍型与代表抗性的定量结果之间的共关联（S. mansoni抗原特异性IgE：IgG 4比率）与血吸虫病的关系以及来自巴西巴伊亚血吸虫病流行地区的500名村民的样品中IL-33和ST 2的血清水平;和（iv）开发与哮喘/血吸虫病的风险/抗性相关的IL 33单倍型的人源化鼠模型，以阐明IL 33基因在这些疾病中的功能作用。这项研究的结果将为IL-33在两种具有高度公共卫生意义的疾病发病机制中的作用提供新的见解。

DESCRIPTION (provided by applicant): Asthma is a complex trait with an established genetic basis that represents a major public health burden. The usual source of the lower airway inflammation characteristic of asthma is a Th2-mediated reaction initiated by common environmental allergens which involves the production of antigen-specific IgE antibodies. An inverse relationship between allergic disease and helminthic infection, also characterized by elevated IgE, has long been observed, and individuals with a history of asthma appear to be 'protected' from helminthic parasites (i.e., Schistosoma mansoni). Many genes have been associated with asthma, but to date very few have replicated. Recently, three independent genome-wide association studies (GWAS) representing over 40,000 DNA samples have identified significant associations between polymorphisms in and flanking the Interleukin-33 (IL33) gene and asthma, rendering IL33 as one of the strongest candidate genes for asthma to date. We observed significant associations between the same IL33 'asthma risk' variants and outcomes associated with schistosomiasis in villagers living in an endemic region in Bahia, Brazil. IL-33 is a new member of the IL-1 family that induces Th2 cytokines. Its receptor, interleukin 1-like (or ST2) exists as membrane and circulating soluble proteins, and ST2 polymorphisms were also associated with asthma in one of the asthma GWAS's. The mechanism(s) by which IL-33 skews the Th2 response at the level of the mucosa, leading to asthma and immunity to parasites, is not known. Our ongoing genetic epidemiology studies in large cohorts characterized for risk of asthma and resistance to schistosomiasis provide a unique opportunity to test the hypothesis that IL33 polymorphisms contribute to both diseases by altering the function of IL-33. To accomplish our goals, we have amassed a multidisciplinary team of investigators from 6 institutions to: (i) quantify circulating IL-33 and its receptor, sST2, in serum from 500 asthma cases and controls using a mass spectrometry (MS)- based method called 'multiple reaction monitoring' (MRM) that provides absolute quantification of protein, and to test for association between IL-33 and sST2 concentrations and IL33 genotypes/haplotypes; (ii) characterize the effects of IL33 genetic variation on production of IL-33 and sST2, in response to Th2-promoting antigens (dust mite, schistosome) in human myeloid cells; (iii) test for co-associations between the IL33 variants/haplotypes that skew the Th2 response in asthma and a quantitative outcome representing resistance (S. mansoni antigen-specific IgE:IgG4 ratio) to schistosomiasis and serum levels of IL-33 and ST2 in samples from 500 villagers living in a region endemic for schistosomiasis in Bahia, Brazil; and (iv) develop a humanized murine model of IL33 haplotypes associated with risk/resistance to asthma/schistosomiasis to elucidate the functional role of the IL33 gene in these diseases. Results from this study will provide novel insights into the role of IL-33 in the pathogenesis of two diseases of high public health significance.