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尘螨(house dust mites,HDMs)是过敏性鼻炎和哮喘最常见的诱因之一,大约85%的过敏性哮喘是由尘螨引起的[1]. 屋尘螨(Dermatophagoides pteronyssinus,Der p)分布最广,广泛分布在全球85%的地区[2]. 目前,人们发现了20种来自于屋尘螨的过敏原,其中,2组过敏原Der p 2是最重要的过敏原之一. 研究表明,90%以上的宿舍和家庭环境灰尘中都能检测到Der p 2[3],80%的尘螨过敏患者都对其有过敏反应[4]. 在10岁以下儿童中,Der p 2是屋尘螨过敏原中患病率最高的过敏原[5]. Der p 2由129个氨基酸组成,其中包括3个酪氨酸残基[6]. Der p 2引起的过敏属于Ⅰ型超敏反应,主要是由IgE介导. 当机体初次接触过敏原蛋白时,机体产生特异性IgE,IgE可以吸附在嗜碱性粒细胞、T细胞和B细胞等细胞表面的IgE受体上. 当机体再次接触过敏原蛋白时,过敏原与细胞表面的IgE特异性结合,诱导释放组胺、白三烯等活性物质,引发各种过敏症状[7]. 整个致敏、激发和效应过程中,过敏原蛋白与细胞表面的IgE结合是关键环节. 过敏原蛋白与细胞表面IgE结合的部分叫做表位. 表位分为线性表位和构象表位,线性表位包含可以与IgE结合的一个连续氨基酸序列,构象表位是由在序列上相距较远但是因为蛋白质立体结构而相邻的几个氨基酸残基组成[8 − 9]. 目前,以线性表位为基础合成的表位肽可以作为生物标志物,用于过敏原的致敏性研究,酶联免疫吸附测定(epitope-ELISA)被广泛应用于临床诊断[10].
近年来的研究表明,空气污染物O3和NO2可引起过敏原的硝基化,即蛋白质中的酪氨酸被硝基化形成3-硝基酪氨酸(3-NT),从而促进其致敏性的增强[11 − 14]. 例如,暴露于NO2和O3的白桦花粉过敏原蛋白Bet v
1.0101 可发生硝基化作用[15],硝基化后的桦树花粉蛋白与桦树花粉过敏患者血清中IgE结合能力显著增强[16]. 此外,也有报道称,NO2和O3 可以改变法国梧桐花粉过敏原Pla a 3的结构,从而提高其与IgE结合能力,加重花粉引起的BALB/c小鼠肺炎[17]. 先前研究已经证实了环境中硝基化Der p 2的存在,并且能定位Der p 2每个酪氨酸位点的硝基化程度,在居家环境中,Der p 2的3个酪氨酸硝化位点Y92、Y103和Y107的硝化率分别为19.12%—95.12%、2.02%—78.39%和1.92%—79.75%,整体呈现Y92>Y107>Y103的趋势[3,18 − 19]. 然而,每个酪氨酸位点的硝基化对于Der p 2的致敏性的影响,尤其对于IgE结合力的影响还未可知.Der p 2包含3个酪氨酸,分别位于其两条线性表位肽上. 本研究通过分析两条线性表位肽及其硝基化产物与特异性IgE的结合能力,鉴别线性表位肽在硝基化前后与IgE结合能力的变化及其与酪氨酸位点的相关性,以此揭示硝基化对Der p 2致敏性的影响.
尘螨过敏原Der p 2线性表位肽及其硝基化产物与IgE结合能力
The IgE binding capability of the linear epitope peptides and their nitration products of house dust mite allergy Der p 2
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摘要: 许多过敏原可以介导Ⅰ型超敏反应,通过与IgE特异性结合,引起过敏症状. 过敏原与细胞表面的特异性IgE结合的部分叫做表位,其与IgE的结合能力可以表征过敏原致敏性的强弱. Der p 2是一种重要的屋尘螨过敏原,其线性表位中含有的酪氨酸可被空气中的NO2和O3硝基化,从而影响线性表位与IgE的结合能力. 本实验研究了Der p 2的线性表位及其硝基化产物与IgE的结合能力. 研究发现,Der p 2的两条表位多肽可以有效地结合IgE,硝基化表位多肽的IgE结合能力显著高于未硝基化的表位多肽,且不同位点的硝基化对于IgE结合能力的增强程度也不同. 结果表明,硝基化能够位点特异性地增强Der p 2的致敏性.Abstract: Many allergies can cause type I hypersensitivity, through binding to specific-IgE and leading the allergic symptoms. The binding ability of epitope, which is the portion of an allergen protein that binds with specific IgE on cell surface, to IgE can indicate the allergenicity of allergen. Der p 2 is an important house dust mite allergic protein. The tyrosine residues in the epitopes of Der p 2 can be nitrated by airborne NO2 and O3, which could subsequently promote the allergenicity. In this study, the abilities of the epitopes and their nitrated products to bind to the specific IgE were investigated. The results reveal that the two epitope peptides effectively bound to the specific IgE, and the IgE binding capacities of the nitrated epitope peptides were significantly higher than the non-nitrated forms. Besides, the contribution of nitration to the enhancement of IgE binding capacity depended on the location of tyrosine. These findings suggest that nitration can enhance the allergenicity of Der p 2 in a tyrosine site-specific manner.
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Key words:
- Der p 2 /
- linear epitope /
- nitration /
- site-specific /
- IgE /
- allergenicity.
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表 1 Der p 2表位多肽和硝基化表位多肽相关信息
Table 1. The information about the linear epitope peptides and nitrated epitope peptides of Der p 2
表位多肽
Epitope peptide氨基酸序列及硝基酪氨酸位置
Amino acid sequence and position of tyrosine纯度/%
PurityEP1-0 VPGIDPNACHY92MKC 98 EP1-1 VPGIDPNACHY(3-NO2)MKC 98 EP2-0 QQY103DIKY107TWNVPKIAPK 98 EP2-1 QQY(3-NO2)DIKYTWNVPKIAPK 98 EP2-2 QQYDIKY(3-NO2)TWNVPKIAPK 98 EP2-12 QQY(3-NO2)DIKY(3-NO2)TWNVPKIAPK 98 注:Y(3-NO2)表示3-硝基酪氨酸(3-NT). Note: Y(3-NO2) means 3- nitrotyrosine (3-NT). 表 2 间接性ELISA血清实验不同工作条件下OD450/OD0
Table 2. OD450/OD0 under different conditions by indirect ELISA with serum IgE
0.5 μg·mL−1 1 μg·mL−1 5 μg·mL−1 1:20 1:2000 2.87 3.49 5.15 1: 5000 2.70 3.30 4.04 1: 10000 2.04 2.84 3.28 1:50 1:2000 1.95 2.38 3.57 1: 5000 1.87 2.24 2.90 1: 10000 1.84 2.67 2.84 1:100 1:2000 2.03 2.28 3.40 1: 5000 1.80 2.38 3.12 1: 10000 1.47 1.78 2.29 注:包被浓度为0.5 μg·mL−1、1 μg·mL−1和5 μg·mL−1,血清稀释倍数为1:20、1:50和1:100,二抗稀释倍数为1:2000、1: 5000 和1:10000 ;n=3,数据以均值表示.
Note: The concentrations of coated solution were 0.5, 1 and5 μg·mL−1. The rates of dilution of the serum IgE were 1:20, 1:50 and 1:100. The rates of dilution of the secondary antibody were 1:2000, 1:5000 , and 1:10000. The data were expressed as mean (n=3).表 3 间接性ELISA单克隆抗体IgE实验不同工作条件下OD450/OD0
Table 3. OD450/OD0 under different conditions by indirect ELISA with monoclonal IgE
一抗稀释倍数 1:500 1:600 1: 1000 1: 5000 1: 10000 1: 50000 OD450/OD0 13.82 30.40 6.93 2.68 2.29 1.63 注:包被浓度为5 μg·mL−1,二抗稀释倍数为1:2000,单克隆抗体IgE稀释倍数为1:500、1:600、1: 1000 、1:5000 、1:10000 和1:50000 ,n=3,数据以均值表示.
Note: The concentration of coated solution was 5 μg·mL−1. The rate of dilution of the secondary antibody was 1:2000. The rates of dilution of the monoclonal IgE were 1:500, 1:600, 1:1000 , 1:50000 , 1:10000 and 1:50000. The data were expressed as mean (n=3). -
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