钙卫蛋白在食物过敏中的作用机制及出生队列研究

Food allergy affects the growth and development of infants and children, the prevalence of food allergy in children in China was 6.2％. Foreign studies have shown that the level of fecal calprotectin in children with food allergy increased, but the specific molecular mechanism of calprotectin in food allergy is still blank. In our preliminary study, we found that the levels of calprotectin in both blood and feces of allergic rats were significantly higher than those in control rats, suggesting that calprotectin may exist and play an important role in food allergy. Published literature reported that calprotectin was an activator of Toll-like receptor 4. Besides, the TLR4 expression also increased significantly in the intestines of children with food allergy. Therefore, we speculated that the calprotectin may activate DC and related signal transduction by TLR4, which may induce allergic and inflammatory related immune responses. On the basis of those results and speculation, the present proposal will establish immature rats model of food allergy and S100A9 knockout rat model to detect the expression levels of allergic and inflammatory factors such as calprotectin, toll-like receptor 4, nuclear factor kappa B, tumor necrosis factor-α, interleukin-6, interleukin-8, interferon-γ, interleukin-4, interleukin-5, interleukin-13 and ovalbumin-IgE in different organizations. Furthermore, the impact of calprotectin on CD4+ T cells and dendritic cell activation at the cellular level and the role of calprotectin in allergy activation will be explored. It is the first time that our study is to explore and determine the role and related molecular mechanism of calprotectin in the occurrence and development of food allergy. Simultaneously, the changes and differences of fecal calprotectin between food allergic and non-allergic infants will be observed and compared through our cohort study for the first time. Moreover, whether calprotectin as a noninvasive and sensitive biological marker could be contributed to the prediction and monitoring of food allergy in infants and young children will be evaluated, in order to reach the purpose of reducing the occurrence and harm of allergic disease in children eventually.

食物过敏影响着婴幼儿的生长发育，我国儿童食物过敏检出率为6.2％。国外研究表明食物过敏儿童粪钙卫蛋白水平增高，但具体分子机制研究尚属空白。我们前期研究发现过敏大鼠血及粪钙卫蛋白水平均显著高于非过敏大鼠，这提示钙卫蛋白存在、并有可能作用于食物过敏反应中。文献报道钙卫蛋白是TLR4的配体，食物过敏儿童中肠粘膜TLR4表达也显著增加。据此我们提出假说：钙卫蛋白可能通过TLR4作用活化DC及相关信号传导等，引起过敏及炎症相关的免疫反应。本课题将通过建立食物过敏大鼠模型检测钙卫蛋白、相关过敏及炎症因子等水平变化，再通过细胞水平研究钙卫蛋白对CD4+T细胞及树突状细胞活化的影响，首次探讨钙卫蛋白在食物过敏发生和发展中的作用及分子机制。首次通过队列研究，比较食物过敏和非过敏婴幼儿粪钙卫蛋白的变化及差异，评估其在婴幼儿食物过敏的预测及监测作用，以最终达到减少儿童食物过敏性疾病发生及引起的相关危害的目的。

背景：食物过敏影响着婴幼儿的生长发育，我国儿童食物过敏检出率为6.2％。本研究探讨钙卫蛋白在IgE介导的食物过敏发生进程中的作用，评估其在婴幼儿食物过敏的预测及监测作用。主要研究内容：将80只3周龄雄性BN大鼠分成对照组和过敏组，对大鼠们进行致敏和激发实验，分析两组大鼠不同时间OVA-IgE、S100A8/A9、FN-γ、IL-4、IL-5、S100A8、S100A9、FC、TLR4、NF-κB、TNF-α、IL-1β和IL-6等的差异。采用经典骨髄来源树突状细胞培养法进行体外培养检测CD86、CD11c及MHC-Ⅱ的水平、Th1相关因子和Th2相关因子的水平。在临床中收集食物过敏的婴幼儿及健康对照组，比较和分析过敏及非过敏婴儿粪钙卫蛋白水平的变化。重要结果及科学意义：各个观察时间点过敏组的血清OVA-IgE、血浆组胺、血浆IL-4和IL-5水平均有不同程度的升高，INF-γ水平自第28天至42天显著降低。过敏组的粪便钙卫蛋白、血浆S100A8/A9、S100A8和S100A9 mRNA的表达、相关炎症因子的水平均高于对照组，粪便钙卫蛋白、空肠S100A8/A9水平及血浆S100A8/A9自第21天至第42天、S100A8和S100A9自第28天至第42天的差异均具有统计学意义。粪便钙卫蛋白与血浆S100A8/A9、TLR4、NF-κB及TNF-α均呈正相关关系。在细胞培养中从空白组、OVA组、S100A8+OVA组、S100A9+OVA组至S100A8/A9+OVA组，Th2相关因子的表达呈逐渐上升的趋势，而Th1相关因子呈逐渐下降的趋势。钙卫蛋白以及其它炎症因子在食物过敏进程中起了促进作用。粪便钙卫蛋白在食物过敏大鼠中显著增加，可考虑用于预测食物过敏的发生。研究招募了180名受试者，90名牛奶过敏婴儿和90名非牛奶过敏婴儿。其中过敏组粪钙钙卫蛋白水平明显高于非过敏组，过敏组LAZ、WAZ、WLZ水平均显著低于非过敏组。对90例牛奶蛋白过敏婴儿进行干预随访发现干预1月及2个月后粪钙卫蛋白水平较干预前出现了明显下降，牛奶蛋白过敏组婴儿干预后一个月及干预后2个月左右的LAZ和WAZ指标显著高于干预前生长水平。由此可见，过敏组粪钙钙卫蛋白水平明显高于非过敏组，通过干预后粪钙卫蛋白水平出现了下降，钙卫蛋白可用于随访和监测儿童肠道过敏中的一个生物学指标。