BIOMARKERS AND MECHANISMS OF FOOD ALLERGY AND ORAL TOLERANCE IN IgE-SENSITISED CHILDREN

食物过敏（FA）的症状是由免疫系统中的肥大细胞和嗜碱性细胞释放某些物质引起的，这些物质是由过敏抗体和食物过敏原之间的相互作用引发的。FA通常通过皮肤点刺试验或检测血液中的IgE（过敏抗体）来诊断。然而，比食物过敏更常见的是对这种食物的过敏测试呈阳性。例如，在英国，对花生过敏测试呈阳性的儿童中，只有五分之一对花生过敏。在模棱两可的情况下（超过50%的患者），需要口服食物挑战（OFC）。OFC包括在受控环境中给予患者可疑食物，以观察患者是否产生过敏反应。OFC非常昂贵，耗时，并使患者面临潜在严重反应的风险，但这是目前诊断FA的金标准。在我的mrc资助的博士项目中，我开发了一种新的血液测试，叫做嗜碱性粒细胞激活测试（BAT），它的工作原理就像试管中的OFC。在花生过敏的诊断中，BAT显示97%的准确率，并将OFC的需求减少了三分之二。在这个项目中，我将开发类似的诊断测试，针对牛奶和鸡蛋过敏，这是儿童最常见的食物过敏，以及芝麻和腰果，这是两种最常见的食物，需要OFC，因为传统的过敏测试不能正确诊断过敏。我预计BAT将显著改善对过敏患者的护理，并减少与ofc相关的成本和焦虑。BAT需要使用新鲜血细胞。作为MRC奖的一部分，我开发了一种类似于BAT的测试，使用在实验室中生长的细胞系，因此很容易获得。我将测试花生过敏和非花生过敏患者的各种样本，以验证该试验作为花生过敏的生物标志物。我已经开发了一种类似的方法来测试非过敏患者血液中抗体阻断IgE的能力——这是抑制肥大细胞激活试验（IMAT），我将验证它作为食物耐受性的生物标志物。这些测定法可用于未来的研究，以测试远离实验室收集的样本，或测试在不同时间点收集的平行样本，与过敏或耐受性有关。为了理解为什么有些患者过敏测试呈阳性而不过敏，我将确定过敏患者和非过敏个体的抗体识别过敏原的哪个特定部分。过敏和耐受患者可能分别识别出过敏原的不同部分，这些部分可能会或可能不会引发过敏症状。也有可能过敏患者和耐受患者识别过敏原分子的相同部分，但耐受患者产生的抗体类型不同，能够阻断IgE。在Brian Sutton和Hannah Gould教授的合作下，人工抗体将基于花生过敏患者的抗体产生，由这些抗体和花生过敏原形成的晶体将有助于研究过敏原的哪一部分被IgE过敏抗体识别。通过改变特定部位的过敏原，会产生突变过敏原。我将测试这些突变过敏原以及天然存在的花生过敏原在MAT中引起过敏症状的能力。将产生针对花生过敏原同一部分的阻断抗体，并在IMAT上测试其阻断活性。准确地了解患者过敏和不过敏时的情况，尽管存在IgE抗体，将有助于我们找到治疗FA患者的方法，并通过改变免疫系统对花生或其他食物过敏原的反应方式来预防FA的发展。

The symptoms of food allergy (FA) result from the release of certain substances by cells of the immune system, called mast cells and basophils, triggered by the interaction between allergy antibodies and food allergens. FA is often diagnosed using skin prick test or by detecting IgE (allergy antibodies) in the blood. However, more common than being food allergic is to have a positive allergy test to that food. For example, only 1 out of 5 children with a positive allergy test to peanut in the United Kingdom has peanut allergy. In the equivocal cases (more than 50% of patients), an oral food challenge (OFC) is required. OFC consists in giving the patient the suspected food in a controlled environment to see whether the patient develops an allergic reaction. OFC are quite expensive, time-consuming and place the patient at risk of a potentially severe reaction, but this is currently the gold-standard for the diagnosis of FA. In my MRC-funded PhD project, I developed a new blood test called the basophil activation test (BAT) that works like an OFC in a test tube. BAT to peanut showed 97% accuracy in the diagnosis of peanut allergy and reduced the need for OFC by two thirds. In this project, I will develop similar diagnostic tests for cow's milk and egg allergies, which are the most common food allergies in childhood, and for sesame and cashew, which are two of the foods that most commonly require OFC as conventional allergy tests fail to diagnose allergy correctly. I anticipate that BAT will lead to a significant improvement of care for allergic patients and will reduce the costs and anxiety associated with OFC.BAT requires the use of fresh blood cells. As part of an MRC Award, I developed a test similar to BAT using a cell line that is grown in the laboratory and thus is readily available. I will test various samples of peanut allergic and non allergic patients to validate this assay as a biomarker of peanut allergy. I have developed a similar assay to test the ability of antibodies in the blood of non allergic patients to block IgE - this is the inhibition of mast cell activation test (IMAT), that I will validate as a biomarker of food tolerance. These assays could be used in future studies to test samples collected far from the laboratory or to test in parallel samples that have been collected at different time points, in relation to allergy or tolerance.To understand why some patients have a positive allergy test and are not allergic, I will determine which specific part of the allergen the antibodies of allergic patients and non allergic individuals recognise. It is possible that allergic and tolerant patients recognise different parts of the allergen that may or may not be able to trigger allergic symptoms, respectively. It is also possible that allergic and tolerant patients recognise the same parts of the allergen molecule but tolerant individuals generate antibodies of a different type that are able to block IgE. In collaboration with Professors Brian Sutton and Hannah Gould, artificial antibodies will be generated based on the antibodies of a peanut allergic patient and a crystal formed by these antibodies and by peanut allergens will help to investigate which part of the allergen is recognised by the IgE allergy antibodies. Mutant allergens will be generated by changing the allergen at specific sites. I will be testing these mutant allergens alongside with naturally occurring peanut allergens regarding their ability to cause allergic symptoms in the MAT. Blocking antibodies directed at the same part of the peanut allergens will be generated and its blocking activity tested on the IMAT. Understanding precisely what is happening when a patient is allergic and when a patient is not allergic despite the presence of IgE antibodies will help us to find ways to treat patients with FA and to prevent the development of FA by modifying the way the immune system responds to peanut or other food allergens.