Targeting Key Factors Involved in Immune Reactions mediated by Tick Bites to the Carbohydrate alpha-Gal

对红肉的迟发性过敏反应依赖于半乳糖-α-1，3-半乳糖(Alpha-Gal)IgE抗体的存在。临床症状是由接触红肉或内脏引发的，但也会引发携带治疗性抗体的明胶或阿尔法-半乳糖。最近，我们从猪肾中鉴定出Alpha-Gal携带蛋白氨基肽酶N和血管紧张素转换酶I，并通过在Alpha-Gal过敏患者的皮肤点刺试验中诱导嗜碱性细胞活化和阳性反应来显示它们的临床意义。与针对Alpha-Gal的抗体不同，后者是在生命早期通过与微生物的接触在生理上诱导的，目前公认的假说是针对Alpha-Gal的IgE的诱导是由扁虱叮咬介导的。这得到了几条证据的支持：来自世界不同地区的Amblyomma，Ixodes和Haemogsalis物种的扁虱叮咬与Alpha-Gal过敏症之间存在很强的相关性，扁虫叮咬后针对Alpha-Gal的IgE增加，以及在蓖麻硬蜱的胃肠道中检测到Alpha-Gal。本建议的目的是：一)分析携带天然和工程分子的α-半乳糖基转移酶的致敏性；二)健康、致敏和最近暴露的个体中与α-半乳糖基转移酶表位免疫反应有关的细胞表型；三)通过诱导对α-半乳糖基转移酶的免疫反应，分析α-1，3-半乳糖基转移酶缺陷小鼠的致敏机制。为此，将研究通过皮肤接触抗原的不同途径，模拟扁虱叮咬，在添加扁虱唾液作为天然佐剂的情况下进行研究。扁虱中IgE活性分子的鉴定将有助于更好地对患者进行诊断和风险管理。更重要的是，使用Alpha-Gal过敏症作为模型疾病，我们的结果将阐明通过皮肤诱发免疫反应和对碳水化合物过敏原致敏的基本机制。

Delayed anaphylaxis to red meat is dependent on the presence of IgE-antibodies to galactose-alpha-1,3-galactose (Alpha-Gal). Clinical symptoms are triggered by contact to red meat or innards but also gelatin or Alpha-Gal carrying therapeutic antibodies. Recently we could identify the Alpha-Gal carrying proteins Aminopeptidase N and Angiotensin converting enzyme I from pork kidney and show their clinical relevance by inducing basophil activation and positive responses in skin prick tests in patients with Alpha-Gal allergy. In contrast to IgG antibodies directed to Alpha-Gal, which are physiologically induced by contact to microbes in early life, the currently accepted hypothesis is that the induction of IgE directed to Alpha-Gal is mediated by tick bites. This is supported by several lines of evidence: a strong correlation between Alpha-Gal allergy and tick bites from Amblyomma, Ixodes and Haemaphysalis species in different parts of the world, a boosting of IgE directed against Alpha-Gal after a tick bite and the detection of Alpha-Gal in the gastrointestinal tract of Ixodes ricinus. The objectives of the present proposal are i) analysing the allergenicity of Alpha-gal carrying natural and engineered molecules, ii) the phenotyping of cells implicated in immune responses to Alpha-gal epitopes in healthy, sensitized and recently exposed individuals, iii) the analysis of the sensitizing mechanism in an alpha-1,3-galactosyltransferase deficient mouse by inducing immune reactions to Alpha-gal. To this end, different routes of antigen contact via the skin, mimicking a tick bite, will be investigated with and without addition of tick saliva as natural adjuvant. The identification of IgE reactive molecules in ticks will contribute to a better diagnosis and risk management of patients. More important, using Alpha-Gal allergy as a model disease, our results will elucidate the basic mechanisms eliciting immune responses and sensitization to carbohydrate allergens via the skin.