Rupa P, Nakamura S, Mine Y
Department of Food Science, University of Guelph, Guelph, ON, Canada N1G 2W1.
Clin Exp Allergy. 2007 Jun;37(6):918-28. doi: 10.1111/j.1365-2222.2007.02720.x.
Food allergies are on the rise and it is estimated that in North America, 8% of the children and 4% of the adults have food allergies. Food allergies tend to occur more often in children than in adults due to their immature digestive and immune systems. Hen's egg is among the most common cause of food-induced allergic reactions in North America.
The present study was undertaken to investigate the role of N-glycans of the third domain of ovomucoid in IgE binding and modulation of allergen-specific immune response in BALB/c mice.
The cDNA encoding the third domain of ovomucoid was inserted into the yeast genome and expressed in Pichia pastoris X-33 cells, under the control of the glyceraldehyde-3-phosphate (GAP) dehydrogenase promoter for constitutive expression to obtain a post-translationally modified and functionally active ovomucoid third domain. Upon expression, the protein was secreted into the extracellular medium and was purified by size exclusion chromatography. The recombinant protein was produced at 10 mg/L of the culture supernatant. BALB/c mice were sensitized with the recombinant and native forms of glycosylated ovomucoid third domain antigen. The allergic response of the native and the recombinant glycosylated forms of ovomucoid third domain antigens were compared using antibody and cytokine measurements.
ELISA tests indicated a significant decrease in specific IgE antibodies to the recombinant N-linked glycosylated form (P-Gly), when compared with the native glycosylated form (DIII+) using mice sera. Immunization with P-Gly induced the production of IFN-gamma [T-helper type 1 (Th1) response] and lowered the production of IL-4 (Th2 response), and a skewed balance towards the Th1 cytokine demonstrated that P-Gly has a modulating ability on Th1/Th2 balance to down-regulate Th2 response. Furthermore, N-linked glycan (N28) in the third domain of ovomucoid was shown to be associated with suppression of the allergic response.
Therefore, we can conclude that P-Gly facilitates and contributes to the discovery of new molecular target for the development of a safe and specific therapeutic vaccine for the treatment of egg allergy, and oligosaccharides do seem to play a major role in the suppression of IgE-binding activity.
食物过敏的发生率正在上升，据估计，在北美，8%的儿童和4%的成年人患有食物过敏。由于儿童的消化和免疫系统不成熟，食物过敏在儿童中比在成年人中更常见。在北美，鸡蛋是食物诱发过敏反应最常见的原因之一。
本研究旨在探讨卵类黏蛋白第三结构域的N-聚糖在BALB/c小鼠中IgE结合及变应原特异性免疫反应调节中的作用。
将编码卵类黏蛋白第三结构域的cDNA插入酵母基因组，并在甘油醛-3-磷酸（GAP）脱氢酶启动子的控制下在毕赤酵母X-33细胞中表达，以进行组成型表达，从而获得翻译后修饰且具有功能活性的卵类黏蛋白第三结构域。表达后，该蛋白分泌到细胞外培养基中，并通过尺寸排阻色谱法进行纯化。重组蛋白在培养上清液中的产量为10 mg/L。用重组和天然形式的糖基化卵类黏蛋白第三结构域抗原对BALB/c小鼠进行致敏。使用抗体和细胞因子检测比较卵类黏蛋白第三结构域抗原的天然和重组糖基化形式的过敏反应。
ELISA检测表明，与使用小鼠血清的天然糖基化形式（DIII+）相比，重组N-连接糖基化形式（P-Gly）的特异性IgE抗体显著减少。用P-Gly免疫诱导了IFN-γ的产生[1型辅助性T细胞（Th1）反应]，并降低了IL-4的产生（Th2反应），向Th1细胞因子的偏向平衡表明P-Gly对Th1/Th2平衡具有调节能力，可下调Th2反应。此外，卵类黏蛋白第三结构域中的N-连接聚糖（N28）被证明与过敏反应的抑制有关。
因此，我们可以得出结论，P-Gly有助于并促进发现用于开发安全、特异性治疗性疫苗治疗鸡蛋过敏的新分子靶点，并且寡糖似乎在抑制IgE结合活性中起主要作用。
