Lisson M, Novak N, Erhardt G
Department of Animal Breeding and Genetics, Justus-Liebig University, 35390 Gießen, Germany.
Department of Dermatology and Allergy, University of Bonn Medical Center, 53105 Bonn, Germany.
J Dairy Sci. 2014;97(4):1939-54. doi: 10.3168/jds.2013-7355. Epub 2014 Jan 31.
The allergenicity of the caseins (CN), one of the major allergens in cow milk, is well characterized and their immunoglobulin E (IgE)-binding epitopes have been identified. However, investigations about the allergenic potential of the genetic variants occurring in the caseins are lacking. Therefore, this study determined the influence of the genetic polymorphism on IgE binding to epitopes of bovine casein variants. Furthermore, differences in IgE binding between epitopes of goats and water buffaloes were analyzed. A set of 187 peptides, covering the previously identified sequential IgE-binding epitopes of αS1-, αS2-, β-, and κ-CN variants from cows and the corresponding homologous peptides of water buffaloes and goats, were synthesized and tested by means of peptide microarray for IgE binding, using sera from 16 cow milk-sensitized individuals. Seven of the 16 sera samples showed positive signals on microarrays and were included in this study. In 5 αS1-CN variants (A, B, C, E, and I), the AA substitution or deletion affected the immunoreactivity of epitopes AA 4 to 23, AA 17 to 36, AA 83 to 102, AA 173 to 192, and AA 175 to 194, as well as of the variant-specific peptides AA 184 to 196, AA 187 to 199, AA 174 to 193, and AA 179 to 198, which were found to resist gastrointestinal digestion. Variation in IgE binding was further detected for peptides AA 103 to 123 and AA 108 to 129 of 3 β-CN variants (A(1), A(2), and B). The majority of sera showed IgE binding to αS1-CN peptides of cows and the homologous counterpart of goats and water buffaloes. However, αS1- and β-CN epitopes from goats and water buffaloes had lower immunoreactivity than those of cows, but, in some cases, higher or exclusive IgE binding was observed. The results of this study indicate that genetic variants of the caseins differ in their allergenicity. This might be useful in the search for a suitable protein source for cow milk-allergic patients. In addition, milk from water buffaloes and goats harbor an allergenic potential due to cross-reactivity of IgE antibodies with cow milk caseins and are, therefore, not an acceptable alternative in the nutrition of cow milk-allergic patients.
酪蛋白（CN）是牛奶中的主要过敏原之一，其致敏性已得到充分表征，并且其免疫球蛋白E（IgE）结合表位也已被确定。然而，关于酪蛋白中出现的基因变体的致敏潜力的研究尚缺。因此，本研究确定了基因多态性对IgE与牛酪蛋白变体表位结合的影响。此外，还分析了山羊和水牛表位之间IgE结合的差异。合成了一组187种肽，涵盖先前鉴定出的来自奶牛的αS1-、αS2-、β-和κ-CN变体的连续IgE结合表位以及水牛和山羊的相应同源肽，并使用来自16名牛奶致敏个体的血清通过肽微阵列检测IgE结合情况。16份血清样本中有7份在微阵列上显示出阳性信号，并被纳入本研究。在5种αS1-CN变体（A、B、C、E和I）中，氨基酸替换或缺失影响了表位AA 4至23、AA 17至36、AA 83至102、AA 173至192和AA 175至194以及变体特异性肽AA 184至196、AA 187至199、AA 174至193和AA 179至198的免疫反应性，这些肽被发现能抵抗胃肠道消化。在3种β-CN变体（A(1)、A(2)和B）的肽AA 103至123和AA 108至129中进一步检测到IgE结合的变化。大多数血清显示IgE与奶牛的αS1-CN肽以及山羊和水牛的同源对应物结合。然而，山羊和水牛的αS-1和β-CN表位的免疫反应性低于奶牛，但在某些情况下，观察到更高或排他性的IgE结合。本研究结果表明，酪蛋白的基因变体在致敏性方面存在差异。这可能有助于为牛奶过敏患者寻找合适的蛋白质来源。此外，由于IgE抗体与牛奶酪蛋白的交叉反应性，水牛和山羊的奶具有致敏潜力，因此，在牛奶过敏患者的营养中不是可接受的替代品。
