Absolute quantification of bovine lactadherin to screen the anti-rotavirus activity of dairy ingredients

The anti-rotavirus components in breast milk and infant formulas play an important role in the prevention of rotavirus infection. The present study examined whether the levels of phospholipids and bovine lactadherin, which are the major components and proteins of the milk fat globule membrane complex, are useful indices of the anti-rotavirus activity of dairy ingredients used in infant formulas. We compared anti-rotavirus activity of two kinds of dairy ingredients enriched in the milk fat globule membrane complex, high-fat whey protein concentrate (high-fat WPC) and butter milk powder (BMP), using 50% inhibition concentration (IC50) and linear inhibition activity for the levels of solid contents, total proteins, phospholipids and bovine lactadherin. Here, we developed a quantification method of bovine lactadherin using full-length isotope-labeled proteins to measure bovine lactadherin levels in these dairy ingredients. The evaluation of anti-rotavirus activity showed that the difference in IC50 was the smallest when the two dairy ingredients were compared at bovine lactadherin level among other indices in this study. Additionally, no significant difference was observed between the inhibition linearity of two dairy ingredients when evaluating only the bovine lactadherin levels. These results indicated that the level of bovine lactadherin was more strongly associated with anti-rotavirus activity than the level of phospholipids. Our results suggest that bovine lactadherin levels easily estimate the anti-rotavirus activity of dairy ingredients, and it can be one of the criteria used in selecting ingredients for infant formulas.

母乳及婴儿配方奶粉中的抗轮状病毒成分在预防轮状病毒感染方面发挥着至关重要的作用。本研究旨在探究磷脂和牛乳清蛋白（牛乳脂肪球膜复合物的主要成分和蛋白质）水平是否可作为评估婴儿配方奶粉中乳制品抗轮状病毒活性的有效指标。研究通过比较富含牛乳脂肪球膜复合物的两种乳制品——高脂乳清蛋白浓缩物（高脂WPC）和黄油粉（BMP）——的50%抑制浓度（IC50）以及线性抑制活性，对固体含量、总蛋白、磷脂和牛乳清蛋白水平进行了分析。本研究开发了一种利用全长同位素标记蛋白的定量方法，以测定这些乳制品中的牛乳清蛋白水平。对抗轮状病毒活性的评估表明，在比较两种乳制品时，以牛乳清蛋白水平为其他指标中的最小差异。此外，在仅评估牛乳清蛋白水平时，两种乳制品的抑制线性无显著差异。这些结果表明，牛乳清蛋白水平与抗轮状病毒活性关联更为紧密，相较于磷脂水平。本研究结果提示，牛乳清蛋白水平易于估计乳制品的抗轮状病毒活性，并可成为选择婴儿配方奶粉成分的标准之一。