Nakashio Maiko, Ohgitani Eriko, Shin-Ya Masaharu, Kawamoto Masaya, Ichitani Masaki, Kobayashi Makoto, Takihara Takanobu, Kinugasa Hitoshi, Ishikura Hiroyasu, Mazda Osam
Department of Immunology, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan.
Department of Emergency and Critical Care Medicine, Faculty of Medicine, Fukuoka University, Fukuoka 814-0180, Japan.
Bioengineering (Basel). 2023 Sep 9;10(9):1068. doi: 10.3390/bioengineering10091068.
Continuing caution is required against the potential emergence of SARS-CoV-2 novel mutants that could pose the next global health and socioeconomical threats. If virus in saliva can be inactivated by a beverage, such a beverage may be useful because the saliva of infected persons is the major origin of droplets and aerosols that mediate human-to-human viral transmission. We previously reported that SARS-CoV-2 was significantly inactivated by treatment in vitro with tea including green tea and black tea. Catechins and its derived compounds galloylated theaflavins (gTFs) bound to the receptor-binding domain (RBD) of the S-protein and blocked interaction between RBD and ACE2. Black tea is often consumed with sugar, milk, lemon juice, etc., and it remains unclarified whether these ingredients may influence the anti-SARS-CoV-2 effect of black tea. Here, we examined the effect of black tea on Omicron subvariants in the presence of these ingredients. The infectivity of Omicron subvariants was decreased to 1/100 or lower after treatment with black tea for 10 s. One or two teaspoons of milk (4~8 mL) completely blocked the anti-viral effect of a cup of tea (125 mL), whereas an addition of sugar or lemon juice failed to do so. The suppressive effect was dose-dependently exerted by milk casein but not whey proteins. gTFs were coprecipitated with casein after acidification of milk-supplemented black tea, strongly suggesting the binding of gTFs to casein. The present study demonstrates for the first time that an addition of milk cancelled the anti-SARS-CoV-2 effect of black tea due to binding of casein to gTFs.
仍需持续警惕可能出现的新型SARS-CoV-2突变体，它们可能构成下一轮全球健康和社会经济威胁。如果一种饮料能使唾液中的病毒失活，那么这种饮料可能会很有用，因为感染者的唾液是介导人际间病毒传播的飞沫和气溶胶的主要来源。我们之前报道过，SARS-CoV-2在体外经绿茶和红茶等茶处理后会显著失活。儿茶素及其衍生化合物没食子酰化茶黄素（gTFs）与S蛋白的受体结合域（RBD）结合，并阻断RBD与ACE2之间的相互作用。红茶通常与糖、牛奶、柠檬汁等一起饮用，这些成分是否会影响红茶对SARS-CoV-2的抗病毒效果尚不清楚。在此，我们研究了在这些成分存在的情况下红茶对奥密克戎亚变体的影响。用红茶处理10秒后，奥密克戎亚变体的感染性降低到1/100或更低。一或两茶匙牛奶（4~8毫升）完全阻断了一杯茶（125毫升）的抗病毒效果，而添加糖或柠檬汁则没有。牛奶酪蛋白呈剂量依赖性发挥抑制作用，而乳清蛋白则不然。在添加牛奶的红茶酸化后，gTFs与酪蛋白共沉淀，强烈表明gTFs与酪蛋白结合。本研究首次证明，由于酪蛋白与gTFs结合，添加牛奶会消除红茶对SARS-CoV-2的抗病毒效果。
