The measurement protocol is as follows: 96-well plates (Thermo, 442,404) were coated with 10?g/ml of Wuhan-hu-1 RBD or mutated RBD in PBS overnight. observed approximately 20 to 30% for Alpha, Kappa, and Delta variant, and 40 to 45% for Beta and Gamma variant. The titers Glyburide against all strains decreased over time, and interestingly, while titers against Wuhan-hu-1 decreased by 23%, those to Delta variant decreased by 70%. Our simple, cost-effective, and non-hazardous system will be relevant to process numerous samples, such as monitoring titers against prevalent strains after contamination or vaccination. Keywords: COVID-19, SARS-CoV-2, Neutralizing antibody, Variants strain, Chronological switch 1.?Introduction SARS-CoV-2 acquires mutations as the infection spreads. In particular, mutations in the receptor binding domain name (RBD) region of the spike protein, which is used by the computer virus to enter cells, may cause changes in infectivity and in the reactivity of neutralizing antibodies [[1], [2], [3]]. Even in the early stage of the pandemic, the D614G mutation increased and replaced the previous strain within a few months; however, since this mutation was outside the RBD, it did not have a serious impact on the titers of neutralizing antibodies, and increased transmissibility is thought to be the cause of its spread [3,4]. Three variants have been reported from 2020 and designated as variants of issues (VOCs) by the World Health Business (WHO): B.1.1.7 (Alpha variant), which first emerged in England; B.1.351 (Beta variant), which first emerged in South Africa; and P.1 Glyburide (Gamma variant), which first emerged in Brazil. The Alpha variant is usually reported to have little effect on neutralizing titer [[5], [6], [7]] or only a mild decrease of 22% [8]. In contrast, strong immune evasion was reported for the Beta and Gamma variants. The Beta variant shows an 8-to 13-fold reduction in convalescent plasma, and a 7- to 9-fold or 65% reduction in vaccinated serum [6,7,9]. The Gamma variant shows a 3- to 5-fold reduction in convalescent and vaccinated plasma/serum [7,10,11]. Even therapeutic monoclonal antibodies have been reported to have reduced or lost neutralizing ability against variants with the E484K mutation [7,9,12]. In April and May 2021, there was a rapid increase in the number of patients in India, mainly due to the B.1.617 strain [13]. Mouse monoclonal to PR This lineage has three main subtypes: B.1.617.1 (Kappa variant) and B.1.617.3, characterized by Glyburide L452R and E484Q mutation in RBD, and B.1.617.2 (Delta variant), characterized by L452R and T478K in RBD. Due to their high transmissibility, these variants have spread to 96 countries as of the end of June, and the WHO has classified the Kappa variant and the Delta variant as a variant of interest (VOI) and a variant of concern (VOC), respectively [13]. These variants have also been reported to escape from humoral immunity, with the Kappa variant showing a 2- to 7-fold decrease in recovered sera and a 3- to 7-fold decrease in post-vaccination sera [[14], [15], [16]], and the Delta variant showing a 6-fold decrease in recovered sera and a 5- to 8-fold decrease in post-vaccination neutralizing titer [16,17]. Immune evasion also shows up in the vaccine’s effectiveness: 89.5 to 93.7% for the Alpha variant, 75.0% for the Beta variant, and 88.0% for the Delta variant compared to 95% for the original Wuhan-hu-1 strain [18,19]. In Japan, variants with the D614G mutation were in the beginning the majority, and VOC and VOI strains were not detected until the end of 2020. Three VOC strains, Alpha, Beta, and Gamma variants, were first detected in airport quarantine on December 25, 2020, December 28, 2020, and January 6, 2021, respectively. A sample taken on January 22 was the first time that this Alpha variant was detected in Japan from a person with no history of travel abroad [20]. Therefore, by the end of 2020, most infected patients were infected with variants having only the D614G mutation. The Alpha variant became dominant in early.