The spike (S) protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) plays a key role in viral infectivity. It is also the major antigen stimulating the host's protective immune response, specifically, the production of neutralizing antibodies. Recently, a new variant of SARS-CoV-2 possessing multiple mutations in the S protein, designated P.1, emerged in Brazil. Here, we characterized a P.1 variant isolated in Japan by using Syrian hamsters, a well-established small animal model for the study of SARS-CoV-2 disease (COVID-19). In hamsters, the variant showed replicative abilities and pathogenicity similar to those of early and contemporary strains (i.e., SARS-CoV-2 bearing aspartic acid [D] or glycine [G] at position 614 of the S protein). Sera and/or plasma from convalescent patients and BNT162b2 messenger RNA vaccinees showed comparable neutralization titers across the P.1 variant, S-614D, and S-614G strains. In contrast, the S-614D and S-614G strains were less well recognized than the P.1 variant by serum from a P.1-infected patient. Prior infection with S-614D or S-614G strains efficiently prevented the replication of the P.1 variant in the lower respiratory tract of hamsters upon reinfection. In addition, passive transfer of neutralizing antibodies to hamsters infected with the P.1 variant or the S-614G strain led to reduced virus replication in the lower respiratory tract. However, the effect was less pronounced against the P.1 variant than the S-614G strain. These findings suggest that the P.1 variant may be somewhat antigenically different from the early and contemporary strains of SARS-CoV-2.

严重急性呼吸系统综合症冠状病毒 2 (SARS-CoV-2) 的刺突 (S) 蛋白在病毒传染性中起关键作用。它也是刺激宿主保护性免疫反应的主要抗原，特别是中和抗体的产生。最近，在巴西出现了一种新的 SARS-CoV-2 变体，它在 S 蛋白中有多个突变，命名为 P.1。在这里，我们通过使用叙利亚仓鼠（一种用于研究 SARS-CoV-2 疾病（COVID-19）的完善的小动物模型，对在日本分离的 P.1 变体进行了表征。在仓鼠中，该变体显示出与早期和当代毒株相似的复制能力和致病性（即，在 S 蛋白的 614 位带有天冬氨酸 [D] 或甘氨酸 [G] 的 SARS-CoV-2）。来自恢复期患者和 BNT162b2 信使 RNA 疫苗接种者的血清和/或血浆在 P.1 变体、S-614D 和 S-614G 菌株中显示出相当的中和效价。相比之下，P.1 感染患者的血清对 S-614D 和 S-614G 菌株的识别不如 P.1 变体。先前感染 S-614D 或 S-614G 菌株有效地阻止了 P.1 变体在再次感染后仓鼠下呼吸道中的复制。此外，将中和抗体被动转移到感染 P.1 变体或 S-614G 毒株的仓鼠，导致下呼吸道病毒复制减少。然而，对 P.1 变体的影响不如 S-614G 菌株明显。这些发现表明 P.