A Japanese Case of COVID-19 Caused by Omicron Strain with Y453F Substitution.

Frequent mutations of SARS-CoV-2 change the strain more transmissible, leading to the pandemic in worldwide. We detected Y453F substitution on Omicron strain, isolated from a Japanese patient in July 2022. While Y453F substitution was identified B1.1.298 lineage in Netherlands and Denmark in 2020, the substitution has not been reported in Omicron strain especially in Japan. Y453F substitution is associated with higher viral infectivity because it is sited in the receptor-binding domain (RBD), and Y453F substitution contributes to increase binding affinity to angiotensin converting enzyme 2 (ACE2). Additionally, Y453F substitution has been reported to escape human leukocyte antigen (HLA), which is known to recognize non-self-antigens in virus-infected cells as cellular immunity, so it should be closely monitored.