Characterization of the immune resistance of SARS-CoV-2 Mu variant and the immunity induced by Mu infection

We have revealed that the SARS-CoV-2 Mu variant is highly resistant to COVID-19 convalescent sera and vaccine sera. ¹ However, it remains unclear how the immune resistance of the Mu variant is determined. Also, although the Mu variant is highly resistant to the sera obtained from COVID-19 convalescent during early pandemic (i.e., infected with prototypic virus) and vaccinated individuals (i.e., immunized based on prototypic virus), it was unaddressed how the convalescent sera from Mu-infected individuals function. In this study, we revealed that the two mutations in the spike protein of Mu variant, YY144-145TSN and E484K, are responsible for the potent immune resistance of Mu variant. Additionally, we showed that the convalescent sera obtained from the Mu-infected individuals can be broadly antiviral against the Mu variant as well as other SARS-CoV-2 variants of concern/interest. Our findings suggest that developing novel vaccines based on the Mu variant can be more effective against a broad range of SARS-CoV-2 variants.