Neutralization of SARS-CoV-2 KP.1, KP.1.1, KP.2 and KP.3 by human and murine sera.

We report SARS-CoV-2 KP.1, KP.1.1, KP.2 and KP.3 neutralizing antibody titers. They displayed increased immune evasion compared to JN.1, especially KP.1 and KP.3, for participants who experienced BF.7/BA.5.2 breakthrough infection or received bivalent (delta/BA.5) vaccine boosting. Second XBB sub-variants breakthrough infection enhanced the neutralization responses. HK.3-JN.1 RBD-heterodimer induced balanced and potent neutralizing responses against recently-circulating SARS-CoV-2 sub-variants in mice, supporting to replace the COVID-19 antigen containing JN.1 or its sub-variants.