Immune evasion of Omicron variants JN.1, KP.2, and KP.3 to the polyclonal and monoclonal antibodies from COVID-19 convalescents and vaccine recipients.

The Omicron BA.2.86 subvariants, JN.1, KP.2, and KP.3, have become predominant globally, raising concerns about their immune evasion from vaccines and monoclonal antibody (mAb) treatments. These variants harbor more receptor-binding domain (RBD) mutations than the XBB and EG.5 sub-lineages, which are already known to compromise vaccine and therapeutic efficacy. We evaluated sera from individuals vaccinated with inactivated vaccines, with or without breakthrough infections, as well as COVID-19 convalescents. Our results showed a substantial decrease in serum neutralizing activity against the JN.1, KP.2, XBB.1.5, and EG.5.1 variants compared to BA.2. Additionally, we developed 19 neutralizing antibodies from memory B cells, with some retaining efficacy against earlier Omicron variants. However, potency was notably diminished against newer subvariants like BF.7, BQ.1, XBB.1.5, and BA.2.86. Of mAbs, those isolated from COVID-19 convalescents, particularly SA-3, exhibited exceptional potency across ten variants from BA.2 to KP.2, with IC50 values ranging from 0.006 to 2.546 μg/mL. However, SA-3 had lost neutralizing activity against the KP.3 due to the Q493E mutation, but the KP.3 became susceptible to neutralization by the other mAb, SA-6. In contrast, SA-6 was unable to neutralize KP.2 because of the presence of R346T mutation. Our findings underscore the importance of continuous surveillance of viral evolution and the need for updated vaccines and therapeutics to combat the ongoing evolution of SARS-CoV-2, particularly in the context of emerging variants that escape both vaccine-induced immunity and monoclonal antibody treatments.