Virological characteristics of the SARS-CoV-2 KP.3.1.1 variant

The SARS-CoV-2 JN.1 variant (BA.2.86.1.1), arising from BA.2.86.1 with spike protein (S) substitution S:L455S, outcompeted the previously predominant XBB lineages by the beginning of 2024.¹ Subsequently, JN.1 subvariants including KP.2 (JN.1.11.1.2) and KP.3 (JN.1.11.1.3), which acquired additional S substitutions (eg, S:R346T, S:F456L, and S:Q493E) have emerged concurrently (appendix pp 19–20).² Thereafter, JN.1 subvariants, such as LB.1 (JN.1.9.2.1), KP.2.3 (JN.1.11.1.2.3), and KP.3.1.1 (JN.1.11.1.3.1.1), which convergently acquired a deletion of serine at position 31 in S (S:S31del) in addition to the above substitutions, have emerged and have spread as of June 2024 (appendix pp 19–20). We recently reported the virological features of JN.1 subvariants including KP.2, KP.3, LB.1, and KP.2.3.^2,3 Here, we investigated the virological properties of KP.3.1.1.