Characterization and immunogenicity of nanoparticle vaccines based on Clade 2 and Clade 3 sarbecovirus S2 proteins

The emergence of SARS-CoV-2 and its subsequent variants in addition to the previous SARS-CoV-1 outbreak indicates the importance of developing broadly protective sarbecovirus vaccines. To date, broadly protective vaccines have primarily focused on clade 1 sarbecoviruses including SARS-CoV-2 variants and SARS-like animal viruses. The discovery of clade 2 and clade 3 sarbecoviruses capable of infecting human cells highlights a need to preemptively develop vaccines that can protect against these viruses. Here, we develop stabilized multivalent subunit vaccines from clade 2 and clade 3 sarbecovirus S2 proteins and evaluate their immunogenicity. Clade 2 and clade 3 S2-subunit vaccines elicit cross-reactive antibodies in mice capable of binding to clade 1, 2, and 3 sarbecovirus antigens. Female mice immunized with these S2-based vaccines also provide protection against sarbecovirus challenges from clades 1a and 1b, including a mouse-adapted SARS-CoV-2 strain, XBB, and WIV1.