The newly emerged severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant, sublineages BA.1 and BA.2, recently became the dominant variants of concern (VOCs) with significantly higher transmissibility than any other variant appeared and markedly greater resistance to neutralization antibodies and original ancestral WA1 spike-matched vaccine. Therefore, it is urgent to develop vaccines against VOCs like Omicron. Unlike the new booming messenger RNA (mRNA) vaccine, protein vaccines have been used for decades to protect people from various kinds of viral infections and have advantages with their inexpensive production protocols and their relative stability in comparison to the mRNA vaccine. Here, we show that sera from BA.1 spike protein vaccinated mice mainly elicited neutralizing antibodies against BA.1 itself. However, a booster with BA.1 spike protein or a bivalent vaccine composed of D614G and BA.1 spike protein-induced not only potent neutralizing antibody response against D614G and BA.1 pseudovirus, but also against BA.2, other four SARS-CoV-2 VOCs (Alpha, Beta, Gamma, and Delta) and SARS-CoV-2-related coronaviruses (pangolin CoV GD-1 and bat CoV RsSHC014). The two recombinant spike protein vaccines method described here lay a foundation for future vaccine development for broad protection against pan-sarbecovirus.
The SARS‐CoV‐2 Omicron BA.1 variant of concern contains more than 30 mutations in the spike protein, with half of these mutations localized in the receptor‐binding domain (RBD). Emerging evidence suggests that these large number of mutations impact the neutralizing efficacy of vaccines and monoclonal antibodies. We investigated the relative contributions of spike protein and RBD mutations in Omicron BA.1 variants on infectivity, cell–cell fusion, and their sensitivity to neutralization by monoclonal antibodies or vaccinated sera from individuals who received homologous (CoronaVac, SinoPharm) or heterologous (CoronaVac—BNT162b2, BioNTech) and nonhuman primates that received a recombinant RBD protein vaccine. Our data overall reveal that the mutations in the spike protein reduced infectivity and cell–cell fusion compared to the D614G variant. The impaired infectivity and cell–cell fusion were dependent on non‐RBD mutations. We also find reduced sensitivity to neutralization by monoclonal antibodies and vaccinated sera. However, our results also show that nonhuman primates receiving a recombinant RBD protein vaccine show substantial neutralization activity. Our study sheds light on the molecular differences in neutralizing antibody escape by the Omicron BA.1 variant, and highlights the promise of recombinant RBD vaccines in neutralizing the threat posed by the Omicron BA.1 variant.
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