A spike-trimer protein-based tetravalent COVID-19 vaccine elicits enhanced breadth of neutralization against SARS-CoV-2 Omicron subvariants and other variants

Multivalent vaccines combining crucial mutations from phylogenetically divergent variants could be an effective approach to defend against existing and future SARS-Co V-2 variants.In this study,we developed a tetravalent COVID-19 vaccine SCTV01E,based on the trimeric Spike protein of SARS-Co V-2 variants Alpha,Beta,Delta,and Omicron BA.1,with a squalenebased oil-in-water adjuvant SCT-VA02B.In the immunogenicity studies in na?ve BALB/c and C57BL/6J mice,SCTV01E exhibited the most favorable immunogenic characteristics to induce balanced and broad-spectrum neutralizing potencies against pre-Omicron variants(D614G,Alpha,Beta,and Delta)and newly emerging Omicron subvariants(BA.1,BA.1.1,BA.2,BA.3,and BA.4/5).Booster studies in C57BL/6J mice previously immunized with D614G monovalent vaccine demonstrated superior neutralizing capacities of SCTV01E against Omicron subvariants,compared with the D614G booster regimen.Furthermore,SCTV01E vaccination elicited na?ve and central memory T cell responses to SARS-Co V-2 ancestral strain and Omicron spike peptides.Together,our comprehensive immunogenicity evaluation results indicate that SCTV01E could become an important COVID-19 vaccine platform to combat surging infections caused by the highly immune evasive BA.4/5 variants.SCTV01E is currently being studied in a head-to-head immunogenicity comparison phase 3 clinical study with inactivated and m RNA vaccines(NCT05323461).

An antibody cocktail with broadened mutational resistance and effective protection against SARS-CoV-2

Neutralizing antibodies have been proven to be highly effective in treating mild and moderate COVID-19 patients,but continuous emergence of SARS-CoV-2 variants poses significant challenges.Antibody cocktail treatments reduce the risk of escape mutants and resistance.In this study,a new cocktail composed of two highly potent neutralizing antibodies(HB27 and H89Y)was developed,whose binding epitope is different from those cocktails that received emergency use authorization.This cocktail showed more potent and balanced neutralizing activities(IC_(50)0.9–11.3 ng mL^(-1))against a broad spectrum of SARS-CoV-2 variants over individual HB27 or H89Y antibodies.Furthermore,the cocktail conferred more effective protection against the SARS-CoV-2 Beta variant in an aged murine model than monotherapy.It was shown to prevent SARS-CoV-2 mutational escape in vitro and effectively neutralize 61 types of pseudoviruses harbouring single amino acid mutation originated from variants and escape strains of Bamlanivimab,Casirivimab and Imdevimab with IC_(50)of 0.6–65 ng mL^(-1).Despite its breadth of variant neutralization,the HB27+H89Y combo and EUA cocktails lost their potencies against Omicron variant.Our results provide important insights that new antibody cocktails covering different epitopes are valuable tools to counter virus mutation and escape,highlighting the need to search for more conserved epitopes to combat Omicron.

Mutation N856K in spike reduces fusogenicity and infectivity of Omicron BA.1

Dear Editor,COVID-19 lung pathology is characterized by interstitial pneumonia with cell-cell fusion-induced syncytia and extensive tissue damage.1 The correlation between viral fusogenicity and pathogenicity has been reported in SARS-CoV-2 variants.2 Compared with the previous Delta or D614G variants,Omicron BA.1 has been proven to be less fusogenic and pathogenic.