Development of a Recombinant Single-Cycle Influenza Viral Vector as an Intranasal Vaccine against SARS-CoV-2 and SARS-like Betacoronaviruses

Munro, J.; Melnyk, D.; Schimanski, L.; Afzal, M.; Cohen, A. A.; Keeffe, J.; Bjorkman, P. J.; James, W. S.; Townsend, A. R.; Tan, T. K.

doi:10.1101/2025.11.28.691177

bioRxiv · 10.1101/2025.11.28.691177

Development of a Recombinant Single-Cycle Influenza Viral Vector as an Intranasal Vaccine against SARS-CoV-2 and SARS-like Betacoronaviruses

Munro, J.·Melnyk, D.·Schimanski, L.·Afzal, M.·Cohen, A. A.·Keeffe, J.·Bjorkman, P. J.·James, W. S.·Townsend, A. R.·Tan, T. K.

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Abstract

The COVID-19 pandemic has demonstrated the detrimental potential of zoonotic coronavirus transmission to human populations. Effective vaccines capable of eliciting immunity to SARS-CoV-2 have been pivotal in mitigating the spread of the virus. In this study, we describe the generation of a non-replicating pseudotyped influenza A virus (S-FLU), where the native haemagglutinin (HA) sequence is replaced with the coding sequence of either a membrane-anchored form (TM) or secretory form (Sec) of the receptor-binding domain (RBD) of the ancestral SARS-CoV-2 Wuhan (S-RBD Wuhan). We showed that both S-RBD-TM and S-RBD-Sec viruses can be generated via reverse genetics and grown to high titre. Intranasal immunisation in mice with S-RBD-TM elicits robust serum binding and neutralisation activity against SARS-CoV-2, superior to S-RBD-Sec. Furthermore, we demonstrate that a heterologous prime-boost immunisation regime in mice with S-RBD-TM Wuhan and S-RBD-TM BM48-31 (a distant Clade 3 SARS-like betacoronavirus (sarbecovirus)) increases antibody breadth against mismatched sarbecoviruses compared to homologous prime-boost with S-RBD-TM Wuhan. These results suggest that S-RBD-TM is a promising intranasal vaccine candidate against SARS-CoV-2 and may offer potential as a broadly protective sarbecovirus vaccine.

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Munro, J., Melnyk, D., Schimanski, L., Afzal, M., Cohen, A. A., Keeffe, J., Bjorkman, P. J., James, W. S., Townsend, A. R., Tan, T. K.. 2025-12-01. Development of a Recombinant Single-Cycle Influenza Viral Vector as an Intranasal Vaccine against SARS-CoV-2 and SARS-like Betacoronaviruses. https://doi.org/10.1101/2025.11.28.691177

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