Coronavirus-based vaccine for a highly pathogenic avian influenza virus

Abstract Negative-sense RNA viruses have been widely used as viral vectors for vaccine delivery for three decades. However, little is known about coronaviruses as vectors for delivering vaccines. We recently developed a yeast- based recombination system for rapid construction of infectious cDNA clones for coronaviruses. Using this system, we found for the first time that a recombinant SARS-CoV-2 Omicron JN.1 expressing the stabilized prefusion hemagglutinin (HA) protein of a highly pathogenic avian influenza (HPAI) A (H5N1) virus (dairy cow H5N1) is not only highly attenuated but also induces high levels of JN.1- and H5N1-specific serum IgG in hamsters. This suggests that coronavirus may be an excellent vector for vaccine delivery. Thus, the goal of this project is to explore the feasibility of using two coronaviruses (human coronavirus HCoV-OC43 and SARS-CoV- 2 Omicron variant) as a vector to deliver vaccines against HPAI H5N1 virus. We hypothesize that coronavirus- based HPAI H5N1 vaccine will be highly immunogenic and induce protection against both coronavirus and HPAI H5N1 infection. In Aim 1, the stabilized, nonfunctional trimeric HA and/or tetrameric neuraminidase (NA) protein genes will be inserted into the genomes of an attenuated HCoV-OC43 and an attenuated SARS-CoV-2 Omicron JN.1 strain, and recombinant coronaviruses expressing HA and/or NA proteins will be recovered. Subsequently, the attenuation of these recombinant viruses will be characterized in ex vivo primary human nasal epithelial (HNE) and human bronchial epithelial (HBE) cultures. In Aim 2, hamsters will be immunized intranasally with these coronavirus-based HPAI H5N1 vaccine candidates, systemic and mucosal immune responses will be characterized. The immunized animals will be challenged with coronaviruses and HPAI H5N1, and their protection efficacy will be determined. Upon completion, we expect that we will develop a coronavirus-vectored influenza virus vaccine that is safe, genetically stable, and induces strong systemic and mucosal immunity that protects against these two major respiratory viruses. This project is innovative as it is the first time that a coronavirus has been developed as a vaccine vector for influenza virus. This project will also have a broad and high impact because this strategy could be easily and rapidly adapted to other coronaviruses for delivering vaccines against other pathogens.