Novel mRNA vaccines targeting epitope-rich regions of avian coronavirus enhance immunogenic efficacy.

Avian coronavirus, also known as infectious bronchitis virus (IBV), poses a significant threat to the poultry industry, with the IBV QX variant strain now endemic in multiple countries. Traditional vaccines have demonstrated limited effectiveness in providing robust immune protection against this pathogen. In this study, we developed two IBV QX strain S1-mRNA vaccines based on different antigen domains and evaluated their safety and immune efficacy. The S1A mRNA-LNP and S1B mRNA-LNP vaccines were successfully produced based on epitope prediction of the S1 protein of the IBV QX strain. Both developed mRNA vaccines, along with a conventional inactivated vaccine, were capable of stimulating serum antibody production. ELISPOT assay results showed that the mRNA vaccines were more potent in stimulating lymphocytes to secrete interferon-γ (IFN-γ) than the inactivated vaccine. This enhanced immunostimulatory capacity translated into a significant reduction in viral load within the kidneys. Moreover, the S1A mRNA vaccine conferred immune protection earlier than the inactivated vaccine. In conclusion, the IBV S1-mRNA vaccines developed in this study can protect against IBV infection by inducing cellular and humoral immune responses. Selecting different S1 regions also affects the immunogenic efficacy of the mRNA vaccine.