Attenuated Infectious Bronchitis Virus (IBV) Vaccination Induces Protective Humoral and Cellular Immunity Against SARS-CoV-2 in Mammals

Occupational exposure to infectious bronchitis virus (IBV) has been associated with cross-reactivity to other coronaviruses such as SARS-CoV-2. In this study, we investigated the immune response of IBV using reconstituted samples of the commercial H120 Mass-I vaccine (Zoetis) against SARS-CoV-2 infection. Bioinformatics analyses, serological assays, and neutralization tests were conducted to evaluate the neutralizing capacity of anti-IBV antibodies against SARS-CoV-2 in serum samples from poultry farm workers exposed to the IBV-H120 vaccine. Mouse immunization assays and flow cytometry analysis were conducted to characterize the immune response triggered by IBV-H120. Finally, a histological analysis of the lungs of Syrian hamsters vaccinated with IBV and challenged with SARS-CoV-2 (Wuhan and Delta strains) was conducted to evaluate the protective potential of the vaccine. Neutralizing antibodies against IBV-H120 were detected in the serum of poultry farm workers, indicating cross-reactivity with SARS-CoV-2. The immune response in mice immunized with IBV-H120 demonstrated that only the intranasal and oral routes were effective against SARS-CoV-2. An increase in the percentage of CD19⁺ induced by IBV-H120 vaccination was demonstrated by flow cytometry. Intranasal administration of the IBV-H120 vaccine reduced lung damage in Syrian hamsters against the Wuhan and Delta variants of SARS-CoV-2. IBV-H120 elicited both humoral and cellular immune responses in mice and reduced lung damage in hamsters challenged with the Wuhan and Delta variants. This indicates that it could be an improved vaccine for controlling SARS-CoV-2.