The establishment and characteristics of cell-adapted IBV strain H120.

Avian infectious bronchitis virus is an important pathogen in poultry worldwide. Vaccination is the only effective way to prevent and control IBV infection. H120, one of the safest vaccine strains, which has been used worldwide as a primary vaccine, cannot adapt to passaged cells, which severely restricts the quality of the vaccine. Based on the reverse genetics of our previous research work, we constructed the recombinant R-H120-Beaudette-p65(S) strain by replacing the complete spike gene of H120 with the corresponding spike gene from the Beaudette p65 strain. Some biological characteristics, including replication kinetics, virulence and immunological properties of R-H120-Beaudette-p65(S) have been evaluated. The results showed that biological characteristics of R-H120-Beaudette-p65(S), such as replication kinetics in embryonated chicken eggs (ECEs) and embryo virulence, were similar to those of H120. In addition, R-H120-Beaudette-p65(S) could induce a similar antibody titre and provide up to 80 % immune protection in chickens challenged with the M41 strain. These results indicate that R-H120-Beaudette-p65(S) has the potential for further development as a cell-adapted vaccine.