Mapping and functional analysis of S1 subunit glycosylation of avian infectious bronchitis virus

Glycosylation of the S1 subunit is a critical post-translational modification in coronavirus antigen proteins and plays a key role in vaccine development. The biological role of highly mutable glycosylation sites in virus evolution, however, remains underexplored. In this study, we identified nine glycosylation sites with high mutation rates on the S1 subunit of Avian Infectious Bronchitis Virus (IBV) through evolutionary analysis. Functional analysis of mutant strains revealed that specific mutations, particularly at position 76 (N → V), significantly enhance the strain's protective efficacy and limit viral replication. These findings provide important insights into the role of glycosylation in viral evolution and offer valuable guidance for the development of more effective IBV vaccines.