Genetic and immunological characterization of commercial infectious bronchitis virus vaccines used in Korea

The aim of the study was to investigate the genetic and immunogenic features of commercial vaccines against infectious bronchitis virus (IBV), which is a major contagious pathogen of poultry. Although numerous vaccines have been developed based on the genetic characteristics of field strains, the continual emergence of variants decreases vaccine efficacy and cross-protection. To address this issue, we compared the S1 gene sequences of three IBV vaccines commercially available in Korea with those of various field isolates. Phylogenetic analysis showed that the vaccine strains clustered into two different lineages. Comparison of commercial vaccines with their parental viruses showed that most of the genetic variability occurred around hypervariable regions (HVRs). Conversely, antigenic stimulation with commercial vaccines and regional IBV variants was not sufficient to alter major immune cell phenotypes. Our study suggests that vaccines should be selected carefully based on their genetic background because genetic variability can affect the antigenicity of vaccines and host immune responses.