The recombinant IBV strain SX/2409 exhibited a significantly higher mortality rate of 60% compared to 20% for its major parent strain SX/2408.
Does recombination with a vaccine strain increase the virulence and mortality of avian infectious bronchitis virus in chicks?
Recombination of an avian infectious bronchitis virus field strain with a live vaccine strain directly drove the evolution of a more virulent phenotype with higher mortality in chicks.
Absolute Event Rate: 0% vs 0%
Avian infectious bronchitis virus (IBV), a major pathogen in the poultry industry, evolves rapidly via genetic mutations and recombination. While recombination between field and live vaccine strains is well-documented, its direct role in viral virulence remains unclear. In this study, four novel IBV field strains (SX/2407, SX/2408, SX/2409, SX/2410) were isolated from a single layer farm in Shanxi Province, China, and genetically characterized. Comprehensive genomic analysis revealed that SX/2409 is a natural recombinant, with SX/2408 (co-isolated) as the major parent and a 4/91-like vaccine lineage as the minor parent. To assess the functional impact of this recombination, pathogenicity was compared in chicks. Notably, SX/2409 exhibited markedly enhanced virulence, with a significantly higher mortality rate (60%) than its major parent SX/2408 (20%). The other isolates, SX/2407 and SX/2410, caused 50% and 0% mortality, respectively. Our findings provide compelling field evidence that recombination with a live vaccine strain can directly drives the evolution of a more virulent IBV phenotype. These results highlight the potential evolutionary risks of current vaccination strategies and emphasize the critical need for robust molecular surveillance and development of safer next-generation vaccines.
Huang et al. (Sun,) reported a other. The recombinant IBV strain SX/2409 exhibited a significantly higher mortality rate of 60% compared to 20% for its major parent strain SX/2408.