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Updated: Apr 2, 2026

Rapid, Seamless Generation of Recombinant Poxviruses using Host Range and Visual Selection
Published on: May 24, 2020
Recombination with a vaccine strain drives the evolution of a more virulent phenotype in avian infectious bronchitis
Zhonglin Huang1, Xu Wang1, Hongfeng Ren1
1Shanxi Key Laboratory of Animal Disease Research, Prevention and Control, College of Veterinary Medicine, Shanxi Agricultural University, Jinzhong 030801, China.
Abstract:
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.
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