Vetnuus | July 2024 27 From these samples, 75 strains of IBV were isolated. The nucleotide and amino acid sequences from the isolated field strains were compared to 42 published references. Phylogenetic analysis revealed that the majority of the strains belonged to the GI-19 lineage, which is the same as the LX4 type that is currently most common. The IBV isolates were genetically diverse and underwent continuing evolution. At least five IBV lineages were co-circulating on commercial broiler chicken farms in the southeast of China. Notably, the GI-19, GI-7, GI-13, and GI-9 lineages were the most common lineages during the two-year observation period and accounted for 85.7% of the isolated strains. Recombination research revealed that several recombinant strains exist among these isolates, resulting in the emergence of novel subbranches, subtypes, and variations. To prevent and control IBV epidemics and outbreaks, a broad-spectrum IBV virus-like particles (VLP) vaccine based on bioinformatics was created, and its ability to protect against GI-19 and GI-1 strains was reviewed. Results demonstrated that administering the IBV VLP vaccine to one-day-olds and 14-day-olds provided excellent protection. We observed a significant increase in the mean antibody titers, reduced virus shedding, and ameliorated histopathology lesions compared to a commercially inactivated vaccine. IBV VLP could stimulate the strongest humoral, cellular, and mucosal immune responses and provide effective protection. In summary, ongoing long-term surveillance is essential for IBV prevention and control, and a vaccine that poses no risk of infection, such as the VLP vaccine, would be a desirable choice for IBV vaccination. v Events I WVAC 2024 W V A C 2 0 2 4
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