Efficacy of a plant-produced infectious bronchitis virus-like particle vaccine in specific pathogen-free chickens

Infectious bronchitis ( IB ) Gammacoronavirus causes a highly contagious respiratory disease in chickens that is listed by the World Organisation for Animal Health ( WOAH ). Its high mutation ability has resulted in numerous variants against which the commercially available live or recombinant vaccines singly offer limited protection. Agrobacterium -mediated transient expression in Nicotiana benthamiana (tobacco) plants was used here to produce a virus-like particle ( VLP ) vaccine expressing a modified full-length IBV spike ( S ) protein of a QX-like IB variant. In a challenge study with the homologous live IB QX-like virus, VLP-vaccinated birds produced S protein-specific antibodies comparable to those produced by live-vaccinated birds seroconverting with mean geometric titers of 6.8 and 7.2 log 2 , respectively. The VLP-vaccinated birds had reduced oropharyngeal and cloacal viral shedding compared to an unvaccinated challenged control and were more protected against tracheal ciliostasis than the live-vaccinated birds. While the results appeared similar, plant-produced IB VLPs are safer, more affordable, easier to produce and update to antigenically match any emerging IB variant, making them a more suitable alternative to IBV control than live-attenuated vaccines.