Protection of chickens against infectious bronchitis virus with a multivalent DNA vaccine and boosting with an inactivated vaccine

Yan, Fang; Zhao, Yujun; Hu, Yongting; Qiu, Jianyang; Lei, Wenxin; Ji, Wenhui; Li, Xuying; Wu, Qian; Shi, Xiumin; Li, Zhong

Three weeks after the third vaccination, all chickens were challenged with 10 3 EID 50 of IBVSX16 through a nasal-ocular route. The chickens were observed daily for 14 days post-challenge. Deceased chickens were necropsied and evaluated for IBV infection. The surviving chickens were euthanized humanely by pectoral muscle injection of ketamine hydrochloride in 22 mg/kg of body weight 14 days post-infection. The trachea and kidneys were collected for virus detection. The number of IBV-positive chickens was confirmed by reverse transcriptasepolymerase chain reaction (RT-PCR). All procedures for RNA isolation and RT-PCR were previously described [15] . Viral RNA was isolated and purified from trachea and kidneys collected from chickens challenged with IBVSX16 using Trizpl reagents (Invitrogen, USA) according to the manufacturer's instructions. Amplification of the specific fragments of N gene by RT-PCR was performed. The RNA pellet was dissolved in 10 mL of DEPC-treated water. The