Protective effect of vaccination in chicks with local infectious bronchitis viruses against field virus challenge

Kuan-Yu Lin, Hui-Chung Wang, Ching-Ho Wang
Graduate Institute of Veterinary Medicine, National Taiwan University, Taipei, Taiwan

Received: January 13, 2004 Revised: July 23, 2004 Accepted: July 26, 2004

Corresponding author: Ching-Ho Wang, Department of Veterinary Medicine, No 1, Sec 4, Roosevelt Rd, Taipei 10617, Taiwan. E-mail:

Avian infectious bronchitis virus (IBV) causes tremendous economic losses to the poultry industry worldwide. Different serotypes of this virus show little cross-protection. The present study investigated the relationship between differences in the genotype based on the N-terminus of the spike protein and the protection provided by vaccination with IBVs. Cross-immunization tests were performed using both killed and live viruses in specific-pathogen-free chicks. One-day-old chicks were immunized with killed or high [10⁵ 50% embryo infectious dose (EID₅₀)] or low (10³ EID₅₀) doses of live IBV viruses and challenged with homologous or heterologous IBV strains. The immunization efficacy was evaluated by virus isolation from the challenged chicks. In the killed-virus and high-dose live-virus test groups, IBV vaccination protected against challenge by homologous but not heterologous IBV strains. However, a low dose of live IBV showed no protection against virulent IBV challenge. These results indicate that both the genotype based on the N-terminus of the spike protein and the virus dose are essential to IBV protection from immunization. Thus, development of vaccines from different local strains is necessary to control infectious bronchitis in poultry.

Key words: Chickens, coronavirus spike glycoprotein, infectious bronchitis virus, virus vaccination

J Microbiol Immunol Infect 2005;38:25-30.