Efficacy of commercial polyvalent avian infectious bronchitis vaccines against Chinese QX-like and TW-like strain via different vaccination strategies

Shao, Guanming; Chen, Tong; Feng, Keyu; Zhao, Qiqi; Zhang, Xinheng; Li, Hongxin; Lin, Wencheng; Xie, Qingmei

Infectious bronchitis virus (IBV) is an acute and highly contagious disease, which affects chickens of all ages. Vaccination is the most important way to control this disease. Nevertheless, novel variant strains are constantly reported because of the lack of proofreading capabilities of RNA polymerase and high frequency of homologous RNA recombination. Cross-protection studies has demonstrated that the vaccines could provide great protective effects against viruses of same serotype or genotype. However, the protective effect of different commercial vaccines and vaccine combinations against the prevalent IBV strains in China has rarely been studied. Due to the multiple genotype or serotype IBV strains prevalence in China, the polyvalent vaccines and their composition were used to expanding the protection spectrum of vaccine in practical application. In order to evaluate the protection of Chinese commercial IBV polyvalent vaccines against prevalent strains (QX-like and TW I-like), an immune-challenge test was conducted. Four polyvalent vaccines, containing 4/91, H120, YX10p90, LDT3-A and 28/86, were combined to form eight vaccination strategies, almost all of which could provide more than 70% protection effects against challenge with QX-like strain. Particularly, the best protection rate (93%) was generated by administration the polyvalent vaccine C (H120 + 28/86 + 4/91) at one-day-old and the polyvalent vaccine B (H120 + 4/91 + YX10p90) at 10-day-old. However, all the vaccination strategies in this study cannot provide great protective effects against TW-like strain, and more vaccines should be included in studies to expand the protection spectrum of vaccine. Therefore, for the newly emerging IBV strains, immunization with polyvalent vaccines via different vaccination strategies could be used to control the prevalence of IBV in a short time, while developing the homologous vaccines was not always necessary.