infections bronchitis virus S2 of 4/91 expressed from recombinant virus does not protect against ark-type challenge

Authors: ELDEMERY, FATMA - Auburn University; LI, YUFENG - Shandong Poultry Research Institute, China; Yu, Qingzhong; VAN SANTEN, VICKY - Auburn University; TORO, HAROLDO - Auburn University

Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/3/2017
Publication Date: 7/3/2017
Citation: Eldemery, F., Li, Y., Yu, Q., Van Santen, V., Toro, H. 2017. infectious bronchitis virus S2 of 4/91 expressed from recombinant virus does not protect against ark-type challenge. Acarology International Congress Proceedings. 61(3):397-401. https://doi.org/10.1637/11632-032017-ResNoteR.

Interpretive Summary: Infectious bronchitis (IB), caused by infectious bronchitis virus (IBV) infection, is one of the most prevalent avian diseases in the world’s poultry industry. Effective control of IBV is particularly difficult due to genotype/phenotype diversity and continuing evolution of the virus. Previously we have demonstrated that chickens vaccinated with recombinant Newcastle disease virus LaSota (rLS) expressing the S2 protein of IBV Ark strain and boosted with an attenuated IBV Massachusetts (Mass)-type vaccine were protected against IBV Arkansas (Ark)-type virulent challenge. In the present study, we evaluated the protective capabilities of the S2 protein of IBV 4/91 by expression from rLS. Chickens vaccinated with attenuated Mass at 1 day of age and boosted with rLS/IBV.S2-4/91 at 14 days of age were challenged with a virulent Ark strain at 28 days of age. The results showed non-significant differences between chickens primed with Mass vaccine and boosted with rLS/IBV.S2-4/91 and chickens vaccinated with Mass only. Thus, the observed level of protection is attributable only to the effect of the Mass vaccine indicating that the S2 of IBV 4/91 does not induce broad cross-protective immunity.

Technical Abstract: We previously demonstrated that chickens primed with a recombinant Newcastle disease virus LaSota (rLS) expressing the S2 gene of infectious bronchitis virus (IBV) and boosted with an attenuated IBV Massachusetts (Mass)-type vaccine were protected against IBV Arkansas (Ark)-type virulent challenge. A possible basis for the reported ability of IBV 4/91 (serotype 793/B) vaccine to protect against divergent IBV strains (e.g., QX, Q1, and D1466) in a prime-boost approach with an IBV Mass vaccine is that an immune response against the S2 protein of IBV 4/91 is cross-protective. Therefore, we evaluated the protective capabilities of the S2 protein of IBV 4/91 expressed from rLS. The level of S2 amino acid sequence identity between 4/91 and the Ark challenge strain used in this study (90.7%) is within the range of S2 amino acid sequence identities between 4/91 and Q1 (91%–94%) and QX (89%–94%) strains. Chickens primed with attenuated Mass IBV at 1 day of age and boosted with rLS/IBV.S2-4/91 at 14 days of age were challenged with a virulent Ark IBV strain at 28 days of age. Protection (reduction of clinical signs and viral loads) assessed 5 days postchallenge showed nonsignificant differences between chickens primed with Mass vaccine and boosted with rLS/IBV.S2-4/91 and chickens vaccinated with Mass only. Thus, the observed level of protection is attributable only to the effect of the Mass vaccine, indicating that the S2 of IBV 4/91 does not induce broad cross-protective immunity.