Infectious Bronchitis Virus S2 of 4/91 Expressed from Recombinant Virus Does Not Protect Against Ark-Type Challenge

• Published in: Avian diseases 2017-09, Vol.61 (3), p.397-401
• Main Authors: Eldemery, Fatma, Li, Yufeng, Yu, Qingzhong, van Santen, Vicky L, Toro, Haroldo
• Format: Article
• Language: English
• Subjects: 4/91; Animals; Coronavirus Infections - immunology; Coronavirus Infections - prevention & control; Coronavirus Infections - veterinary; Coronavirus Infections - virology; infectious bronchitis virus; Infectious bronchitis virus - immunology; Newcastle disease virus - immunology; Poultry Diseases - immunology; Poultry Diseases - prevention & control; Poultry Diseases - virology; recombinant Newcastle disease virus; Research Notes; S2; Spike Glycoprotein, Coronavirus - immunology; Vaccines, Attenuated - immunology; Vaccines, Synthetic - immunology; Viral Vaccines - immunology
• ISSN: 0005-2086; 1938-4351
• DOI: 10.1637/11632-032017-ResNoteR

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.