Arezoo Salarpour - Department of Veterinary Research and Biotechnology, Razi Vaccine and Serum Research Institute, Agricultural Research, Education and ‎Extension Organization, Mashhad, Iran
Reza Toroghi - Department of Veterinary Research and Biotechnology, Razi Vaccine and Serum Research Institute, Agricultural Research, Education and ‎Extension Organization, Mashhad, Iran
Gholamreza Nikbakht Brujeni - Department of Microbiology and Immunology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran
Reza Momayez - Department of Poultry Disease Research and Diagnosis, Razi Vaccine and Serum Research Institute, Karaj, Iran‎

Neutralizing, serotype-specific, and hemagglutination-inhibiting antibodies against infectious bronchitis virus (IBV) are induced by epitopes in the S۱ protein. Most changes in the virus genome due to mutation and recombination during serial passaging in embryonated chicken eggs occur in the S۱ gene. In the current study, we tried to predict the potential linear B-cell epitopes of the S۱ subunit of two Iranian ۷۹۳/B isolates and then we analyzed their changes at passage level ۹۰ due to mutations at this passage level. To predict linear B-cell epitopes of the S۱ protein belonging to two Iranian ۷۹۳/B isolates, we used two online epitope prediction programs called BepiPred and ABCpred. Some of the most important features of proteins including antigenicity, physicochemical properties, and secondary structure composition were analyzed. The predicted epitopes were studied between wild viruses and their passage level ۹۰ viruses. We identified ۱۵ potential linear B-cell epitopes among which six epitopes had the highest scores of physicochemical properties and antigenicity. Due to amino acid substitutions, seven predicted epitopes had different amino acid sequences at passage level ۹۰. Among eight epitopes with no amino acid substitution at passage level ۹۰, three epitopes had the highest scores. These three conserved epitopes including NH۲-NQLGSCPLTGMI-COOH,NH۲-GNFSDGFYPFTNSSLVKD-COOH,andNH۲-GPIQGGC-COOHmight be strategic and potential candidates for use in designing epitope-based vaccine researches. In conclusion, based on scores of physicochemical properties and antigenicity, it seemed that the sequence of most epitopes in wild viruses might be more antigenic and immunogenic compared to their sequence in viruses of passage ۹۰.

Antigenicity, ‎ Infectious bronchitis virus, ‎ Linear B-cell epitopes, ‎ Physicochemical properties, ‎ Secondary structure composition ‎