Sequence analysis of the S1,N, 3´UTR gene of the vaccinal strains (H120 H52) of infectious bronchitis virus

Objectives: Infectious bronchitis (IB) is an economically important disease of chickens. The existence of a very large number of IBV- serotypes and variants which insufficiently induce cross protection against each other is the major problem to control the disease. The purpose of this study was to determine the Sequence analysis of the S1, N, 3´UTR gene of the vaccinal strains (H120 H52) of infectious bronchitis virus.Materials Methods: Among IBV viral proteins, the subunit protein S1 (Spike) plays the principle role in inducing neutralizing antibodies which defines serotypes and attachment to the host cells. A few amino acid differences in the S1 result in the change of strains and serotypes. Therefore, analysis of sequences of S1 is very important to characterize field isolates and to define their degree of identity with vaccine strains. Furthermore, the N protein plays a role in viral replication and assembly and it binds to the viral RNA forming a helical nucleocapsid. Immediately downstream of the N gene is the 3 untranslated region (UTR), which is presumably important in the initiation of negative-strand RNA Synthesis Most previous studies have focused on the molecular analysis of the S1 gene. However, like the S1 protein, the N protein has also been shown to play an important role in the induction of immune responses against IBV. To characterize H52 and H120 strains and their embryonated egg - passaged of Razi institute, this study was performed the subunit protein S1 (Spike) the nucleocapsid gene (N) and 3 untranslated region (3 UTR) of two IBV vaccine (H120 –H52) were sequenced and compared with other IBV standard strains.Results Conclusion: The results revealed that H52 and H120 strains of Razi institute are identical to the standard of strains in the Gene Bank. Based on nucleotide identity, the S1, N gene and 3 UTR sequences of Iranian IBVs vaccines showed 100% similarity to the commonly standard IBV strains. To better characterization of these strains and their serial embryonated egg - passaged, analysis of other genes involved in virulence and pathogenesis of the virus and performing protective tests against field strains are recommended.