Genetic Analysis of Three Structural Proteins in Iranian Infectious Bronchitis Virus Isolate

Infectious bronchitis virus (IBV) is a contagious pathogen in fowl that results in economic loss in the poul-try industry. In this study, the amino acids sequences of three structural proteins M, N, and S1 for five Ira-nian IBV isolated during 1998-2011 have been analyzed. Conserved and variable regions, hydrophobic characteristics and identity matrix were determined after alignment by Bioedit ver 7.0.4.1. The phylogenetic tree was obtained by using the neighbor-joining method within MEGA4. Similarity for M and S1 protein was lowest for IR-3654-VM and TW2575 / 98 isolate (0.862) and IR1061-PH and Georgia 1998 isolate / strain (0.41), respectively. For the N protein, highest similarity was found between Ur1 / 09 and Arkansas DPI (0.948). Four conserved regions for M and N proteins were recognized. In the S1 protein three hyper-variable regions were detected in 52-90, 124-150 and 265-315 residues. In a phylogeny analysis all proteins were distributed in three clusters. Iranian IBV belonged to Mass cluster in phylogeny tree of M and N pro-teins. But S1 protein showed a close relationship with the California serotype and was distantly related to Mass serotype. The results showed that the Iranian IBV isolate was probably diverted from Mass strain that might be brought to Iran as a vaccine strain.