Background and Aims: Avian infectious bronchitis virus (IBV) has a worldwide distribution and mutations occurring in the large viral genome of IBV have led to extensive antigenic variations among IBVs. This is the first study conducted to determine the complete membrane (M) gene sequences of different Iranian IBV genotypes.
Materials and Methods: The M gene of three 793/B (IBKG1,6,7), one Massachusetts (IBKG3), three Variant 2 (IBKG2,4,9), four QX(IBKG5,10,11,12) and one IR-1(IBKG8) Iranian IBV isolates were sequenced and analyzed. Also, post-translational modifications of the M glycoprotein were predicted.
Results: Sequence analysis of the M gene indicated IBKG1, 6, 7, and 8 shared the highest homology to 793/B genotype. IBKG2, 4, 5, 9, 10, 11, and 12 showed the highest similarity to QX-like IBV. IBKG3 (Massachusetts) isolate shared 99/53% identities with H120 vaccine strain, respectively. Although M proteins are moderately well conserved within each coronavirus genus, the sequence differences of M gene reached to 12% among Iranian IBV isolates. Based on M gene analysis, IBKG-8 (IR-1 genotype) and all Variant2 IBVs, classified as a 793/B and QX IBV according to the M gene sequences, respectively.
Conclusions: It is the first characterization of IR-1 (Iranian local genotype) based on M gene. Also, the data shows M gene of variant 2 IBV strains are derived from QX genotypes. The results complete the Iranian IBVs genetic puzzle.