phylogenetic analysis comparing partial s1 gene of avian infectious bronchitis virus to commercial vaccine strains in iran

background: infectious bronchitis is a highly contagious disease which may cause poor weight gain and low feed efficiency in infected chickens. there are a large number of reported serotypes/genotypes, which makes the control of the disease more difficult through vaccination. however, there are only a few amino acid differences in the s1 protein of vaccine and wild type strains which are responsible for protection. objectives: the purpose of this study is to compare ibv variants isolated from commercial chicken flocks in iran with currently used vaccine strains. methodes: the partial s1 gene of the spike protein, covering a hypervariable and constant regions, was amplified and sequenced using conventional rt-pcr. results: phylogenetic analysis of amino acid sequences revealed that eight of total nine isolates were divergence at least 21.8% from vaccinal massachusetts serotypes, and six of nine isolates were divergence at least 22.7% from 4/91, and none of the nine isolates were similar to dutch-type, d274,vaccine serotypes. conclusions: these findings are essential for continuous surveillance disease control strategies and monitoring of variants, and thus emphasize on the importance of improving the vaccination program in iran.