molecular analysis of the nucleocapsid gene and 3' untranslated region of two infectious bronchitis virus field isolates from iranian poultry farms

infectious bronchitis (ib) is an economically important disease of chickens. due to the emergence of new variants of infectious bronchitis virus (ibv), the control of ib has become a serious problem for the poultry industry worldwide. in the present study, the nucleocapsid gene (n) and 3' untranslated region (utr) of two ibvs isolated from iranian poultry farms were sequenced and compared with other ibv strains. based on nucleotide identity, the n gene and 3' utr sequences of iranian ibvs showed 90% similarity to the commonly used ibv vaccine strains, h52 and h120. however, based on phylogenetic analyses, iranian ibvs were found to cluster separately from the ibv vaccine strains used in iran as well as other ibvs isolated in china, australia and the united states. it was concluded that ibvs circulating in iran are genetically distinct from ibv vaccine strains that have been used in iran for many years. therefore, it is important to develop a new vaccine based on these newly identified strains for controlling ib in iranian poultry farms.