RESUMEN
Background: avian infectious bronchitis [IB] is an economically important poultry disease. The emergence of new infectious bronchitis virus genotypes has complicated IB control programs
Objectives: this is the first comprehensive molecular analysis of the Nucleocapsid [N] gene of Iranian IBVs
Methods: the nucleocapsid gene of ten IBV isolates [which belonges to four different genotypes] was amplified using specific primers. The phylogenetic trees were constructed based on nucleotide and amino acid sequences of "N" gene
Results: IBV genotyping based on "N" gene showed similar IBV classification which was obtained from spike gene analysis and ten isolates belonged to Massachusetts, QX, 793/B and Variant-2 genotypes. Different strains had 89.97- 99.75% homology in their amino acid sequences. The highest nucleotide sequence similarity was observed between IBKG-1 and IBKG-8 [793/B type IBVs], while the lowest was seen between IBKG-5 and IBKG-9 [QX- type and Variant-2 type] IBV isolates. This low similarity is of an interest because the N protein is highly conserved among different IBV strains. "N" Protein structural analysis revealed that the isolates has 8to 10 alpha helices and 6 to 8 beta sheets
Conclusions: the present study provided basic information to develop recombinant nucleocapsid proteins that are applicable in rapid diagnostic tests and ELISA and recombinant vaccines