Abstract: The study was aimed to determine the differences between the N nucleoprotein of domestic pandemic kidney type avian infectious bronchitis virus (IBV) strains and other strains such as the ones already existed on the market and the abroad ones isolated in rencent years. Biological products research center of Tianjin RingPu bio-technology Co., Ltd. isolated a strain of new virus in renal tissue of chickens obtained from Shandong farm. It was finally identified to be a positive one belonging to IBV by PCR and named SD03. The primers were designed according to the conserved regions from NCBI. Then constructed the recombinant bacteria named pMD18-T-N/DH5α by RT-PCR and got the gene sequences of N domain through sequencing. The strain of SD03 was identified as kidney type IBV strain, and its homologies of nucleotide and amino acid to LDT3 and partridge/GD/S14/2003 strians (kideny type) were > 99.0% and its homologies of amino acid were 90.0% to 94.6% compared to classical kidney type strains such as Ma5, W93, Gray and Holte strains. While compared to the respiratory vaccine strains (H120, H52, M41) the homologies of amino acid were 89.7% to 91.0%. This research deeply analyzed the physicochemical properties of N domain protein of current reference epidemic strains through DNAStar software and ExPASY website (http://www.expasy.org/). This study provided a theoretical reference for N protein subunit vaccines expression and purification in different systems, and also laid some theoretical foundation for the prevention of IBV.

Key words: infectious bronchitis virus; RT-PCR; N gene; N protein; homology; phylogenetic tree; physicochemical properties of N protein