Nucleocapsid gene based identification and phylogenetic analysis of infectious bronchitis virus isolates from India

The nucleocapsid (N) protein, a major structural protein of Infectious bronchitis virus (IBV), has high immunogenicity and readily induces humoral and cell mediated immune response in chickens. Isolation and characterization of two field isolates suspected for IBV was performed by egg inoculation and RT-PCR amplification of the N gene. The nucleotide sequence of the nucleocapsid segment of the two IBV isolates 13N/M/2009 (KF360986) and 22N/M/2008 (KF360987) were determined by DNA sequencing and found to be 1230 nucleotides in length. On phylogenetic analysis, the two nucleocapsid gene sequences formed a unique and identical cluster with previously reported Indian isolates but within the M41 genotype. Percent identity of 13N/M/2009 and 22N/M/2008 with each other at nucleotide and amino acid level were 94% and 92.5%, respectively. In addition the highest homology of KF360986 and KF360987 was observed with strain EF025537, at nucleotide level 95% and 94% and at amino acid level 94.2% and 92.7%, respectively. Based on sequencing and analysis of N gene, two Indian isolates were correctly placed in Indian cluster of IBV. Due to conserved nature of the N gene, it should be further explored for possibilities to develop vaccineand diagnostics against Infectious bronchitis.