Variations in the nucleocapsid protein gene of infectious bronchitis viruses isolated in Korea

Fourteen infectious bronchitis viruses (IBVs) were isolated in Korea between 2001 and 2003 from chickens suspected to be infected with IBVs. The nucleocapsid (N) protein genes of the various IBVs were amplified by reverse transcriptase-polymerase chain reaction (RT-PCR) and were cloned and sequenced, and the nucleotide and deduced amino acid sequences were compared with published sequences for non-Korean IBV strains. The Korean IBV isolates shared amino acid sequence similarity of between 89.2% (K203-02 and K1255-03) and 98.3% (K434-01 and K281-01) with each other and exhibited amino acid sequence similarity between 57.0% (K774-01 and V18/91) and 96.6% (K507-01 and JP8147) with non-Korean IBV strains. Phylogenetic analysis of the deduced N protein amino acid sequences resulted in the segregation of Korean IBV isolates into three different clusters, with cluster assignments differing for some of the isolates from those obtained with analysis of the S1 glycoprotein. Korean IBV isolates K069-01, K281-01, K434-01, K504-01, K774-01, K748-01, K044-02, K058-02, K161-02, K203-02, and K234-02 formed an independent cluster comprised only of Korean IBV isolates. Another Korean IBV isolate, K210-02, belonged to a cluster that included IBV strains isolated in USA, the Netherlands and China. Recent Korean IBV isolates K514-03 and K1255-03 grouped into a third distinct cluster related to a Chinese IBV strain. As deduced from phylogenetic analysis, some IBV isolates appear to have arisen from the recombination of IBV strains with different origins.