variation analysis of VP2 genes of infectious bursal disease virus isolates acquired in different periods

The VP2 genes of 8 IBDV field strains that isolated from Luoyang area in 1991 and 2001 were amplified by reverse transcription-polymerase chain reaction (RT-PCR) and sequenced. The results showed that the 4 IBDV strains isolated in 1991 and 4 strains isolated in 2001 were all very-virulent IBDV (vvIBDV),but there were a little difference between 8 isolates. They could be divided obviously into three groups based on their homology of nucleotide and deduced amino acid. The first group included L912, L914 and L916 strains isolated in 1991; the second group included L017, L018 and L913; the third group included L015 and L016 strains isolated in 2001.The homology of nucleotide were higher in same group and lower between each group, the lowest homology of nucleotide were between L015 and L017, L016 and L018 strains (were all 95%). The amino acid sequences of the 4 vvIBDV strains isolated in 1991 had no changes in all hydrophilic regions and seven peptide region, but the other 4 vvIBDV strains isolated in 2001 had 1 to 2 amino acids changes in hydrophilic regions, particularly L015 and L016 isolates, the amino acid sequence had variations beyond hydrophilic regions and seven peptide region. It suggested that the isolates at present may have a little variation in antigenicity.