Sequence and Analysis of Genomic Segment A and B of Very Virulent Infectious Bursal Disease Virus Isolated from China

Sun, J.H.; Lu, Ponzy; Yan, Y.X.; Hua, X.G.; Jiang, J.; Zhao, Y.

Sequence and Analysis of Genomic Segment A and B of Very Virulent Infectious Bursal Disease Virus Isolated from China

2003

A very virulent infectious bursal disease virus (vvIBDV) field strain, named SH95, was identified and characterized from flocks with vaccination failure in Shanghai. The use of random primer and a reverse transcriptase lacking RNase-H activity produced full-length cDNA copies of the viral genomic A and B segments of SH95. The 3259 base pairs (bp) of segment A and 2827 bp of segment B were amplified by long and accurate PCR in a single step, then successfully cloned and sequenced. There were five to 27 amino acid substitutions compared with other IBDV strains within the segment A polyprotein (of these, three are unique) and about nine to 38 amino acid substitutions within VP1 (of which, four are unique). The comparison of sequences encoding the polyprotein showed that vvIBDV SH95 was most closely related to Asiatic vvIBDVs, which formed a closely related group clearly distinguishable from other classical strains of IBDV. Phylogenetic analysis suggested that vvIBDV SH95 and some other Asiatic vvIBDVs were derived from similar origin. But the topology tree performed on segment B was quite different from that performed on segment A, indicating that a genetic reassortment had played an important role in the emergence of vvIBDV SH95.

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