The genome segment B encoding the RNA-dependent RNA polymerase protein VP1 of very virulent infectious bursal disease virus (IBDV) is phylogenetically distinct from that of all other IBDV strains

• DOI: 10.1007/s007050170018
• Publication Date: 2003-02-12T18:05:56Z
• Authors: M. R. Islam; K. Zierenberg; H. Müller
• Keywords: Viral Structural Proteins; 0301 basic medicine; DNA, Complementary; Virulence; Brief Report; Molecular Sequence Data; Genome, Viral; Sequence Analysis, DNA; Birnaviridae Infections; RNA-Dependent RNA Polymerase; Infectious bursal disease virus; 3. Good health; 03 medical and health sciences; Animals; Amino Acid Sequence; Cloning, Molecular; Chickens; Sequence Alignment; Phylogeny; Poultry Diseases

A full-length cDNA clone of the segment B of the very virulent infectious bursal disease virus (IBDV) strain BD 3/99 was constructed and the full-length nucleotide sequence was established. The nucleotide sequence encoding VP1, an RNA-dependent RNA polymerase, of BD 3/99 was aligned with that of 17 other IBDV strains including six very virulent, three classical virulent, five classical attenuated, one antigenic variant and two serotype 2 strains. The VP1 genes of all very virulent strains were 97.5% to 99.8% identical. With the exception of an atypical Australian strain, 002-73, all of the classical virulent or attenuated and antigenic variant strains were also 97.5% to 100% identical. Serotype 2 strains showed only 4-6% divergence from serotype 1 classical virulent or attenuated strains; in contrast, however, the very virulent strains were 10.5% to 12.5% divergent from the classical virulent or attenuated strains as well as serotype 2 strains. Analysis of the deduced amino acid sequence of VP1 revealed 17 common, including 8 unique amino acid substitutions in the very virulent strains. In the phylogenetic tree the very virulent strains formed a distinct cluster and all other strains including classical virulent, attenuated and antigenic variant strains and even serotype 2 strains were grouped together. It is suggested that the VP1 of very virulent IBDV is phylogenetically distinct from that of all other IBDV strains and probably originated from a hitherto unidentified source.