title: The enhanced virulence of very virulent infectious bursal disease virus is partly determined by its B-segment.
abstract: There is a remarkable difference in virulence of infectious bursal disease virus (IBDV) strains ranging from sub-clinical infections for serotype 2 and cell culture adapted serotype 1 strains, to 100% mortality for very virulent serotype 1 strains in young SPF chickens. It is known that cell culture adaptation related attenuation is determined by distinct mutations in the hypervariable region of the VP2 outer capsid protein, encoded on the A-segment. Amino acid mutations in the hypervariable VP2 region however, offer no explanation for the difference in virulence of classical and very virulent serotype 1 strains. Here we show by in vitro and in vivo analysis of rescued segment re-asserted IBDVs that virulence factors are not only located on the A-segment, but on the RNA Dependent RNA Polymerase (VP1) encoding B-segment as well. Insight into the virulence factors of very virulent IBDV will contribute to the improvement of live IBDV vaccines.
authors.affiliation: Animal Sciences Group, Wageningen University and Research Centre, Lelystad, The Netherlands. Hein.Boot@RIVM.NL
authors.forename: H J
authors.initials: HJ
authors.lastname: Boot
authors.forename: A J W
authors.initials: AJ
authors.lastname: Hoekman
authors.forename: A L J
authors.initials: AL
authors.lastname: Gielkens
mesh_terms: D000818:Animals; D018175:Birnaviridae Infections / Q000821:virology; D018929:Cell Culture Techniques; D002645:Chickens; D007243:Infectious bursal disease virus / Q000145:classification / Q000235:genetics / Q000472:pathogenicity*; D015678:Viral Structural Proteins / Q000737:chemistry / Q000235:genetics*; D014774:Virulence
chemical_list: C107669:VP1 protein, infectious bursal disease virus; D015678:Viral Structural Proteins