title: Simultaneous alteration of residues 279 and 284 of the VP2 major capsid protein of a very virulent Infectious Bursal Disease Virus (vvIBDV) strain did not lead to attenuation in chickens.
abstract: BACKGROUND
  Cell culture adaptation of very virulent infectious bursal disease virus (vvIBDV) was shown to be mainly associated with the VP2 capsid protein residues 253, 279, and 284. The single mutation A284T proved critical for cell culture tropism, but did not confer efficient virus replication, which at least required one additional mutation, Q253H or D279N. While the double mutation Q253H/A284T was unambiguously shown to confer both efficient replication in cell culture and attenuation in chickens, conflicting results have been reported regarding the replication efficiency of vvIBDV mutants bearing the D279N/A284T double mutation, and no data are hitherto available on their virulence in chickens.
  
  
  RESULTS
  Here we used an in vivo reverse genetics system to assess the impact of the D279N/A284T double mutation on the replication and attenuation of a chimeric IBDV virus, whose polyprotein derived from a non-culturable vvIBDV clinical isolate. We found that the D279N/A284T double mutation did indeed confer efficient replication in chicken embryo fibroblast (CEF) cell culture, but the mutant virus remained highly pathogenic to chickens.
  
  
  CONCLUSIONS
  The double mutation D279N/A284T of the VP2 major capsid protein of vvIBDV is sufficient to confer cell culture tropism and replication efficiency, but does not necessarily lead to virus attenuation.
authors.forename: Nawel
authors.initials: N
authors.lastname: Ben Abdeljelil
authors.forename: Neila
authors.initials: N
authors.lastname: Khabouchi
authors.forename: Selma
authors.initials: S
authors.lastname: Kassar
authors.forename: Khaled
authors.initials: K
authors.lastname: Miled
authors.forename: Samir
authors.initials: S
authors.lastname: Boubaker
authors.forename: Abdeljelil
authors.initials: A
authors.lastname: Ghram
authors.forename: Helmi
authors.initials: H
authors.lastname: Mardassi
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D018175:Birnaviridae Infections / Q000662:veterinary* / Q000821:virology; D036022:Capsid Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D002642:Chick Embryo; D002645:Chickens; D007243:Infectious bursal disease virus / Q000737:chemistry / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D011201:Poultry Diseases / Q000821:virology*; D016415:Sequence Alignment; D056189:Viral Tropism; D014774:Virulence; D014779:Virus Replication
chemical_list: D036022:Capsid Proteins