Reversion of molecularly engineered, partially attenuated, very virulent infectious bursal disease virus during infection of commercial chickens.
A molecularly cloned, tissue culture-adapted infectious bursal disease virus (BD-3tc) was generated from a very virulent strain by the reverse genetics approach following site-directed mutagenesis (Q253H and A284T in VP2). The pathogenicity of BD-3tc was tested in commercial chickens. The wild-type strain (BD-3wt) and the molecularly cloned parental strain (BD-3mc) were included for comparison. The subclinical course of the disease, with delayed and milder pathological lesions followed by quick follicular regeneration in the bursa of Fabricius in BD-3tc-inoculated birds, suggested that these amino acid substitutions made BD-3tc partially attenuated. However, severe bursa atrophy was observed at 14 days after inoculation. Reverse transcription-polymerase chain reaction coupled with restriction enzyme analysis revealed that both point mutations in BD-3tc had reverted 14 days after inoculation. Further investigations demonstrated that the codon for amino acid at position 284 had already reverted to the wild-type phenotype (T284A) 3 days after inoculation.
Institute for Virology, Faculty of Veterinary Medicine University of Leipzig D-04103 Leipzig.
R
R
Raue
M R
MR
Islam
M N
MN
Islam
K M
KM
Islam
S C
SC
Badhy
P M
PM
Das
H
H
Müller
D000818:Animals; D001483:Base Sequence; D018175:Birnaviridae Infections / Q000662:veterinary* / Q000821:virology; D001835:Body Weight; D002060:Bursa of Fabricius / Q000473:pathology / Q000821:virology; D002645:Chickens / Q000821:virology*; D005818:Genetic Engineering; D007243:Infectious bursal disease virus / Q000235:genetics* / Q000472:pathogenicity*; D016297:Mutagenesis, Site-Directed; D009929:Organ Size; D011201:Poultry Diseases / Q000821:virology*; D012367:RNA, Viral / Q000302:isolation & purification; D014774:Virulence; D014779:Virus Replication
D012367:RNA, Viral