Molecular changes of the fusion protein gene of chicken embryo fibroblast-adapted velogenic Newcastle disease virus: effect on its pathogenicity.
Molecular changes of cell culture-adapted Newcastle disease virus (NDV) were studied by adapting a velogenic NDV isolated from commercial layer chicken-to-chicken embryo fibroblast (CEF) cells. The isolate was passaged 50 times in CEF cells. At every 10th passage the virus was characterized conventionally by mean death time analysis, intracerebral pathogenicity index, and virus titration. As the passage level increased, a gradual reduction in the virulence of the virus was observed. Molecular characterization of the virus included cloning and sequencing of a portion of the fusion gene (1349 bp) encompassing the fusion protein cleavage site (FPCS), which was previously amplified by reverse transcription-polymerase chain reaction. Sequence analysis revealed a total of 134 nucleotide substitutions, which resulted in the change of 41 amino acids between the parent and the 50th passage virus. Pathogenicity studies conducted in 20-wk-old seronegative chickens revealed gross and histopathologic changes in the chickens injected with the parent virus and absence of the lesions in chickens injected with the adapted virus. The 50th passage cell culture virus was back-passaged five times in susceptible chickens and was subjected to virulence attribute analysis and sequence analysis of the FPCS region, with minor differences between them.
Mohan
C Madhan
CM
National Biotechnology Centre, Indian Veterinary Research Institute, Izatnagar-243 122, India.
Dey
Sohini
S
Kumanan
K
K
D000220:Adaptation, Biological / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002642:Chick Embryo; D002645:Chickens / Q000821:virology*; D003001:Cloning, Molecular; D003470:Culture Media; D017931:DNA Primers; D005347:Fibroblasts / Q000821:virology*; D007194:India; D008969:Molecular Sequence Data; D009522:Newcastle disease virus / Q000235:genetics* / Q000472:pathogenicity*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D017422:Sequence Analysis, DNA / Q000662:veterinary; D012692:Serial Passage / Q000662:veterinary; D014760:Viral Fusion Proteins / Q000235:genetics*
D003470:Culture Media; D017931:DNA Primers; D014760:Viral Fusion Proteins