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Journal of Virology, January 2000, p. 390-400, Vol. 74, No. 1
Federal Research Centre for Virus Diseases of
Animals, D-72076 Tübingen, Germany
Received 23 August 1999/Accepted 29 September 1999
Cytopathogenicity of Bovine viral diarrhea virus (BVDV)
is correlated with expression of the nonstructural protein NS3, which can be generated by processing of a fusion protein termed NS2-3. For
the cytopathogenic (cp) BVDV strain Oregon, NS2-3 processing is based
on a set of point mutations within NS2. To analyze the correlation
between NS2-3 cleavage and cytopathogenicity, a full-length cDNA clone
composed of cDNA from BVDV Oregon and the utmost 5'- and 3'-terminal
sequences of a published infectious BVDV clone was established. After
transfection of RNA transcribed from this cDNA clone, infectious virus
with similar growth characteristics to wild-type BVDV Oregon could be
recovered that also exhibited a cytopathic effect. Based on this cDNA
construct and published cp and noncp infectious clones, chimeric
full-length cDNA clones were constructed. Analysis of the recovered
viruses demonstrated that the presence of the NS2 gene of BVDV Oregon
in a chimeric construct is sufficient for NS2-3 processing and a cp
phenotype. Since previous studies had revealed that the amino acid
serine at position 1555 of BVDV Oregon plays an important role in
efficient NS2-3 cleavage, mutants of BVDV Oregon with different amino
acids at this position were constructed. Some of these mutants showed NS2-3 cleavage efficiencies in the range of the wild-type sequence and
allowed the recovery of viruses that behaved similarly to wild-type
virus with regard to growth characteristics and cytopathogenicity. In
contrast, other mutants with considerably reduced NS2-3 cleavage efficiencies propagated much more slowly and reverted to viruses expressing polyproteins with sequences allowing efficient NS2-3 cleavage. These viruses apparently induced cytopathic effects only
after reversion.
0022-538X/0/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Correlation between Point Mutations in NS2 and the
Viability and Cytopathogenicity of Bovine Viral Diarrhea Virus Strain
Oregon Analyzed with an Infectious cDNA Clone
and
*
Corresponding author. Mailing address: Federal Research
Centre for Virus Diseases of Animals, P.O. Box 1149, D-72001
Tübingen, Germany. Phone: 49 7071-967207. Fax: 49 7071-967303. E-mail: gregor.meyers{at}tue.bfav.de.
Present address: Department of Molecular Microbiology, Washington
University School of Medicine, St. Louis, MO 63110-1093.
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