Attenuation of a virulent type 2 bovine viral diarrhea virus.
The purpose of this study was to produce an attenuated bovine viral diarrhea virus (BVDV) type 2 strain as a tool for identifying potential virulence markers in the BVDV2 genome. The attenuation of the virulent strain, BVDV2-24515, was accomplished by in vivo and in vitro passage. The strain was initially used to infect an elk (Cervus elaphus) [J. Wildl. Dis. 35 (1999) 671], re-isolated at 7 days post-inoculation from serum, and then subsequently passaged 56 times in cell culture. Two groups of calves were inoculated intranasally with either BVDV2-24515 or the putative attenuated virus, designated BVDV2-LATT. Calves inoculated with BVDV2-24515 had cumulative clinical scores which ranged from 6 to 53. Clinical signs in these calves consisted of anorexia, depression, dehydration, diarrhea (+/-bloody), and pneumonia. Several calves developed leukocytopenia, primarily a neutrocytopenia, and presented lesions of enteritis or pneumonia at necropsy. In contrast, cattle inoculated with BVDV2-LATT had cumulative clinical scores which ranged from 0 to 2. This was not significantly different from that of controls which received no virus (range: 0-1). Calves inoculated with BVDV2-LATT produced high neutralizing antibody titers against BVDV2. Thus, in addition to its potential use as a tool for identifying virulence markers, the attenuated virus is also worthy of further study as a candidate virus for inclusion in a modified-live vaccine.
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Canadian Food Inspection Agency, Lethbridge, Alta., Canada T1J 3Z4. deregtd@inspection.gc.ca
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D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D001831:Body Temperature; D001912:Bovine Virus Diarrhea-Mucosal Disease / Q000473:pathology / Q000821:virology*; D002417:Cattle; D018929:Cell Culture Techniques; D030242:Diarrhea Virus 2, Bovine Viral / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity*; D005260:Female; D007958:Leukocyte Count / Q000662:veterinary; D009500:Neutralization Tests / Q000662:veterinary; D012367:RNA, Viral / Q000737:chemistry / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D014613:Vaccines, Attenuated / Q000276:immunology; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000235:genetics; D014765:Viral Vaccines / Q000276:immunology; D014774:Virulence
D000914:Antibodies, Viral; D012367:RNA, Viral; D014613:Vaccines, Attenuated; D014759:Viral Envelope Proteins; D014765:Viral Vaccines