A 45-nucleotide insertion in the NS2 gene is responsible for the cytopathogenicity of a bovine viral diarrhoea virus strain

A novel NS3/4A protease dependent cleavage site within pestiviral NS2

Pestiviruses like bovine viral diarrhoea virus (BVDV) and classical swine fever virus (CSFV) belong to the family Flaviviridae. A special feature of the Flaviviridae is the importance of nonstructural (NS) proteins for both genome replication and virion morphogenesis. The NS2-3-4A region and its regulated processing by the NS2 autoprotease and the NS3/4A protease plays a central role in the pestiviral life cycle. We report the identification and characterization of a novel internal cleavage in BVDV NS2, which is mediated by the NS3/4A protease. Further mapping using the NS2 of BVDV-1 strain NCP7 showed that cleavage occurs between L188 and G189. This cleavage site represents a novel sequence motif recognized by the NS3/4A protease and is conserved between the pestivirus species A, B and D. Inhibition of this internal NS2 cleavage by mutating the cleavage site did not cause obvious effects on RNA replication or virion morphogenesis in cultured cell lines. Accordingly, this novel internal NS2 cleavage adds an additional layer to the already complex polyprotein processing of Pestiviruses and might further extend the repertoires of the multifunctional NS2. However, unravelling of the functional relevance of this novel processing event in NS2, therefore, awaits future in vivo studies.

The Molecular Biology of Pestiviruses

Pestiviruses are among the economically most important pathogens of livestock. The biology of these viruses is characterized by unique and interesting features that are both crucial for their success as pathogens and challenging from a scientific point of view. Elucidation of these features at the molecular level has made striking progress during recent years. The analyses revealed that major aspects of pestivirus biology show significant similarity to the biology of human hepatitis C virus (HCV). The detailed molecular analyses conducted for pestiviruses and HCV supported and complemented each other during the last three decades resulting in elucidation of the functions of viral proteins and RNA elements in replication and virus-host interaction. For pestiviruses, the analyses also helped to shed light on the molecular basis of persistent infection, a special strategy these viruses have evolved to be maintained within their host population. The results of these investigations are summarized in this chapter.

Complete genome sequences of both biotypes of a virus pair of bovine viral diarrhea virus subgenotype 1k

We determined the complete genome sequences of both biotypes of a virus pair of bovine viral diarrhea virus (BVDV) subgenotype 1k. The viruses were isolated from a persistently infected calf suffering from mucosal disease. Compared to the noncytopathic biotype, the cytopathic biotype contains an insertion of 84 nucleotides and 22 nucleotide changes.

Herpetiform genital lesions in a heifer with mucosal disease

A 14-month-old heifer with a 17-day history of unresponsive bloody diarrhea was necropsied. There were focal, pink-red erosions of the nares and hard palate; ulcers and fissures of the tongue; and multiple ulcerative lesions of the alimentary canal. Interdigital skin of both rear limbs was ulcerated and bleeding; and the margins of the vulva contained punctiform red ulcers. The gross lesions were consistent with mucosal disease. Histopathology and laboratory testing ruled out rinderpest, foot-and-mouth disease, and vesicular stomatitis, and identified bovine virus diarrhea virus to be the cause of this disease. Lesions of the vulva similar to those seen in some stages of infectious pustular vulvovaginitis were negative for bovine herpesvirus-1 and tested positive for bovine viral diarrhea virus antigen by immunohistochemistry.