Regeneration and characterization of a recombinant bovine viral diarrhea virus and determination of its efficacy to cross the bovine placenta

Development of a reporter bovine viral diarrhea virus and initial evaluation of its application for high throughput antiviral drug screening

Bovine viral diarrhea virus (BVDV) causes lethal mucosal disease of cattle and leads to severe economic loss of cattle production and reproduction worldwide. Over the past decades, vaccination was not very successful in providing prevention of BVDV infection. This reality demands that anti-BVDV drugs should be used as an alternative treatment strategy. In this study, a BAC cDNA of noncytopathic BVDV strain SD-1 is constructed to contain an enhanced green fluorescence protein (eGFP) gene between viral NS3 and NS4A coding sequences. The recombinant reporter virus is generated subsequently by transfection of MDBK cells with the transcripts produced in vitro. The rescued reporter virus is stable in MDBK cells and the eGFP protein is expressed and processed properly. Of most importance, the reporter virus shows a growth property similar to the SD-1 parent and the fluorescent signal intensity increases in parallel to the reporter virus RNA and protein replication. In addition, two known anti-BVDV drug G418 (viral assembly/release inhibitor) and ribavirin (viral RNA replication inhibitor) are identified as hits in a high-throughput format, suggesting that this system is capable of identifying BVDV inhibitors that target different steps in viral life cycle. The cell-based system developed provides a useful and versatile tool which should facilitate the identification of BVDV inhibitors on a large scale.

An alternative -1/+2 open reading frame exists within viral N(pro)(1-19) region of bovine viral diarrhea virus SD-1

We previously reported the engineering of an N(pro)-disrupted bovine viral diarrhea virus (BVDV), BSD1-N(pro)/eGFP2A (Fan and Bird, 2008a). Here, we report that BSD1-N(pro)/eGFP2A survives a single nucleotide missing in its C-terminal eGFP region. By using our established reverse genetics system for BVDV, we confirm that the viral mutant is rescued through a -1/+2 ORF initiated in the N(pro)(1-19)/eGFP region of the mutant viral genome. We furthermore uncover that this event occurs in the N(pro)(1-19) region of BVDV strain SD-1. The rescued viral mutant showed dramatic reductions in levels of both viral RNA and viral protein in host cells. Although the mutant is similar to the native strain in viral kinetics, the peak yield of the mutant is decreased dramatically. These findings reveal the existence of an alternative -1/+2 ORF in the N(pro)(1-19) region during the replication of BVDV and open a new avenue to understand the life cycle and pathogenesis of pestiviruses.