Bovine viral diarrhea virus is a suitable viral vector for stable expression of heterologous gene when inserted in between Npro and C genes

Bovine viral diarrhea virus (BVDV) is a group of small enveloped viruses with a single-stranded, positive-oriented RNA genome of 12.3 kb. BVDV genome directs the production of a viral polyprotein that is subsequently cleaved to release the mature viral proteins. To explore the potential of using BVDV as viral vector for stable expression of heterologous genes, eGFP2A was inserted in between Npro and C genes of a noncytopathic type-I BVDV strain SD1. eGFP2A was designed with eGFP protein in frame fused to the N terminus of the foot-and-mouth disease virus 2A protease. This strategy promised not only the correct processing of both viral Npro and C protein but also releasing of the chimeric protein from the nascent viral polyprotein. The recombinant reporter virus was successfully rescued in MDBK cells. In vitro study showed that eGFP2A protein, as expected, was expressed and processed properly from the nascent viral polyprotein. The reporter virus was similar to wt SD1 in viral RNA replication and protein expression and comparable to wt SD1 in growth kinetics except that this virus had a peak virus titer approximately 0.5 log10 lower and a maximum yield about 4 h later than wt SD1. In summary, these results indicated that BVDV is a suitable viral vector for stable expression of heterologous genes when inserted in between Npro and C genes.