Effect of ORF119 gene deletion on the replication and virulence of orf virus.

Orf is a severe infectious disease of sheep and goats caused by orf virus (ORFV). To investigate the role of ORF119 gene of ORFV, we constructed ORFV with deleted ORF119 gene and LacZ as reporter gene (ORFV-Δ119-LacZ) via homologous recombination. The results showed that wild-type ORF-SHZ1 and ORFV-Δ119-LacZ deletion viruses replicated in Vero cells to similar titers. Relative transcriptional levels of virulence genes OVIFNR, GIF, VEGF and VIL-10 of ORFV-Δ119-LacZ deletion virus were slightly but not significantly lower after 24 hr compared with the wtORF-SHZ1 virus. In vivo experiments showed that 2-month-old lambs inoculated with ORFV-Δ119-LacZ deletion virus exhibited a similar total clinical score compared with those inoculated with wtORF-SHZ1 virus. Based on these results, we conclude that deletion of the ORF119 gene has no significant effect on ORFV replication and virulence.