Biological characteristic and cytokines response of passages duck plague virus in ducks

To better understand the pathogenicity of duck plague virus (DPV). The DPV Chinese standard challenge strain (DPV CSC) was continuously passaged 20 times in duck embryo fibroblasts (DEFs). DPV F1 was lethal for 2-week-ducks, but DPV F10 and F20 were not lethal for 2-week ducks, the 528 bp in UL2 region of DPV F1-F20 was deleted, which suggested that the deletion in UL2 region was not related with the virulence of DPV. Compared with DPV F20 infected ducks, IL-8 in DPV F1 infected ducks was significantly upregulated, but IL-1, IL-2,IFNγ and MHC-II were significantly downregulated. ISKNV copies in DPV F10 and F20 infected ducks were lower than the DPV F1 infected ducks. These results showed that massive viruses replication, upregulation of IL-8 expresssion, repression of IL-1, IL-2, IFNγ and MHC-II expression resulted in serious lesions and high mortality. This study provided a in-depth understanding of the immune-related genes expression in the different virulence of DPV.