The UL24 gene affects duck plague virus replication, and its deletion attenuates virulence, enabling use as a vaccine.

Duck plague virus (DPV) is the causative agent of duck plague (DP), which poses a significant threat to production safety in the duck industry. Little is known about the UL24 protein (pUL24) encoded by the DPV UL24 gene. In this study, pUL24, when transfected into duck embryo fibroblasts, localized to the nucleus, as demonstrated by immunofluorescence techniques. We discovered that UL24 contains two nuclear localization signals (NLS), with the first also serving as a nucleolar localization signal (NoLS). To further analyse the function of pUL24, two viral strains were constructed: a UL24 deletion strain and a UL24 NLS motif deletion strain. These deletion strains affected the replication of DPV to varying degrees. Notably, the virulence of the UL24 deletion strain (DPV-UL24_null) was significantly reduced in ducks, indicating good safety, genetic stability, and immunogenicity. Ducks immunized with DPV-UL24_null have a 100 % protective effect against challenge with a DPV Chinese virulent strain (DPV-CHv); thus this strain has the potential to be used as an attenuated vaccine. In summary, these findings provide new insights into the function and pathogenic mechanisms of the UL24 gene and present novel concepts for the development of a duck plague vaccine.