[Studies on the propagation characteristics of duck plague virulent virus in duck embryo fibroblasts].

The propagation characteristics of virulent duck plague virus (DPV) in duck embryo fibroblast (DEF) were studied by the method of light microscopy observation of DEF cell culture monolayer, electron microscopy observation of infected DEF cell culture, real-time PCR detecting virus propagation. The results demonstrated that on duck embryo fibroblast a number of plaques were formed by DPV 42 h postinfection. Electron microscopy of the ultrathin section of infected duck embryo fibroblasts demonstrated that the nucleic acid of DPV was round in shape with diameter of 35-45 nm and was often in a cluster in the nucleus of DEF. The nucleocapsid of DPV was round in shape with diameter of 90-100 nm and could be observed both in nucleus and cytoplasm of DEF. The mature DPV which had the structures of envelop and tegument was spherical in shape with diameter of 150-300 nm and was located in cytoplasmic vacuoles. DPV penetrated the DEF cell membrane by direct fusion between the viral envelop and the plasma membrane. Progeny viral nucleic acid was produced in the nucleus and the assembled nucleocapsids obtained the structure of tegument in the cytoplasm and obtained the structure of envelop by budding into the cytoplasmic vesicles. The mature DPV particles were released out of the cell through exocytosis of the cytoplasmic vesicles. Detection of DPV by real-time PCR demonstrated that virus in DEF began its obvious propagation 10 h postinfection and virus amount tended to increase until 30 h postinfection. DPV began to be released into the supernatant 22 h postinfection and the DPV amount peaked 50 h postinfection, when the virus content in DEF and supernatant both underwent approximately 10(3) fold increase. DPV mainly existed in the DEF and the virus content in DEF was 10(2)-10(3) fold than the supernatant.