1. Institute of Virology; University of Veterinary Medicine Hannover; Hannover Germany
2. Chinese Academy of Agricultural Sciences, Lanzhou Veterinary Research Institute; State Key Laboratory of Veterinary Etiological Biology; Lanzhou Gansu Province China
3. Central Facility for Microscopy; Helmholtz Centre for Infection Research, HZI; Braunschweig Germany
4. Institute of Microbiology; University of Veterinary Medicine Hannover; Hannover Germany