Differences in Pathogenicity and Vaccine Resistance Discovered between Two Epidemic Strains of Marek’s Disease Virus in China
Zheng-Hao Yu,
Yan-Ping Zhang,
Xing-Ge Lan,
Ya-Nan Wang,
Rong-Rong Guo,
Kai Li,
Li Gao,
Xiao-Le Qi,
Hong-Yu Cui,
Xiao-Mei Wang,
Yu-Long Gao,
Chang-Jun Liu
Affiliations
Zheng-Hao Yu
Avian Immunosuppressive Diseases Division, State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute of the Chinese Academy of Agricultural Sciences, Harbin 150069, China
Yan-Ping Zhang
Avian Immunosuppressive Diseases Division, State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute of the Chinese Academy of Agricultural Sciences, Harbin 150069, China
Xing-Ge Lan
Avian Immunosuppressive Diseases Division, State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute of the Chinese Academy of Agricultural Sciences, Harbin 150069, China
Ya-Nan Wang
Avian Immunosuppressive Diseases Division, State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute of the Chinese Academy of Agricultural Sciences, Harbin 150069, China
Rong-Rong Guo
Avian Immunosuppressive Diseases Division, State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute of the Chinese Academy of Agricultural Sciences, Harbin 150069, China
Kai Li
Avian Immunosuppressive Diseases Division, State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute of the Chinese Academy of Agricultural Sciences, Harbin 150069, China
Li Gao
Avian Immunosuppressive Diseases Division, State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute of the Chinese Academy of Agricultural Sciences, Harbin 150069, China
Xiao-Le Qi
Avian Immunosuppressive Diseases Division, State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute of the Chinese Academy of Agricultural Sciences, Harbin 150069, China
Hong-Yu Cui
Avian Immunosuppressive Diseases Division, State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute of the Chinese Academy of Agricultural Sciences, Harbin 150069, China
Xiao-Mei Wang
Avian Immunosuppressive Diseases Division, State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute of the Chinese Academy of Agricultural Sciences, Harbin 150069, China
Yu-Long Gao
Avian Immunosuppressive Diseases Division, State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute of the Chinese Academy of Agricultural Sciences, Harbin 150069, China
Chang-Jun Liu
Avian Immunosuppressive Diseases Division, State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute of the Chinese Academy of Agricultural Sciences, Harbin 150069, China
Despite highly effective vaccines, Marek’s disease (MD) causes great economic loss to the poultry industry annually, largely due to the continuous emergence of new MD virus (MDV) strains. To explore the pathogenic characteristics of newly emerged MDV strains, we selected two strains (AH/1807 and DH/18) with clinically different pathotypes. We studied each strain’s infection process and pathogenicity and observed differences in immunosuppression and vaccine resistance. Specific pathogen-free chickens, unvaccinated or vaccinated with CVI988, were challenged with AH/1807 or DH/18. Both infections induced MD damage; however, differences were observed in terms of mortality (AH/1807: 77.8%, DH/18: 50%) and tumor rates (AH/1807: 50%, DH/18: 33.3%). The immune protection indices of the vaccine also differed (AH/1807: 94.1, DH/18: 61.1). Additionally, while both strains caused interferon-β and interferon-γ expression to decline, DH/18 infection caused stronger immunosuppression than AH/1807. This inhibition persisted even after vaccination, leading to increased replication of DH/18 that ultimately broke through vaccine immune protection. These results indicate that both strains have different characteristics, and that strains such as DH/18, which cause weaker pathogenic damage but can break through vaccine immune protection, require further attention. Our findings increase the understanding of the differences between epidemic strains and factors underlying MD vaccination failure in China.
