*Correspondence:
Zhi Zheng, Institute of Basic Medical Sciences, Chinese Academy of
Medical Sciences, School of Basic Medicine, Peking Union Medical
College, 5 Dongdan Santiao Beijing, 100005 P. R. China
Tel: +86-010-69156961
E-mail: zhizheng100@126.com,
Jifei Yang,
Lanzhou
Veterinary Research Institute, Chinese Academy of Agricultural Sciences,
Xujiaping 1, Lanzhou, Gansu, 730046, P. R. China
Tel: +86-931-8342671
E-mail:
yangjifei@caas.cn