1. College of Veterinary Medicine, China Agricultural University, Beijing 100094
2. CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101
3. Graduate University, Chinese Academy of Sciences, Beijing 100049
4. National Laboratory of Macromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101
5. School of Life Sciences, Sichuan University, Chengdu 610064, Sichuan
6. Beijing Institutes of Life Science, Chinese Academy of Sciences, Beijing 100101 People's Republic of China