1. Key Laboratory of Pathogen Biology of Jiangsu Province, Nanjing Medical University, Nanjing, China
2. Department of Microbiology, Nanjing Medical University, Nanjing, China
3. Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY USA
4. State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing, China