1. Department of Virology III, National Institute of Infectious Diseases, Tokyo, Japan
2. Faculty of Veterinary Medicine, Research Center for Animal Life Sciences, Nippon Veterinary and Life Science University, Tokyo, Japan
3. Department of Infectious Diseases and Host Defense, Gunma University Graduate School of Medicine, Gunma, Japan
4. Department of Virology I, National Institute of Infectious Diseases, Tokyo, Japan