1. Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo
2. Core Research for Evolutional Science and Technology, Japan Science and Technology Corporation, Saitama
3. Department of Virology, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima
4. Laboratory of Microbiology, Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
5. Department of Pathological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin