1. Laboratory of Microbiology, Department of Food and Nutritional Sciences, Graduate School of Nutritional and Environmental Sciences and Global COE Program, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka-shi, Shizuoka 422-8526, Japan
2. Virus Division, Saitama Institute of Public Health, 639-1 Kamiokubo, Sakura-ku, Saitama-shi, Saitama 338-0824, Japan