1. Department of Microbiology, Fukui Medical University School of Medicine, 23-3 Matsuoka-cho, Yoshida-gun, Fukui 910-1193, Japan
2. Laboratory of Virology, Research Institute for Disease Mechanism and Control, Nagoya University School of Medicine, Aichi, Japan
3. Department of Microbiology and Immunology, Research Center for Infectious Disease, Aichi Medical University School of Medicine, Aichi, Japan