1. Division of Advanced Biomedical Sciences, Department of Microbiology, Graduate School of Medical Sciences, Kumamoto University, Honjo 1-1-1, Kumamoto 860-8556, Japan, Hakuaikai Hospital, 4-3 Konnya-ima machi, Kumamoto 860-0012, Japan, and Biodynamics Research Laboratory, Cooperative Research Center, Kumamoto University, Techno Research Park, 2081-7 Tabaru, Mashiki-machi, Kumamoto, 861-2202, Japan