1. Department of Microbiology, and COE Program in the 21st Century, University of Shizuoka School of Pharmaceutical Sciences, Shizuoka 422-8526, Japan 2Department of Parasitology, Aichi Medical University, Aichi 480-1195, Japan 3Okinawa Prefectural Institute of Health and Environment, Okinawa 901-1202, Japan 4Department of Bacteriology, National Institute of Infectious Diseases, Tokyo 162-8640, Japan