1. Laboratory of Molecular Epidemiology for Infectious Agents, Kitasato Institute for Life Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan
2. Pharmaceutical Research Center, Meiji Seika Kaisha, Ltd., 760 Morooka, Kohoku-ku, Yokohama, Kanagawa 222-8567, Japan