1. Department of Medicine and Therapeutics, Control and Prevention of Infectious Diseases, Graduate School of Medicine; University of the Ryukyus; Okinawa 903-0215 Japan
2. Department of Molecular Virology and Oncology, Graduate School of Medicine; University of the Ryukyus; Okinawa 903-0215 Japan
3. Institut für Molekulare Infektionsbiologie; Universität Würzburg; Röntgenring 11 97070 Würzburg Germany