1. Molecular Microbiology Group, Center of Molecular Biosciences; University of the Ryukyus; Okinawa 903-0213 Japan
2. Division of Host Defense and Vaccinology, Graduate School of Medicine; University of the Ryukyus; Okinawa 903-0215 Japan
3. Division of Molecular Immunology, Institute of Genetics, School of Medicine; Hokkaido University; Sapporo Hokkaido 060-0815 Japan
4. Division of Child Health Welfare, Graduate School of Medicine; University of the Ryukyus; Okinawa 903-0215 Japan
5. Division of Digestive and Genetics Surgery, Graduate School of Medicine; University of the Ryukyus; Okinawa 903-0215 Japan
6. Department of Infectious Diseases, Faculty of Medicine; Oita University; Oita 879-5593 Japan