1 Divisions of Molecular Virology and Oncology and Control and Prevention of Infectious Diseases, Graduate School of Medicine, Divisions of Child Health and Welfare and Endocrinology and Metabolism, Faculty of Medicine, and Department of Endoscopy, University Hospital, University of the Ryukyus, Nishihara, Okinawa 903-0215, Japan; Department of Pathology, Institute of Tropical Medicine, Nagasaki University, Nagasaki 852-8523, Japan; and Division of Cytokine Signaling, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki 852-8523, Japan