1. Department of Virology 1, National Institute of Infectious Diseases, Tokyo, Japan.
2. Department of Rheumatology and Clinical Immunology, Clinical Research Center for Allergy and Rheumatology, Sagamihara National Hospital, National Hospital Organization, Sagamihara, Japan.
3. Department of Virology, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.