1. AIDS Research Center, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, 162-8640 Tokyo, Japan
2. The Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, 108-8639 Tokyo, Japan
3. Laboratory of Viral Genomics, Pathogen Genomics Center, National Institute of Infectious Diseases, 4-7-1 Gakuen, Musashi Murayama-shi, 208-0011 Tokyo, Japan
4. Vietnam Research Station, Institute of Tropical Medicine, Nagasaki University, 1-12-4 Sakamoto, 852-8523 Nagasaki, Japan
5. Kureha Corporation, 3-26-2, Hyakunin-cho, Shinjuku-ku, 169-8503 Tokyo, Japan
6. Department of Medical Virology, Faculty of Life Sciences, Kumamoto University, 1-1-1 Honjo, 860-8556 Kumamoto, Japan