1. Laboratory of Virus Control, Institute for Virus Research, Kyoto University, 53 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan
2. Department of Hematology and Infectious Diseases, Kumamoto University School of Medicine, 1-1-1 Honjo, Kumamoto 860-0811, Japan
3. Department of Retrovirology and Self-Defense, Faculty of Medical and Pharmaceutical Sciences, Kumamoto University School of Medicine, 1-1-1 Honjo, Kumamoto 860-0811, Japan
4. Molecular Retrovirology Unit, Institut Pasteur, 28 rue du Dr. Roux 75724 Paris Cedex 15, France