1. Department of Infectious Diseases
2. Department of Hematology, Kumamoto University School of Medicine, Kumamoto 860-8556, Japan
3. Experimental Retrovirology Section, HIV and AIDS Malignancy Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892
4. Laboratory of Virus Immunology, Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan
5. Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520
6. Biochemicals Division, Yamasa Corporation, Chosi 288-0056, Japan