[1] Univ Tokyo, Sch Med, Dept Mol Prevent Med, Bunkyo Ku, Tokyo 1130033, Japan
[2] Univ Tokyo, CREST, Tokyo 1130033, Japan
[3] Kanazawa Univ, Sch Med, Dept Hyg, Kanazawa, Ishikawa 920, Japan
[4] Kumamoto Univ, Sch Med, AIDS Res Ctr, Kumamoto 860, Japan
[5] Univ Tokyo, Inst Med Sci, Dept Virol, Tokyo, Japan