[1] Hokkaido Univ, Grad Sch Med, Dept Microbiol & Immunol, Kita Ku, Sapporo, Hokkaido 0608638, Japan
[2] Hokkaido Univ, Creat Res Inst, Lab Viral Hepatitis & Host Def, Kita Ku, Sapporo, Hokkaido 0608638, Japan
[3] Chiba Inst Technol, Res Inst, Narashino, Chiba 2750016, Japan
[4] Kyoto Univ, Dept Virol, Inst Virus Res, Kyoto 6068507, Japan