[1] Univ Tokyo, Inst Med Sci, Dept Microbiol & Immunol, Div Virol,Minato Ku, Tokyo 1088639, Japan
[2] Univ Tokyo, Inst Med Sci, Int Res Ctr Infect Dis, Dept Special Pathogens,Minato Ku, Tokyo 1088639, Japan
[3] Japan Sci & Technol Agcy, ERATO Infect Induced Host Responses Project, Kawaguchi, Saitama 3320012, Japan
[4] Univ Wisconsin, Sch Vet Med, Dept Pathobiol Sci, Influenza Res Inst, Madison, WI 53711 USA