[1] Tohoku Univ, Sch Med, Dept Geriatr & Resp Med, Aoba Ku, Sendai, Miyagi 9808574, Japan
[2] Tohoku Univ Hosp, Dept Pharmacol Sci, Sendai, Miyagi 9808574, Japan
[3] Univ Tsukuba, Inst Clin Med, Dept Pulm Med, Tsukuba, Ibaraki 3058575, Japan
[4] Natl Hosp Org, Sendai Med Ctr, Virus Res Ctr, Div Clin Res, Sendai, Miyagi 9830045, Japan