6 Laboratory for Drug Discovery and Disease Research, Shionogi & Co., Ltd., 3-1-1, Futaba-cho, Toyonaka, Osaka, 561-0825, Japan.
7 Medical Science Department, Shionogi & Co., Ltd., 8F, Nissei East Building, 3-3-16, Imabashi, Chuo-ku, Osaka, 541-0032, Japan.
8 Laboratory of Medical Virology, Institute for Life and Medical Sciences, Kyoto University, 53 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan.
9 Department of Virology, Faculty of Medicine, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
11 Center for Influenza and Respiratory Virus Research, National Institute of Infectious Diseases, 4-7-1, Gakuen, Musashimurayama-shi, Tokyo, 208-0011, Japan. hasegawa@niid.go.jp.