1. Department of Virology II; National Institute of Infectious Diseases; Tokyo
2. Division of Gastroenterology, Department of Medicine; Showa University School of Medicine; Tokyo
3. Department of Gastroenterology and Hepatology; Shin-Yurigaoka General Hospital; Kawasaki
4. Division of Gastroenterology, Saitama Medical Center; Jichi Medical University; Saitama
5. Research Institute for Gastrointestinal and Liver Diseases; Shin-Yurigaoka General Hospital; Kawasaki Japan