1. Division of Gastroenterological and Hepatobiliary Surgery, and Organ Transplantation, Department of Surgery, Faculty of Medicine, University of Tsukuba
2. Department of Gastroenterology, University of Tsukuba
3. Department of Gastroenterology, Tsukuba Gakuen Hospital
4. Division of Virology, Department of Infection and Immunity, Jichi Medical University School of Medicine