1. Department of Gastroenterology, Gunma Saiseikai Maebashi Hospital, Japan
2. Department of Clinical Research, National Hospital Organization Takasaki General Medical Center, Japan
3. Department of Pathology, Gunma Saiseikai Maebashi Hospital, Japan
4. Department of Gastroenterology, National Hospital Organization Takasaki General Medical Center, Japan
5. Department of Gastroenterology and Hepatology, Gunma University Graduate School of Medicine, Japan
6. Division of Virology, Department of Infection and Immunity, Jichi Medical University School of Medicine, Japan