1. Division of Gastroenterological and Hepatobiliary Surgery and Organ Transplantation, University of Tsukuba, Tsukuba, Japan
2. Animal Genome Research Unit, National Institute of Agrobiological Sciences, Tsukuba, Japan
3. Japan Blood Products Organization, Kobe, Japan
4. Department of Infection Biology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Japan
5. Kawasaki Medical School, Okayama, Japan