1. Frontier Science Research Center, Kagoshima University, Kagoshima 890-8544, Japan
2. Division of Antiviral Chemotherapy, Center for Chronic Viral Diseases, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8544, Japan
3. Rega Institute for Medical Research, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium