1. Division of Pathology; National Institute of Health Sciences; Tokyo 158-8501 Japan
2. Pathogenetic Veterinary Science, United Graduate School of Veterinary Sciences; Gifu University; Gifu 501-1193 Japan
3. Department of Pharmacology, School of Pharmacy; Showa University; Tokyo 142-8555 Japan
4. Faculty of Life and Environmental Sciences; Kyoto Prefectural University; Kyoto 606-8522 Japan
5. Kyoto Prefectural Agriculture; Forestry & Fisheries Technology Center; Kyoto 621-0806 Japan
6. Department of Food Science and Biotechnology; Kagoshima University; Kagoshima Kagoshima 890-0065 Japan
7. Biological Safety Research Center; National Institute of Health Sciences; Tokyo 158-8501 Japan