1. Division of Pathology, Biological Safety Research Center; National Institute of Health Sciences; 1-18-1, Kamiyoga, Setagaya-ku Tokyo 158-8501 Japan
2. Division of Toxicology, Department of Pharmacology, Toxicology and Therapeutics, School of Pharmacy; Showa University; 1-5-8 Hatanodai, Shinagawa Tokyo 142-8555 Japan
3. Pathogenetic Veterinary Science, United Graduate School of Veterinary Sciences; Gifu University; 1-1, Yanagido Gifu 501-1193 Japan
4. National Institute of Health Science; Biological Safety Research Center; 1-18-1, Kamiyoga, Setagaya-ku Tokyo 158-8501 Japan