1. Division of Biomedical Food Research, National Institute of Health Sciences, Kanagawa, Japan
2. Department of Agriculture, Utsunomiya University, Tochigi, Japan
3. National Institute of Infectious Diseases, Murayama Branch, Tokyo, Japan
4. Department of Applied Veterinary Science, the United Graduate School of Veterinary Science, Gifu University, Gifu, Japan
5. National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, Tokyo, Japan