1. Department of Immunology, National Institute of Animal Health, 3-1-5, Kannondai, Tsukuba, Ibaraki 305-0856, Japan
2. Department of Planning and Coordination, National Institute of Animal Health, 3-1-5, Kannondai, Tsukuba, Ibaraki 305-0856, Japan
3. Department of Molecular Biology and Immunology, National Institute of Agrobiological Sciences, 3-1-5, Kannondai, Tsukuba, Ibaraki 305-8602, Japan
4. Department of Infectious Diseases, National Institute of Animal Health, 3-1-5, Kannondai, Tsukuba, Ibaraki 305-0856, Japan