1. Department of Laboratory Animal Medicine, College of Veterinary Medicine, Seoul National University, Seoul 151-742, Korea.
2. Department of Animal Experimentation, College of Medicine, Seoul National University, Seoul 110-799, Korea.
3. Laboratory of Public Health, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan.
4. Biological Diagnostic Products Team, Biologics Headquarters, Korea Food and Drug Administration, Seoul 122-704, Korea.