1. Department of Pathobiology, College of Veterinary Medicine, University of Illinois-Urbana-Champaign, Urbana, IL 61802, USA.
2. Department of Infectious Diseases, College of Veterinary Medicine, Seoul National University, Seoul 08826, Korea.
3. Optipharm Inc., Cheongju 28158, Korea.
4. Choong Ang Vaccine Laboratories Co. (Ltd.), Daejeon 34055, Korea.