1. Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health , Rocky Mountain Laboratories, Hamilton, Montana , USA
2. Rocky Mountain Veterinary Branch, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health , Rocky Mountain Laboratories, Hamilton, Montana , USA
3. Research Technology Branch, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health , Rocky Mountain Laboratories, Hamilton, Montana , USA