1. Department of Pathobiology and Veterinary Science and Center of Excellence for Vaccine Research, College of Agriculture and Natural Resources, University of Connecticut, Storrs, Connecticut.
2. International Laboratory of Molecular Biology for Tropical Disease Agents, School of Veterinary Medicine, University of California, Davis, California.
3. Department of Medical Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, California.