1. Center for Infection and Immunity, Columbia University, New York 10032, USA
2. College of Veterinary Medicine at Cornell, Ithaca, NY 14853, USA
3. Centre for Immunology, Infection and Evolution, University of Edinburgh, Edinburgh EH9 3JT, UK
4. Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32610, USA
5. Pfizer Veterinary Medicine Research and Development, New York 10017, USA