1. Department of Biological Sciences, Dartmouth College , 78 College Street, Hanover, NH, USA
2. Department of Microbiology and Immunology, University of British Columbia , 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
3. Integrated Research Facility at Fort Detrick, Division of Clinical Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health , B-8200 Research Plaza, Fort Detrick, Frederick, MD 21702, USA
4. Department of Biology, Memorial University of Newfoundland , 45 Arctic Ave., St. John’s, NL A1C 5S7, Canada