1. Department of Pathology and Microbiology; University of Nebraska Medical Center; Omaha NE 68198 USA
2. Department of Microbiology and Immunology; Loyola University Chicago, Stritch School of Medicine; Maywood IL 60153 USA
3. Emergent BioSolutions Lansing; MI 48906 USA
4. Battelle Memorial Institute; Fort Detrick; MD 21702 USA