1. University of Vermont (UVM) College of Medicine, Department of Medicine, Unit of Infectious Diseases and Vaccine Testing Center, Burlington, Vermont
2. Naval Medical Research Center (NMRC), Department of Enteric Diseases, Silver Spring, Maryland
3. Uniformed Services University of the Health Sciences, Department of Preventive Medicine and Biometrics, Bethesda, Maryland
4. ACE Biosciences, Hillerød, Denmark