1. Department of Civil and Environmental Engineering, The George Washington University, Washington, District of Columbia 20052, United States
2. Laboratory of Host−Pathogen Dynamics, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
3. Electron Microcopy Core, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
4. Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, United States