1. Laboratory of Intracellular Parasites; Rocky Mountain Laboratories; National Institute of Allergy and Infectious Diseases, National Institutes of Health; Hamilton MT 59840 USA
2. Electron Microscopy Unit; Research Technologies Branch; Rocky Mountain Laboratories; National Institute of Allergy and Infectious Diseases, National Institutes of Health; Hamilton MT 59840 USA
3. Department of Pathology and Immunology and Midwest Regional Center of Excellence for Biodefense and Emerging Infectious Diseases Research; Washington University School of Medicine; St Louis MO 63110 USA