1. Department of Biology and South Texas Center for Emerging Infectious Diseases, University of Texas, San Antonio, Texas, USA
2. Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
3. Infectious Diseases Section, VA Healthcare San Diego, California, USA
4. Department of Medicine, Division of Infectious Diseases, University of California San Diego School of Medicine, San Diego, California, USA