1. Department of Pediatrics, University of Texas Medical Branch (UTMB), Galveston, Texas 77555
2. Department of Pathology, UTMB, Galveston, Texas 77555
3. Department of Microbiology and Immunology, UTMB, Galveston, Texas 77555
4. Sealy Center for Vaccine Development, UTMB, Galveston, Texas 77555
5. Department of Microbiology, North Carolina State University, Raleigh, North Carolina 27695