1. Department of Immunology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105
2. Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, Tennessee 38105; Department of Pediatrics, University of Tennessee, Memphis, Tennessee 38163
3. Department of Virology and Molecular Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105; Department of Pathology, University of Tennessee, Memphis, Tennessee 38163
4. Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105
5. Department of Immunology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105; Department of Pathology, University of Tennessee, Memphis Tennessee 38163