1. Department of Pediatrics, University of California School of Medicine and University of California San Francisco Benioff Children's Hospital, San Francisco, San Francisco, California
2. Departments of Microbiology, Immunology and Molecular Genetics and Pediatrics, University of California Los Angeles, Los Angeles, California
3. Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota
4. Department of Medical and Molecular Genetics, Indiana University, and the Indiana University Viral Production Facility, Indianapolis, Indiana
5. Institute for Experimental Hematology, Hannover Medical School, Hannover, Germany
6. Laboratory of Host Defenses, National Institute of Allergy and Infectious Diseases, Division of Intramural Research, National Institutes of Health, Bethesda, Maryland.