1. Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
2. Program in Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
3. Department of Pediatrics, University of Rochester School of Medicine and Dentistry, Rochester, New York, USA
4. Division of Pediatric Infectious Disease, University of Iowa, Iowa City, Iowa, USA
5. Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, California, USA
6. Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, California, USA
7. Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada