1. Section of Infectious Diseases, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts, USA
2. National Institute for Biological Standards and Control, Hertfordshire, United Kingdom
3. Department of Molecular Genetics, University of Toronto, Toronto, Canada
4. Department of Microbiology and Immunology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
5. Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
6. Division of Microbiology and Infectious Diseases, NIAID, Bethesda, Maryland, USA