1. Center for Vaccine Research, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
2. Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
3. Department of Microbiology, Boston University School of Medicine, Boston, Massachusetts, USA
4. Viral Special Pathogens Branch, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
5. Department of Viroscience, Erasmus MC, University Medical Centre Rotterdam, Rotterdam, The Netherlands
6. J. Craig Venter Institute, Rockville, Maryland, USA