1. Center for Virology and Vaccine Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA
2. Theoretical Biology and Biophysics, Los Alamos National Laboratory, and the New Mexico Consortium, Los Alamos, New Mexico, USA
3. Department of Pathology and Immunology, Washington University School of Medicine, Saint Louis, Missouri, USA
4. Ragon Institute of MGH, MIT, and Harvard, Boston, Massachusetts, USA