1. Center for Vaccine Research, University of Pittsburgh, Pittsburgh, PA, USA.
2. Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, PA, USA.
3. Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA, USA.
4. University of Pittsburgh–Carnegie Mellon University Program in Computational Biology, Pittsburgh, PA, USA.
5. Department of Immunology, University of Pittsburgh, Pittsburgh, PA, USA.
6. Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, MA, USA.
7. National Emerging Infectious Diseases Laboratories, Boston University, Boston, MA, USA.