1. Tsinghua University School of Medicine, Beijing, China
2. Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
3. Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, USA
4. Department of Ecology and Evolutionary Biology, University of California, Los Angeles, California, USA
5. Center for Vaccine Research, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
6. Department of Medicine, Division of Pulmonary, Allergy, and Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
7. Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, Virginia, USA
8. Department of Microbiology and Immunology, Emory University, Atlanta, Georgia, USA