1. Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda MD, 20892–0440, USA.
2. Department of Microbiology and Immunology, Pennsylvania State University Huck Institute for Life Sciences, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA.
3. Integrative Biosciences Graduate Program, Option in Molecular Medicine, Pennsylvania State University Huck Institute for Life Sciences, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA.