1. Department of Pathology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA
2. Department of Infectious Diseases and Microbiology, School of Public Health, University of Pittsburgh, Pittsburgh, PA 15261, USA
3. Tulane National Primate Research Center, Tulane University, Covington, LA 70433, USA
4. Division of Infectious Diseases, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA
5. Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, NM 87545, USA