1 Department of Medicine, Division of Infectious Diseases and International Medicine, Program in Infection and Immunity, University of Minnesota, Minneapolis, MN 55455, USA.
2 Institute for Molecular Virology Training Program, University of Minnesota, Minneapolis, MN 55455, USA.
3 Graduate Program in Comparative and Molecular Bioscience, University of Minnesota, Minneapolis, MN 55455, USA.
4 Department of Biochemistry & Molecular Biology, The Pennsylvania State University 201 Althouse Laboratory, University Park, PA 16802, USA.
5 Department of Microbiology and Immunology, University of Minnesota, Minneapolis, MN 55455, USA.