John R Brannon1, Matthew A Mulvey2. 1. Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN 37232, USA. Electronic address: john.r.brannon@vumc.org. 2. Division of Microbiology and Immunology, Department of Pathology, University of Utah School of Medicine, Salt Lake City, UT 84112, USA.