1. Department of Microbiology and Immunology, University of Iowa , Iowa City, Iowa , USA
2. Department of Pediatrics-Endocrinology and Diabetes, University of Iowa , Iowa City, Iowa , USA
3. Center for Infectious Disease and Vaccine Research, La Jolla Institute for Immunology , La Jolla, California , USA
4. Fraternal Order of Eagles Diabetes Research Center, University of Iowa , Iowa City, Iowa , USA