1. Rocky Mountain Regional Veterans Affairs Medical Center, Aurora, Colorado, USA
2. Office of Academic Affairs, National Jewish Health, Denver, Colorado, USA
3. Department of Medicine, National Jewish Health, Denver, Colorado, USA
4. Division of Pulmonary Sciences and Critical Care Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
5. Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA