RESEARCH ARTICLE The tetraspanin CD9 facilitates MERS- coronavirus entry by scaffolding host cell receptors and proteases James T. Earnest1, Michael P. Hantak1, Kun Li2, Paul B. McCray, Jr2, Stanley Perlman2,3, Tom Gallagher1* 1 Department of Microbiology and Immunology, Loyola University Medical Center, Maywood, IL, United States of America, 2 Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, IA, United States of America, 3 Department of Microbiology, University of Iowa, Iowa City, IA, United States of America *