Ralph Baric, of the University of North Carolina, opened the workshop session with a general description of coronavirus structure, as illustrated in Figure WO-11. Focusing on the spike (S) glycoprotein, which is embedded in the lipid bilayer surrounding the nucleocapsid, he noted that it mediates viral binding to host receptors and encodes critical determinants for cross-species transmission. The S glycoproteins of SARS-CoV and of another human coronavirus, known as HCoV-NL63, bind angiotensin I converting enzyme 2 (ACE2) on the surface of host cells for docking and entry; their more distant relative MERS-CoV recog-nizes instead dipeptidyl peptidase 4 (DPP4). “The spike glycoprotein is the major target for vaccine development because it encodes neutralizing epitopes, as well as T-cell epitopes, and it encodes the major component of protective immunity,” he explained.