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.