ACE2 and COVID-19: The spike protein, the major envelope protein of HCoV-NL63, specifically binds to the zinc peptidase angiotensin-converting enzyme 2 (ACE2) identified as the receptor for pathogenic coronaviruses SARS-CoV and COVID-19 (formerly known as Wuhan coronavirus, 2019-nCoV, and SARS-CoV-2) [16,17,18,19].