ACE2 and infection: Infection with SARS-CoV-1 is initiated by binding of the receptor binding domain (RBD) of the Spike protein to the angiotensin-converting enzyme 2 (ACE2) receptor on host cells (Du et al., 2009; Li W. et al., 2003; Davidson et al., 2020), followed by viral fusion via the heptad repeat 2 (HR2) domain (Du et al., 2009).