Moreover, a difference in the open or closed conformation of the ACE2 receptor together with the glycosylation rate of some amino acid residues in the PD domain could affect ACE2-SARS-CoV-2 interaction [105,108], as demonstrated by chloroquine treatment of SARS-CoV patients, in which chloroquine inhibited virus infection by interfering with the terminal glycosylation of ACE2 receptor [109]. Here, ACE2 is linked to viral infectious disease.