ACE2 and infection: Clinically important features of SARS-CoV-2 pathogenesis include infection of cells via binding of the viral spike protein to angiotensin-converting enzyme 2 (ACE2) receptors, with cell entry requiring type 2 transmembrane serine protease to cleave ACE2 receptor and activate viral spike protein, infection nasal and bronchial epithelial cells and pneumocytes in early stage, and acceleration the viral replication and compromised epithelial-endothelial barrier integrity in later stages (1, 2, 4).