ACE2 and infection: Of note, by contrast to low-multiplicity of infection (MOI) infection of A549 cells expressing angiotensin I converting enzyme 2 (ACE2), normal human bronchial epithelial (NHBE) cells, and patient samples, high-MOI infections of A549-ACE2 and Calu-3 cells led to the high induction of IFNs and ISGs, including ISGs with broad antiviral activities [20] (Table 2).