ISG15 and infection: Consistent with the pathway analysis, SARS-CoV-2 infection led to the robust induction of multiple cytokines (e.g., IL-1α, IL-1β and IL-6) and chemokines (e.g., CCL2, CCL5 and CCL20) at 24 h post-infection (Figure 5A), whereas the induction of interferon signaling and expression of the downstream interferon signaling genes (ISGs) (e.g., DDX58, ISG15 and MX1) was delayed and apparent at 48 h post-infection (Figure 5B).