IFIH1 and infection: Interestingly, the PLP enzymes of other coronaviruses such as SARS-CoV, MERS-CoV, murine hepatitis virus (MHV), and HCoV-NL63 were all able to bind to the MDA5 CARDs and to antagonize their ISGylation [22], suggesting that this immune evasion mechanism is widely conserved among coronaviruses, which warrants further investigation using authentic infection with these coronaviruses (Figure 1).