5.2 Rational: Recombinant type I IFN can effectively inhibit SARS-CoV2 replication In 24–48 h after infection, SARS-CoV2 replication reaches titer that causes the cytopathic effect in Vero E6 cells, which express ACE2 and thus are susceptible to SARS-CoV2 infection [25]. It is similar to the viral replication kinetics for SARS-CoV [25]. Pretreatment with recombinant type I IFN could effectively inhibit SARS-CoV2 replication at both 24 and 48 h after infection [25]. For SARS-CoV, such an effect was present at 24 h but absent at 48 h after infection [25]. The difference between SARS-CoV2 and SARS-CoV in response to type I IFN treatment may be due to differences in structural proteins of these viruses, including NSP3, ORF3b, and ORF6 [25].