In the context of infection, ORF4a antagonizes IFN production and signaling, as A549DPP4 cells infected with a recombinant MERS-CoV-Δ4a showed increased mRNA expression levels of interferon lambda (IFNL1) and ISGs OAS2 and IFIT1 (Comar et al., 2019; Comar et al., 2022). Here, OAS2 is linked to infection.