IFNAR1 and viral infectious disease: Just like the parent HEK293T cells, HEK293T/17 (ACE2+, TMPRSS2+, IFNAR1 KO) cells not only constitutively express the SV40 large T antigen (LTag) which is required for SV40 DNA replication, but also have the additional modifications i.e.: (1) IFNAR1 knock out (which is helpful in supporting viral infection and preventing the host cell apoptosis), (2) ACE2 knocked in (being a receptor of SARS-CoV-2, presence of ACE2 is very helpful in continued viral infection after transfection), and (3) TMPRSS2 knocked in (is the serine protease that cleaves the viral spike during infection.