FIG 5.

PACT is required for efficient IFN-I production upon IVA infection in the absence of NS1. (A) Stable knockdown of PACT in HEK293T cells by two different, retrovirally delivered shRNAs against PACT mRNA (sh1, sh2) and control shRNA (ctrl), analyzed by IB with antibodies against PACT and β-actin. (B and C) The HEK293T cells described in panel A were infected with PR8-wt and PR8 ΔNS1 at an MOI of 0.001 for 72 h or with PR8 ΔNS1 at an MOI of 5 for 24 h as indicated. The IFN-I activity (B) and virus titer (C) were determined by IFN bioassay and limiting dilution, after 72 h (MOI of 0.001) and 24 h (MOI of 5), respectively. nd, not detectable; ***, P < 0.001; ****, P < 0.0001.