roteasome-mediated degradation or constitutive expression of the parainfluenza type 5 virus V protein , which blocks IFN signaling by targeting STAT1 for proteasome-mediated degradation . In these engineered IFN incompetent cells vaccine candidate viruses and slow-growing wild-type viruses formed bigger plaques and grew to increased titers , demonstrating the potential use of these cell-lines for the applications described above. In addition such IFN incompetent cell-lines can be useful in virus diagnostics, isolation of newly emerging viruses and basic research . However, genetically engineering cell-lines is time consuming and their use creates regulatory problems for vaccine manufacturers. We hypothesize that small molecule inhibitors of the IFN response would offer a simple and flexible solution, as an effective inhibitor could easily supplement the tissue culture medium of cell-lines of choice. Eight small molecules that have previously been described to inhibit the cellular IFN response were obtained; four inhibitors that target components of the IFN PD1-PDL1 inhibitor 2 induction pathway: TBK1 inhibitors BX795, MRT68844, MRT67307 and the IKK- 2 inhibitor TPCA-1 , plus four inhibitors that target JAK1 a component of the IFN signaling pathway: Cyt387, AZD1480, Ruxolitinib and Tofacitinib . We verified the ability of these molecules to inhibit IFN induction or IFN signaling using two A549 reporter cell-lines in which a GFP gene is placed under the control of MEDChem Express NAN-190 (hydrobromide) either the IFN-b promoter .GFP) or an ISRE promoter .GFP) . The four inhibitors targeting components of the IFN induction pathway were tested using the A549/pr .GFP reporter cell-line. The IFN induction pathway and hence GFP expression was optimally activated in this cell-line by infection with a PIV-5/VDC virus stock rich in DIs . Inhibitors that target components of the IFN induction pathway would be expected to block GFP expression. The IKK-2 inhibitor TPCA-1 demonstrated a significant block to GFP expression, while the TBK1 inhibitor BX795 showed a weak effect at a concentration of 4 mM, however no activity was observed for the MRT68844 and MRT67307 inhibitors . The JAK1 inhibitors were similarly tested in the A549/pr .G
