Murine or human ifn β

WT and TAM receptor-deficient BMECs and WT HCMEC/D3 cells were grown until fully polarized in transwell cultures²² . BMECs were grown above astrocyte cultures, whereas HCMEC/D3s were grown without astrocytes. TEER was measured via chopstick electrode with an EVOM voltmeter (World Precision Instruments). Resistance values are reported as Ω/cm², with the resistance value for transwell inserts with no cells subtracted as background. TEER measurements were collected at 6 h following infection with WNV at MOI 0.01 or treatment with murine IFN-λ3 (100 ng/ml), murine or human IFN-β (10 ng/ml) (PBL Assay Science); mock wells were treated with culture medium. To block IFN-α/β signaling, BMEC cultures were treated with 25 μg/ml of the blocking MAb MAR1-5A3 for one hour prior to infection. A non-binding MAb (GIR-208) was used as an isotype control. To measure virus transit across the endothelial barrier, WNV was added to the upper chamber of the transwell at an MOI of 0.01. After 6 h, virus in the lower chamber was measured by qRT-PCR. Recombinant full-length Gas6 was generated in HEK293 EBNA cells as previously described⁴ . Human Protein S was purchased from Haematologic Technologies (HCPS-0090).