2.1. Cell Lines, Viruses, and Compounds

Huh7 cells were obtained from JCRB Cell Bank (Japan). Vero and Vero-E6 cells were obtained from ATCC, Manassas, VA, USA, (CRL-81 and CRL-1586, respectively). Vero cells were maintained in Dulbecco’s modified Eagle’s medium (DMEM) supplemented with 10% fetal bovine serum (FBS), 100 IU streptomycin/penicillin per mL, and 10 μg/mL plasmocin (InvivoGen, San Diego, CA, USA). Huh7 cells were maintained in minimum essential medium (MEM) supplemented with 10% FBS, 100 IU streptomycin/penicillin per mL, 1 mM sodium pyruvate, 1X non-essential amino acids (NEA), 5 μg/mL plasmocin (InvivoGen), and 1X Glutamax. Vero-E6 cells were maintained in DMEM supplemented with 5% FBS, 100 IU streptomycin/penicillin per mL, 1 mM sodium pyruvate, 1X NEA, 5 μg/mL plasmocin (InvivoGen), and 1X Glutamax. Human foreskin fibroblasts (HFFs) were maintained in Dulbecco’s modified Eagle’s medium (DMEM) supplemented with 10% fetal bovine serum (FBS), 100 IU streptomycin/penicillin per mL, and 10 μg/mL plasmocin (InvivoGen).

Dengue virus (DENV) type 2 New Guinea C strain (ATCC VR-1584) was generated in C6/36 mosquito cell cultures (ATCC CRL-1660) as described [13]. SARS-CoV-2 isolate USA-WA1/2020 (NR-52281) was obtained through BEI Resources and propagated in Vero-E6 cells. ZIKV H/PAN/2015/CDC-259359 (BEI Resources NR-50219) stocks were generated in C6/36 mosquito cell cultures (ATCC CRL-1660) as described [13]. IAV A/WS/33 (H1N1) was obtained from ATCC (VR-825) and stocks were prepared as described [28]. HCoV-OC43 was a kind gift from J. Wang (University of Arizona) and stocks were prepared in Vero cells. Vero cells in 175 mL flasks (85% confluence) were inoculated with HCoV-OC43 at MOI of 0.01 in 10 mL of infection medium (MEM with 1% FBS, 100 IU streptomycin/penicillin per mL, and 10 mM HEPES). After 2 h, an additional 10 mL of infection medium was added. The supernatant was collected after 7 days (50% CPE) and precleared by centrifugation at 3000 RPM for 15 min (4 °C). Titer (PFU/mL) was estimated by plaque assay.

Cell lines and viral reagents used for experiments in the Supplementary Materials are described in the Supplementary Materials and Methods.

Compounds T-1105, favipiravir (T-705), 6MMPr, and T-1106 were purchased from Alfa Aesar (Haverhill, MA, USA), Asta Tech (Bristol, PA, USA), Millipore Sigma (Burlington, MA, USA), and Biosynth Carbosynth (Newbury, UK), respectively. All compounds were resuspended in DMSO to a 20 mM stock solution prior to diluting in DMSO and then into a cell culture medium for a final DMSO concentration of 0.5% in all experiments. All compounds and dilutions were stored at −20 °C.