The murine macrophage cell line RAW264.7 and human embryonic kidney 293 T (HEK293T) cell line were purchased from American Type Culture Collection (ATCC; Rockville, MD, USA) and cultured in Dulbecco’s modified Eagle’s medium (DMEM) supplemented with 10% fetal bovine serum (FBS), 100 U/ml penicillin, and 100 µg/mL streptomycin. The HG23 cell line stably harboring a HuNoV (Norwalk virus) replicon17 was cultured in DMEM supplemented with 10% FBS, 2 mM l-glutamine, 100 U/ml penicillin, 100 µg/ml streptomycin, and 0.1 mM nonessential amino acids in the presence of 1 mg/ml neomycin (G418 sulfate). Cells were maintained at 37 °C in a 5% CO2 humidified incubator.