For the inhibition experiments, cells were treated with 10 mg/ml human IL-1 receptor antagonist (IL-1Ra) [63] and extracellular TNF neutralization was achieved by treating cells with 10 mg/ml recombinant human soluble TNF receptor (sTNFR) [64] . Both IL-1Ra and/or sTNFR were added to the cells for 45 min before virus inoculation. DMEM alone was used as vehicle control for both inhibitors. After inoculation, cells were washed and cultured with the inhibitors for an additional 24 h.