ISG15 and viral infectious disease: When we treated cells with EGCG before HCV dsRNAs stimulation, the HCV dsRNAs-induced IFN-λ1, RIG-I, TLR3 and several antiviral ISGs (ISG15, MxA) expressions were significantly enhanced, indicating that EGCG might be used as an agent to enhance the innate immune responses during viral infections.