Huh7.5 cells and HCV replicon cells will be incubated for 12 hours with increasing doses of IFNa2b (0, 1,10 and 100U/ml), IFNb (0,10,100 and 1000 U/ml ), or IFNg (0,10,100 and 1000 U/ml), and ISG 15, UBP43, and HCV mRNA levels determined by real-time PCR. ISG15 protein levels will be determined by western blot (mAb the kind gift of Dr. E.C. Borden, Scripps Institute); UBP43 western studies will be performed after we create antibodies or as the antibody becomes available (currently it is being developed in the lab of Dr. D.E. Zhang, Scripps Institute). RNA isolation will be performed by standard Trizol extraction, and protein extraction by lysing the cells in RIPA buffer. These studies will establish mRNA and protein levels for ISG15 and UBP43 at baseline, and in response to IFN, replicon and replicon/IFN.