To determine if oxidative stress played a role in HCV-mediated activation of autophagy, cellular redox state was altered by either enhancing the cellular antioxidant capacity through dual overex-pression of superoxide dismutase (SOD) and catalase (CAT), or increasing cellular oxidative stress by xanthine/xanthine oxidase (X/XO) treatment. Changes in total LC3 and LC3-II levels were used as indicators of autophagy. Significant reduction of total LC3 and LC3-II levels was observed in subgenomic replicon, Core-on, and Core-off cells with overexpression of CuZnSOD/cytosolic catalase (SOD1/cCAT) or MnSOD/mitochondrial catalase (SOD2/mCAT) ( Figure 4A ). Although similar trends were observed in Huh7 cells, the extent of reduction did not reach a significant level. Despite comparable levels of CuZnSOD, MnSOD, and catalase expression ( Figure S4 ), LC3 levels were not altered in genome-length replicon cells. In contrast, X/XO treatment significantly increased total LC3 levels in genomic replicon, subgenomic replicon, and Core-off cells ( Figure 4B , left panel). However, LC3-II levels were only significantly increased in genomic replicon and Core-off cells ( Figure 4B , right panel). No significant change in LC3-II level was observed in Huh7, subgenomic replicon, and Core-on cells. Furthermore, addition of CAT to the X/XO treatment diminished the increase of total LC3 in genome-length and subgenomic cells ( Figure 4B ). The data suggest that the enhanced autophagy from X/XO treatment is mediated through H 2 O 2 in genome-length and subgenomic replicon cells.