Oxidative stress promotes PCV2 replication in PCV2-infeced PK15 cells. PK15 cells were infected with PCV2 at MOI of 1, after 2 h infection, the cells were further cultured in fresh medium with different concentrations of H2O2 for 48 h. A, B Cells were stained with H2DCF-DA to measure intracellular ROS. C The determination of GSH content was performed according to the procedures described in materials and methods. D, E The number of infected cells was detected by immunofluorescence assay. F Real-time PCR was used to detect the PCV2 viral DNA copies. G, H The expression of viral cap protein was detected by Western blotting. Scale bar: 10 µm. All results are presented as mean ± SEM (n = 3, each). Significance compared with control (*P < 0.05 and **P < 0.01). Significance compared with single PCV2-infected group (#P < 0.05 and ##P < 0.01).