*2.8. Binding Assay and Flow Cytometry*

PCV2 virions enriched with ultra-centrifugation were added to PK-15 cells with MOI = 5.0 in the presence of 100 μM EGCG. After binding for 1 h or 4 h at 4 ◦C, the mixture was then washed off and the cells were harvested. The amount of the attached virions was determined using qPCR. The ratio of attached cells was measured by flow cytometry, the trypsin digested PK15 cells were resuspended and incubated with the mAb 5E11 for 1.5 h at 37 ◦C, followed by staining with FITC-conjugated goat anti-mouse IgG for 1 h, mouse IgG1 was used as isotype control, finally the samples were measured by BD Accuri™ C6 flow cytometer (BD bioscience, San Jose, CA, USA) and the results were analyzed by FlowJo X software (Version 10.0.7, FlowJo, San Jose, CA, USA ).
