Abstract: 【Objective】 The experiment was to establish a model of the inflammatory response of 3D4/2 cells infected with Porcine circovirus type 2 (PCV2) in vitro by exploring the relationship between the concentration, time and the inflammatory level of PCV2 in vitro infection, and lay a foundation for the study of the later drug regulation of PCV2-induced 3D4/2 cells inflammatory response.【Method】 3D4/2 cells were divided into control group and different dilutions PCV2 infected groups (10⁰, 10^-1, 10^-2 and 10^-3 dilutions), with 3 replicates per group.The control group was treated with DMEM, and PCV2 infected groups were treated with PCV2 in different concentrations, then replaced with DMEM maintenance solution containing 5% FBS for culture after 2 h.After 4, 8, 12 and 24 h of culture, cells and cell supernatant were collected, respectively.NO level was detected by Griess method, ROS level was detected by DCFH-DA fluorescent probe method, GSH level was detected by enzyme-conjugated method, XOD and MPO enzyme activities were detected by spectrophotometry.IL-1β, IL-6, TNF-α, IL-10, IFN-γ, IL-8, MCP-1, COX-1 and COX-2 inflammatory factor levels were determined by ELISA method.【Result】 10⁰ to 10^-3 concentrations of PCV2 could successfully infect 3D4/2 cells after 4, 8, 12 and 24 h.Compared with control group, after 3D4/2 cells were infected with PCV2 at 10⁰ concentrations for 4, 8, 12 and 24 h, the ROS level was extremely significantly increased (P<0.01), and after 3D4/2 cells were infected with PCV2 at 10^-1 to 10^-3 concentrations for 8, 12 and 24 h, the ROS level was significantly or extremely significantly increased (P<0.05;P<0.01).After 3D4/2 cells were infected with 10⁰ to 10^-3 concentrations of PCV2 for 8, 12 and 24 h, the intracellular NO concentration and MPO activity were significantly increased (P<0.05).The levels of IL-1β, IL-6, TNF-α, IL-10, IFN-γ, IL-8, MCP-1 and the activity of COX-1 in cell supernatant or cells were significantly or extremely significantly increased (P<0.05;P<0.01).Among which, after 10⁰ concentration of PCV2 infected 3D4/2 cells, the increase of each inflammatory factor was the most significant, and with the prolongation of time, the NO concentration was gradually increased, and the activity of XOD was gradually decreased.【Conclusion】 PCV2 could induce inflammatory responses in 3D4/2 cells, and infection of 3D4/2 cells with 10⁰ dilution PCV2 in vitro for 4-12 h was the best condition for establishing an inflammatory model.

Key words: Porcine circovirus type 2 (PCV2); inflammatory cytokines; 3D4/2 cells