Reduced antigen presentation capability and modified inflammatory/immunosuppressive cytokine expression of induced monocyte-derived dendritic cells from peripheral blood of piglets infected with porcine circovirus type 2.

The efficiency of immune responses and host defense against pathogens largely depends on the function of dendritic cells (DCs). Porcine circovirus type 2 (PCV2) infection causes viremia and extensive modulation of immune activities in the blood. The objective of the present study was to investigate the effects of PCV2 infection in vivo on the immunological function of DCs induced from peripheral blood monocytes (MoDCs). At different points after infection with PCV2, peripheral blood monocytes from PCV2-infected pigs were used to induce differentiation of DCs in vitro. Flow cytometry and quantitative real-time reverse transcription PCR were conducted to detect mRNA expression of surface markers related to antigen presentation and inflammatory/immunosuppressive cytokines of the induced MoDCs. The ability of induced MoDCs to stimulate T cells was measured using an MTS assay. In the early phase of infection at 3 days post-inoculation (DPI), IL-10, IL-8 and MIP-1β in MoDCs were upregulated significantly. By the peak of virus proliferation at 7 DPI, antigen presentation molecules SLA-DR (MHC II) and CD80/86 together with cytokines IL-12 and IL-10 had decreased, accompanied by a rapid reduction of IL-8 and MIP-1β. The T cell stimulation index of induced MoDCs in PCV2 groups after different infection times declined to some extent, with a significant difference at 7 DPI. PCV2 infection in vivo functionally reduced the antigen presentation capability of induced MoDCs from peripheral blood and modified expression of inflammatory/immunosuppressive cytokines that may be related to PCV2-induced immunosuppression.