| Abstrakt: |
Stimulation of the porcine immune system causes increased replication of porcine circovirus 2 (PCV2) in vivo. In the present study, we investigated whether various cytokines (interleukin-1 [IL-1], IL-6, IL-10, tumor necrosis factor-α [TNF-α], interferon-α [IFN-α], and IFN-γ) are able to influence PCV2 infection in vitro. No changes were observed in IL-1, IL-6, TNF-α, or IL-10-treated cells. However, it was demonstrated that IFN- α and IFN-γ influenced PCV2 infection in porcine kidney cells (PK-15) and porcine monocytic cells (3D4/31). IFN-γ added to the culture medium before, during, or after inoculation increased the number of PCV2 antigen- positive cells, respectively, by 418%, 171%, and 691% in PK-15 cells and by 706%, 114%, and 423% in 3D4/31 cells. IFN-α pretreatment decreased the number of infected PK-15 cells. When it was added after inoculation, IFN-α enhanced PCV2 infection by 529% in PK-15 cells and by 308% in 3D4/31 cells. The effect of both IFNs on PCV2 infection was dose dependent and could be blocked with IFN-α or IFN-γ neutralizing antibodies. Leukocyte-derived porcine IFN-γ induced a similar effect on PCV2 infection. Treatment of PK- 15 cultures with IFN-γ caused a 20 times higher production of progeny virus. Confocal microscopy studies showed that the enhancing effect of IFN-γ on PCV2 infection was achieved by increased internalization of PCV2 virionlike particles (VLPs). Binding of the VLPs to the cell or expression kinetics of PCV2 proteins in infected cells were not altered by IFN-γ treatment. To our knowledge, this study reports the first enhancement of a viral infection by treatment with type I or type II IFNs. |
