T-cell factor-4 and MHC upregulation in pigs receiving a live attenuated classical swine fever virus (CSFV) vaccine strain with interferon-gamma adjuvant

• Pigs receiving IFN-γ plus LPC vaccine showed upregulated Tcf-4 expression.
• Pigs receiving IFN-γ plus LPC vaccine showed increased MHC-I and MHC-II.
• Pigs receiving IFN-γ plus LPC vaccine showed enhanced IgG2 levels.
• Pigs receiving IFN-γ plus LPC vaccine were protected from virulent CSFV.
• This is the first to report Tcf-4 involvement in IFN-γ-mediated immune regulation.

The effect of co-administration of interferon (IFN)-γ in pigs undergoing vaccination with an attenuated strain (LPC) of classical swine fever virus (CSFV) was investigated.Unvaccinated pigs demonstrated pyrexia and died 7–9 days after challenge with virulent CSFV. Pigs receiving the attenuated vaccine remained healthy after virus challenge, except for mild, transient pyrexia, whereas pigs receiving IFN-γ simultaneously with the vaccine demonstrated normal body temperatures after virus challenge. Examination by nested RT-PCR revealed greater viral load in the spleens of the pigs vaccinated with the attenuated CSFV, compared with those that had additionally received IFN-γ. Expression of major histocompatibility complex (MHC) class I and MHC class II molecules was upregulated in the spleens of the IFN-γ treated vaccinated pigs, demonstrated by immunohistochemistry. Based on Western blot analysis, anti-CSFV IgG2 antibodies were elevated in vaccinated pigs by co-administration of IFN-γ (IFN-γHi: P < 0.01; IFN-γLo: P < 0.05). By employing the suppression subtractive hybridization technique, RT-PCR, in situ hybridization, and immunohistochemistry, T-cell factor-4 (Tcf-4) mRNA and protein expression were found to be upregulated in the spleens of vaccinated pigs that had received IFN-γ. This study suggests involvement of Tcf-4 in IFN-γ-mediated immune regulation following CSFV vaccination.