Secretory expression of porcine interferon-gamma in baculovirus using HBM signal peptide and its inhibition activity on the replication of porcine reproductive and respiratory syndrome virus

The gene sequence encoding mature porcine interferon-gamma (PoIFN-γ) fused with a C-terminal 6× histidine tag was cloned into the baculovirus pFastBac™ Dual vector of the Bac-to-Bac Baculovirus expression system under the control of PH promoter. The authentic signal sequence of porcine interferon-gamma was substituted with the honeybee melittin (HBM) signal sequence, and expressed in insect cells. The recombinant proteins were detected by SDS-PAGE and immunofluorescence assay. The nickel affinity column purified recombinant porcine interferon-gamma with HBM signal peptide (rPoIFN-γH) was shown to be a 19 kDa protein as confirmed by Western blot analysis. The recombinant PoIFN-γH was shown to have cytokine activity, inhibiting the cytopathic effect of vesicular stomatitis virus (VSV) in PK-15 cells at about 1.07 × 106 U/mL. The 2−7 dilution of the rPoIFN-γH in culture supernatant protected the MARC-145 cells from the cytopathic effect caused by 100TCID50 of porcine reproductive and respiratory syndrome virus.