Prolonged Circulation Half-life of Interferon γ Activity by Gene Delivery of Interferon γ-Serum Albumin Fusion Protein in Mice

Gene delivery of mouse interferon (IFN) γ has been shown to inhibit metastatic tumor growth and onset of atopic dermatitis in mouse models. In this study, we tried to increase the circulation half-life of IFNγ after its gene delivery by designing a novel fusion protein of IFNγ with mouse serum albumin (MSA). Western blot analysis confirmed that IFNγ-MSA was expressed as a fusion protein, but hardly formed dimer as IFNγ did. The biological activity of IFNγ-MSA, which was examined using a plasmid expressing luciferase under the control of gamma-activated sequence elements, was about 200-fold lower than the activity of IFNγ. Intravenous injection of the proteins into mice confirmed that the circulation half-life of IFNγ was significantly prolonged by the modification. A hydrodynamic injection of a plasmid expressing IFNγ-MSA resulted in a sustained concentration in mouse serum; it resulted in about sixfold greater area under the concentration-time curve and about threefold longer mean residence time of IFNγ activity than those of IFNγ. Gene delivery of IFNγ-MSA inhibited tumor metastasis to a similar level to that of IFNγ despite the reduced activity of IFNγ-MSA. These results indicate that gene delivery of IFNγ-MSA is a promising approach to prolong the circulation half-life of IFNγ activity.