Expression of canine interferon-γ by a recombinant vaccinia virus and its antiviral effect

A recombinant vaccinia virus-expressing canine interferon (IFN)-γ (vv/cIFN-γ) was constructed. In rabbit kidney (RK13) and canine A72 cells infected with vv/cIFN-γ, IFN activity was detected in the culture supernatants of both cell types. Canine IFN-γ was also detected in both cell extracts by Western blot. The activity of the recombinant canine IFN-γ in RK13 cells was higher than that in A72 cells. The vv/cIFN-γ could not grow in A72 cells at a low multiplicity of infection, probably due to the antiviral activity of the canine IFN-γ produced. Although exogenous IFN-γ did not inhibit the growth of vaccinia virus, addition of anti-canine IFN-γ serum recovered the growth of the vv/cIFN-γ on A72 cells in a dose-dependent manner. These results suggest that the growth of vv/cIFN-γ was inhibited by IFN-γ produced in a paracrine and autocrine manner. In addition, the recombinant canine IFN-γ inhibited the multiplication of canine herpesvirus, pseudorabies virus and canine adenovirus type 1 in Madin–Darby canine kidney cells. The antiviral effect of canine IFN-γ was more effective than that of canine IFN-β. From the present studies, we concluded the recombinant virus may be a useful suicide viral vector.