Apoptin enhances the oncolytic activity of vaccinia virus in vitro

The chicken anemia virus gene that encodes apoptin, a selective killer of cancer cells, was synthe-sized and inserted into the vaccinia virus (strain L-IVP) genome. The insertion replaces a major part of the viral C11R gene that encodes viral growth factor, which is important for virulence. The recombinant virus VVdGF-ApoS24/2 was obtained by transient dominant selection using the gene of puromycin resistance as a selective marker. The expression of the apoptin gene from a synthetic early-late promoter of vaccinia virus ensured the efficient accumulation of the target protein in VVdGF-ApoS24/2-infected cells. Although recombinant apoptin carried the signal peptide of the virus growth factor at the N-end, the protein was not secreted into the culture medium. The recombinant virus VVdGF-ApoS24/2 exhibited significantly higher selective lytic activity in human cancer cell lines (A549, A431, U87MG, RD, and MCF7) than the parent strain L-IVP and its VVdGF2/6 variant with C11R deletion. These results suggest that the use of apoptin can be an efficient means of enhancing the natural anticancer activity of vaccinia virus.