A recent study presents gene therapy with semliki forest viral vector expressing high levels of murine IL-12 (SFV-enhIL-12) on remission of HCC in chronically WHV-infected woodchucks. In the research, the vector was delivered by surgery into multiple sites of HCC tumors in the liver [75] . A total of nine woodchucks were enrolled in the experiment. Six of the woodchucks, two animals each, received different doses of SFV-enhIL-12: 3 × 10 9 vp, 6 × 10 9 vp, and 1, 2 × 10 10 vp, and three animals served as a control and received saline injections. The tumor size was monitored by ultrasound examination for 23 to 24 weeks. In all woodchucks, reduction in tumor volume was observed, however, this effect was transient and dose dependent. Animals treated with the highest dose of SFV-enhIL-12 showed the most spectacular reduction of the tumor size 71% and 80%. Nevertheless, the tumors started to grow between 6 and 14 weeks after the treatment. The antitumoral effect was associated with the induction of the immune response towards the tumor antigens, demonstrated by T cell proliferation assay, upregulation of leukocyte markers expression, and cytokine production, such as IFNγ, TNFα, IL-6, and IL-12. In addition, the therapy resulted in transient induction of lymphoproliferative responses against WHcAg and WHsAg and led to short-term reduction in WHV viral load [75] .