The present invention concerns methods and compositions for the treatment ofcancer and cancer cells using altered poxviruses, including a vaccinia virusthat has been altered to generate a more effective therapeutic agent. Suchpoxviruses are engineered to be attenuated or weakened in their ability toaffect normal cells. In some embodiments, methods and compositions involvepoxviruses that possess mutations that result in poxviruses with diminished oreliminated capability to implement an antiviral response in a host. Poxviruseswith these mutations in combination with other mutations can be employed formore effective treatment of cancer.
