Oncolytic virus therapy using genetically engineered herpes simplex viruses

An increasing number of oncolytic virus vectors has been developed lately for cancer therapy. Herpes simplex virus type 1 (HSV-1) vectors are particularly useful, because they can be genetically engineered to replicate and spread highly selectively in tumor cells and can also express multiple foreign transgenes. These vectors can manifest cytopathic effect in a wide variety of tumor types without damaging normal tissues, provide amplified gene delivery within the tumor, and induce specific antitumor immunity. Multiple recombinant HSV-1 vectors have been tested in patients with brain tumors and other cancers, which showed the feasibility of administering replication-competent HSV-1 vectors safely in human organs including the brain. Different approaches are currently undertaken to improve the efficacy of oncolytic HSV-1 therapy which include development of new generation vectors via further genetic engineering of existing safe vectors, combination with immune gene therapy, and combination with conventional therapies. Oncolytic virus therapy is a promising therapeutic modality that awaits establishing as an important treatment option for cancer patients in the near future.