Engineering oncolytic vaccinia virus with functional peptides through mild and universal strategy

Anti-cancer Virotherapy in Russia: Lessons from the Past, Current Challenges and Prospects for the Future

The idea of using the lytic power of viruses against malignant cells has been entertained for many decades. However, oncolytic viruses gained broad attention as an emerging anti-cancer therapy only recently with the successful implementation of several oncolytic viruses to treat advanced melanoma. Here we review the history of oncolytic viruses in the Russian Federation and recent biotechnological advances in connection with the perspectives of their practical use against aggressive tumors such as glioblastoma or pancreatic cancer. A particular emphasis is made on novel applications of safe non-lytic virus-derived vectors armed with prodrug-converting enzyme transgenes. Rational improvement of oncotropism by conjugation with biopolymers and nanoformulations is also discussed.

An oncolytic vaccinia virus armed with anti-human-PD-1 antibody and anti-human-4-1BB antibody double genes for cancer-targeted therapy

Oncolytic virus can selectively recognize cancer cells, target tumors, and stimulate an oncolytic and immune response. Recombinant armed oncolytic vaccinia virus has emerged as an attractive tool in oncolytic virotherapy because it has tumor-specific cytotoxicity and serves as a vector to express immune genes. A novel thymidine kinase (TK) gene-deleted oncolytic vaccinia virus (named ΔTK-Armed-VACV) armed with anti-human-programed cell death-1 protein (PD-1) antibody and anti-human-tumor necrosis factor receptor superfamily, member 9 (4-1BB) antibody genes was constructed based on Western Reserve in our previous study. The present study evaluated the ability of this virus for cancer-targeted therapy both in vitro and in vivo. A complete morphological structure of ΔTK-Armed-VACV was verified using transmission electron microscopy. The antibody was co-expressed with the replication of ΔTK-Armed-VACV in vitro assessed by Western blot analysis, enzyme-linked immunosorbent assay, and quantitative real-time polymerase chain reaction. The 3-(4,5-dimethylthiazol-2-yl)-5-(3-rboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt assay showed that the ΔTK-Armed-VACV exhibited significant tumor-specific cytotoxicity in vitro. The ΔTK-Armed-VACV inhibited the tumor growth in a 4T1 or A549 tumor-bearing mouse model. ELISpot assay showed that ΔTK-Armed-VACV-treated mice induced the expression of interferon-gamma, and lactate dehydrogenase-dependent cytotoxicity assay revealed that the ΔTK-Armed-VACV treatment activated tumor-specific cytotoxic T lymphocytes. The results indicated that oncolytic VACV with Western Reserve-mediated anti-human-PD-1 and anti-human-4-1BB antibody co-expression exerted a significant antitumor effect, indicating that the combination of oncolytic virotherapy and immunotherapy by the oncolytic VACV expressing one or more immune checkpoint genes might have satisfactory clinical expectations.

Delivery and Biosafety of Oncolytic Virotherapy

In recent years, oncolytic virotherapy has emerged as a promising anticancer therapy. Oncolytic viruses destroy cancer cells, without damaging normal tissues, through virus self-replication and antitumor immunity responses, showing great potential for cancer treatment. However, the clinical guidelines for administering oncolytic virotherapy remain unclear. Delivery routes for oncolytic virotherapy to patients vary in existing studies, depending on the tumor sites and the objective of studies. Moreover, the biosafety of oncolytic virotherapy, including mainly uncontrolled adverse events and long-term complications, remains a serious concern that needs to be accurately measured. This review provides a comprehensive and detailed overview of the delivery and biosafety of oncolytic virotherapy.

Recent advances in oncolytic virus-based cancer therapy

Administration of oncolytic viruses (OVs) is an emerging anticancer strategy that exploits the lytic nature of viral replication to enhance the killing of malignant cells. OVs can be used as tools to directly induce cancer cell death and to trigger local and/or systemic immune responses to metastatic cancer in vivo. The effectiveness of OV therapy was initially highlighted by the clinical use of the genetically modified herpes virus, talimogene laherparepvec, for melanoma therapy. A number of OVs are now being evaluated as potential treatments for cancer in clinical trials. In spite of being engineered to specifically target tumor cells, the safety and off-target effects of OV therapy are a concern. The potential safety concerns of OVs are highlighted by current clinical trial criteria, which exclude individuals harbouring other viral infections and people who are immunocompromised. Despite the potential for adverse effects, clinical trials to date revealed relatively minimal adverse immune-related effects, such as fever. With advances in our understanding of virus replication cycles, several novel OVs have emerged. Reverse genetic systems have facilitated the insertion of anticancer genes into a range of OVs to further enhance their tumor-killing capacity. In this review, we highlight the recent advances in OV therapy for a range of human cancers in in vitro and in in vivo animal studies. We further discuss the future of OVs as a therapeutic strategy for a range of life-threatening cancers.