Recent cancer immunotherapy breakthroughs have fundamentally changed oncology and revived the fading hope for a cancer cure. The immune checkpoint inhibitors (ICI) became an indispensable tool for the treatment of many malignant tumors. Alongside ICI, the application of oncolytic viruses in clinical trials is demonstrating encouraging outcomes. Dozens of combinations of oncolytic viruses with conventional radiotherapy and chemotherapy are widely used or studied, but it seems quite complicated to highlight the most effective combinations. Our review summarizes the results of clinical trials evaluating oncolytic viruses with or without genetic alterations in combination with immune checkpoint blockade, cytokines, antigens and other oncolytic viruses as well. This review is focused on the efficacy and safety of virotherapy and the most promising combinations based on the published clinical data, rather than presenting all oncolytic virus variations, which are discussed in comprehensive literature reviews. We briefly revise the research landscape of oncolytic viruses and discuss future perspectives in virus immunotherapy, in order to provide an insight for novel strategies of cancer treatment.

Anti-cancer therapy based on oncolytic viruses (OVs) is a targeted approach that takes advantage of OVs’ ability to selectively infect and replicate in tumor cells, activate the host immune response, and destroy malignant cells over healthy ones. Vesicular stomatitis virus (VSV) is known for its wide range of advantages: a lack of pre-existing immunity, a genome that is easily amenable to manipulation, and rapid growth to high titers in a broad range of cell lines, to name a few. VSV-induced tumor immunity can be enhanced by the delivery of immunostimulatory cytokines. The targeted cytokine delivery to tumors avoids the significant toxicity associated with systemic delivery while also boosting the immune response. To demonstrate this enhanced effect on both tumor growth and survival, a novel recombinant VSV (rVSV)-mIL12-mGMCSF, co-expressing mouse IL-12 (interleukin-12) and GM-CSF (granulocyte-macrophage colony-stimulating factor), was tested alongside rVSV-dM51-GFP (rVSV-GFP) that was injected intratumorally in a syngeneic in vivo C57BL/6 mouse model infused subcutaneously with B16-F10 melanoma cells. The pilot study tested the effect of two viral injections 4 days apart and demonstrated that treatment with the two rVSVs resulted in partial inhibition of tumor growth (TGII of around 40%) and an increased survival rate in animals from the treatment groups. The effect of the two VSVs on immune cell populations will be investigated in future in vivo studies with an optimized experimental design with multiple higher viral doses, as a lack of this information presents a limitation of this study.

The design of new effective cancer treatment methods is a promising and important research field in translational medicine. Oncolytic viruses can induce immunogenic cell death by activating the body’s immune system to recognize tumor cells. This work presents the results for optimizing the production of recombinant vesicular stomatitis viruses (rVSVs). To ensure the assembly of viral particles, we developed the HEK293TN-T7 cell line, which stably expresses DNA-dependent RNA polymerase 7 for viral genome transcription, and obtained helper plasmids encoding viral genes under the control of the CAG promoter. The oncolytic activity of the purified virus preparation was assessed in a murine model of B16F10Red melanoma cells expressing a red fluorescent protein. The presented method makes it possible to obtain purified viral preparations with a high titer and oncolytic activity. The amplification of viral particles in a HEK293 suspension culture allows for rapid scalability. Therefore, the developed approach can be used to obtain other recombinant VSV-based oncolytic viruses for tumor immunotherapy.

The unique ability of oncolytic viruses (OVs) to replicate in and destroy malignant cells while leaving healthy cells intact and activating the host immune response makes them powerful targeted anti-cancer therapeutic agents. Vesicular stomatitis virus (VSV) only causes mild and asymptomatic infection, lacks pre-existing immunity, can be genetically engineered for enhanced efficiency and improved safety, and has a broad cell tropism. VSV can facilitate targeted delivery of immunostimulatory cytokines for an enhanced immune response against cancer cells, thus decreasing the possible toxicity frequently observed as a result of systemic delivery. In this study, the oncolytic potency of the two rVSV versions, rVSV-dM51-GFP, delivering green fluorescent protein (GFP), and rVSV-dM51-mIL12-mGMCSF, delivering mouse interleukin-12 (mIL-12) and granulocyte-macrophage colony-stimulating factor (mGMCSF), was compared on the four murine cancer cell lines of different origin and healthy mesenchymal stem cells (MSCs) at 24 h post-infection by flow cytometry. Lewis lung carcinoma (LL/2) cells were demonstrated to be more susceptible to the lytic effects of both rVSV versions compared to melanoma (B16-F10) cells. Detection of expression levels of antiviral and pro-apoptotic genes in response to the rVSV-dM51-GFP infection by quantitative PCR (qPCR) showed lower levels of IFIT, RIG-I, and N-cadherin and higher levels of IFNβ and p53 in LL/2 cells. Subsequently, C57BL/6 mice, infused subcutaneously with the LL/2 cells, were injected intratumorally with the rVSV-dM51-mIL12-mGMCSF 7 days later to assess the synergistic effect of rVSV and immunostimulatory factors. The in vivo study demonstrated that treatment with two rVSV-dM51-mIL12-mGMCSF doses 3 days apart resulted in a tumor growth inhibition index (TGII) of over 50%.

Cancer is one of the leading causes of death worldwide. Traditional cancer treatments include surgery, radiotherapy, and chemotherapy, as well as combinations of these treatments. Despite significant advances in these fields, the search for innovative ways to treat malignant tumors, including the application of oncolytic viruses, remains relevant. One such virus is the vesicular stomatitis virus (VSV), which possess a number of useful oncolytic properties. However, VSV-based drugs are still in their infancy and are yet to be approved for clinical use. This review discusses the mechanisms of oncogenesis, the antiviral response of tumor and normal cells, and markers of tumor cell resistance to VSV virotherapy. In addition, it examines methods for producing and arming recombinant VSV and provides examples of clinical trials. The data presented will allow better assessment of the prospects of using VSV as an oncolytic.

Background: Glioblastoma (GBM) is characterised by therapeutic resistance and high invasiveness, so the development of new treatments is essential. Oncolytic virotherapy using the vesicular stomatitis virus (VSV) is a promising approach as it is inherently tumour-selective and immunostimulatory. This study evaluated the antitumour efficacy of a recombinant VSV engineered to co-express mouse interleukin-12 and granulocyte-macrophage colony-stimulating factor (rVSV-dM51-mIL12-mGMCSF) using in vitro and in vivo U-87 MG models. Methods: The oncolytic activity of rVSV-dM51-mIL12-mGMCSF was evaluated in vitro against human U-87 MG and mouse GL-261 glioblastoma cells using flow cytometry (MOI 0.1) and MTT assays (MOIs 0.1 and 0.001). In vivo, tumour progression was monitored in U-87 MG xenograft mice for 30 days after inoculation. At the study endpoint, tumour tissues from treated and control animals were subjected to immunohistochemical (IHC) analysis; the H-score method was used to quantify expression of the Ki-67 proliferation marker, VSV glycoprotein (VSV-G), and mIL-12. Results: rVSV-dM51-mIL12-mGMCSF demonstrated oncolytic activity against both cell lines in vitro; however, its cytotoxicity was lower compared to the parental control virus (rVSV-dM51-GFP). In contrast, treatment in vivo resulted in greater tumour growth inhibition. IHC analysis revealed a significant reduction in the Ki-67 H-score alongside high levels of VSV glycoprotein and mIL-12 expression. These results confirm that, although the payloads do not enhance direct viral oncolysis in vitro, they significantly improve antitumour efficacy in vivo. Conclusions: rVSV-dM51-mIL12-mGMCSF effectively inhibited tumour growth in the U-87 MG xenograft model, supporting further evaluation of glioblastoma-directed oncolytic virotherapy.