Oncolytic herpes simplex viruses for the treatment of glioma and targeting glioblastoma stem-like cells

Safety of non-replicative and oncolytic replication-selective HSV vectors

Herpes simplex virus type 1 (HSV-1) is a DNA virus and human pathogen used to construct promising therapeutic vectors. HSV-1 vectors fall into two classes: replication-selective oncolytic vectors for cancer therapy and defective non-replicative vectors for gene therapy. Vectors from each class can accommodate ≥30 kb of inserts, have been approved clinically, and demonstrate a relatively benign safety profile. Despite oncolytic HSV (oHSV) replication in tumors and elicited immune responses, the virus is well tolerated in cancer patients. Current non-replicative vectors elicit only limited immune responses. Seropositivity and immune responses against HSV-1 do not eliminate either the vector or infected cells, and the vectors can therefore be re-administered. In this review we highlight vectors that have been translated to the clinic and host-virus immune interactions that impact on the safety and efficacy of HSVs.

Nanoparticles for efficient drug delivery and drug resistance in glioma: New perspectives

Gliomas are the most common primary tumors of the central nervous system, with glioblastoma multiforme (GBM) having the highest incidence, and their therapeutic efficacy depends primarily on the extent of surgical resection and the efficacy of postoperative chemotherapy. The role of the intracranial blood-brain barrier and the occurrence of the drug-resistant gene O6-methylguanine-DNA methyltransferase have greatly limited the efficacy of chemotherapeutic agents in patients with GBM and made it difficult to achieve the expected clinical response. In recent years, the rapid development of nanotechnology has brought new hope for the treatment of tumors. Nanoparticles (NPs) have shown great potential in tumor therapy due to their unique properties such as light, heat, electromagnetic effects, and passive targeting. Furthermore, NPs can effectively load chemotherapeutic drugs, significantly reduce the side effects of chemotherapeutic drugs, and improve chemotherapeutic efficacy, showing great potential in the chemotherapy of glioma. In this article, we reviewed the mechanisms of glioma drug resistance, the physicochemical properties of NPs, and recent advances in NPs in glioma chemotherapy resistance. We aimed to provide new perspectives on the clinical treatment of glioma.

Oncolytic herpes simplex virus expressing IL-2 controls glioblastoma growth and improves survival

BACKGROUND

Glioblastoma (GBM), a highly immunosuppressive and often fatal primary brain tumor, lacks effective treatment options. GBMs contain a subpopulation of GBM stem-like cells (GSCs) that play a central role in tumor initiation, progression, and treatment resistance. Oncolytic viruses, especially oncolytic herpes simplex virus (oHSV), replicate selectively in cancer cells and trigger antitumor immunity-a phenomenon termed the "in situ vaccine" effect. Although talimogene laherparepvec (T-VEC), an oHSV armed with granulocyte macrophage-colony stimulating factor (GM-CSF), is Food and Drug Administration (FDA)-approved for melanoma, its use in patients with GBM has not been reported. Interleukin 2 (IL-2) is another established immunotherapy that stimulates T cell growth and orchestrates antitumor responses. IL-2 is FDA-approved for melanoma and renal cell carcinoma but has not been widely evaluated in GBM, and IL-2 treatment is limited by its short half-life, minimal tumor accumulation, and significant systemic toxicity. We hypothesize that local intratumoral expression of IL-2 by an oHSV would avoid the systemic IL-2-related therapeutic drawbacks while simultaneously producing beneficial antitumor immunity.

METHODS

We developed G47Δ-mIL2 (an oHSV expressing IL-2) using the flip-flop HSV BAC system to deliver IL-2 locally within the tumor microenvironment (TME). We then tested its efficacy in orthotopic mouse GBM models (005 GSC, CT-2A, and GL261) and evaluated immune profiles in the treated tumors and spleens by flow cytometry and immunohistochemistry.

RESULTS

G47Δ-mIL2 significantly prolonged median survival without any observable systemic IL-2-related toxicity in the 005 and CT-2A models but not in the GL261 model due to the non-permissive nature of GL261 cells to HSV infection. The therapeutic activity of G47Δ-mIL2 in the 005 GBM model was associated with increased intratumoral infiltration of CD8+ T cells, critically dependent on the release of IL-2 within the TME, and CD4+ T cells as their depletion completely abrogated therapeutic efficacy. The use of anti-PD-1 immune checkpoint blockade did not improve the therapeutic outcome of G47Δ-mIL2.

CONCLUSIONS

Our findings illustrate that G47Δ-mIL2 is efficacious, stimulates antitumor immunity against orthotopic GBM, and may also target GSC. OHSV expressing IL-2 may represent an agent that merits further exploration in patients with GBM.

Combination of Oncolytic Virotherapy with Different Antitumor Approaches against Glioblastoma

Glioblastoma is one of the most malignant and aggressive tumors of the central nervous system. Despite the standard therapy consisting of maximal surgical resection and chemo- and radiotherapy, the median survival of patients with this diagnosis is about 15 months. Oncolytic virus therapy is one of the promising areas for the treatment of malignant neoplasms. In this review, we have focused on emphasizing recent achievements in virotherapy, both as a monotherapy and in combination with other therapeutic schemes to improve survival rate and quality of life among patients with glioblastoma.

Repurposing of Zika virus live-attenuated vaccine (ZIKV-LAV) strains as oncolytic viruses targeting human glioblastoma multiforme cells

Glioblastoma multiforme (GBM) is the most common malignant primary brain cancer affecting the adult population. Median overall survival for GBM patients is poor (15 months), primarily due to high rates of tumour recurrence and the paucity of treatment options. Oncolytic virotherapy is a promising treatment alternative for GBM patients, where engineered viruses selectively infect and eradicate cancer cells by inducing cell lysis and eliciting robust anti-tumour immune response. In this study, we evaluated the oncolytic potency of live-attenuated vaccine strains of Zika virus (ZIKV-LAV) against human GBM cells in vitro. Our findings revealed that Axl and integrin αvβ5 function as cellular receptors mediating ZIKV-LAV infection in GBM cells. ZIKV-LAV strains productively infected and lysed human GBM cells but not primary endothelia and terminally differentiated neurons. Upon infection, ZIKV-LAV mediated GBM cell death via apoptosis and pyroptosis. This is the first in-depth molecular dissection of how oncolytic ZIKV infects and induces death in tumour cells.

Advances in oncolytic herpes simplex virus and adenovirus therapy for recurrent glioma

Recurrent glioma treatment is challenging due to molecular heterogeneity and treatment resistance commonly observed in these tumors. Researchers are actively pursuing new therapeutic strategies. Oncolytic viruses have emerged as a promising option. Oncolytic viruses selectively replicate within tumor cells, destroying them and stimulating the immune system for an enhanced anticancer response. Among Oncolytic viruses investigated for recurrent gliomas, oncolytic herpes simplex virus and oncolytic adenovirus show notable potential. Genetic modifications play a crucial role in optimizing their therapeutic efficacy. Different generations of replicative conditioned oncolytic human adenovirus and oncolytic HSV have been developed, incorporating specific modifications to enhance tumor selectivity, replication efficiency, and immune activation. This review article summarizes these genetic modifications, offering insights into the underlying mechanisms of Oncolytic viruses' therapy. It also aims to identify strategies for further enhancing the therapeutic benefits of Oncolytic viruses. However, it is important to acknowledge that additional research and clinical trials are necessary to establish the safety, efficacy, and optimal utilization of Oncolytic viruses in treating recurrent glioblastoma.