Reprogramming the Immunosuppressive Microenvironment in Glioblastoma Through Oncolytic Herpes Simplex Virus Therapy:...

Glioblastoma (GBM) is characterized by a profoundly immunosuppressive tumor microenvironment that limits the efficacy of conventional and immune-based therapies. Oncolytic herpes simplex virus (oHSV) therapy has emerged as a strategy capable of both tumor-selective infection and immune microenvironment modulation. This systematic review aimed to synthesize current evidence on how oHSV therapy reshapes the immunosuppressive microenvironment of GBM. A systematic search of PubMed (MEDLINE) and Embase identified original studies published between 2016 and 2025 investigating immunological or microenvironmental effects of oHSV-based therapies in GBM (final search: 28 January 2026). Preclinical and clinical studies were included, whereas reviews, editorials, conference abstracts, and studies of non-herpes oncolytic viruses were excluded. Study selection and data extraction were performed independently by two reviewers. Due to heterogeneity in models, viral constructs, and outcome measures, a qualitative narrative synthesis was conducted. Of 214 records, 22 studies met the inclusion criteria. Most were preclinical studies using orthotopic immunocompetent murine models, with limited clinical evidence including an early-phase trial in recurrent high-grade glioma. Therapeutic efficacy frequently correlated with tumor microenvironment remodeling rather than viral replication alone. oHSV infection promoted inflammatory signaling, antigen presentation, macrophage polarization, and effector T-cell recruitment but also induced counter-regulatory mechanisms such as myeloid-mediated immunosuppression and vascular or stromal barriers. The clinical significance and durability of these effects remain to be established in larger prospective studies. Despite heterogeneous designs and limited clinical data, current evidence suggests that oHSV may function as a platform for immune microenvironment reprogramming in glioblastoma.