Oncolytic Cytomegaloviruses Expressing EGFR-Retargeted Fusogenic Glycoprotein Complex and Drug-Controllable Interleukin-12
The Potential of Oncolytic Cytomegaloviruses Expressing EGFR-Retargeted Fusogenic Glycoprotein Complex and Drug-Controlled IL-12 in Cancer Immunotherapy
Background and Objectives
In recent years, cancer viroimmunotherapy has emerged as a promising research focus in the field of cancer treatment. This therapy leverages viruses to infect tumor cells, reshape the immunosuppressive tumor environment, and activate systemic antitumor immune responses. In this domain, HSV (herpes simplex virus)-based oncolytic viral therapies, such as Talimogene laherparepvec (T-VEC), have shown success in treating advanced or metastatic melanoma. However, extending these approaches to other cancer types remains a significant challenge. In contrast, cytomegalovirus (CMV) has attracted researchers’ attention for its broad cellular tropism, including the ability to infect tumor-associated myeloid cells and glioblastoma cells, suggesting its potential utility in cancer immunotherapy.
Previous clinical observations have indicated a possible association between CMV reactivation and prolonged survival in certain cancer patients, linked to specific immune responses. However, no systematic oncolytic platform for CMV has been developed to date. Therefore, this study aims to reconstruct the CMV genome into a platform with attenuated virulence, enhanced tumor-specific targeting, and potent immune activation for the treatment of glioblastoma multiforme (GBM).
Research Source and Authors
This study was conducted by a research team comprising Haifei Jiang, Rebecca Nace, Coryn Ferguson, Lianwen Zhang, Kah Whye Peng, and Stephen J. Russell, affiliated with the Mayo Clinic and Vyriad Inc., USA. The findings were published in Cell Reports Medicine, Volume 6, on January 21, 2025.
Research Workflow and Methods
This original research can be summarized into the following steps:
1. Genome Engineering and Construction of Recombinant Oncolytic CMV:
The research team synthesized oncolytic CMV based on the AD169R strain, repairing the functionality of the pentamer glycoprotein complex (PC) and simultaneously deleting the UL1-UL20 and UL/b’ regions to reduce viral virulence. To enhance CMV tumor-targeting capabilities, the EGFR (epidermal growth factor receptor)-retargeted fusogenic glycoprotein complex was embedded in the viral genome along with a Tet-Off controlled single-chain IL-12 gene module.
2. In Vitro Experiments:
Using U87 and U251 glioma cell lines, the team validated viral infectivity, oncolytic effects, and replication efficiency. They employed western blotting and flow cytometry to detect the expression of novel fusion proteins (e.g., MeV H/F complex) and their related biological effects.
3. Mouse Xenograft GBM Models:
Nude mice were used to establish U87 and U251 xenografts, and intratumoral injections were performed to evaluate the impact of oncolytic viruses on tumor growth and intratumoral virus spread. The efficacy of Tet-Off IL-12 regulation was further confirmed.
4. Immunological Studies in Syngeneic Mouse GBM Models:
In immunocompetent mouse models, the systemic immune responses induced by oncolytic CMV were studied, focusing on the virus’s effects on CD4+ T cells, CD8+ T cells, and unclassified T cells (CD4-/CD8- T cells).
Research Results and Key Findings
1. CMV Genome Modification and Fusogenic Protein Effects:
After restoring PC function, the infectivity spectrum of the oncolytic CMV was significantly expanded, especially for U251 cells. The EGFR-retargeted fusogenic glycoprotein H/F substantially enhanced the oncolytic effect against glioma cells while reducing persistent viral replication, thereby improving safety.
2. Controlled IL-12 Expression and Immune Activation:
The Tet-Off system successfully regulated IL-12 in a dose-dependent manner. Although IL-12 displayed no significant effect in immunocompromised mouse models, it exhibited robust antitumor activity in immunocompetent models by enhancing T cell activity.
3. Antitumor Efficacy in Animal Models:
In U87 and U251 xenograft models, CMV viruses carrying H/F fusion proteins significantly improved intratumoral viral spread in the earlier stages (12 days post-treatment), suppressed tumor growth, and significantly prolonged mouse survival. Moreover, in syngeneic mouse models, IL-12-expressing oncolytic viruses demonstrated potent systemic immune responses, particularly strong inhibition of untreated contralateral tumors.
Research Conclusions and Implications
This study successfully developed a novel oncolytic CMV platform with the following features: attenuation of viral virulence through deletion of key genomic segments; enhanced tumor-specific oncolytic effects leveraging EGFR-targeted fusogenic glycoproteins; and precise control of IL-12 expression via the Tet-Off system, boosting virus-induced systemic immune responses.
The findings offer critical genetic engineering strategies for oncolytic viral development, highlighting CMV’s tremendous potential in cancer immunotherapy. In particular, CMV’s ability to activate T cell responses and improve the tumor microenvironment shows promise for treating human GBM.
Research Highlights and Value
- Innovative Genomic Engineering: Significant safety and infectivity improvements through deletion of UL1-UL20 and UL/b’ regions and restoring PC functionality.
- Fusion Protein Technology: First introduction of EGFR-retargeted MeV or CDV H/F proteins into CMV to enhance tumor-specific cytotoxicity.
- Immune Activation Effects: Controlled IL-12 expression amplified systemic antitumor T cell responses, enabling effective suppression of distant untreated tumors.
Future studies should explore CMV’s immune effects in MHC-matched tumor models and accelerate clinical trials to validate this platform’s translational potential in human GBM therapy.