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Evaluation of genetically engineered herpes simplex viruses as oncolytic agents for human malignant brain tumors
S Andreansky1, L Soroceanu, E R Flotte
1Department of Surgery, University of Alabama at Birmingham School of Medicine, 35294-0006, USA.
Abstract:
Earlier studies have shown that genetically engineered herpes simplex viruses (e.g., HSV-1) are effective in killing malignant tumor cells both in vitro and in various murine tumor models. This report focuses on a panel of five genetically engineered viral mutants of the gamma(1)34.5 gene, which was shown previously to cause reduction in viral replication and associated neurovirulence of HSV. These include R3616, which has both copies of gamma(1)34.5 deleted, R4009, which has a stop codon inserted after codon 28 in both copies of the gamma(1)34.5 gene, R849, which contains a lacZ gene inserted in place of the gamma(1)34.5, R908, which lacks 41 codons in frame after codon 72 of the gamma(1)34.5, and R939, which carries a stop codon precluding the translation of the COOH-terminal domain of the gamma(1)34.5 gene. We report the following: (a) all five mutant HSVs were avirulent in experimental animals but were cytotoxic for human tumor cells in vitro and in vivo; (b) the gamma(1)34.5- HSV replicated in human glioma cells almost as efficiently as wild-type HSV-1(F) based on replication assays, in situ hybridization for viral DNA, and expression of infected cell protein 27; (c) capacity of mutant HSVs to kill human cells derived from glioblastoma multiforme (CH-235MG, D-37MG, D-54MG, D-65MG, U-251MG, U-373MG, and SK-MG-1), anaplastic astrocytoma (Hs-683), anaplastic glioma (U-87MG and U-138MG), gliosarcoma (D-32GS), or normal human astrocytes demonstrated that glioma cells varied in their susceptibility to HSV-mediated cytotoxicity and that cultured astrocytes were two to three orders of magnitude less susceptible to killing than were malignant glia; and (d) scid mice, which received 0.5 or 5 x 10(6) plaque-forming units of R4009, either were coinoculated at the time of intracranial transplantation with 106 U251MG or D-54MG human glioma cells or received the cells intratumorally 5 days after tumor induction and experienced significant increases in median survivals, with no histopathological indication of an infectious encephalitic process. Genetically engineered gamma(1)34.5- HSV mutants appear to be a potentially safe biotherapeutic agent for experimental treatment of uniformly fatal malignant brain tumors.
Insights
Genetically engineered herpes simplex virus (HSV) mutants targeting the gamma(1)34.5 gene show promise for treating brain tumors. These modified viruses are effective against glioma cells while remaining safe for experimental animals.
Area of Science:
- Virology
- Oncology
- Gene Therapy
Background:
- Genetically engineered herpes simplex virus type 1 (HSV-1) demonstrates efficacy in targeting and destroying malignant tumor cells.
- The gamma(1)34.5 gene in HSV is crucial for viral replication and neurovirulence, making its modification a target for oncolytic virus development.
Purpose of the Study:
- To evaluate the safety and efficacy of five distinct gamma(1)34.5-deleted HSV-1 mutants as potential oncolytic agents.
- To assess the replication, cytotoxicity, and in vivo therapeutic potential of these engineered HSV mutants against human glioma cells.
Main Methods:
- Generation and characterization of five HSV-1 mutants with modifications in the gamma(1)34.5 gene (R3616, R4009, R849, R908, R939).
- In vitro cytotoxicity assays on various human glioma cell lines and normal astrocytes.
- In vivo efficacy studies in severe combined immunodeficient (scid) mice bearing human glioma xenografts, assessing survival rates and neurovirulence.
Main Results:
- All five gamma(1)34.5-mutant HSVs were avirulent in animals but exhibited potent cytotoxicity against human glioma cells in vitro and in vivo.
- Mutant HSVs replicated efficiently in human glioma cells, comparable to wild-type HSV-1(F), with glioma cells showing higher susceptibility than normal astrocytes.
- Treatment with R4009 mutant HSV in scid mice significantly increased median survival rates in glioma models without inducing infectious encephalitic processes.
Conclusions:
- Engineered gamma(1)34.5- HSV mutants are safe and effective oncolytic agents against malignant brain tumors.
- These modified viruses represent a promising biotherapeutic strategy for the experimental treatment of glioblastoma and other malignant gliomas.