Oncolytic HSV-IL27 expression improves CD8 T cell function and therapeutic activity in syngeneic glioma models

Background

Malignant gliomas (MG) are the most common primary brain malignancies and are considered universally fatal. Oncolytic HSVs (oHSV) are promising immunotherapeutics capable of selectively lysing cancer cells, eliciting anti-tumor immunity, and providing local delivery of immune-activating transgenes. IL-27 is a pleiotropic cytokine capable of enhancing tumor-reactive cytotoxic T cell (CTL) function while also possessing neuroprotective properties. We hypothesized that IL-27 expression by oHSV would enhance CTL function and improve anti-glioma therapeutic activity.

Methods

We developed an oncolytic herpes simplex virus (oHSV) that expresses IL-27 (C027). The anti-glioma efficacy of C027 was tested in three syngeneic orthotopic glioma models derived from both chemical (CT-2A) and genetic (SB28, KR158) glioma lines. Spectral flow cytometry was used to assess immunophenotypic and functional changes in the tumor infiltrates and systemically. To further investigate the C027-related CTL activity, we employed in vivo cell specific depletion and IL-27 blockade alongside in vitro T cell stimulation assays. Local and systemic antitumor memory was evaluated by both orthotopic and flank tumor rechallenge of C027-treated long-term survivors.

Results

C027 significantly prolonged survival in syngeneic orthotopic glioma models derived from both chemical (CT-2A) and genetic (KR158, SB28) glioma lines. In the CT-2A model, IL-27-expressing oHSV treatment was associated with increased intratumoral multifunctional effector cytotoxic T lymphocytes (CTL) and functional T cell populations systemically. Mechanistically, both CD8 T cells and IL-27 were required for the C027 survival benefit in vivo and IL-27 enhanced CTL function in vitro . C027-treated mice that survived their initial tumors had local and systemic anti-glioma memory rejecting tumors on rechallenge.

Conclusions

Our findings demonstrate that IL-27 expression by oHSV significantly improves anti-glioma therapeutic efficacy, enhances CTL effector function, and induces durable immune memory. Thus, IL-27-oHSV may provide a promising therapeutic approach for malignant gliomas.

• What is already known on this topic – Malignant gliomas are highly aggressive tumors largely resistant to current immunotherapies. Oncolytic herpes simplex viruses (oHSV) are promising immunotherapy agents for malignant gliomas and provide a platform for immunomodulatory gene expression.

• What this study adds – In this study, we present a novel IL-27 expressing oHSV (C027) that improves survival in syngeneic glioma-bearing mice through a CD8 T cell and IL-27 dependent mechanism and induces durable immune memory.

• How this study might affect research, practice or policy – Our study demonstrates that IL-27-expression by oHSV enhances anti-tumor immunity and glioma efficacy suggesting its potential as a novel therapeutic.