Evaluation of immunologic parameters in canine glioma patients treated with an oncolytic herpes virus

AIM

To molecularly characterize the tumor microenvironment and evaluate immunologic parameters in canine glioma patients before and after treatment with oncolytic human IL-12-expressing herpes simplex virus (M032) and in treatment naïve canine gliomas.

METHODS

We assessed pet dogs with sporadically occurring gliomas enrolled in Stage 1 of a veterinary clinical trial that was designed to establish the safety of intratumoral oncoviral therapy with M032, a genetically modified oncolytic herpes simplex virus. Specimens from dogs in the trial and dogs not enrolled in the trial were evaluated with immunohistochemistry, NanoString, Luminex cytokine profiling, and multi-parameter flow cytometry.

RESULTS

Treatment-naive canine glioma microenvironment had enrichment of Iba1 positive macrophages and minimal numbers of T and B cells, consistent with previous studies identifying these tumors as immunologically "cold". NanoString mRNA profiling revealed enrichment for tumor intrinsic pathways consistent with suppression of tumor-specific immunity and support of tumor progression. Oncolytic viral treatment induced an intratumoral mRNA transcription signature of tumor-specific immune responses in 83% (5/6) of canine glioma patients. Changes included mRNA signatures corresponding with interferon signaling, lymphoid and myeloid cell activation, recruitment, and T and B cell immunity. Multiplexed protein analysis identified a subset of oligodendroglioma subjects with increased concentrations of IL-2, IL-7, IL-6, IL-10, IL-15, TNFα, GM-CSF between 14 and 28 days after treatment, with evidence of CD4⁺ T cell activation and modulation of IL-4 and IFNγ production in CD4⁺ and CD8⁺ T cells isolated from peripheral blood.

CONCLUSION

These findings indicate that M032 modulates the tumor-immune microenvironment in the canine glioma model.

Herpesvirus vectors for therapy of brain tumors

Genetically modified, conditionally-replicating Herpes Simplex Virus Type 1 (HSV-1) vectors for the treatment of malignant glioma have provided encouraging results in the handful of Phase I and Phase II clinical trials conducted to date. In recent years, a number of new strategies have been developed to improve anti-tumor activity of these attenuated vectors, through either introduction of foreign gene inserts to enhance tumor killing through a variety of mechanisms, or through combination with existing treatment regimens, including radiation and/or chemotherapeutics. Another promising new approach has been the engineering of novel oncolytic HSV vectors that retain wildtype replication, but are targeted to tumor cells through a variety of mechanisms. This review summarizes the latest advances in herpesvirus-mediated oncolytic therapies from both preclinical results and clinical trials with oncolytic HSV vectors in patients, and their implication for design of future trials.