The Impact of Macrophage- and Microglia-Secreted TNFα on Oncolytic HSV-1 Therapy in the Glioblastoma Tumor Microenvironment

Abstract

Purpose Oncolytic herpes simplex viruses [oHSV] represent a promising therapy for glioblastoma [GB], but their clinical success has been limited. Early innate immune responses to viral infection reduce oHSV replication, tumor destruction, and efficacy. Here, we characterized the antiviral effects of macrophages and microglia on viral therapy for GB. Experimental Design Quantitative flow cytometry of mice with intracranial gliomas [± oHSV] was utilized to examine macrophage/microglia infiltration and activation. In vitro co-culture assays of infected glioma cells with microglia/macrophages were utilized to test their impact on oHSV replication. Macrophages from TNFα knockout mice and blocking antibodies were used to evaluate the biological effects of TNFα on virus replication. TNFα blocking antibodies were utilized to evaluate the impact of TNFα on oHSV therapy in vivo. Results Flow cytometry analysis revealed a 7.9 fold increase in macrophage infiltration after virus treatment. Tumor infiltrating macrophages/microglia were polarized towards a M1, pro-inflammatory phenotype and they expressed high levels of CD86, MHCII, and Ly6C. Macrophages/microglia produced significant amounts of TNFα in response to infected glioma cells in vitro and in vivo. Utilizing TNFα blocking antibodies and macrophages derived from TNFα knockout mice we discovered TNFα induced apoptosis in infected tumor cells and inhibited virus replication. Finally, we demonstrated the transient blockade of TNFα from the tumor microenvironment with TNFα blocking antibodies significantly enhanced virus replication and survival in GB intracranial tumors. Conclusions The results of these studies suggest FDA approved TNFα inhibitors may significantly improve the efficacy of oncolytic virus therapy.

Bortezomib Treatment Sensitizes Oncolytic HSV-1–Treated Tumors to NK Cell Immunotherapy

“…We and others have previously shown that modulation of host immune responses can limit intra-tumoral infiltration of innate immune response mediators, such macrophages and NK cells, and thereby result in increased viral propagation and enhanced anti-tumor efficacy (10, 38, 39). We have also recently shown that elevated TNFα production in the tumor microenvironment leads to oHSV infected cell apoptosis and can limit viral replication and efficacy (40). We hypothesize that a major limitation to exploiting endogenous NK cells to augment immunotherapy of infected tumors is likely due to low effector to target cell ratios.…”

Dual inhibition of Ang-2 and VEGF receptors normalizes tumor vasculature and prolongs survival in glioblastoma by altering macrophages

“…However, additional interventions may be necessary to decrease the MDSCs and further activate cytotoxic T lymphocytes-for example by immune checkpoint inhibition-to enhance antitumor adaptive immunity further (30,62,63). Taken together, our data warrant further studies to assess the therapeutic potential of the anti-VEGF/Ang-2 combination with novel immunotherapeutics in GBM (51,64).…”

Ang-2/VEGF bispecific antibody reprograms macrophages and resident microglia to anti-tumor phenotype and prolongs glioblastoma survival

“…Our finding that A2V treatment reprograms TAMs along the M1-M2 continuum toward the M1 phenotype in both Gl261 and MGG8 tumors may explain the survival benefit observed in these preclinical models, including the benefits seen with anti-Ang-2 monotherapy. This finding could have implications for the sequencing of potential combinatorial regimens of antiangiogenic agents with immunotherapy, because M1-polarized macrophages and microglia may hamper the efficacy of oncolytic herpes simplex virus-1 GBM therapy (55). The role of TAMs in GBM progression is highlighted further by the data presented in our companion paper (43), in which we demonstrate that TAM depletion with anti-CSF-1 antibody compromises the survival benefit of dual antiangiogenic therapy (Table S2).…”