IL-21 arming potentiates the anti-tumor activity of an oncolytic vaccinia virus in monotherapy and combination therapy

Abstract

BackgroundOncolytic viruses (OVs) have shown promise in containing cancer progression in both animal models and clinical trials. How to further improve the efficacy of OVs are intensively explored. Arming OVs with immunoregulatory molecules has emerged as an important means to enhance their oncolytic activities majorly based on the mechanism of reverting the immunosuppressive nature of tumor environment. In this study, we aimed to identify the optimal combination of different OVs and immunomodulatory molecules for solid tumor treatment as well as the underlying mechanism, and subsequently evaluated its potential synergy with other immunotherapies.MethodsPanels of oncolytic viruses and cells stably expressing immunoregulatory molecules were separately evaluated for treating solid tumors in mouse model. A tumor-targeted replicating vaccinia virus Tian Tan strain with deletion of TK gene (TTVΔTK) was armed rationally with IL-21 to create rTTVΔTK-IL21 through recombination. CAR-T cells and iNKT cells were generated from human peripheral blood mononuclear cells. The impact of rTTVΔTK-IL21 on tumor-infiltrating lymphocytes was assessed by flow cytometry, and its therapeutic efficacy as monotherapy or in combination with CAR-T and iNKT therapy was assessed in mouse tumor models.ResultsIL-21 and TTV was respectively identified as most potent immunomodulatory molecule and oncolytic virus for solid tumor suppression in mouse models. A novel recombinant oncolytic virus that resulted from their combination, namely rTTVΔTK-mIL21, led to significant tumor regression in mice, even for noninjected distant tumor. Mechanistically, rTTV∆TK-mIL21 induced a selective enrichment of immune effector cells over Treg cells and engage a systemic response of therapeutic effect. Moreover, its human form showed a notable synergy with CAR-T or iNKT therapy for tumor treatment when coupled in humanized mice.ConclusionWith a strong potency of shaping tumor microenvironment toward favoring TIL activities, rTTVΔTK-IL21 represents a new opportunity worthy of further exploration in clinical settings for solid tumor control, particularly in combinatorial strategies with other immunotherapies.One sentence summaryIL21-armed recombinant oncolytic vaccinia virus has potent anti-tumor activities as monotherapy and in combination with other immunotherapies.

Humanized Mice as a Valuable Pre-Clinical Model for Cancer Immunotherapy Research

“…A recent study identified IL-21 to be a good candidate to improve Torque Teno oncolytic virus (TTV) efficacy in lung carcinoma tumors alone or in combination with chimeric antigen receptor T (CAR-T) or invariant natural killer T (iNKT) cell therapy in a humanized mouse model. The study showed a synergistic effect of both combination therapies, suggesting that other immunotherapies may also work synergistically with IL-21-armed TTV ( 90 ) ( Figures 2B, E ).…”

The role of NK cells in oncolytic viral therapy: a focus on hepatocellular carcinoma

“…IL-21 is related to IL-2 and IL-15 as part of the common gamma-chain family of cytokines and has a key role in modulating NK cell activation, maturation and proliferation [108] . Insertion of the IL-21 gene into a modified vaccinia virus Tian Tan strain promoted the recruitment of immune effector cells to the tumour bed, reduced regulatory T cell numbers and synergised with CAR-T and invariant natural killer cell following intratumoural injection of the OV [109] .…”

“…IL-21 is related to IL-2 and IL-15 as part of the common gamma-chain family of cytokines and has a key role in modulating NK cell activation, maturation and proliferation [ 108 ] . Insertion of the IL-21 gene into a modified vaccinia virus Tian Tan strain promoted the recruitment of immune effector cells to the tumour bed, reduced regulatory T cell numbers and synergised with CAR-T and invariant natural killer cell following intratumoural injection of the OV [ 109 ] . Notably, an abscopal effect was also evident, whereby distant non-injected tumour growth was inhibited, and this was also associated with increased numbers of immune effectors, including NK cells within the distant tumours [ 109 ] .…”

“…Insertion of the IL-21 gene into a modified vaccinia virus Tian Tan strain promoted the recruitment of immune effector cells to the tumour bed, reduced regulatory T cell numbers and synergised with CAR-T and invariant natural killer cell following intratumoural injection of the OV [ 109 ] . Notably, an abscopal effect was also evident, whereby distant non-injected tumour growth was inhibited, and this was also associated with increased numbers of immune effectors, including NK cells within the distant tumours [ 109 ] . Interestingly oncolytic adenovirus armed with CCL5 and IL-15 enhanced CAR-T recruitment to tumour sites and cytotoxicity in an in vivo model of neuroblastoma [ 110 ] .…”

Enhancing co-stimulation of CAR T cells to improve treatment outcomes in solid cancers

“…OV-mediated expression of a bispecific engager worked synergistically with CAR T cell activity in two tumour models [ 71 ]. In a tumour model of B16 melanoma, modified OV expressing IL-21 enhanced the survival of mice compared to a panel of co-stimulatory molecules including CD86 and 4-1BB [ 72 ]. Other therapies utilising OVs to express molecules such as OX40, IL-2, and CD40 have also been studied [ 73 , 74 ].…”