Diaz Marcano, Rosa M

Abstract The paradigm in the field of oncolytic virotherapy proposes that tumor cell killing by an oncolytic virus (OV) culminates in the priming of antitumor CD8+ T cells. However, this ignores the impact a highly immunodominant antiviral response against the OV has on the subdominant antitumor response, particularly with regard to the naturally low affinity of tumor antigens to their cognate T-cell receptors. To investigate this experimentally, we first studied the interaction between the two responses in B16 and MC38 tumor models, both expressing ovalbumin (OVA). Contrary to the accepted paradigm, the inflammatory vesicular stomatitis virus (VSV) failed to expand OVA-specific T cells in vivo unless armed with tumor-associated antigen (TAA). In fact, treatment with the control VSV led to the ablation of antitumor T cells and a shift toward dysfunction as determined by the upregulation of markers, including LAG3 and CD39, correlating with lower rates of survival. Combination with anti–PD-1 immune checkpoint blockade therapy significantly improved survival only when VSV expressed TAA. VSV-expressing altered peptide ligand variants of tumor antigens, which evade mechanisms of central tolerance, expanded near self-antigen–specific T cells with the ability to cross-react with tolerized tumor antigens, thus providing an antitumor effector population capable of proliferating in the presence of a potent antiviral response. Taken together, these findings offer a rational approach to OV design which preserves acute antitumor therapy provided by antiviral innate and T-cell responses while promoting the induction of tumor-specific T cells. Significance: Oncolytic viruses can induce an antiviral T-cell response that occludes an antitumor response, challenging the paradigm in the field and elucidating strategies to optimize the efficacy of oncolytic viroimmunotherapy.

Abstract T-cell immune tolerance is established in part through the activity of the autoimmune regulator (AIRE) transcription factor in medullary thymic epithelial cells (mTEC) of the thymus. AIRE induces expression of peripheral tissue–specific self-antigens for presentation to naïve T cells to promote activation/deletion of autoreactive T cells. This traditional role of AIRE in mTECs is to prevent autoimmunity. Herein, we demonstrate that tumors mimic the role of AIRE in mTECs to evade immune rejection. We found that AIRE induced a profile of “selfness” at the RNA and protein levels which, when presented on major histocompatibility complexes (MHC), shielded the tumor from inherently self-tolerized T cells. Moreover, we describe an in vivo immunotherapy in which engineered changes in AIRE expression in tumor cells altered their profile of selfness, exposing both AIRE-modified and parental unmodified tumor cells to T-cell attack. Therefore, by resetting the immunologic selfness of cancer cells, this AIRE-mediated immunotherapy (i) converted a highly tolerized T-cell compartment into a tumor-reactive T-cell population; (ii) conferred upon nonimmunogenic tumors de novo sensitivity to immune checkpoint blockade; (iii) removed the need to identify potentially immunogenic tumor-associated antigens as targets for generation of T-cell responses; and (iv) lead to potent T cell–mediated rejection of aggressive, immunologically cold, nonimmunogenic tumors. Patient RNA sequencing data showed that the expression of AIRE predicted response to immune therapies with a strong correlation between AIRE expression and markers of T-cell receptor signaling, suggesting that our studies have therapeutic translational value.

Abstract Purpose: VV1 is designed to induce selective oncolysis of tumor cells and amplify cellular antitumor immune responses. This open-label, phase I, multicenter clinical trial assessed the safety and tolerability of VV1 monotherapy administered intratumorally or intravenously or administered intravenously in combination with avelumab. Patients and Methods: Patients with advanced solid tumors received intratumoral (n = 27) or intravenous VV1 monotherapy (n = 33) or intravenous VV1 plus avelumab (n = 16). Infusion durations (15–180 minutes) and viral dose (1.7 × 1010 or 1 × 1011 TCID50) were also evaluated. Study objectives included VV1 safety and tolerability, pharmacokinetics, pharmacodynamics, preliminary efficacy, and immune responses. Results: Intratumoral and intravenous VV1 were well tolerated, and injection reactions were infrequent. The most common adverse events of any grade related to VV1 were cytokine release syndrome (58%), fatigue (33%), and decreased lymphocyte count (32%). Virus infection of tumors was confirmed by NIS imaging and increases in serum levels of virally encoded interferon-β (IFNβ). Histologic tumor analysis at 28 days after intratumoral VV1 administration indicated increases in tumor-infiltrating immune cells. Two durable partial responses were recorded: a patient with pheochromocytoma after one intravenous dose of VV1 and a patient with thymic cancer in the combination arm. Stable disease was observed in 17 of 49 patients (34.7%) who received intravenous VV1. Conclusions: This first-in-human study demonstrates that intratumoral or intravenous VV1 administration had an acceptable safety profile as monotherapy and intravenously in combination with avelumab. There is preliminary antitumor activity. Intratumoral VV1 plus cemiplimab is now showing promise in the neoadjuvant setting. Significance: VV1 is a tumor-selective oncolytic vesicular stomatitis virus engineered to express IFNβ and the thyroidal NIS reporter gene. In this phase I study, we have demonstrated that a single administration of VV1, as a monotherapy or with an immune checkpoint inhibitor is safe, infects tumor lesions resulting in intratumoral infiltration of immune cells, and exhibits early signs of antitumor activity in patients with advanced unresectable and metastatic solid tumors.

Abstract Glioblastoma (GBM) is the most common malignant brain tumor in adults, responsible for approximately 225,000 deaths per year. Despite preclinical successes, most interventions have failed to extend patient survival by more than a few months. Treatment with anti—programmed cell death protein 1 (anti–PD-1) immune checkpoint blockade (ICB) monotherapy has been beneficial for malignant tumors such as melanoma and lung cancers but has yet to be effectively employed in GBM. This study aimed to determine whether supplementing anti–PD-1 ICB with engineered extended half-life IL2, a potent lymphoproliferative cytokine, could improve outcomes. This combination therapy, subsequently referred to as enhanced checkpoint blockade (ECB), delivered intraperitoneally, reliably cures approximately 50% of C57BL/6 mice bearing orthotopic GL261 gliomas and extends median survival of the treated cohort. In the CT2A model, characterized as being resistant to CBI, ECB caused a decrease in CT2A tumor volume in half of measured animals similar to what was observed in GL261-bearing mice, promoting a trending survival increase. ECB generates robust immunologic responses, features of which include secondary lymphoid organ enlargement and increased activation status of both CD4 and CD8 T cells. This immunity is durable, with long-term ECB survivors able to resist GL261 rechallenge. Through employment of depletion strategies, ECB's efficacy was shown to be independent of host MHC class I–restricted antigen presentation but reliant on CD4 T cells. These results demonstrate ECB is efficacious against the GL261 glioma model through an MHC class I–independent mechanism and supporting further investigation into IL2-supplemented ICB therapies for tumors of the central nervous system.