Citations

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 Introduction We have shown that combining CAR T cells with oncolytic viruses (OVs) generates a subpopulation of highly cytotoxic CAR T cells that can mediate long-term solid tumor therapy. Methods To profile these CAR T cells, we used C57BL/6 mice bearing B16F10 tumors expressing EGFRviii, treated with anti-EGFRviii CAR T cells and the OV vesicular stomatitis virus (VSV). TCR signaling in CAR T cells was investigated using the novel Tocky transgenic mouse model, which reports T cell activation over time using an unstable fluorescent protein reporter of Nr4a3. We further investigated CAR T phenotypes using CyTOF and scRNA-Seq. Results Using an MHC I tetramer for the dominant VSV epitope VSV N52-59, we found that 20-50% of transfused CAR T adopted TCR specificity against VSV N (referred to as TCR-primed), indicating significant in vivo expansion. Ex vivo, these TCR-primed CAR T produced increased levels of granzyme B and IFNγ over tetramer-negative CAR T against either TCR or CAR targets. However, TCR-primed CAR T cells were notably less activated via Nr4a3 as compared to non-TCR-primed CAR T. CyTOF and scRNA-Seq analyses demonstrated a hypereffector phenotype among TCR-primed CAR, with increased expression of T-bet, CD44, granzyme B, IFNγ, and perforin. TCR sequencing revealed hyperexpansion of VSV N-specific CAR T cells and little overlap in clonotypes between CAR T co-treated with PBS versus VSV. These TCR-primed CAR T cells exhibited a CD4-helped phenotype with increased expression of chemotactic and migratory transcripts. When CAR T and OV were administered with antibody-mediated CD4 depletion, the TCR-primed CAR population was significantly diminished, emphasizing the importance of the immune triad for CAR T expansion. Conclusion Overall, CAR T cells that undergo endogenous anti-viral TCR priming and signaling adopt a unique phenotype that promotes their expansion and cytotoxic function. Interactions with CD4 T cells appear to be integral for the generation of this subpopulation of CD8 CAR T cells. Funding Source NIH Topic Categories Tumor Immunology: Checkpoints, Prevention, and Treatment (TIPT)

Chimeric antigen receptor (CAR) T cell therapy faces many challenges against solid tumors including T cell exhaustion and poor CAR durability. Here, we show that engaging the CAR T cell endogenous T cell receptor (TCR) using an oncolytic virus enhances CAR T cell functionality, durability, and therapy. Upon combination therapy of solid tumors with CAR T cells and vesicular stomatitis virus (VSV), a subpopulation of antiviral, TCR-primed CAR T cells was generated with enhanced effector functions, altered activation states, and differential gene and protein expression when compared to non–TCR-primed CAR T cells. Single-cell RNA sequencing showed clonal expansion of anti-VSV CAR T cells and enhancement of effector-associated genes with VSV-mediated CAR T cell expansion. CD4 T cells played a pivotal role in the development of these TCR-primed CAR T cells. These results provide a strong rationale both for a novel use of systemic oncolytic virotherapy and for directly exploiting the CAR T cell TCR to fine tune the CAR T cell phenotype and function.

Abstract Description We used C57BL/6 mice bearing B16-F10 tumors expressing EGFRviii, treated with anti-EGFRviii CAR T cells and the oncolytic virus vesicular stomatitis virus (VSV). TCR signaling in CAR T cells was investigated using the novel Tocky transgenic mouse model, which reports T cell activation over time using an unstable fluorescent protein reporter of Nr4a3. We further investigated CAR T phenotypes using CyTOF and scRNA-Seq. Using an MHC I tetramer for the dominant VSV epitope VSV-N52-59, we found that 20-50% of transfused CAR T adopted TCR specificity against VSV-N (TCR-primed), far above the predicted frequency in a naïve T cell repertoire. Ex vivo, these TCR-primed CAR T produced increased levels of Granzyme B and IFNγ over tetramer negative CAR T against either TCR or CAR targets. TCR-primed CAR had decreased levels of T cell activation as compared to non-TCR-primed CAR. CyTOF and scRNA-Seq analyses demonstrated a hyper-effector phenotype among TCR-primed CAR, with increased expression of T-bet, CD44, Granzyme B, IFNγ, and perforin. TCR sequencing revealed hyper-expansion of VSV N-specific CAR T cells and little overlap in clonotypes between CAR T co-treated with PBS versus VSV. Overall, CAR T cells that undergo endogenous anti-viral TCR priming and signaling appear to adopt a unique phenotype that promotes their cytotoxic function. These data suggest that engineering anti-viral TCRs into CAR T could be used to improve efficacy with OV boosting. Funding Sources Supported by NIH T32GM145408 and NIH R01CA269384. Topic Categories Vaccines and Immunotherapy (VAC)

Abstract Chimeric antigen receptor (CAR) T cell therapy has revolutionized the treatment of liquid tumors but faces many challenges against solid tumors including T cell exhaustion and poor CAR durability. Here, we show that engaging the CAR T cell endogenous TCR using an oncolytic virus (OV) enhances CAR T cell functionality, durability, and therapy. Upon combination therapy of solid tumors with CAR T cells and vesicular stomatitis virus (VSV), a subpopulation of antiviral, TCR-primed CAR T cells was generated with enhanced effector functions, altered activation states, and differential gene and protein expression when compared to CAR T cells that do not undergo TCR priming. Single cell RNA-sequencing showed clonal expansion of anti-VSV CAR T cells, selective avoidance of exhaustion, and enhancement of effector-associated genes with VSV-mediated CAR T cell expansion. CD4 T cells played a pivotal role in both the generation and polarization of these TCR-primed CAR T cells. These results provide a strong rationale both for a novel use of intravenous administration of oncolytic viruses with separate applications from their direct oncolytic activity and for directly exploiting the TCR and its endogenous interactions as tools for fine tuning the phenotype and function of CAR T cells, with particular efficacy against solid tumors.

Metabolic dysfunction–associated steatohepatitis (MASH) is a progressive liver disease characterized by complex interactions between lipotoxicity, ER stress responses, and immune-mediated inflammation. We identified enrichment of the proinflammatory alarmin S100 calcium-binding protein A11 (S100A11) on extracellular vesicles stimulated by palmitate-induced lipotoxic ER stress with concomitant upregulation of hepatocellular S100A11 abundance in an IRE1A-XBP1s–dependent manner. We next investigated the epigenetic mechanisms that regulate this stress response. Publicly available human liver ChIP-Seq GEO datasets demonstrated a region of histone H3 lysine 27 (H3K27) acetylation upstream of the S100A11 promoter. H3K27 acetylation ChIP-qPCR demonstrated a positive correlation between lipotoxic ER stress and H3K27 acetylation of the region, which we termed the lipotoxicity-influenced enhancer (LIE) domain. CRISPR-mediated repression of the LIE domain reduced palmitate-induced H3K27 acetylation and corresponding S100A11 upregulation in Huh7 cells and immortalized mouse hepatocytes. Silencing of the murine LIE in 2 independent steatohepatitis models demonstrated reduced S100a11 upregulation and attenuated liver injury. We confirmed H3K27 acetylation and XBP1s occupancy at the LIE domain in human MASH liver samples and an increase in hepatocyte-derived S100A11-enriched extracellular vesicles in MASH patient plasma. Our studies demonstrate a LIE domain that mediates hepatic S100A11 upregulation. This pathway may be a potential therapeutic target in MASH.

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 antitumor response which has been weakened by mechanisms of central tolerance. Here, we show that inflammatory Vesicular Stomatitis Virus (VSV) failed to prime an adoptively transferred, or pre-existing, population of tumor-reactive T cells.Combination with αPD1 immune checkpoint blockade therapy improved survival only when VSV expressed tumor associated antigens (TAA). These data show that, in this model, the highly inflammatory OV VSV alone actively outcompetes antitumor immunity. However, we also show that viral expression of a mutant near-self TAA can break central tolerance expanding heteroclitic self-reactive and near-self-reactive T cells, thus overcoming viral immunodominance by promoting tumor-specific T cell proliferation in parallel with expanding antiviral T cells.

Abstract T cell immune tolerance is established in part through the activity of the Auto-immune Regulator (AIRE) transcription factor in the medullary Thymic Epithelial Cells (mTEC) of the thymus. AIRE induces expression of SELF peripheral tissue-specific antigens for presentation to naïve T cells to promote activation/deletion of potentially autoreactive T cells. We show, for the first time to our knowledge, that tumors mimic the role of AIRE in mTEC to evade immune rejection. Thus, by expressing a broad range of SELF epitopes against which minimal functional T cell reactivities exist because of thymic deletion, AIRE acts as a master controller of SELFNESS, effectively cloaking the tumor from T cell attack. Moreover, we describe a completely novel immunotherapy in which engineered changes in AIRE expression in tumor cells alters their profile of SELFNESS, exposing both AIRE-modified, and parental unmodified, tumor cells to T cell attack. Consistent with our studies, patient RNAseq shows expression of AIRE predicts response to immune therapies with a strong correlation between AIRE expression and markers of TCR signaling. Therefore, by re-setting the immunological SELFNESS of cancer cells, this novel AIRE-mediated immunotherapy 1). converts a highly tolerized T cell compartment into a heteroclitic tumor-reactive T cell population; 2) confers de novo sensitivity to immune checkpoint blockade upon non-immunogenic tumors; 3). completely removes the need to identify potentially immunogenic tumor-associated antigens as targets for generation of de novo CD8+ and helper CD4+ T cell responses; and 4) leads to potent T cell-mediated rejection of aggressive, immunologically cold, non-immunogenic tumors.