Effector CD8 Research Articles

Abstract C015: IL-27R signaling modulates protective versus pathogenic T cell responses in hepatocellular carcinoma

Abstract Liver cancer is the 3rd leading cause of cancer death. Hepatocellular carcinoma (HCC) is the major form of primary liver cancer, with a growing incidence rate estimated to surge by 50% in the coming twenty years. Although some success has been achieved with immune checkpoint blockade inhibitors, many HCC patients do not respond well to the treatments. Therefore, it is critical to better understand immune mechanisms regulating HCC to identify new biomarkers and develop novel immunotherapies for HCC patients. HCC is driven by chronic liver diseases and is frequently associated with chronic inflammation in the liver. Cytokines are small mediators of inflammation that play an essential role in inflammatory diseases and tumorigenesis. IL27 is a member of the IL6/IL12 superfamily with context-dependent roles in various inflammatory disorders and cancer. IL27 receptor (R) is expressed by most immune cells and several non-immune cells and plays pivotal roles in the regulation of immune responses. Recent work from our lab shows that IL27R signaling suppresses anti-cancer immune response in HCC, acting via the control of innate cytotoxic cells, and Il27ra -/- mice develop significantly less HCC. However, how IL27R signaling regulates T cell subsets in HCC in vivo remains elusive. Here, using diethylnitrosamine (DEN)-induced mouse model of HCC we found a reduction of regulatory T cells (Tregs) in tumor-bearing Il27ra-/-mice along with lowered HCC burden. ScRNA sequencing of CD45+ cells isolated from HCC tumors indicated a less proliferative phenotype of Tregs and more cytotoxic and less exhausted CD8 T cells in mice with Il27ra deficiency. Pathway analysis suggested that IL27R-deficient Tregs were more quiescent, as characterized by the downregulation of various metabolic pathways. Our newly generated Foxp3 cre Il27ra flox mice show a significant reduction of DEN-driven HCC accompanied by an increase of tumor-infiltrating activated CD8 T cells compared to IL27R sufficient controls. Treg-specific deletion of IL27R caused the upregulation of TCF1 in Tregs which has been recently demonstrated to control Treg immune-suppressive functions in colorectal cancer. Meanwhile, tumor-infiltrating effector CD8 T cells were increased in Foxp3 cre+ Il27ra flox mice relative to their Foxp3 cre- Il27ra flox littermate controls. Interestingly, CD8 T cell specific deletion of IL27R did not impact HCC growth in CD8 cre Il27ra flox mice. Overall, our data suggest that IL27R signaling suppresses anti-HCC immunity by enhancing the pro-tumorigenic Tregs and suppressing anti-tumor effector CD8 T cell functions. Citation Format: Zhengzheng Shi, Jiani Zhu, Aleksandra Mazitova, Anastasiia Marchenko, Sergei Grivennikov, Ekaterina Koltsova. IL-27R signaling modulates protective versus pathogenic T cell responses in hepatocellular carcinoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr C015.

Abstract B015: Targeting CX3CL1 transforms a cold tumor microenvironment into a hot one by enhancing T cells and DCs locally and systemically

Abstract Intratumoral heterogeneity (ITH) is associated with immunotherapy failure and a weaker anti- tumor immune response. Using a series of carcinogen-induced tumor (CIT) squamous cell skin carcinoma cell lines, our lab has sought to identify tumor-intrinsic factors—particularly chemokines and cytokines—which can have a “dominant negative” effect on the immune microenvironment when present within a heterogeneous tumor. We identified CX3CL1 as a one such critical mediator of a cold (T cell low) immune microenvironment and found that tumors containing as few as 10% CX3CL1high tumor cells exhibit a diminished T cell response compared to tumors which lack CX3CL1high tumor cells. We predicted that targeting CX3CL1 could therefore transform a cold tumor microenvironment (TME) into an inflammatory hot (T cell high) TME. Supporting this, we found that CRISPR-Cas9-mediated deletion of CX3CL1 in a tumor cell line that typically gives rise to cold tumors led to higher T cell infiltration and fewer immunosuppressive macrophages in the TME of CX3CL1-/- tumors. Building on this, we further explored T cell populations in the TME and found that CX3CL1-/- tumors had significantly increased activation and decreased exhaustion markers on T cells. Flow cytometry analysis showed higher expression of CD44 on effector CD4 T cells and an increase in the number of activated CD44+ PD1low CD4 T cells. By contrast, the frequency of CD4 T cells which were PD1High TIM3+ and PD1High TIM3+ TIGIT+ which represent a likely exhausted effector CD4 population was lower in CX3CL1-/- tumors than in counterpart control tumors. An interrogation of DC subsets in the TME further revealed a higher number of cDC1 and cDC2 populations in CX3CL1−/− tumors. To determine the effect of tumor-produced CX3CL1 on immune activity in lymphoid organs, we investigated T cell and DC markers in the spleen and tumor-draining lymph nodes during early tumor development. Spleens harvested 10 days after tumor injection showed higher infiltration of cDC1 CCR7+ and cDC2 CCR7+ mature DCs in CX3CL1-/- tumor-bearing mice. Thus, in the absence of tumor-produced CX3CL1, both cDC1 and cDC2 dendritic cell subsets attain more mature phenotypes in both the TME and the spleen. At the same time point, tumor-draining lymph nodes also exhibited a shift in immune cell composition characterized by an increased frequency of T cells, particularly CD4+ T cells, and a decreased frequency of B cells. Moreover, the percentage of PD1+ CD8 cells was also higher, indicating better priming and activation of CD8 T cells via DCs in tumor-draining lymph nodes. These findings indicate that tumor-produced CX3CL1 drives a cold immune microenvironment through both tumor-localized and systemic effects. These studies suggest therapeutically targeting CX3CL1 particularly in tumors where tumor cells produce high levels of CX3CL1 holds promise to transform a cold TME into a hot immune inflammatory TME and potentiate better anti-tumor immunity. Citation Format: Piyush Chaudhary, Savannah Hughes, Joshua Tay, Robert Letchworth, Miho Tanaka, Melissa Reeves. Targeting CX3CL1 transforms a cold tumor microenvironment into a hot one by enhancing T cells and DCs locally and systemically [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr B015.

Abstract C021: Tumor-associated microbiota suppresses anti-tumor immunity by driving cDC1 dysfunction in lung cancer

Abstract Type 1 conventional dendritic cells (cDC1s) are critical for initiating and sustaining tumor-reactive CD8 T cells; lack of functional cDC1s is a key driver for failed tumor immunosurveillance and immunotherapy. However, what factors cause the cDC1 insufficiency in the tumor microenvironment (TME) remain poorly understood. Commensal microbiota has emerged as a key regulator of TME and the efficacy of cancer immunotherapies. Nonetheless, most studies have focused on the intestinal microbiome; it remains underexplored whether and how the local microbiota within tumors influences the anti-cancer immunity. Using the autochthonous Kras LSL-G12D/+ ; p53 flox/flox (KP) mouse model of lung cancer, we found an increased local bacterial burden and altered bacterial composition associated with lung tumors. Importantly, this local microbiota suppresses the anti-tumor CD8 T cell response both at baseline and in response to ICB therapies. Specifically, single-cell RNA-seq analysis revealed that the microbiota shapes the functional subsets of tumor-reactive CD8 T cells. Bacterial depletion promotes the accumulation of stem-like Tpex cells (precursor of exhausted T cells) in the TME, which serve as a reservoir of effector CD8 T cells and mediate an effective response upon ICB treatment. To distinguish the function of the local microbiota within TME from the distal gut microbiota, we developed a new method of aerosolized antibiotic treatment, which selectively ablates the intra-tumoral lung microbiota while preserving the intact gut microbiota. Using this approach, we demonstrated that removal of the intra-tumoral lung microbiota markedly improves the tumor-reactive T cell response and sensitizing “cold” lung tumors to ICB therapies. Mechanistically, we identified cDC1s as a central player in microbiota-mediated suppression of anti-tumor immunity. Local microbiota diminishes cDC1 quality and quantity in the lung TME, resulting in impaired T cell priming and Tpex maintenance. At the molecular level, our data revealed that bacterial products derived from the local microbiota induce type I interferon expression in tumor-associated myeloid cells and enhance GM-CSF production from cancer cells: chronic type I interferon and GM-CSF signaling acts cooperatively to reduce the functional cDC1 population. Combining in vitro cDC1 assays, competitive bone marrow chimera experiments and cDC1-specific knockout models, we establish the causal relationships between the local microbiota, IFN-I and GM-CSF signaling in cDC1s, and the tumor response to ICB. Altogether, our study uncovered a dominant role of tumor-associated microbiota in inhibiting cDC1s and suppressing anti-tumor immunity through type I IFN and GM-CSF dependent pathways in lung cancer. Our findings not only identify the intra-tumoral microbiota as a critical therapeutic target for lung cancer treatment, but also provide new insights into the tissue-specific, context-dependent regulatory mechanisms of cDC1s in the TME. Citation Format: Qiang Dong, Chengcheng Jin. Tumor-associated microbiota suppresses anti-tumor immunity by driving cDC1 dysfunction in lung cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr C021.

Abstract C039: The impact of antiangiogenic therapy on blood vessels and CD8 infiltration in renal cancer metastases is space, time, site, dose, and drug dependent

Abstract Clear cell renal cell carcinoma (ccRCC) is the most prevalent renal neoplasm, with bone as a major site for distant spread in 35% to 40% of the patients. These metastases are typically osteolytic, resistant to treatments, hence result in a variety of skeletal-related complications strongly contributing to mortality. A key feature of ccRCC is the loss of function of the von Hippel–Lindau (VHL) protein leading to extensive angiogenesis. Consequently, different anti-angiogenic tyrosine kinase inhibitors (TKIs) are used as the first or subsequent line of treatment for these patients as single agents or in combination with immune checkpoint inhibitors. However, limited data about their efficacy in bone metastasis is available, and their impact on the immune infiltrate, including effector CD8 cells, is unclear. We hypothesized that TKIs, by inhibiting angiogenesis, significantly reprogram the microenvironment and limit immune infiltration in space, time, dose, and drug dependent fashion. To test these hypotheses, we developed an immunocompetent mouse model of bone metastasis by orthotopical intratibial implantation of luciferase-GFP-positive mouse RENCA-VHL- cell line. Interestingly, intratibial injections gave rise to metastases in lungs, creating a unique opportunity to study two metastatic sites. Three different TKIs currently used in patients were tested and compared to control: axitinib (A), cabozantinib (C), and lenvantinib (L). Outcomes were monitored by macroscopic bioluminescence detection in vivo, 3D multiparametric spatial analysis of bones and lungs, in vivo, and ex vivo. Compared to control-treated mice, high doses of A, C, and L significantly reduced tumor progression in both tumor sites. Even though these TKIs are clinically considered equal, significant differences in their efficacy were noted. Spatial analysis of tumor cells and blood vessels showed a significant decrease in blood vessels formation in both an organ- and TKI-specific pattern over time. Additionally, the reduction of neo angiogenesis in treated tumors directly limited the infiltration of CD8 cells, which localized at the interface with tumor free bone/lung tissue. Interestingly, TKI dose reduction significantly improved CD8 infiltration, while controlling tumor size. TKI withdrawal, instead, led to rapid progression of tumor in both sites and significantly shortened mice survival. In conclusion, we established bone and lung metastatic models of ccRCC and characterized and compared the effects of three antiangiogenic TKIs on angiogenesis and CD8 infiltration. TKIs reduced tumor growth and progression, because of blood vessel formation inhibition. Furthermore, TKI treatment reduced the infiltration of effector T cells in tumors in a dose-dependent manner, an outcome that can have a major impact when TKIs are combined with immunotherapy, a preferential therapeutic regimen for ccRCC patients. Overall, we believe our studies provide important insights and efficacy predictions for innovative therapeutic applications in ccRCC bone metastatic patients. Citation Format: Stefan Maksimovic, Nina Costanza Boscolo, Ludovica La Posta, Matthew T. Campbell, Eleonora Dondossola. The impact of antiangiogenic therapy on blood vessels and CD8 infiltration in renal cancer metastases is space, time, site, dose, and drug dependent [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr C039.

The HDAC6 inhibitor AVS100 (SS208) induces a pro-inflammatory tumor microenvironment and potentiates immunotherapy.

Histone deacetylase 6 (HDAC6) inhibition is associated with an increased pro-inflammatory tumor microenvironment and antitumoral immune responses. Here, we show that the HDAC6 inhibitor AVS100 (SS208) had an antitumoral effect in SM1 melanoma and CT26 colon cancer models and increased the efficacy of anti-programmed cell death protein 1 treatment, leading to complete remission in melanoma and increased response in colon cancer. AVS100 treatment increased pro-inflammatory tumor-infiltrating macrophages and CD8 effector T cells with an inflammatory and T cell effector gene signature. Acquired T cell immunity and long-term protection were evidenced as increased immunodominant T cell clones after AVS100 treatment. Last, AVS100 showed no mutagenicity, toxicity, or adverse effects in preclinical good laboratory practice studies, part of the package that has led to US Food and Drug Administration clearance of an investigational new drug application for initiating clinical trials. This would be a first-in-human combination therapy of pembrolizumab with HDAC6 inhibition for locally advanced or metastatic solid tumors.

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Cell-mediated Ab Response Disrupted in MIS-C See article p. 1452 CHD7 Promotes Anti-viral Short-lived Effector CD8+ T Cells See article p. 1528

The UBA1-STUB1 axis mediates cancer immune escape and resistance to checkpoint blockade.

How cancer cells escape immune surveillance and resist immune checkpoint blockade (ICB) remains to be fully elucidated. By screening candidate genes frequently gained in cancer, we identified expression of ubiquitin-like modifier activating enzyme 1 (UBA1) as being the most negatively correlated with signatures related to effector CD8+ T-cells. High UBA1 expression was strongly predictive of treatment resistance and poor survival in ICB cohorts. Functional studies revealed that UBA1 mediated immune escape to promote tumor growth. Immune profiling further showed that Uba1 overexpression or depletion markedly decreased or increased functional intratumoral CD8+ T-cells, respectively. Importantly, a selective UBA1 inhibitor, TAK-243, significantly synergized with ICB in multiple syngeneic models. Mechanistically, depletion or inactivation of the UBA1-STUB1 axis stabilized a key interferon pathway component (JAK1), enhanced IFN-signaling, and elevated key immune modulators, including CXCL9, CXCL10, and MHC class I. Our study warrants clinical evaluation of the combination of UBA1 inhibitors and ICB.

IMMU-48. CRACKING THE ROLE OF ONCOMETABOLITES IN VIROIMMUNOTHERAPY FOR PEDIATRIC MALIGNANT BRAIN TUMORS

Abstract Diffuse midline gliomas (DMGs) are among the most frequent and lethal pediatric tumors. The standard of care for DMGs is palliative, resulting in a median survival of 12 months. Viroimmunotherapy is an emerging alternative treatment for these tumors. Our group developed a platform of oncolytic adenoviruses that was translated to the clinic. Specifically, Delta-24-RGD was recently tested in a Phase I clinical trial for patients with newly diagnosed DMG (NCT03178032) with encouraging results. To further stimulate the immune arm of this therapy, we developed Delta-24-RGDOX, expressing the T-cell activator OX40L (NCT03714334, NCT04714983). Using bulk RNAseq, we showed that treatment with Delta-24-RGDOX upregulated the immunosuppressive immunometabolic IDO-AhR pathway. Of importance, treatment with Th1-related cytokine IFNg resulted in the upregulation of IDO1 expression in a panel of human and murine DMG cells. In agreement with these data, we showed synergy between the oncolytic virus and several IDO1-AhR inhibitors in tumor and immune cell co-cultures, as indicated by T-cell activation and proliferation. To further dissect the reshaping of the TME in clinically relevant DMG models treated with Delta-24-RGD or Delta-24-RGDOX, we performed scRNA seq analysis. We showed a pronounced T-cell infiltration in virus-treated animals versus control-treated mice, further confirmed by flow cytometry. Additionally, Th1 and CD8 effector memory subsets were preferentially enriched in the Delta-24-RGDOX group, indicating an enhanced proinflammatory shift. Importantly, we detected, for the first time, upregulation of IDO-AhR downstream effectors in the myeloid compartment in the virus-treated groups. Interestingly, we detected IL4I1 in myeloid cells, a recently discovered checkpoint upstream of AhR never described in the context of virotherapy. Preliminary data using a combination of Delta-24-RGDOX and AhR inhibitors prolongs the survival of glioma-bearing mice. Collectively, our in vivo and in vitro data support the rationale to propel a future clinical trial combining Delta-24-RGDOX with AhR inhibitors for DMG.

Mycophenolate Mofetil, an Inhibitor of Inosine Monophosphate Dehydrogenase, and Tofacitinib, a Janus Kinase Inhibitor, Attenuate Airway Inflammation and Hyperresponsiveness in a Mouse Model of Allergic Asthma

Treatment-resistant asthma remains an unresolved clinical problem and a challenge for current medical science. Consequently, there is a growing and urgent need to develop novel or alternative therapeutic options for the treatment of asthma. The research problem raised in this study was to assess and compare mycophenolate mofetil (MMF), an inhibitor of inosine monophosphate dehydrogenase, and tofacitinib (TFB), a Janus kinase inhibitor, for anti-asthmatic properties, and consequently to determine whether these agents may have potential as alternative options for treatment of allergic asthma. For this purpose, we assessed the effect of administration of MMF and TFB on the development of a mouse model of allergic airway inflammation (AAI) and accompanying CD4+ (cluster of differentiation 4) T-cell immune response in the lung-draining mediastinal lymph nodes (MLNs) and lungs, i.e., in the inductive and effector sites, respectively, of the immune response underlying the development of allergic asthma. The results from a histopathological scoring system demonstrated that the administration of MMF and TFB did not prevent or abolish ovalbumin-induced AAI, but strongly attenuated its severity. The pulmonary function tests revealed that the treatment with MMF and TFB significantly reduced methacholine-induced bronchoconstriction. These results indicate that the treatment with TFB and MMF attenuated the development of ovalbumin-induced AAI. The magnitude of the anti-asthmatic effect was comparable between both agents. The study revealed that the impairment of the clonal expansion of effector CD4+ T cells in the MLNs is a critical event in the mechanism underlying the anti-asthmatic effect of MMF and TFB. Apart from this, the findings of the study strongly suggest that the suppression of the interleukin-33/suppression of tumorigenicity-2 signaling pathway may constitute an additional mechanism responsible for producing this effect. In turn, the results indicate that the anti-asthmatic action induced by the studied agents is not mediated by the generation of forkhead box protein 3-expressing CD4+ regulatory T cells. Clinical implication of the results: the results suggest that MMF and TFB may exert anti-asthmatic action, and thus they may be considered therapeutic options for the treatment of allergic asthma cases resistant to conventional/existing treatment.

YTHDF2 upregulation and subcellular localization dictate CD8 T cell polyfunctionality in anti-tumor immunity.

RNA methylation is an important regulatory process to determine immune cell function but how it affects the anti-tumor activity of CD8 T cells is not fully understood. Here we show that the N6-methyladenosine (m6A) RNA reader YTHDF2 is highly expressed in early effector or effector-like CD8 T cells. We find that YTHDF2 facilitates nascent RNA synthesis, and m6A recognition is fundamental for this distinctively nuclear function of the protein, which also reinforces its autoregulation at the RNA level. Loss of YTHDF2 in T cells exacerbates tumor progression and confers unresponsiveness to PD-1 blockade in mice and in humans. In addition to initiating RNA decay that is necessary for mitochondrial fitness, YTHDF2 orchestrates chromatin changes that promote T cell polyfunctionality. YTHDF2 interacts with IKZF1/3, which is important for sustained transcription of their target genes. Accordingly, immunotherapy-induced efficacy could be largely restored in YTHDF2-deficient T cells through combinational use of IKZF1/3 inhibitor lenalidomide in a mouse model. Thus, YTHDF2 coordinates epi-transcriptional and transcriptional networks to potentiate T cell immunity, which could inform therapeutic intervention.

Crucial immunological roles of the invasion front in innate and adaptive immunity in cervical cancer.

The immunostimulatory actions of innate and adaptive immune responses play a crucial role in the cancer-immunity cycle. Although cervical cancer (CC) exhibits a high recurrence rate, the relation with lymphocytes in the tumor tissue have not been analyzed. We analyzed NKT, NK, and T cells, not only in peripheral blood (PB), but also tumor tissue through histological analysis from 23 patients with CC collected before treatment. A correlation of them between PB and the tumor tissue were assessed. We detected functional NKT and NKG2Dhi NK cells and effector CD4+ Tregs in PB. In the tumor, we detected the infiltration of LAG-3+ TIM-3+ CD4+ and CD8+ T cells rather than NK cells particularly in the invasion front (IF) by fluorescent multiplex immunohistochemistry. The heatmap and correlation analysis revealed that LAG-3+ TIM-3+ CD8+ T cells are highly associated with CD69+ CD103- exhausted CD8+ T cells. We identified the statistical relationship between CD4+Tregs in PB and the number of LAG-3+ TIM-3+ CD4+ T cells in the IF, which may be related to recurrence in patients with CC. LAG-3+ TIM-3+ T cells located in the IF may play a key role in regulation of the tumor immune microenvironment.

Differentiation fate of a stem-like CD4 T cell controls immunity to cancer.

The T cell response to cancer controls disease progression and response to immunotherapy1-3. Despite extensive knowledge regarding CD8 T cells, how CD4 T cells contribute to this process is less well understood. Here we identified a population of PD1+TCF1+ CD4 T cells with stem-like properties that are capable of self-renewal and differentiation into canonical CD4 effector cells. Primarily residing in tumour-draining lymph nodes (TDLNs), these tumour-specific CD4 T cells are restricted by T regulatory (Treg) cells to a stem-like fate that predominantly generated induced Treg (iTreg) cells, limiting effector CD8 T cell responses to the tumour. By contrast, upon Treg depletion, stem-like CD4 T cells differentiated into T helper 1 (TH1) cells, and via IFNγ production induced robust effector differentiation from TCF1+ CD8 T cells in TDLNs, a state we defined as 'active'. Notably, enforcing TBET expression in transferred stem-like CD4 T cells was sufficient to overcome the established restricted T cell state. Despite the presence of Treg cells, endogenous stem-like CD4 T cells actively generated TH1 cells, which were required to restore TDLN effector CD8 T cell differentiation, enhance tumour control and rescue response to immunotherapy. In agreement, TH1 differentiation in patients with kidney cancer predicted successful immunotherapy responses and improved progression-free survival. Together, these findings identify a stem-like CD4 T cell population that through alternative differentiation fates controls the switch between restricted and active T cell states with implications for cancer immunotherapies.

Cancer new treatment series: Comparison immune changes of HCC by scRNA-Seq following HELC treatment one case study

Immunotherapy has emerged as a novel treatment strategy for many types of cancers, among them, liver cancer. The major advances and achievements in recent years is the use of programmed death-1 (PD-1) blockers for cancer treatment. Since patients’ immune systems are already weak following concurrent surgery plus chemo or radiotherapy, it is necessary to restore and awake their immune cells to maximize the effect for immune therapy. Methods: Liver cancers were treated twice with hapten enhanced local chemotherapy (HELC) like tumor lysates vaccine and following PD-1. Single-cell RNA sequencing (scRNA-seq) was used to analyze the changes of immune responses prior and after treatments. Results: We observed upregulation of cytotoxicity-related genes of CD8 effector T cells and NK cells in untreated tumor; Both Bmem and Naive B cells in untreated tumor showed a significant increase in MHC II signaling pathway-related genes, while MHC I-related genes was upregulated in plasma cells. Significant tumor size shrinkage was observed in both treated and untreated tumors following the HELC+PD-1 therapy. Conclusions: This study provides new biological insights into the abscopal effect at the single-cell level related to the composition of T and B cells in untreated liver cancers before and after major primary tumors treated by HELC. Our data showed that intra-tumor HELC can kill tumor cells and induced immune activity, which is likely vital in modifying tumor associate antigens (TAAs) into neo TAAs. It induces immune response just like vaccine can wake up immune cells and therefore increasing the efficacy of PD1 therapy.

JunB is required for CD8+ T cell responses to acute infections.

Basic-leucine zipper transcription factor ATF-like (BATF) and interferon regulatory factor 4 (IRF4) are crucial transcription factors for generation of cytotoxic effector and memory CD8+ T cells. JunB is required for expression of genes controlled by BATF and IRF4 in CD4+ T cell responses, but the role of JunB in CD8+ T cells remains unknown. Here, we demonstrate that JunB is essential for cytotoxic CD8+ T cell responses. JunB expression is transiently induced, depending on T cell receptor (TCR) signal strength. JunB deficiency severely impairs clonal expansion of effector CD8+ T cells in response to acute infection with Listeria monocytogenes. Junb-deficient CD8+ T cells fail to control transcription and chromatin accessibility of a specific set of genes regulated by BATF and IRF4, resulting in impaired cell survival, glycolysis, and cytotoxic CD8+ T cell differentiation. Furthermore, JunB deficiency enhances expression of coinhibitory receptors, including programmed death receptor 1 (PD-1) and T-cell immunoglobulin mucin-3 (TIM3) upon activation of naïve CD8+ T cells. These results indicate that JunB, in collaboration with BATF and IRF4, promotes multiple key events in the early stage of cytotoxic CD8+ T cell responses.

Stimulator of interferon gene facilitates recruitment of effector CD8 T cells that drive neurofibromatosis type 1 nerve tumor initiation and maintenance.

Plexiform neurofibromas (PNFs) are benign nerve tumors driven by loss of the NF1 tumor suppressor in Schwann cells. PNFs are rich in immune cells, but whether immune cells are necessary for tumorigenesis is unknown. We show that inhibition of stimulator of interferon gene (STING) reduces plasma CXCL10, tumor T cell and dendritic cell (DC) recruitment, and tumor formation. Further, mice lacking XCR-1+ DCs showed reduced tumor-infiltrating T cells and PNF tumors. Antigen-presenting cells from tumor-bearing mice promoted CD8+ T cell proliferation in vitro, and PNF T cells expressed high levels of CCL5, implicating T cell activation. Notably, tumors and nerve-associated macrophages were absent in Rag1-/-; Nf1f/f; DhhCre mice and adoptive transfer of CD8+ T cells from tumor-bearing mice restored PNF initiation. In this setting, PNF shrunk upon subsequent T cell removal. Thus, STING pathway activation contributes to CD8+ T cell-dependent inflammatory responses required for PNF initiation and maintenance.

Abstract A030: CD4 neoantigen mRNA vaccine enhances endogenous CD8 responses and tumor control

Abstract CD4 T cells have long been known to be critical for priming CD8 T cells, a process referred to as CD4 T cell help. Recent data have suggested that CD4 help may be delivered at the surface of conventional type 1 dendritic cells (cDC1s), which can efficiently present antigens (Ag) on both MHC class I and class II molecules. However, the actual mechanisms underlying CD4 T cell help remain poorly characterized. We sought to understand how anti-tumor T cell responses are generated in the context of mRNA vaccines, which have been shown to elicit protective CD4 and/or CD8 T cells. For this purpose, we compared two mRNA-Lipoplex (mRNA-LPX) vaccines that express a single MHC-II-restricted Ag either tumor-specific (neoAg) or tumor-irrelevant. mRNA-LPX is injected intravenously and taken up predominantly by cDCs in the spleen.As expected, both vaccines elicited systemic CD4 T cell responses. However, only the anti-tumor CD4 T cell response elicited the accumulation of tumor-infiltrating CD8 lymphocytes (CD8 TILs) that led to tumor regression in a CD8-dependant manner. Single cell RNA-sequencing revealed higher expression of effector molecules and genes associated with stem-like progenitor T cell states in CD8 TILs following neoAg vaccine. In contrast, inhibitory molecules were down-regulated in CD8 TILs from neoAg-vaccinated mice.We next characterized the role of cDCs in the response to the vaccines. We found that both mRNA-LPX vaccines induced better maturation of cDC1s than cDC2s in the spleen. Surprisingly, priming of CD4 T cells was dependent on cDC1s, rather than cDC2s. cDC1s were also required for neoAg CD4 vaccine-induced CD8 TIL accumulation and for vaccine efficacy. We investigated whether neoAg-specific CD4 T cells were i) sufficient to enhance anti-tumor CD8 responses and ii) needed to maintain effector CD8 TIL activity in situ. Using adoptive cell transfer (ACT) into the tumor, we found that the transfer of neoAg-specific CD4 T cells alone significantly delayed tumor growth, suggesting an increased CD8 TIL activity. Interestingly, while the transfer of CD8 TILs alone was insufficient to control tumors; ACT of both CD4 and CD8 T cells was required for efficient tumor rejection. cDC1s were required for the efficacy of both, the ACT of CD4 T cells alone and the CD4 and CD8 ACT combination. Taken together, our data suggest a novel mechanism whereby immunizing with exogenous CD4 T cell epitopes can produce tumor immunity by generating endogenous CD8 responses. These results emphasize the importance of cDC1s for both, eliciting tumor-specific CD4 T cells in the setting of mRNA-LPX vaccine expressing a single MHC-II-restricted Ag and improving in situ anti-tumor CD8 responses and tumor control. We are currently investigating the mechanisms and location of the MHC-II-restricted neoAg dependent-cDC1 help using both in vivo and cell culture approaches.This model provides fundamental insight for the development of cancer vaccines and highlights the need of tumor-specific CD4 T cells and mature tumor-Ag loaded cDC1s. Citation Format: Camille-Charlotte Balanca, Aude-Hélène Capietto, Catherine Carbone, Alan Gutierrez, Yajun Chestnut, Ellen Duong, Aditya Anand, Anthony Antonelli, Jeanne Cheung, Shiuh Luoh, Ariane Nissembaum, Keiko Hokeness, Sara Wichner, Emily Freund, Vincent Javinal, Romain Bouziat, Joshua Gober, Adel ElSohly, Jon Linehan, Ugur Sahin, Lélia Delamarre, Ira Mellman. CD4 neoantigen mRNA vaccine enhances endogenous CD8 responses and tumor control [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2024 Oct 18-21; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2024;12(10 Suppl):Abstract nr A030.

Brief Communication: Combination of an MIP3α-Antigen Fusion Therapeutic DNA Vaccine With Treatments of IFNα and 5-Aza-2'Deoxycytidine Enhances Activated Effector CD8+ T Cells Expressing CD11c in the B16F10 Melanoma Model.

Previous studies in the B16F10 mouse melanoma model have demonstrated that combining a DNA vaccine comprised of regions of gp100 and tyrosinase-related protein 2 fused to macrophage-inflammatory protein 3-alpha (MIP3α) with recombinant interferon alpha (IFN) and 5-Aza-2'-deoxycytidine (5Aza) treatments resulted in significantly greater antitumor activity and immunogenicity in the tumor microenvironment (TME). This brief report details that the combination of vaccine with treatments IFN and 5Aza results in an increase in the TME of a distinct CD11c+ CD8+ T-cell population. This cell population correlates with tumor size, is primarily comprised of effector or effector memory T cells, and has a more robust response to ex vivo stimulation as compared with CD11c- CD8+ T cells. In conclusion, this combination therapy results in a greater presence of highly active effector CD8+ T cells expressing CD11c in the TME, which are likely primary contributors to treatment efficacy.

CD4+ T cell help during early acute hepacivirus infection is critical for viral clearance and the generation of a liver-homing CD103+CD49a+ effector CD8+ T cell subset.

In hepatitis C virus (HCV) infection, CD4+ and CD8+ T cells are crucial for viral control. However, a detailed understanding of the kinetic of CD4+ T cell help and its role in the generation of different CD8+ T cell subsets during acute infection is lacking. The absence of a small HCV animal model has impeded mechanistic studies of hepatic antiviral T cell immunity and HCV vaccine development. In this study, we used a recently developed HCV-related rodent hepacivirus infection mouse model to investigate the impact of CD4+ T cell help on the hepatic CD8+ T cell response and viral clearance during hepacivirus infection in vivo. Our results revealed a specific kinetic of CD4+ T cell dependency during acute infection. Early CD4+ T cell help was essential for CD8+ T cell priming and viral clearance, while CD4+ T cells became dispensable during later stages of acute infection. Effector CD8+ T cells directly mediated timely hepacivirus clearance. An analysis of hepatic CD8+ T cells specific for two different viral epitopes revealed the induction of subsets of liver-homing CD103+CD49a+ and CD103-CD49a+ effector CD8+ T cells with elevated IFN-γ and TNF-α production. CD103+CD49a+ T cells further persisted as tissue-resident memory subsets. A lack of CD4+ T cell help and CD40L-CD40 interactions resulted in reduced effector functions and phenotypical changes in effector CD8+ T cells and a specific loss of the CD103+CD49a+ subset. In summary, our study shows that early CD4+ T cell help through CD40L signaling is essential for priming functional effector CD8+ T cell subsets, including unique liver-homing subsets, and hepacivirus clearance.

An abnormal increase in CD26(-)CD28(-) cytotoxic effector CD4 and CD8 T cell populations in patients with systemic lupus erythematosus.

CD26 is a human T cell costimulatory molecule as well as a T cell subset marker, and increase of CD26+ T cells in inflamed tissues and peripheral blood has been reported in diverse autoimmune diseases. In contrast, our group has previously shown that levels of circulating CD26+ T cells are decreased in patients with systemic lupus erythematosus (SLE), although the role of reduced CD26 T cell surface expression in SLE pathology remains to be elucidated. In the present study, we conducted CD26-based T cell subset analyses utilizing peripheral blood mononuclear cells from 57 SLE patients and 31 healthy adult volunteers. We show that the increase in CD26(-) T cell population reflects the abnormal expansion of CD26(-)CD28(-) cytotoxic subsets of both CD8 T cells and CD4 T cells in SLE patients. Single cell RNA sequencing analysis of the CD26(-)CD28(-) CD4 and CD8 T cell populations reveals unique characteristics with similarities to natural killer T cells. In addition, the level of CD26(-)CD28(-) T cells is increased in some active stage SLE patients with renal manifestation. Meanwhile, effect of prednisolone treatment on these populations varies from patient to patient, with levels of these cytotoxic effector populations still being elevated in some inactive stage SLE patients. Taken together, our data suggest that analysis of these populations in SLE may be a useful tool to classify this markedly heterogeneous condition.

8439 Targeting Interferon Gamma-Mediated CXCL16-CXCR6 Chemokine-Receptor Interactions As A Strategy To Prevent Immune Checkpoint Inhibitor Autoimmune Diabetes

Abstract Disclosure: S. Wang: None. N. Huang: None. J.G. Ortega: None. J. Lee: None. K. Kimbrell: None. J. Nguyen: None. J. Olay: None. E. McCarthy: None. E. Peluso: None. H. Chen: None. M.G. Lechner: None. Autoimmune diabetes mellitus is a rare but life-threatening side effect of immune checkpoint inhibitor (ICI) cancer therapy. Checkpoint inhibitors increase immune activation by blocking regulatory molecules on T cells, including programmed death protein (PD1). As a result of this heightened immune activation, patients can develop autoimmunity in healthy tissues, known as immune related adverse events (IRAEs). ICI-associated diabetes mellitus (ICI-T1DM) is an IRAE that results in autoimmune destruction of insulin-producing pancreatic beta-cells. Patients with ICI-T1DM require life-long insulin therapy and more than half present initially with diabetic ketoacidosis. Unfortunately, the mechanism of this IRAE is not fully understood. Anti-PD1 antibody treatment (10mg/kg/dose, twice weekly, i.p.) of male and female non-obese diabetic (NOD) mice leads to autoimmune infiltrates in multiple tissues, including accelerated insulitis and DM. Single cell RNA sequencing of islet infiltrating immune cells from ICI-treated mice previously showed a role for CD8+ T cells and cytokine interferon gamma (IFNγ) in the development of ICI-T1DM. Using CellChat to perform receptor-ligand interaction analysis of these data, we identified both CD8+ and CD4+ T cells as the primary source of IFNγ in immune infiltrates and islet myeloid cells as the primary target. Furthermore, CellChat analysis showed increased receptor-ligand interactions between T cell receptor CXCR6 and its chemokine CXCL16, as well as CXCR3 and chemokines CXCL9 and CXCL10. In vitro IFNγ stimulation of myeloid cells induced strong expression of CXCL16, 9, and 10, suggesting a potential mechanism by which effector T cells are recruited to islets during ICI therapy. Immunophenotyping of islet-infiltrating immune cells indeed showed increased IFNγ+CXCR6+ effector CD8+ cells in anti-PD1 treated mice compared to isotype-treated controls. Moreover, these IFNγ+CXCR6+CD8+ T cells stained positively for the NRP-V7 mimotope tetramer, a known antigen for CD8+ T cells in spontaneous autoimmune diabetes in NOD mice, suggesting this as an antigen-specific population contributing to the immunopathogenesis of ICI-T1DM. Finally, genetic deletion of CXCR6 in NOD mice delayed the onset of autoimmune diabetes during anti-PD1 treatment in female (p=0.0162) but not male mice (p=0.3656). In summary, these data further elucidate the cellular mechanisms by which IFNγ and chemokine signaling pathways drive the development of ICI-T1DM and identify the CXCR6-CXCL16 axis as a potential therapeutic target to prevent this IRAE in checkpoint inhibitor-treated cancer patients. Presentation: 6/2/2024