Citations

Abstract Description Generation of T cells requires dynamic epigenetic alteration of histones to control gene expression at each developmental stage. The Class I deacetylases HDAC1, HDAC2, and HDAC3 have been shown to have 3 functions: adaptor, decrotonylase, and deacetylase activity. The relative importance of each function in T cells is not known. CD2icre HDAC3 cKO mice develop severe colitis and demonstrate that HDAC3 is required during thymocyte development for positive selection, DP survival, and CD4 lineage commitment. Recently, a mutation was identified in HDAC3 that eradicated deacetylase activity (“VRPP”). We generated a novel mouse model with Cre-mediated deletion of endogenous HDAC3 and linked re-expression of HDAC3 VRPP, which maintained adaptor function but lacks both deacetylase and decrotonylase enzymatic activity. Similar to CD2icre HDAC3 cKO mice, HDAC3 VRPP mice have a block in positive selection due to failure to down regulate RORγt and decreased DP cell survival due to increased expression of P2RX7, demonstrating that HDAC3 enzymatic activity is required for these functions. However, when the positive selection defect is bypassed in HDAC3 VRPP mice, CD4+ lineage commitment is restored. Strikingly, this mouse does not develop spontaneous colitis even up to one year of age, although T cell development is still impaired. Thus, there are different roles for HDAC3 enzymatic vs. adaptor function during T cell development which are made evident in HDAC3 VRPP mice. Funding Sources NIAID RO1 AI150100; T32 AI170478; Mayo Clinic Graduate School of Biomedical Sciences Topic Categories Lymphocyte Differentiation and Peripheral Maintenance (LYM)

Abstract Description Inflammatory bowel disease (IBD) affects between 1-3 million people in the United States, and patients present with symptoms including diarrhea, rectal bleeding, and fatigue. ST8Sia6 is a sialic acid transferase that adds terminal a2,8 disialic acids to O-linked glycoproteins, and a SNP in ST8Sia6 is associated with Crohn’s Disease. We have found that ST8Sia6 knockout (KO) and heterozygous (het) mice exhibit a 30-fold increase in small bowel immune infiltrate, along with an increased proportion of Th1 and pathogenic Th17 CD4 cells. These mice also exhibit activated gut epithelia, increased inflammatory cytokines, and increased innate cell activation, indicative of gut inflammation. Both ST8Sia6 KO and het mice exhibit increased weight loss and decreased survival when challenged with low dose dextran sodium sulfate-induced colitis. CellChat pathway analysis demonstrates enhanced TNF and IL-1 pathway activation in ST8Sia6 KO small bowel epithelium as compared to WT mice. In addition, ST8Sia6 KO small bowel epithelium produces significantly more CCL5, which may drive immune cell migration. These data demonstrate a role for ST8Sia6 in regulating gut immune homeostasis. As TNF blockade is a first line therapy for IBD patients, elucidating the role of ST8Sia6 in regulating this pathway is critical for a mechanistic understanding of IBD pathogenesis, and this may help to improve immunotherapy options for the disease. Funding Sources NIH R01CA243545 & NIH 5T32DK124190 Topic Categories Basic Autoimmunity (BA)

Abstract Description Traditional methods for identifying neoantigen-specific TCRs rely on labor-intensive in vitro co-cultures, which can alter T cell characteristics. We aim to identify endogenous neoantigen-specific TCRs in their natural state using antigen-mapping single-cell RNA and TCR sequencing. We profiled circulating CD8+ T cells from patients with KRAS-mutant metastatic colorectal adenocarcinoma (CRA) to identify TCRs that target HLA-A restricted (*02:01 or *11:01) mutant KRAS epitopes (G12D or G12V) using Barcode Enabled Antigen Mapping (BEAM; 10x Genomics) and performed cluster analysis to decipher T cell function. CD8+ T cells were isolated from peripheral blood and stained with peptide-MHC complexes for KRAS G12D/V epitopes (HLA-A02:01 and HLA-A11:01). Sequencing data were processed with Cell Ranger and Seurat. We analyzed 12 specimens from 6 patients who were receiving fluorouracil-based chemotherapy for metastatic CRA and detected neoantigen-specific TCR clonotypes in 11 specimens, suggesting their persistent presence in peripheral blood. TCR clonotypes displayed varying functional states, with some showing cytotoxic effector markers (GZMB, NKG7) and others showing markers of Naïve T cells (LEF1, TCF7, SELL, CCR7). These findings show that neoantigen-specific TCRs have diverse functional states and evolve over time. This approach is a promising tool for identifying endogenous neoantigen-specific TCRs and provides insights into TCR structure and function for adoptive therapy. Funding Sources This project is supported by the Eric & Wendy Schmidt Fund for AI Research & Innovation at Mayo Clinic (MZ and HD), and Mayo Clinic Comprehensive Cancer Center Distinguished Senior Scientist Award (HD). Topic Categories Tumor Immunology: Checkpoints, Prevention, and Treatment (TIPT)

Abstract Description Cholangiocarcinoma (CCA) is an aggressive epithelial malignancy of the bile duct, with rising global incidence and poor prognosis. Current treatments achieve only 20-30% response rates in advanced cases, highlighting the need for novel therapeutic approaches. The tumor microenvironment (TME) has emerged as a critical focus for innovative therapies. Sulfatase 2 (SULF2) is a heparan sulfate (HS)-editing enzyme that alters HS chain affinity for growth factors and receptors, modulating heparan sulfate proteoglycans (HSPG) in cell signaling pathways. Specific sulfatases in HSPGs have been implicated as therapeutic targets in CCA. This study investigates the potential of anti-SULF2 antibodies to modulate immune cells within the TME using a C57BL6 syngeneic mouse model. Anti-SULF2-treated mice were compared to untreated controls, with tumors analyzed via CyTOF. Treatment resulted in reduced immunosuppressive cells and increased anti-tumor immune cells, suggesting that SULF2 inhibition shifts the TME toward an anti-tumorigenic state. These findings highlight SULF2 as a promising target for therapeutic intervention. Future studies will explore spatial transcriptomic and proteomics to elucidate the interplay between SULF2 expression in the TME makeup. We will also explore the molecular mechanisms of SULF2 suppression and its influence on cytokine signaling pathways within the TME. Funding Sources Supported by CTSA Grant Number TL1 TR002380 from the National Center for Advancing Translational Science (NCATS). Topic Categories Tumor Immunology: Cellular Responses and Tumor Microevironment (TIME)

Abstract Description Peripheral nervous system innervation of various organs has been associated with the development and maintenance of the immune system. Various neurological insults including brain tumors induce thymic involution. Using flow cytometry and confocal microscopy, we identified a population of cells within the thymus that contained neuronal markers and morphology. Subsets expressed tyrosine hydroxylase, BIII tubulin and/or NeuN, distinguishing them from thymic epithelial cells. These cells do not express AIRE. Neuronal cell bodies and/or axonal processes were identified within the thymus. Using retrograde rabies vector neurotracers, we confirmed axonal connections and the identity of thymic neurons. To determine developmental T cell stages that support neuronal development, we evaluated RAG1/2 KO, TCRβ KO, TCRα KO, TCRγδ KO, CD4 KO, CD8 KO and OT-I and -II transgenics. RAG1/2 and TCRβ deficiency resulted in complete loss of thymic neurons. This is while TCRα KO, TCRγδ KO, CD4/8 KO and OT-II transgenics had normal thymic neuron development. Importantly, OT-I transgenics had a significant loss of neuron-like cells, indicating developing CD8 T cells pre-alpha arrangement control thymic innervation. Finally, introduction of healthy bone marrow into irradiated RAG KO mice can restore neuron development. To summarize, we describe a novel population of neuronal cells within the thymus that interact with developing thymocytes to establish optimal thymic innervation. Funding Sources R00NS117799 Topic Categories Neuroimmunology (NEUR)

Abstract Description Therapeutic in situ chimeric antigen receptor (isCAR) T cells can be generated by targeting activated T cells within a lymph node (LN) with retroviruses encoding CARs. While isCAR T cells are successfully generated by intradermal LN priming using adenovirus encoding allogeneic MHC in all mouse lines tested, differences in emerging therapeutic peripheral isCAR T cells are found in a strain dependent manner. Potentially harmful off target retroviral transduction of B cells with CARs is observed within the targeted LN. Here we report the blockade of B cell transduction using anti-CD20 antibody B cell depletion with the introduction of anti-CD19 chimeric antigen receptors into the activated CD8+ T cells. Lymphocytes were analyzed in blood and LN following isCAR T cell generation. When B cells were depleted by systemic administration of anti-CD20 antibodies during isCAR T cell induction, >97.5% systemic depletion of B cells was achieved. Whereas very small numbers of CAR transduced B cells were found in the blood of mice not treated with anti-CD20, none were observed in animals systemically depleted of B cells. In contrast, CAR B cells persisted in the LN of local anti-CD20 treated animals. However, animals expressing dominant CD8+ isCAR T cell populations eliminated LN B cells expressing CARs by week two. Furthermore, systemic treatment of lymphoma in animals with anti-CD20 antibody complemented anti-CD19 isCAR T therapy while blocking off target B cell transduction. Funding Sources Mayo Clinic Ventures Mayo Clinic Graduate School of Biomedical Sciences Mayo Clinic Topic Categories Tumor Immunology: Checkpoints, Prevention, and Treatment (TIPT)

Abstract Description Background ISG15 is induced in neurons by demyelination and elevated in MS patient cortical neurons. Our hypothesis is that ISGylation contributes to neuron loss in MS by impairing ubiquitin-dependent protein and mitochondrial turnover. Methods ISGylation was induced by IFNg treatment. Protein turnover: cortical neurons were transduced with AAV1.TRE.mCherry-DD to drive Tet-ON expression of the mCherry tagged with a degradation domain (DD). Following induction DD-mCherry is rapidly degraded allowing measurement of proteasome activity. Mitophagy: cortical neurons were transduced with AAV1.Syn.GFP-mCherry-FIS1 which targets mitochondria. Upon entry into the lysosome, GFP is rapidly quenched allowing quantification of mitophagy (non-colocalizing mCherry signal). C57BL/6 and ISG15 KO mice were subjected to a cuprizone diet, immunofluorescence and confocal imaging to assess neuronal density changes in the cortex over time. Results In WT but not ISG15 deficient neurons IFNg treatment delayed DD-mCherry degradation. Using the mito-QC reporter, elevated mitochondrial content and mitophagy levels were observed in ISG15 KO cortical neurons. Neuron density was preserved in ISG15 KO compared to WT. Conclusion IFNg-induced ISG15 impairs protein and mitochondrial turnover in neurons, and ISG15 deficiency protects neurons during demyelination. Future work will test how neuronal ISG15 impacts c-Gas STING pathway activation and ferroptosis in neurons during neurodegeneration. Funding Sources Generous donation from Don and Fran Herdrich. Topic Categories Neuroimmunology (NEUR)

Abstract Description Rationale Lab mice, although not germ-free, lack normal exposures to diverse commensal and environmental microorganisms. Dirty mice, as those found in the wild or in pet stores are referred to, have diverse microbiomes and history of infection with multiple pathogens; their immune systems mirror those of adult humans. It is possible to turn lab mice dirty by co-housing C57BL/6, or other genetically inbred mouse strains, with pet store mice or their dirty bedding. Due to concerns regarding aggression, dirty mouse studies typically only include female mice; if they do include male mice, they are co-housed with dirty bedding only. Methods We used divided rat cages to co-house C57BL/6J mice of both sexes for 8 weeks with either pet store mice or their dirty bedding before assessing pathogen transfer and immune profiles of brain and spleen. Results Live co-housing resulted in increased pathogen transfer and sex-dependent immune changes in brain and spleen compared to clean mice or dirty bedding alone. Co-housed males became ill later and more severely than females, showing active infection after 8 weeks while the illnesses of females had resolved. Conclusions These findings suggest that co-housing method is important in determining the changes that occur as lab mice get dirty. The sex-dependent nature of these changes suggests female-only dirty mouse studies are insufficient in representing the altered immunology of these immune-appropriate mouse models. Funding Sources Supported by Mayo Clinic Graduate School of Biomedical Sciences Topic Categories Mucosal and Regional Immunology (MUC)

Abstract Description Glioblastoma (GBM), the most common and malignant primary brain tumor, exhibits profound immune suppression, hindering immunotherapy efficacy. GBM-derived extracellular vesicles (EVs) play a major role through the immunosuppressive polarization of myeloid cells. Inhibition of EV-myeloid cell interactions thus represents a novel target to mitigate GBM-mediated immune suppression. However, there are multiple mechanisms of EV-target interaction, and downstream pathways of GBM-EV signaling are poorly understood. We explored two pharmacological agents targeting different mechanisms of EV uptake: Methyl-B-cyclodextrin (MBCD), which disrupts lipid rafts, and cytochalasin D, which inhibits actin polymerization. Our results showed immunosuppressive myeloid cell (CD11b+/ CD15-/ HLA-DRlow/ CD14high) populations increased upon GBM-EV treatment. Following cytochalasin D treatment, fewer immunosuppressive myeloid cells were observed (7.40%±1.01 vs. untreated 9.66%±2.86), with rescuing T cell proliferation. Conversely, MBCD treatment increased immunosuppressive myeloid cell levels (10.42%±2.38 vs. untreated 8.87%±3.97) without impacting T cell proliferation. This study demonstrates the feasibility of pharmacologically targeting EV-myeloid cell interactions to rescue tumor mediated immune suppression by inhibiting actin-dependent endocytosis with cytochalasin D. The converse results using MBCD treatment indicate differential importance of different EV uptake pathways in monocyte regulation. Topic Categories Tumor Immunology: Cellular Responses and Tumor Microevironment (TIME)

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)