T-cell Populations Research Articles

Spatially mapping the single-cell immune landscapes of melanoma brain metastases using imaging mass cytometry.

e21517 Background: Up to 60% of metastatic melanoma patients develop brain metastases, and 5% develop leptomeningeal disease (LD), which presents with the worst prognosis of any melanoma brain metastasis (MBM) infiltration pattern. Median survival duration for MBM is ~12 months, however for LD patients it can be < 10 weeks. The spatial immune landscape of MBM with and without LD remains poorly understood. Methods: To spatially characterize the tumor microenvironment (TME) of MBM, we performed CyTOF Imaging Mass Cytometry (CyTOF-IMC) on a highly multiplexed panel of 35 antibodies for 21 MBMs (13 with LD, 8 without LD). We performed a novel cell segmentation, cell type assignment and identification approach to identify cell lineages to spatially characterize the TME of MBMs, segmenting and classifying 130,000 cells into 19 cell types. Results: We found enrichment of dendritic cells in the direct neighbourhood of melanoma cells of patients with LD (p = 0.019) and trends towards elevation of anti-tumoral monocyte populations in the TME of patients without LD. To investigate survival outcomes, we divided our cohort into long (≥365days) and short-survivors ( < 365 days), and found significant elevation of anti-tumoral T-cell populations (Total T-cells, CD8+ T-cells, CD4+ T-cells and CD3+CD4-CD8- T-cells, p < 0.05), and closer proximity of T-cells (CD8+ & CD4+ T-cells) to melanoma cells (p < 0.05). Survival analysis using median cell-proportion for each T-cell subset showed statistically significant (p < 0.05) survival differences between patients with high and low cell-proportions of CD8+ T-cells and CD4+ T-cells, with similar trends observed for a subset of patients (n = 13) with LD and a subset of patients treated with ICIs (n = 10), and results were confirmed by a Cox Regression Model. Cellular neighborhood (CN) analysis was performed generating N = 12 stable CNs. We found patients with higher proportions of CN9 (M1-like-microglia/M2-like-microglia/melanoma), CN10 (M1-like-macrophages/M2-like-macrophages/melanoma) and CN12 (Cytotoxic-T-cells/Helper-T-cells/melanoma) was associated with longer overall survival after diagnosis with MBM (p < 0.01). Conclusions: Proportion and proximity of anti-tumoral monocyte and T-cell populations may play a key role in modulating tumor response and overall survival for patients with MBM, including for patients with LD or for patients treated with ICIs.

Low-dose radiation as a preconditioning regimen for dendritic cell vaccines.

e14519 Background: Dendritic cells are potent antigen-presenting cells that induce the adaptive immune system to protect against cancer. While anti-tumor immunity can be improved with dendritic cell vaccines, it is not fully known what approved preconditioning agents, if any, improve dendritic cell vaccine-induced antitumor T-cell response and tumor elimination. We explored the effect of low-dose radiation (LDR), cyclophosphamide, and paclitaxel as preconditioning regiments for a dendritic cell vaccine. Methods: KP tumors were engineered with ovalbumin and orthotopically injected subcutaneously (SQ) into the flank of wild type B6 mice. Preconditioning regiments of a control, LDR (2 Gy), cyclophosphamide (20mg/kg), LDR (2 Gy) + cyclophosphamide (20mg/kg), and paclitaxel (20mg/kg) were given on day 4. Bone marrow dendritic cells (DCs) were electroporated with ovalbumin peptide SIINFEKL and then one million cells were injected i.v. on day 5 and 8. Blood collection was done and ovalbumin-specific T-cell populations were examined by tetramer staining for SIINFEKL-specific TCR over time. Tumor size was measured over time and survival data was analyzed accordingly. Results: LDR effectively produced a significant increase in CD8+ SIINFEKL tetramer+ T-cell count per uL of blood compared to the non-preconditioned group. In addition, this LDR preconditioning regiment produced a significantly improved tumor response over time. The overall survival rate of subjects receiving LDR was significantly improved compared to all other groups. Conclusions: Here, we find that LDR is most effective as a preconditioning regimen prior to dendritic cell vaccination for inducing an antitumor T-cell response and achieving tumor control over time. LDR provides a promising method to supplement dendritic cell vaccination and potentially improve patient outcomes. Further study is needed to confirm its efficacy.

CyTRBC1 evaluation rapidly identifies sCD3-negative peripheral T-cell lymphomas and reveals a novel type of sCD3-negative T-cell clone with uncertain significance.

The flow cytometry-based evaluation of TRBC1 expression has been demonstrated as a rapid and specific method for detecting T-cell clones in sCD3-positive TCRαβ+ mature T-cell lymphoma. The aim of the study was to validate the utility of surface (s) TRBC1 and cytoplastic (cy) TRBC1 assessment in detecting clonality of sCD3-negative peripheral T-cell lymphomas (PTCLs), as well as exploring the existence and characteristics of sCD3-negative clonal T-cell populations with uncertain significance (T-CUS). Evaluation of sTRBC1 and cyTRBC1 were assessed on 61 samples from 37 patients with sCD3-negative PTCLs, including 26 angioimmunoblastic T-cell lymphoma (AITL) patients and 11 non-AITL patients. The sCD3-negative T-CUS were screened from 1602 patients without T-cell malignancy and 100 healthy individuals. Additionally, the clonality of cells was further detected through T-cell gene rearrangement analysis. We demonstrated the monotypic expression patterns of cyTRBC1 in all sCD3-negative PTCLs. Utilizing the cyTRBC1 evaluation assay, we identified a novel and rare subtype of sCD3-negative T-CUS for the first time among 13 out of 1602 (0.8%) patients without T-cell malignancy. The clonality of these cells was further confirmed through T-cell gene rearrangement analysis. This subset exhibited characteristics such as sCD3-cyCD3 + CD4 + CD45RO+, closely resembling AITL rather than non-AITL. Further analysis revealed that sCD3-negative T-CUS exhibited a smaller clone size in the lymph node and mass specimens compared to AITL patients. However, the clone size of sCD3-negative T-CUS was significantly lower than that of non-AITL patients in both specimen groups. In conclusion, we validated the diagnostic utility of cyTRBC1 in detecting sCD3-negative T-cell clonality, provided a comprehensive analysis of sCD3-negative T-CUS, and established a framework and provided valuable insights for distinguishing sCD3-negative T-CUS from sCD3-negative PTCLs based on their phenotypic properties and clone size.

Polyclonal but not monoclonal circulating memory CD4+ T cells attenuate the severity of Staphylococcus aureus bacteremia.

Staphylococcus aureus bacteremia causes significant morbidity and mortality. Treatment of staphylococcal infections is hindered by widespread antibiotic resistance, and attempts to develop an S. aureus vaccine have failed. Improved S. aureus treatment and infection prevention options require a deeper understanding of the correlates of protective immunity. CD4+ T cells have been identified as key orchestrators in the defense against S. aureus, but uncertainties persist regarding the subset, polarity, and breadth of the memory CD4+ T-cell pool required for protection. Here, using a mouse model of systemic S. aureus infection, we discovered that the breadth of bacterium-specific memory CD4+ T-cell pool is a critical factor for protective immunity against invasive S. aureus infections. Seeding mice with a monoclonal bacterium-specific circulating memory CD4+ T-cell population failed to protect against systemic S. aureus infection; however, the introduction of a polyclonal and polyfunctional memory CD4+ T-cell pool significantly reduced the bacterial burden. Our findings support the development of a multi-epitope T-cell-based S. aureus vaccine, as a strategy to mitigate the severity of S. aureus bacteremia.

A standardized combination of Terminalia chebula and Withania somnifera extracts enhances immune function in adults: a pilot randomized, double-blind, placebo-controlled clinical study.

The use of botanical medicine has been demonstrated as a potential strategy to manage or treat a variety of health issues. Terminalia chebula (Retz) fruit and Withania somnifera (L.) Dunal roots are important medicinal herbs described in Ayurveda and traditional therapy for diverse health benefits. This pilot study aimed to evaluate the immune function-enhancing potential of a unique blend of T. chebula fruit and W. somnifera root extracts, LN20189, in healthy men and women. Forty healthy volunteers (age: 35-60 years) were randomized into two groups receiving either LN20189 (500 mg per day) or a matched placebo over 28 consecutive days. The total T-cell population was the primary efficacy measure in this study. The secondary efficacy measures included counts of CD4, CD8, natural killer (NK) cells, serum levels of interleukin-2 (IL-2), interferon-gamma (IFN-γ), total immunoglobulin-G (IgG), and Immune Function Questionnaire (IFQ) scores. Safety parameter assessments were also conducted. Post-trial, in LN20189-supplemented subjects, T cells, CD4, NK cells count, and the CD4:CD8 ratio were increased by 9.32, 10.10, 19.91, and 17.43%, respectively, as compared to baseline. LN20189 supplementation increased serum IFN-γ and IgG levels by 14.57 and 27.09% from baseline and by 13.98 and 21.99%, compared to placebo, respectively. Also, the IFQ scores in the LN20189 group were 84.68% (vs. baseline) and 69.44% (vs. placebo) lower at the end of the trial. LN20189 improved the study volunteers' cellular and humoral immune functions. In summary, LN20189 supplementation was found tolerable and improved the key cellular and humoral factors of the immune system and helped improve immune function of the trial volunteers.

Gαz-independent and -dependent Improvements With EPA Supplementation on the Early Type 1 Diabetes Phenotype of NOD Mice.

Prostaglandin E2 (PGE2) is a key mediator of inflammation and is derived from the omega-6 polyunsaturated fatty acid, arachidonic acid (AA). In the β-cell, the PGE2 receptor, Prostaglandin EP3 receptor (EP3), is coupled to the unique heterotrimeric G protein alpha subunit, Gɑz to reduce the production of cyclic adenosine monophosphate (cAMP), a key signaling molecule that activates β-cell function, proliferation, and survival pathways. Nonobese diabetic (NOD) mice are a strong model of type 1 diabetes (T1D), and NOD mice lacking Gɑz are protected from hyperglycemia. Therefore, limiting systemic PGE2 production could potentially improve both the inflammatory and β-cell dysfunction phenotype of T1D. Here, we sought to evaluate the effect of eicosapentaenoic acid (EPA) feeding, which limits PGE2 production, on the early T1D phenotype of NOD mice in the presence and absence of Gαz. Wild-type and Gαz knockout NOD mice were fed a control or EPA-enriched diet for 12 weeks, beginning at age 4 to 5 weeks. Oral glucose tolerance, splenic T-cell populations, islet cytokine/chemokine gene expression, islet insulitis, measurements of β-cell mass, and measurements of β-cell function were quantified. EPA diet feeding and Gɑz loss independently improved different aspects of the early NOD T1D phenotype and coordinated to alter the expression of certain cytokine/chemokine genes and enhance incretin-potentiated insulin secretion. Our results shed critical light on the Gαz-dependent and -independent effects of dietary EPA enrichment and provide a rationale for future research into novel pharmacological and dietary adjuvant therapies for T1D.

Optimizing cancer therapy: a review of the multifaceted effects of metronomic chemotherapy.

Metronomic chemotherapy (MCT), characterized by the continuous administration of chemotherapeutics at a lower dose without prolonged drug-free periods, has garnered significant attention over the last 2decades. Extensive evidence from both pre-clinical and clinical settings indicates that MCT induces distinct biological effects than the standard Maximum Tolerated Dose (MTD) chemotherapy. The low toxicity profile, reduced likelihood of inducing acquired therapeutic resistance, and low cost of MCT render it an attractive chemotherapeutic regimen option. One of the most prominent aspects of MCT is its anti-angiogenesis effects. It has been shown to stimulate the expression of anti-angiogenic molecules, thereby inhibiting angiogenesis. In addition, MCT has been shown to decrease the regulatory T-cell population and promote anti-tumor immune response through inducing dendritic cell maturation and increasing the number of cytotoxic T-cells. Combination therapies utilizing MCT along with oncolytic virotherapy, radiotherapy or other chemotherapeutic regimens have been studied extensively. This review provides an overview of the current status of MCT research and the established mechanisms of action of MCT treatment and also offers insights into potential avenues of development for MCT in the future.

KMT2D regulates activation, localization, and integrin expression by T-cells.

Individuals with Kabuki syndrome present with immunodeficiency; however, how pathogenic variants in the gene encoding the histone-modifying enzyme lysine methyltransferase 2D (KMT2D) lead to immune alterations remain poorly understood. Following up on our prior report of KMT2D-altered integrin expression in B-cells, we performed targeted analyses of KMT2D's influence on integrin expression in T-cells throughout development (thymocytes through peripheral T-cells) in murine cells with constitutive- and conditional-targeted Kmt2d deletion. Using high-throughput RNA-sequencing and flow cytometry, we reveal decreased expression (both at the transcriptional and translational levels) of a cluster of leukocyte-specific integrins, which perturb aspects of T-cell activation, maturation, adhesion/localization, and effector function. H3K4me3 ChIP-PCR suggests that these evolutionary similar integrins are under direct control of KMT2D. KMT2D loss also alters multiple downstream programming/signaling pathways, including integrin-based localization, which can influence T-cell populations. We further demonstrated that KMT2D deficiency is associated with the accumulation of murine CD8+ single-positive (SP) thymocytes and shifts in both human and murine peripheral T-cell populations, including the reduction of the CD4+ recent thymic emigrant (RTE) population. Together, these data show that the targeted loss of Kmt2d in the T-cell lineage recapitulates several distinct features of Kabuki syndrome-associated immune deficiency and implicates epigenetic mechanisms in the regulation of integrin signaling.

Abstract PO3-26-08: Genetic modification of tumor associated macrophages using CRISPR lipid nanoparticle platform altered tumor microenvironment and induced cancer cell elimination

Abstract More than half of patients with stage IV breast cancer will eventually develop liver metastasis. Due to their nature, liver metastases are hard to treat, and the five-year survival rate for stage IV breast cancer is very low (~11%). In the recent years, vital roles macrophages play in cancer progression and immune evasion have become increasingly clear, making them an appealing target for therapeutic intervention. As one of the most abundant cell populations recruited to the tumor microenvironment, tumor-associated macrophages (TAM) are typically immunosuppressive Arg1+ M2-like macrophages, which support cancer growth, metastasis progression, and drug resistance. Numerous studies, including from our laboratory, have shown that reversal of the macrophage phenotype to the classical inflammatory CD80+ M1-like macrophages is very promising for cancer eradication. In this study, we used CRISPR loaded into lipid nanoparticles (CRISPR-LNP) to modulate macrophage polarization in breast cancer metastasis in vivo. We hypothesize that CRISPR-mediated gene editing through lipid nanoparticle (LNP) delivery of CRISPR enzyme and target gRNA (CRISPR-LNP) is a highly effective and safe approach. Using our CRISPR-LNP platform, we screened multiple genes with significant roles in macrophage polarization and found that targeting the RICTOR gene alone enabled reprograming of pro-tumorigenic M2 TAMs to anti-tumorigenic M1 phenotype in vitro and in vivo. We administered the CRISPR-LNP targeting RICTOR (CRISPR-RIC-LNP) on a syngeneic liver metastasis mouse model via intravenous injection. Single dose studies were conducted to determine biodistribution, treatment efficacy, and shift in immune landscape of the tumor after treatment via immunofluorescence staining, Imaging Mass Cytometry, and single cell RNA sequencing. A spatial map was built using digital pathology analysis for investigation of the interactions amongst immune and tumor cells within the tumor immune microenvironment. In 4T1 breast cancer liver metastatic model, we observed that CRISPR-RIC-LNP treatment: (i) accumulated in the liver metastases lesions in vivo 24 hours after injection. ~0.5% of total injected dose, which corresponds to ~75% of fluorescence from the whole body at 24h time point was confined only in the metastatic regions; (ii) led to modest increase of macrophage number, and (iii) significant shift of macrophage phenotype from immunosuppressive, pro-tumorigenic Arg1+, CD206+ macrophages to inflammatory, anti-tumor CD80+ phenotype (from ~5 to ~9% of total cell in the tumor lesions) 24 hours after injection; (iv) reduced the cancer cell number by almost 80%; and (v) dramatically reduced exhausted T-cell and regulatory T-cell population, as determined by single cell RNA sequencing analysis. We plan to validate our preliminary finding with flow cytometry analysis of metastatic lesions, and evalute the efficacy of CRISPR-RIC-LNP as single and in combinatorial therapies in survival studies. These data showed that reprograming macrophages from cancer-supporting to cancer-eliminating phenotype is a promising tool to suppress cancer cell growth and increase the presence of cytotoxic CD8+ T-cells. We propose that this approach can be efficiently used as single therapy or as combination with immune checkpoint inhibitors to obtain synergistic effects and efficiently eradicate cancer cells. We will assess the safety, optimize the accumulation in TME, and devise methods to limit exposure to healthy cells. In the future, we also aim to expand scope of our candidate therapy as therapeutics for other types of breast cancer metastases. Citation Format: Fransisca Leonard, Tyler Galbraith, Nourhan Abdelfattah, Arturas Ziemys, Chihiro Hashimoto, Harlan Cook, Yitian Xu, Shu-Hsia Chen, Roberto Rosato, Kyuson Yun. Genetic modification of tumor associated macrophages using CRISPR lipid nanoparticle platform altered tumor microenvironment and induced cancer cell elimination [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-26-08.

Recruitment of T-cells to the lung using an ex vivo co-culture paradigm

Precision cut lung slices (PCLS) bridge a gap between in vivo and in vitro studies by maintaining anatomical organization with structural integrity and intercellular signaling pathways. Applications of PCLS have included the modeling of inflammatory lung diseases, metabolism studies, and drug development. In the lungs, immune responses are carried out by a network of T- and B- cells, the latter of which are resident. The limited resident T-cell population of the lung diminishes accurate representations of pathogen response capacity in PCLS. Addressing this, we set out to increase pulmonary T-cell populations ex vivo. We hypothesized that thymus and bone marrow-derived T-cells would work synergistically to populate the lung in co-culture experiments. A murine organotypic lung co-culture model was developed and characterized for tissue health and T-cell recruitment over 3 days ex vivo using adult neurobasal media with 4 mM glucose + 2% B27 supplement. Lung slices were cultured independently, with bone marrow, thymus, or both. Immune colonization of the lung was assessed using immunohistochemistry for CD3+ T-cells and ACK2+ cells. Cells were counted in alveolar and airway spaces after 3 days of culture. Co-culture of lung slices with bone marrow did not increase CD3+ immunoreactive T-cells while thymus co-culture increased CD3+ T-cells by 76% in the alveolar space and by 39% in the airway, relative to lung alone. When lung slices were cultured with bone marrow plus thymus, CD3+ T-cells increased by 206% in the alveolar space and by 251% in the airway, relative to the lung alone. Co-culture with thymus increased ACK2+ cells by 48% in the airway, while lung culture with both thymus and bone marrow, ACK2+ cells increased by 35% in the alveolar space and 85% in the airway, relative to the lung alone. These results suggest that the increased T-cell population corresponding with thymus and bone marrow co-culture could be a result of cell-cell interaction or the secretion of growth factors. Cell secretions or growth factor release could stimulate thymic secretion of T-cells or could stimulate T-cell proliferation in the lung, suggesting that co-culture with thymus and bone marrow can elicit a T-cell response ex vivo. Future studies will center around differentiating what drives T-cell population to be increased in lung co-cultures and what T-cell subsets are being recruited in PCLS co-cultures while analyzing their capacity for response to pathogens ex vivo. Anschutz Foundation Pandemic Preparedness Grant. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A Role of T-Lymphocyte β-Arrestins in Hypertension

The adaptive immune system and T-cells play a central role in the development of essential hypertension. The renin-angiotensin system regulates blood pressure (BP) through multiple mechanisms including effects on the immune system. Among several G-protein coupled receptors (GPCR) that regulate T-cell function, it has been hypothesized that specific T-cell populations use the angiotensin receptor (AT1R) to modulate immune responses in hypertension. Selective ablation of AT1R in T-cells paradoxically increases hypertensive end-organ damage (EOD). While AT1R typically induces the classical G protein signaling, recent studies have uncovered an alternative protective signaling-cascade at this receptor via β-Arrestin ( ARRB) proteins. Thus, we hypothesized that ARRB in T-lymphocytes mediates an anti-hypertensive and anti-inflammatory role in response to angiotensin II (ANG II) thereby decreasing EOD in hypertension. Transgenic mice with T-lymphocyte-specific knock outs of the Arrb1 gene were developed using a CD4-Cre x Arrb1-Flox system. Hypertensive conditions were modeled with a 3-pronged approach designed to induce kidney damage consisting of unilateral nephrectomy (UNX), maintenance on a 4% salt diet, and a continuous infusion of ANG II (1,000 ng/kg/min). Age and sex-matched Cre negative x Arrb1-Flox littermates were used as controls. BP was measured at baseline before and after UNX, and for the following three weeks using radiotelemetry. Inflammation was assessed using quantitative PCR (q-PCR). Preliminary data suggest that loss of T-cell specific Arrb1 is protective against ANG II-induced hypertension. At baseline CD4Arrb1-null and CD4Arrb1-WT mice had similar systolic BP (123.0±2.9 mmHg and 119.6±2.3 mmHg, respectively, n=5-7). However, CD4Arrb1-null mice exhibited an attenuated response to ANG II infusion after three weeks (162.5±11.8 mmHg vs 187.0±5.9 mmHg n=3-5; p = 0.03). After 15 days of ANG II, mice were placed in metabolic cages and urine was collected. In a 24-hour period, CD4Arrb1-null mice excreted significantly more sodium (1.98±0.07 mg/24hrs vs 1.66±0.03 mg/24hrs, n=3-4; p = 0.01). Tissue collected from the renal cortex following three weeks of ANG II infusion was analyzed for inflammatory cytokines using q-PCR. Gene expression was normalized to 18s expression in CD4Arrb1-WT mice under sham experimental conditions. Expression of tumor necrosis factor α (TNF-α) transcripts was attenuated in CD4Arrb1-null mice when compared to CD4Arrb1-WT (1.62±0.24-fold increase vs 0.67±0.07-fold decrease, respectively, n=3-4; p=0.006). Contrary to our hypothesis, these preliminary data suggest that T-cell Arrb1 does not protect against hypertensive or inflammatory responses to ANG II. However, these studies highlight the role of β-arrestin-1 proteins endogenous to T-lymphocytes in the modulation of the hypertensive response to ANG II. Supported by grants from the AHA and NIH. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

PI3K/mTOR inhibition induces tumour microenvironment remodelling and sensitises pS6high uterine leiomyosarcoma to PD-1 blockade.

Uterine leiomyosarcomas (uLMS) are aggressive tumours with poor prognosis and limited treatment options. Although immune checkpoint blockade (ICB) has proven effective in some 'challenging-to-treat' cancers, clinical trials showed that uLMS do not respond to ICB. Emerging evidence suggests that aberrant PI3K/mTOR signalling can drive resistance to ICB. We therefore explored the relevance of the PI3K/mTOR pathway for ICB treatment in uLMS and explored pharmacological inhibition of this pathway to sensitise these tumours to ICB. We performed an integrated multiomics analysis based on TCGA data to explore the correlation between PI3K/mTOR dysregulation and immune infiltration in 101 LMS. We assessed response to PI3K/mTOR inhibitors in immunodeficient and humanized uLMS patient-derived xenografts (PDXs) by evaluating tumour microenvironment modulation using multiplex immunofluorescence. We explored response to single-agent and a combination of PI3K/mTOR inhibitors with PD-1 blockade in humanized uLMS PDXs. We mapped intratumoural dynamics using single-cell RNA/TCR sequencing of serially collected biopsies. PI3K/mTOR over-activation (pS6high) associated with lymphocyte depletion and wound healing immune landscapes in (u)LMS, suggesting it contributes to immune evasion. In contrast, PI3K/mTOR inhibition induced profound tumour microenvironment remodelling in an ICB-resistant humanized uLMS PDX model, fostering adaptive anti-tumour immune responses. Indeed, PI3K/mTOR inhibition induced macrophage repolarisation towards an anti-tumourigenic phenotype and increased antigen presentation on dendritic and tumour cells, but also promoted infiltration of PD-1+ T cells displaying an exhausted phenotype. When combined with anti-PD-1, PI3K/mTOR inhibition led to partial or complete tumour responses, whereas no response to single-agent anti-PD-1 was observed. Combination therapy reinvigorated exhausted T cells and induced clonal hyper-expansion of a cytotoxic CD8+ T-cell population supported by a CD4+ Th1 niche. Our findings indicate that aberrant PI3K/mTOR pathway activation contributes to immune escape in uLMS and provides a rationale for combining PI3K/mTOR inhibition with ICB for the treatment of this patient population.

Single-cell transcriptome reveals highly complement activated microglia cells in association with pediatric tuberculous meningitis.

Tuberculous meningitis (TBM) is a devastating form of tuberculosis (TB) causing high mortality and disability. TBM arises due to immune dysregulation, but the underlying immune mechanisms are unclear. We performed single-cell RNA sequencing on peripheral blood mononuclear cells (PBMCs) and cerebrospinal fluid (CSF) cells isolated from children (n=6) with TBM using 10 xGenomics platform. We used unsupervised clustering of cells and cluster visualization based on the gene expression profiles, and validated the protein and cytokines by ELISA analysis. We revealed for the first time 33 monocyte populations across the CSF cells and PBMCs of children with TBM. Within these populations, we saw that CD4_C04 cells with Th17 and Th1 phenotypes and Macro_C01 cells with a microglia phenotype, were enriched in the CSF. Lineage tracking analysis of monocyte populations revealed myeloid cell populations, as well as subsets of CD4 and CD8 T-cell populations with distinct effector functions. Importantly, we discovered that complement-activated microglial Macro_C01 cells are associated with a neuroinflammatory response that leads to persistent meningitis. Consistently, we saw an increase in complement protein (C1Q), inflammatory markers (CRP) and inflammatory factor (TNF-α and IL-6) in CSF cells but not blood. Finally, we inferred that Macro_C01 cells recruit CD4_C04 cells through CXCL16/CXCR6. We proposed that the microglial Macro_C01 subset activates complement and interacts with the CD4_C04 cell subset to amplify inflammatory signals, which could potentially contribute to augment inflammatory signals, resulting in hyperinflammation and an immune response elicited by Mtb-infected tissues.

Relationship between the outcomes of intensive phase therapy in patients with newly diagnosed infiltrative pulmonary tuberculosis and activity of purine metabolism enzymes as well as CD3+CD8+ lymphocyte level

Monitoring activity of inflammatory process and lymphocyte subsets can help assess the effectiveness of intensive phase therapy (IPT) already in the early stages of treatment. The goal is to evaluate changes in the concentration and activity of enzymes associated with purine metabolism and peripheral blood lymphocyte subset composition, and to determine their relationship with IPT effectiveness in patients with newly diagnosed infiltrative pulmonary tuberculosis (IPTb). Materials and methods. In 141 IPTb patients, the IPT data were presented as follows: “significant improvement” (SI) — disappearance of intoxication symptoms, abacillation, closure of decay cavities; “less pronounced improvement” (LMI) — eliminated symptoms of intoxication, abacillation, pronounced resorption of focal and infiltrative changes, reduction of decay cavities. We assessed the activity of adenosine deaminase in blood serum (eADA-1, 2), mononuclear cells and neutrophils, the concentration of blood serum ecto-5'-nucleotidase (eHT5E), CD26 (DPPV) in blood serum (s, soluble form) and mononuclear cells (m, membrane form), subpopulation composition. Results. Patients exhibit increased concentrations of eNT5E, mCD26 (DPPIV) and eADA-2 activity, and decreased intracellular ADA-1 activity. In the “LMI” group, after IPT, an increased sCD26 (DPPV) level was noted. The groups differed in lymphocyte counts and percentage of CD3+CD8+ cells. eADA-2 activity was higher in the LMI group and increased after IPT, in contrast to comparison group. mCD26 (DPPIV) concentrations are higher in PD patients before therapy and after IPT. Conclusion. Thus, the outcome of IPT in IPTb patients is associated with altered T-lymphocyte populations and severity of the inflammatory process. Studying the activity of membrane and soluble eADA-2, CD26 (DPPIV) and percentage of CD3+CD8+ T-lymphocytes in the early stages of therapy can provide the necessary information for correcting personalized pathogenetic therapy of patients with newly diagnosed IPTb.

P124 Elucidating the role of risk variants in the BIM gene enhancer in T-Cell dysregulation and rheumatoid arthritis pathogenesis

Abstract Background/Aims The balance governing T-cell responses is pivotal for immune homeostasis. Disruptions to this balance may lead to aberrant behaviours, potentially resulting in autoimmunity. Rheumatoid Arthritis (RA), an autoimmune disorder primarily manifesting in the joints, is characterised by a defective immune response, resulting in chronic inflammation. Enhanced T-cell apoptosis resistance in this context can contribute to sustained activation and abnormal proliferation in a pro-inflammatory environment. Understanding these disease mechanisms could lead to improvements in clinical care. Genome-wide association studies (GWAS) have identified hundreds of single nucleotide polymorphisms (SNPs) associated with RA, preferentially enriched in non-coding, T-cell-specific putative enhancers. Enhancers are DNA elements that can regulate the transcription of specific genes, often from many kilobases away. Our previous work identified BCL2L11, or BIM, as the probable causal gene within the RA locus rs13396472, despite the GWAS variants' intronic positioning relative to ACOXL. The RA risk variant disrupts a distant enhancer regulating the BIM gene, pivotal for apoptosis. Given the role of apoptosis in immune tolerance, disruption of this pathway driven by RA risk variants could pave the way for autoimmune responses. Our aim was to investigate the effect of this enhancer on T-cell proliferation and function in an in vivo model. Methods We mapped the human RA-locus to the mouse genome and utilised CRISPR-Cas9 to delete this putative RA enhancer in mice. Two sgRNAs, combined with Cas9, were microinjected into C57BL6/J zygote pronuclei, followed by embryo transfer to pseudo-pregnant mice. PCR and Sanger sequencing confirmed enhancer deletion in pups, establishing an RA-enhancer deletion colony. To gauge cell proportion differences, murine splenocytes or thymocytes were stained with specific fluorochrome markers and analysed via a flow cytometer. For the antigen-induced arthritis (AIA) model, wildtype and RA-enhancer deletion mice were subjected to arthritis induction via intra-articular injection of methylated bovine serum albumin, following prior immunisation, and monitored for arthritis signs. Results We observed an increased CD4+CD8+ double positive (DP) T-cell population in aged mice homozygous and heterozygous for the RA-enhancer deletion, but not in younger and wild-type controls. Knockout mice exhibited visibly enlarged spleens in response to the immunisation step prior to AIA induction. Further work will establish the mechanisms underlying this and disease progression after arthritis induction. These observations underscore a potential impact this enhancer might have on immune responses and survival upon immune system alteration. Conclusion Our research indicates that perturbing mouse non-coding sequences syntenic to human GWAS loci can provide a physiological model to elucidate novel mechanisms underlying RA, potentially suggesting therapeutic targets. Future research will explore the mechanism by which the enhancer deletion leads to an increase in DP T-cells and the altered phenotype, and the implications of such a change for T- and B-cell biology and RA. Disclosure S. Rossi: None. E. Richards: None. J. Ding: None. C. Shi: None. M. Menon: None. J. Gibbs: None. R. Grencis: None. A. Adamson: None. G. Orozco: None.

OA36 Systemic juvenile idiopathic arthritis: the Great Ormond Street Hospital experience (2005-2021)

Abstract Background/Aims sJIA is a complex, systemic-inflammatory disorder. The proposed biphasic model of disease suggests that unchecked early auto-inflammation driven by increased innate immune activation, including dysregulation of IL-1 and IL-6, may lead to a state of chronic T-lymphocyte activation. This leads to an unfavourable balance of T-effector and regulatory cells that can drive chronic arthritis over time. It is therefore unsurprising that there is growing evidence to support instigation of IL-1 or IL-6 blockade as first-line treatment in sJIA. Early cytokine antagonist therapy could abrogate development of a population of these arthritis-causing T-cells to avert chronic systemic inflammation and arthritis. Aims: 1) describe clinical presentations, therapeutic interventions, complications, and remission rates at different time-points over disease course in sJIA; 2) identify potential therapeutic signals in patients with sJIA who received biologic treatment early in disease course compared to those who did not. Methods Retrospective review of all patients with sJIA at GOSH (02/10/05-21/10/21, inclusive). Data collected: patient demographics; clinical and laboratory data; treatment history; adverse events. Time-points for data collection: at diagnosis; 3-months; 1-year; last follow-up. Descriptive statistics reported as median and range or IQR for continuous variables, and as absolute frequencies and percentages for categorical variables. Comparisons of quantitative variables were made by Mann-Whitney U-test. Categorical data were compared using Fisher’s exact test (p-values<0.05 were considered significant). Results A total of 76 children (female n = 40, 53%) were diagnosed with sJIA; median age was 4.5 years (range 0.6-14.1). A biologic disease modifying anti-rheumatic drug (bDMARD) alone was commenced as first-line treatment in 28% (n = 21/76) of the cohort; however, at last review, 84% (n = 64/76) had received treatment with a bDMARD. Clinically inactive disease (CID) was achieved by 88% (n = 67/76) of the cohort at last review; however, only 32% (24/76) achieved treatment-free CID. At 1-year follow-up, CID was achieved in a significantly greater proportion of children who received treatment with a bDMARD within 3-months of diagnosis compared to those who did not (90% versus 53%, p = 0.002). Conclusion We propose a UK treatment-algorithm for children diagnosed with sJIA (see figure). We recommend reappraisal of the current NHS England commissioning policy. Disclosure C. Foley: None. D. McKenna: None. K. Gallagher: None. K. McLellan: None. H. Alkhdher: None. S. Lacassagne: None. E. Moraitis: None. C. Papadopoulou: None. C. Pilkington: None. M. Al Obaidi: None. D. Eleftheriou: None. P. Brogan: None.

Refined analytical pipeline for the pharmacodynamic assessment of T-cell responses to vaccine antigens.

Pharmacodynamic assessment of T-cell-based cancer immunotherapies often focus on detecting rare circulating T-cell populations. The therapy-induced immune cells in blood-derived clinical samples are often present in very low frequencies and with the currently available T-cell analytical assays, amplification of the cells of interest prior to analysis is often required. Current approaches aiming to enrich antigen-specific T cells from human Peripheral Blood Mononuclear Cells (PBMCs) depend on in vitro culturing in presence of their cognate peptides and cytokines. In the present work, we improved a standard, publicly available protocol for T-cell immune analyses based on the in vitro expansion of T cells. We used PBMCs from healthy subjects and well-described viral antigens as a model system for optimizing the experimental procedures and conditions. Using the standard protocol, we first demonstrated significant enrichment of antigen-specific T cells, even when their starting frequency ex vivo was low. Importantly, this amplification occurred with high specificity, with no or neglectable enrichment of irrelevant T-cell clones being observed in the cultures. Testing of modified culturing timelines suggested that the protocol can be adjusted accordingly to allow for greater cell yield with strong preservation of the functionality of antigen-specific T cells. Overall, our work has led to the refinement of a standard protocol for in vitro stimulation of antigen-specific T cells and highlighted its reliability and reproducibility. We envision that the optimized protocol could be applied for longitudinal monitoring of rare blood-circulating T cells in scenarios with limited sample material.

CD3 aptamers promote expansion and persistence of tumor-reactive T cells for adoptive T cell therapy in cancer

The CD3/TCR complex is responsible for antigen-specific pathogen recognition by T cells, and initiates the signaling cascade necessary for activation of effector functions. CD3 agonistic antibodies are commonly used to expand T lymphocytes in a wide range of clinical applications, including in adoptive T-cell therapy for cancer patients. A major drawback of expanding T-cell populations ex vivo using CD3 agonistic antibodies is that they expand and activate T cells independent of their TCR antigen specificity. Therapeutic agents that facilitate expansion of T cells in an antigen-specific manner and reduce their threshold of T-cell activation, are therefore of great interest for adoptive T-cell therapy protocols. To identify CD3-specific T-cell agonists, several RNA aptamers were selected against CD3 using SELEX combined with high-throughput sequencing. The extent and specificity of aptamer binding to target CD3 were assessed through SPR, P32 double filter assays and flow cytometry. Aptamer-mediated modulation of the threshold of T-cell activation was observed in vitro and in pre-clinical transgenic TCR mouse models. The aptamers improved efficacy and persistence of adoptive T-cell therapy by low affinity TCR-reactive T lymphocytes in melanoma-bearing mice. Thus, CD3-specific aptamers can be applied as therapeutic agents which facilitate the expansion of tumor-reactive T lymphocytes while conserving their tumor specificity. Furthermore, selected CD3 aptamers also exhibit cross-reactivity to human CD3, expanding their potential for clinical translation and application in the future.

IGF-1 Genome-Edited Human MSCs Exhibit Robust Anti-Arthritogenicity in Collagen-Induced Arthritis.

Stem cell therapy stands out as a promising avenue for addressing arthritis treatment. However, its therapeutic efficacy requires further enhancement. In this study, we investigated the anti-arthritogenic potential of human amniotic mesenchymal stem cells (AMM) overexpressing insulin-like growth factor 1 (IGF-1) in a collagen-induced mouse model. The IGF-1 gene was introduced into the genome of AMM through transcription activator-like effector nucleases (TALENs). We assessed the in vitro immunomodulatory properties and in vivo anti-arthritogenic effects of IGF-1-overexpressing AMM (AMM/I). Co-culture of AMM/I with interleukin (IL)-1β-treated synovial fibroblasts significantly suppressed NF-kB levels. Transplantation of AMM/I into mice with collagen-induced arthritis (CIA) led to significant attenuation of CIA progression. Furthermore, AMM/I administration resulted in the expansion of regulatory T-cell populations and suppression of T-helper-17 cell activation in CIA mice. In addition, AMM/I transplantation led to an increase in proteoglycan expression within cartilage and reduced infiltration by inflammatory cells and also levels of pro-inflammatory factors including cyclooxygenase-2 (COX-2), IL-1β, NF-kB, and tumor necrosis factor (TNF)-α. In conclusion, our findings suggest that IGF-1 gene-edited human AMM represent a novel alternative therapeutic strategy for the treatment of arthritis.

Metabolic priming of GD2 TRAC-CAR T cells during manufacturing promotes memory phenotypes while enhancing persistence

Manufacturing chimeric antigen receptor (CAR) Tcell therapies is complex, with limited understanding of how medium composition impacts Tcell phenotypes. CRISPR-Cas9 ribonucleoproteins can precisely insert a CAR sequence while disrupting the endogenous Tcell receptor alpha constant (TRAC) gene resulting in TRAC-CAR Tcells with an enriched stem cell memory Tcell population, a process that could be further optimized through modifications to the medium composition. In this study we generated anti-GD2 TRAC-CAR Tcells using "metabolic priming" (MP), where the cells were activated in glucose/glutamine-low medium and then expanded in glucose/glutamine-high medium. Tcell products were evaluated using spectral flow cytometry, metabolic assays, cytokine production, cytotoxicity assays invitro, and potency against human GD2+ xenograft neuroblastoma models invivo. Compared with standard TRAC-CAR Tcells, MP TRAC-CAR Tcells showed less glycolysis, higher CCR7/CD62L expression, more bound NAD(P)H activity, and reduced IFN-γ, IL-2, IP-10, IL-1β, IL-17, and TGF-β production at the end of manufacturing exvivo, with increased central memory CAR Tcells and better persistence observed invivo. MP with medium during CAR Tcell biomanufacturing can minimize glycolysis and enrich memory phenotypes exvivo, which could lead to better responses against solid tumors invivo.