Expression Of Activation Markers Research Articles

Sufficiently activated mature natural killer cells derived from peripheral blood mononuclear cells substantially enhance antitumor activity.

Peripheral blood-derived natural killer (NK) cells spontaneously lyse tumor cells without prior sensitization. However, NK cells in peripheral blood (PBNK cells) are in a resting state and exhibit inhibitory phenotypes and impaired cytotoxicity. Thus, strengthening the cytotoxic effector function of PBNK cells and improving NK cell expansion in vitro for a convenient allogeneic therapy are essential. Pure cytokine activation and expansion of NK cells (super NK [SNK])from peripheral blood mononuclear cells were studied. Markers of activated and inhibited NK cells and cytokine secretion by NK cells were examined using flow cytometry. NK cell antitumor activity in vitro was assessed using lactate dehydrogenase (LDH) cytotoxicity assay and an Incucyte real-time imaging system. Additionally, the function of SNK cells against ascites caused by ovarian cancer in NOD-Prkdc(em26Cd52)il2rg(em26Cd22)/Nju (NCG)mice was determined. In a further investigation of the differences between PBNK and SNK, the mRNA of both cells was sequenced and analyzed. Human peripheral blood mononuclear cells showed selective NK cell expansion upon cytokine activation and culture. Both SNK and PBNK cells expressed activation markers, but at different levels, and SNK cells secreted more cytokines related to cytotoxicity than PBNK cells did. Accordingly, SNK cells exhibited strong antitumor activity ex vivo and improved NCG mice survival after intraperitoneal ovarian cancer transplantation. Mechanistically, SNK cells expressed more genes associated with nucleotide metabolism, fatty acid, and ATP metabolism than PBNK cells. SNK cells derived from peripheral blood mononuclear cells have sufficiently activated mature characteristics and high antitumor activity, rendering them a highly promising and essential therapeutic approach for cancer treatment.

Hyperactive Natural Killer cells in Rag2 knockout mice inhibit the development of acute myeloid leukemia

Immunotherapy has attracted considerable attention as a therapeutic strategy for cancers including acute myeloid leukemia (AML). In this study, we found that the development of several aggressive subtypes of AML is slower in Rag2−/− mice despite the lack of B and T lymphocytes, even compared to the immunologically normal C57BL/6 mice. Furthermore, an orally active p53-activating drug shows stronger antileukemia effect on AML in Rag2−/− mice than C57BL/6 mice. Intriguingly, Natural Killer (NK) cells in Rag2−/− mice are increased in number, highly express activation markers, and show increased cytotoxicity to leukemia cells in a coculture assay. B2m depletion that triggers missing-self recognition of NK cells impairs the growth of AML cells in vivo. In contrast, NK cell depletion accelerates AML progression in Rag2−/− mice. Interestingly, immunogenicity of AML keeps changing during tumor evolution, showing a trend that the aggressive AMLs generate through serial transplantations are susceptible to NK cell-mediated tumor suppression in Rag2−/− mice. Thus, we show the critical role of NK cells in suppressing the development of certain subtypes of AML using Rag2−/− mice, which lack functional lymphocytes but have hyperactive NK cells.

HIF-1α/MMP-9 Axis Is Required in the Early Phases of Skeletal Myoblast Differentiation under Normoxia Condition In Vitro.

Hypoxia-inducible factor (HIF)-1α represents an oxygen-sensitive subunit of HIF transcriptional factor, which is usually degraded in normoxia and stabilized in hypoxia to regulate several target gene expressions. Nevertheless, in the skeletal muscle satellite stem cells (SCs), an oxygen level-independent regulation of HIF-1α has been observed. Although HIF-1α has been highlighted as a SC function regulator, its spatio-temporal expression and role during myogenic progression remain controversial. Herein, using biomolecular, biochemical, morphological and electrophysiological analyses, we analyzed HIF-1α expression, localization and role in differentiating murine C2C12 myoblasts and SCs under normoxia. In addition, we evaluated the role of matrix metalloproteinase (MMP)-9 as an HIF-1α effector, considering that MMP-9 is involved in myogenesis and is an HIF-1α target in different cell types. HIF-1α expression increased after 24/48 h of differentiating culture and tended to decline after 72 h/5 days. Committed and proliferating mononuclear myoblasts exhibited nuclear HIF-1α expression. Differently, the more differentiated elongated and parallel-aligned cells, which are likely ready to fuse with each other, show a mainly cytoplasmic localization of the factor. Multinucleated myotubes displayed both nuclear and cytoplasmic HIF-1α expression. The MMP-9 and MyoD (myogenic activation marker) expression synchronized with that of HIF-1α, increasing after 24 h of differentiation. By means of silencing HIF-1α and MMP-9 by short-interfering RNA and MMP-9 pharmacological inhibition, this study unraveled MMP-9's role as an HIF-1α downstream effector and the fact that the HIF-1α/MMP-9 axis is essential in morpho-functional cell myogenic commitment.

Tonabersat Significantly Reduces Disease Progression in an Experimental Mouse Model of Multiple Sclerosis.

Multiple sclerosis (MS) is a neurodegenerative disease marked by chronic neuroinflammation thought to be mediated by the inflammasome pathway. Connexin 43 (Cx43) hemichannels contribute to the activation of the inflammasome through the release of adenosine triphosphate (ATP) inflammasome activation signals. The objective of the study was to evaluate if the Cx43 hemichannel blocker, tonabersat, is effective in modulating the inflammatory response and reducing disability in the myelin oligodendrocyte glycoprotein 35-55-induced experimental autoimmune encephalomyelitis (MOG35-55 EAE) model of MS. Here, we show that the Cx43 hemichannel blocking drug, tonabersat, significantly reduced expression of neuroinflammatory markers for microglial activation (ionized calcium-binding adapter molecule 1 (Iba1)) and astrogliosis (glial fibrillary acidic protein (GFAP)) while preserving myelin basic protein (MBP) expression levels in the corpus callosum, motor cortex, and striatum regions of the brain in MOG35-55 EAE mice. Reduced NOD-like receptor protein 3 (NLRP3) inflammasome complex assembly and Caspase-1 activation confirmed the drug's mode of action. MOG35-55 EAE mice showed clinical signs of MS, but MOG35-55 EAE mice treated with tonabersat retained behavior closer to normal. These data suggest that clinical trial phase IIb-ready tonabersat may merit further investigation as a promising candidate for MS treatment.

SARS-CoV-2 antigen-carrying extracellular vesicles activate T cell responses in a human immunogenicity model

Extracellular vesicles (EVs) are entering the clinical arena as novel biologics for infectious diseases, potentially serving as the immunogenic components of next generation vaccines. However, relevant human assays to evaluate the immunogenicity of EVs carrying viral antigens are lacking, contributing to challenges in translating rodent studies to human clinical trials. Here, we engineered EVs to carry SARS-CoV-2 Spike to evaluate the immunogenicity of antigen-carrying EVs using human peripheral blood mononuclear cells (PBMCs). Delivery of Spike EVs to PBMCs resulted in specific immune cell activation as assessed through Tcell activation marker expression. Further, Spike EVs were taken up largely by antigen-presenting cells (monocytes, dendritic cells and B cells). Taken together, this human PBMC-based system models physiologically relevant pathways of antigen delivery, uptake and presentation. In summary, the current study highlights the suitability of using human PBMCs for evaluating the immunogenicity of EVs engineered to carry antigens for infectious disease therapeutics.

Abstract A173: ASP2074, a novel tetraspanin 8 x CD3 bispecific antibody, demonstrates selectivity and antitumor activity in preclinical cancer models

Abstract ASP2074 is a novel bispecific antibody that targets the tumor-associated antigen tetraspanin 8 (TSPAN8) and CD3, which is expressed on the plasma membrane of all T cells. By engaging with both TSPAN8 and CD3, ASP2074 enables the retargeting of cytotoxic T cells specifically against TSPAN8-expressing tumor cells in a human leukocyte antigen-independent manner. TSPAN8 is a member of the tetraspanin superfamily of proteins that plays a crucial role in intracellular signal transduction and regulates various cellular functions, including leukocyte trafficking, angiogenesis, and wound repair. TSPAN8 is highly expressed in various types of cancer, such as colorectal cancer, gastric cancer, pancreatic cancer, esophageal adenocarcinoma, and gastroesophageal junction (GEJ) adenocarcinoma. Its overexpression has been associated with tumor cell growth, angiogenesis, invasion, metastasis, and poor prognosis, making it an attractive target for antibody-based cancer immunotherapy. ASP2074 is currently undergoing phase 1 clinical trials for the treatment of patients with colorectal cancer, esophageal adenocarcinoma, pancreatic cancer, gastric cancer, and GEJ adenocarcinoma. In this study, we examined the selectivity and antitumor activity of ASP2074 in vitro and in vivo. Methods: Retrogenix Cell Microarray Technology was used to evaluate the selective binding of ASP2074 to TSPAN8 and CD3 in 6018 full-length human plasma membrane proteins, secreted and cell surface-tethered human secreted proteins, and 397 human heterodimers containing homologs and isoforms of tetraspanin. Cytotoxicity and T-cell activation of ASP2074 were examined using TSPAN8-expressing tumor cells in combination with human peripheral blood mononuclear cells (PBMCs) as effector cells in a redirected T-cell cytotoxicity assay. Furthermore, the antitumor effect of ASP2074 was examined in a human PBMC-engrafted NOG mouse model bearing human TSPAN8-expressing colorectal cancer cells. Results: Our results showed that ASP2074 selectively bound to TSPAN8 and CD3 without significant binding to other human plasma membrane proteins, secreted proteins, and heterodimers. ASP2074 exhibited cytotoxicity against TSPAN8-expressing cancer cells and increased interferon-gamma production and expression of T-cell activation markers. The cytotoxic activities were dependent on the TSPAN8 expression levels in tumor cells. In the NOG mouse model, ASP2074 exhibited an antitumor effect on human TSPAN8-expressing colorectal cancer cells in vivo. Conclusion: Our findings suggest that ASP2074 has potent antitumor activity through cytotoxicity against TSPAN8-expressing tumor cells by T-cell activation via selective binding to TSPAN8 and CD3. These preclinical results support the continued development of ASP2074 as a promising immunotherapy for the treatment of TSPAN8-expressing cancers. Citation Format: Yoshiyuki Tenda, Yuichi Hanada, Hiroaki Tanaka, Masashi Shimazaki, Kenna Shirasuna. ASP2074, a novel tetraspanin 8 x CD3 bispecific antibody, demonstrates selectivity and antitumor activity in preclinical cancer models [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr A173.

Inhibition of mitochondrial carbonic anhydrases prevents Amyloid β‐induced cell death and blood brain barrier permeability in cerebrovascular endothelial cells

AbstractBackgroundThe Neurovascular Unit (NVU) is an important multicellular structure of the central nervous system (CNS) which has been observed to become dysfunctional in Alzheimer Disease (AD) and cerebral amyloid angiopathy (CAA). Amyloidosis disrupts the function of cerebrovascular endothelial cells (ECs) through the activation of the intrinsic apoptotic pathway, and the induction of blood brain barrier (BBB) permeability. Previous findings in our lab demonstrate that Acetazolamide (ATZ) and methazolamide (MTZ), pan‐Carbonic Anhydrase (CA) inhibitors, prevent mitochondria mediated apoptosis in cerebrovascular ECs through the reduction of Aβ induced cytochrome C release from the mitochondria, caspase‐9 activation, and mitochondrial H2O2 production. Due to the reduction of mitochondria mediated cell death via pan‐CA inhibitors we hypothesize that the mitochondrial isoforms, CA‐VA/B, are involved in cell death and other deleterious mechanisms induced by Aβ. Thus, we anticipate using selective CA‐V inhibitors will reduce cerebrovascular EC apoptosis and prevent the loss of BBB resistance.MethodHuman cerebral microvascular ECs (hCMECs) were treated with Aβ40‐Q22 Dutch mutant alone and in combination with a CA‐V inhibitor. We measured outcomes of mitochondria mediated apoptosis and BBB integrity. Apoptosis was evaluated by measuring the changes in the protein expression of caspase‐9, BAX, and BCL‐2 with western blot. We used live‐cell imaging to measure active caspase‐3. The release of cytochrome C and the mitochondrial membrane potential was detected using immunocytochemistry (ICC). Mitochondria H2O2 production was measured by isolating mitochondria and using a commercially available kit, Amplex Red (Invitrogen). We assessed the permeability of hCMECs using the ECIS ZΘ technology. The changes in protein expression of EC activation markers, VCAM‐1 and ICAM‐1, were determined with western blot.ResultInhibition of CA‐VA/B prevented Aβ40‐Q22 induced DNA fragmentation, caspase‐9 and ‐3 activation, cytochrome C release from the mitochondria, loss of mitochondria membrane potential, and mitochondrial H2O2 production in human cerebrovascular ECs. The inhibition of CA‐VA/B also reduced Aβ40‐Q22 induced BBB permeability and increase in vascular adhesion protein VCAM‐1 in hCMECs.ConclusionThe inhibition of CA‐V is protective to cerebrovascular ECs in models of amyloidosis, through the prevention of mitochondria‐mediated cell death and loss of cerebral EC barrier function.

Influence of physiological glucose levels on SIM‐A9 microglial cell immune response

AbstractBackgroundMicroglia play an important role in the early onset of Alzheimer’s disease pathology1. They are responsible for maintaining brain homeostasis, where changes in energy metabolism alter microglial metabolic profile and function2. The majority of cell culture‐based studies have relied on growing microglia under optimal media conditions, not reflecting the brain’s physiological levels of key metabolites. This study aims to define a suitable experimental culture system that reflects the brain’s physiological glucose level, approximately 1mM3, so the effects of altered glucose concentration can be tested.MethodSIM‐A9 mouse immortalised microglial cells were initially grown in DMEM/F‐12 medium (17.5mM glucose) containing 10% FBS and 0.1% Penicillin/Streptomycin (Gibco, UK). After 20 hours cells were re‐seeded in Neurobasal medium containing 1x B‐27 supplement (Gibco, UK) and either 1mM or 5mM glucose and grown for 20 hours. Cell proliferation and viability was assessed over 40 hours using an Incucyte imaging system (Essen BioScience, UK) and Trypan Blue assay. Media glucose concentration, cellular glucose uptake (Promega, UK), microglia activation and metabolic marker expression using qRT‐PCR were measured following stimulation of cells with Lipopolysaccharide (LPS) (2.5ng/ml)ResultMaintaining SIM‐A9 cells in 1mM and 5mM glucose medium showed static proliferation but similar viability over 20 hours compared to growth in DMEM/F12. LPS treatment increased TNFa and IL1b expression in SIM‐A9 cells in all glucose conditions, indicating the cells’ competency to produce a pro‐inflammatory response. No change in pro‐inflammatory activation markers (TNFa, IL1b) was seen after maintenance in 1mM, but in 5mM glucose for 20 hours, compared to LPS treated cells. Media glucose concentration was 0.7mM over 20 hours in 1mM and 1mM in 5mM glucose media. Expression of glucose transporters Glut1 and Glut3 and glycolysis marker PFKFB3 under these glucose conditions was investigated.ConclusionUntil now microglial metabolic studies have not always reflected the physiological concentrations of glucose in the brain. The results show that culturing microglia in 1mM glucose medium does not induce pro‐inflammatory activation, while maintaining minimal cell death and unvaried confluency.

CD8+ T cells in fetal membranes display a unique phenotype, and their activation is involved in the pathophysiology of spontaneous preterm birth.

Preterm labor/birth is the leading cause of perinatal mortality and morbidity worldwide. Previous studies demonstrated that T cells were crucial for maintaining maternal-fetal immune tolerance during the first trimester of pregnancy; however, their phenotypes and functions in labor and delivery remain largely unknown. We recruited three cohorts of women at delivery for T-cell immunophenotyping in the placentas, fetal membranes, umbilical cord blood, and maternal peripheral blood. Our data showed a differential enrichment of T cells during the third trimester of human pregnancy, with CD4+ T cells being more observable within the umbilical cord blood, whereas CD8+ T cells became relatively more abundant in fetal membranes. CD4+ and CD8+ T cells derived from fetal membranes were dominated by effector memory T cells and exhibited extensive expression of activation markers but decreased expression of homing receptor. In comparison with term births, fetal membrane CD8+ T cells, especially the central memory subset, were significantly increased in frequency and showed more profound activation in spontaneous preterm birth patients. Finally, using an allogeneic mouse model, we found that T-cell-activation-induced preterm birth could be alleviated by the depletion of CD8+ T but not CD4+ T cells in vivo. Collectively, we showed that CD8+ T cells in fetal membranes displayed a unique phenotype, and their activation was involved in the pathophysiology of spontaneous preterm birth, which provides novel insights into the immune mechanisms of preterm birth and potential targets for the prevention of this syndrome. © 2023 The Pathological Society of Great Britain and Ireland.

Macrophages Play a Key Role in Controlling Tumor Growth and Response to Immunotherapy in Primary Central Nervous System Lymphoma

Introduction Primary Central Nervous System Lymphoma (PCNSL) represents 5% of extranodal lymphomas. Current treatments include high-dose chemotherapy in combination with an anti-CD20 antibody, and whole-brain radiation, both of which are limited by their toxicity. Although some advances have been achieved during the last few years, the prognosis of patients with CNS lymphoma is substantially worse than those with other type of lymphomas, with 5-year survival rates around 30%. The highly aggressive nature of CNS lymphomas is in part due to the fact that the brain is an immunoprivileged organ; it presents very low levels of immunosurveillance, which contributes to inefficient immune responses against malignant cells. Of note, up to 70% of patients diagnosed with PCNSL also exhibit genetic alterations to avoid recognition by the immune system, like loss of MHC-I, that prevent presentation of tumor antigens, and amplifications in PD-L1, which increase the negative stimuli in cytotoxic T cells. The PD-1/PD-L1 interaction has mainly been considered to be a checkpoint that regulates T cells. However, it has recently been found that tumor-associated macrophages can also express PD-1 and become activated to attack tumor cells when it is blocked. Moreover, macrophages have also been found to be inhibited by MHC-I expression on cancer cells. Thus, cancer cells that downregulate MHC-I to avoid T cell surveillance are particularly vulnerable to macrophages phagocytosis, especially when other macrophage immune checkpoints are blocked, such as CD47. Against this background, we aimed to decipher the differential role of macrophages and T cells in the tumor growth and response to immunotherapy in primary CNS lymphoma. Methods Luciferase-expressing A20 murine B-cell lymphoma cells were genetically modified to knock-out MHCI or MHCII by CRISPR-Cas9 and injected into the brain of immunocompetent (IC) or macrophage-depleted (MD) mice. Once tumours were stablished, mice were treated intravenously with seven injections, twice a week, of anti-PD1, anti-CD47 or the combination of both. We monitored mice for survival and tumoral growth. Additionally, brains were collected from mice treated with three injections for analysis of macrophages, B cells and T cells using flow cytometry and IHC. Results In IC mice, all anti-PD1 treated mice showed significant differences in tumoral growth and survival compared to vehicle; however, MHCI- tumors had the lowest overall survival (Figure 1A). With anti-CD47 therapy, only MHCI- PCNSL mice had a significantly increased survival compared to vehicle. Combination was effective in all groups, but no drug synergy was seen. In MD mice, all tumors were more aggressive than in IC mice. With anti-PD1, MHCI+ PCNSL mice achieved a complete tumor regression and survived longer in comparison to vehicle. On the contrary, MHCI- PCNSL mice didn't respond to anti-PD1 therapy (Figure 1B). Of notice, MHCI+ PCNSL in both MD and IC models had a higher infiltration of active T cells when treated with anti-PD1. In MHCI- PCNSL, infiltrated T cells had less expression of activation markers in both models and macrophages were polarized to an M2 phenotype in IC mice. Conclusions Our study revealed a remarkable response to anti-PD1 therapy in MHCI+ CNS lymphoma tumors, regardless of the presence of macrophages in the tumor microenvironment. This indicates that T cells would be primarily responsible for the observed tumour regression. However, targeting CD47 in MHCI+ PCNSL was found to be insufficient in restoring macrophage phagocytosis. Despite observing positive effects of anti-PD1 and anti-CD47 drugs in our MHCI- immunocompetent mouse model, MHCI downregulation still induces a very aggressive, lethal disease. This suggests that these tumors can only be controlled by macrophages, as supported by the lack of treatment response in a MD microenvironment. Our findings highlight the critical role of macrophages in controlling the growth of lymphoma cells in the brain and their significance in the immunotherapy response for CNS lymphomas, particularly when MHCI expression is deficient. Blocking PD1 exhibits superior efficacy when macrophages are present, indicating T cells are not the only player in this tumoral scenario. As a result, our study suggests that a promising approach for treating primary CNS lymphomas would involve targeting both T cells and macrophages.

The Effect of Voxelotor on Erythrocyte Deformability, Neutrophil Phenotype and Endothelial Activation

Introduction Sickle cell disease (SCD) is characterized by chronic intravascular hemolysis, caused by polymerization of abnormal sickle hemoglobin. The ongoing intravascular hemolysis leads to release of cell-free heme and iron, resulting in widespread oxidative damage, inflammation, neutrophil activation, endothelial activation and hypercoagulability, all contributing to vaso-occlusive events and end organ damage. Voxelotor, a small molecule reversibly binding to hemoglobin S (HbS) increases its oxygen affinity, thereby decreasing HbS polymerization and sickling, resulting in decreased hemolysis. The decrease in erythrocyte sickling might lead to improved erythrocyte deformability and decreased adhesion, while reductions in cell-free heme and labile plasma iron levels might result in decreased neutrophil activation, adhesion and aging and decreased endothelial activation. The aim of this study is to assess the effects of voxelotor on erythrocyte deformability, neutrophil activation, adhesion and aging and endothelial activation. Methods SCD patients (HbSS and HbSβ 0-thalassemia), with hemoglobin (Hb) ≤ 10.5 g/dL were treated with voxelotor 1500 mg in a single arm interventional study. Blood was collected at baseline and after 3 months of treatment. Erythrocyte deformability was assessed by ektacytometry (Lorrca, RR mechatronics), measuring elongation index (EI) and point of sickling (PoS). EI max and EI min indicate the highest and lowest erythrocyte deformability upon oxygenation and deoxygenation respectively. PoS is the oxygen tension at which 5% reduction of the EI max is observed. Antigen expression of neutrophil markers for activation, adhesion and aging were assessed with flow cytometry. Reactive oxygen species (ROS) production of neutrophils was measured by Amplex Red Assay (Molecular probes), measuring hydrogen peroxide (H 2O 2) production under unstimulated and stimulated (zymosan, streptozotocin (STZ), factor-n-formyl-MET-LEU-Phe (fMLP), Phorbol myristate acetate (PMA)) and platelet-activating factor-fMLP (PAF-fMLP)). Endothelial activation was assessed by measuring von Willebrand Factor antigen (vWF-Ag) using enzyme-linked immunosorbent assay (ELISA) (Glostrup). Prothrombin fragment 1+2 (F 1+2), thrombin-antithrombin complexes (TAT) and D-dimer were measured using ELISA. Data are presented as median with interquartile range (IQR), unless stated otherwise. A P value of <0.05 was considered significant. Results 15 SCD patients (11 HbSS, 4 HbSβ 0-thalassemia), 5 female, median age 35 years (IQR 27-46)) completed 3-month follow-up. Hb levels increased significantly after 3 months of treatment (from 7.4 (6.9 - 8.1) g/dL to 9.7 (7.9 - 11.0) g/dL, p=0.002), corresponding to significant decreases in LDH and bilirubin levels and reticulocyte counts as markers of hemolysis (p<0.05). PoS decreased significantly after 3 months (from 20.1 (17.5 - 26.1) mmHg to 16.1 (10.3 - 18.1) mmHg, p=0.006). Both EI max and EI min increased after 3 months of treatment (from 0.33 (0.24 - 0.42) to 0.38 (0.28 - 0.48), p=0.029 and from 0.13 (0.07 - 0.26) to 0.21 (0.16 - 0.41), p=0.007 respectively). Markers of neutrophil activation, adhesion and aging were generally lower after 3 months of treatment, though the differences were not statistically significant (Figure 1 A-C). Neutrophil ROS production in both unstimulated and stimulated condition remained unchanged (Figure 1D). After 3 months of treatment vWF-Ag significantly decreased (from 252 (187 - 284) % to 183 (153-205) %, p = 0.033). No changes were observed in markers of coagulation activation (F 1+2 and TAT, and D-dimer). Conclusion Voxelotor significantly improved erythrocyte deformability as suggested by decreased PoS and increased EI max and EI min, potentially leading to improved rheological properties. While markers of neutrophil activation seem to decrease, the differences are not statistically significant, possibly due to the relatively small sample size. A reduction in vWF-Ag was observed possibly reflecting diminished endothelial activation, due to a decrease in intravascular hemolysis.

Immune Profiling of Respiratory Syncytial Virus (RSV) for the Development of Targeted Immunotherapy

Introduction: RSV-associated respiratory viral infections are a major public health problem affecting the immunologically naïve/compromised population. For example, RSV-induced bronchiolitis and pneumonia are the leading cause of hospitalization in infants and young children worldwide, while in adult allogeneic hematopoietic transplant (HCT) recipients the incidence of progression from upper to lower respiratory tract infection (LRTI) is 40-60%, with mortality rates as high as 80%. At the national level, the Fall 2022-Spring 2023 RSV surge translated into a sharp rise in hospitalization rates surpassing last season's respective rate by almost 5-fold (https://www.cdc.gov/rsv/research/rsv-net). Our group has previously demonstrated the feasibility, safety and clinical efficacy of administering allogeneic ex vivo expanded multivirus-specific T cells (multi-VSTs) as a banked, off-the-shelf product for the treatment of EBV, CMV, BKV, HHV6, AdV and SARS-CoV-2 infections/disease in immunocompromised individuals. Given the RSV-associated morbidity and the paucity of therapeutic agents, we sought to characterize the cellular immune responses to RSV with a view to developing a targeted T-cell therapy product for those at highest risk of severe disease (i.e. HCT recipients, elderly/immunocompromised patients). Methods: To first identify immunogenic and protective RSV antigens we exposed PBMCs from healthy adult donors to pepmixes (overlapping peptide libraries) spanning the 11 RSV-encoded antigens and found that 7 induced highly reactive T cells. However, Nucleoprotein (N) and Fusion Protein (F) proved to be immunogenic in all donors and were thus advanced for VST manufacturing. We subsequently utilized our optimized VST manufacturing process and culture in a G-Rex device in medium supplemented with activating cytokines to generate RSV-specific VSTs (RSV-STs) with activity against this combination of immunodominant targets. Results: We achieved a mean 5.2±1-fold expansion (mean±SEM; n=13) of cells that were comprised almost exclusively of CD3+ T cells (94.08±1.15%), with a mixture of cytotoxic (CD8+; 28.91±5.16%) and helper (CD4+; 71.09±5.15%) T cells. These cells had a phenotype consistent with effector function and memory potential, as evidenced by upregulation of the activation markers CD25, CD69, and CD28 and expression of central (CD45RO+/CD62L+) and effector memory markers (CD45RO+/CD62L-) with minimal expression of exhaustion-related markers such as PD1, Tim3 and LAG3. The anti-viral activity of the expanded cells was confirmed in an IFNγ ELISpot using both stimulating antigens as an immunogen and all lines proved to be reactive against the target antigens (N: 3587±939 SFC/2x10 5; F: 3526±743). As demonstrated by surface and intracellular flow cytometry, the immune response was mediated by both CD4+ and CD8+ T cell subsets through IFNγ/TNFα production and upregulation of activation/costimulatory markers. Reactive cells were polyfunctional and primarily Th1-polarized as evidenced by IFNγ, Granzyme-B, IL-2 and GM-CSF production measured by FluoroSpot and Luminex array. Finally, the expanded cells were able to kill viral pepmix-loaded autologous PHA blasts with minimal/no activity against non-antigen-expressing autologous and allogeneic targets. Conclusion: Healthy donor-derived RSV-STs are Th1-polarized, polyfunctional and selectively able to kill viral antigen-expressing targets with no auto- or alloreactivity, indicative of their safety for clinical use. A clinical trial evaluating their safety and activity in HCT recipients as part of an off-the-shelf multi-respiratory virus-directed product is currently underway (NCT04933968, https://clinicaltrials.gov).

4-1bb Enrichment Enhances Adoptive T Cell Therapy for Hematological Malignancies Using a Novel Approach for Ex Vivo Immune Cell Priming with DC/Tumor Fusion Vaccine

Introduction: While CAR T cells have transformed outcomes for patients with hematologic malignancies, application to patients with acute myeloid leukemia (AML) is limited by lack of surface antigens that differentiate between malignant and normal hematopoietic precursors. We have developed a personalized vaccine created by fusion of patient-derived tumor with autologous dendritic cells (DCs). The vaccine presents an array of tumor antigens stimulating polyclonal immunity. In a phase II clinical trial of patients with AML in first remission, vaccination with DC/AML fusions resulted in expansion of leukemia specific T cells associated with durable disease remission. The ex vivo generation of vaccine educated T cells provides a powerful substrate of effector cells for adoptive immunotherapy that are selective and capture tumor heterogeneity. This novel adoptive cell therapy enhances T-cell potency with potential to mediate disease regression. Enrichment of vaccine-educated T cells for activated antigen-specific effector cells via agonistic 4-1bb antibody-based selection further enhances for activation and memory cell phenotype; superior T cell efficacy was observed in AML and MM models. Methods: DC/tumor fusion vaccines were generated from C57BL/6J mice DCs and syngeneic C1498 mCh/luc + AML cells or C57BL/KaLwRij and syngeneic 5TGM1 mCh/luc + MM cells, respectively. T cells isolated from spleen were co-cultured with autologous irradiated DC/tumor fusions in presence of IL-2/7/15. Vaccine-educated T cells underwent selection with agonistic 4-1bb (3H3) followed by expansion with anti-CD3/CD28 activation beads. T cells were phenotyped for markers of activation (CD25/CD69), immune checkpoint (PD1/LAG3/TIM3), and memory (CD44+CD62L-) and for enrichment (anti-rat H&L). Cytotoxicity was evaluated on luminescent assay. Mice engrafted with C1498 mCh/luc + received the T cell therapy 7 days later. Disease progression and survival was monitored for 100 days by BLI. Results: In the C1498 model, vaccine-educated T cells demonstrated evidence of immune activation (CD25+CD69+) and memory (CD44+CD62L-) phenotype compared to unstimulated naïve T-cell controls (TN) (4-fold, p=0.1143; 1.3-fold, p=0.0195, respectively). Vaccine-educated T cells selected based on 4-1bb expression showed 9-fold higher expression of activation markers (p=0.0034) while memory markers were 4.4-fold higher compared to TN (p=0.0274). Selection enriched for 4-1bb + vaccine-educated T cells resulting in enhanced antigen-specific recognition as measured by induction of IFNg expression. Tumor specificity and activation was maintained following CD3/CD28-mediated expansion. The 4-1bb positive vaccine-educated T cells showed 11-fold enhanced cytotoxicity compared to TN at 10:1 E:T (P=0.0005), while vaccine-educated T cells showed 4-fold increase (P=0.0226). Phenotypic and functional analysis support 4 days as the optimal duration of time for T-cell vaccine education. Cell fold-expansion supports 3-5 days as the optimal duration for anti-CD3/CD28 expansion. In vivo, 60% of mice treated with 4-1bb + vaccine-educated cells were alive at 60 days vs 20% treated with unselected vaccine-educated cells. In the 5TGM1 model, activation, memory, immune checkpoint phenotype and cytotoxicity were increased in vaccine-educated T cells selected for 4-1bb expression. Conclusion: Vaccine-educated T cells represent a unique platform for adoptive immunotherapy for AML further enhanced by selection for 4-1bb expression by agonistic antibody. T-cell stimulation by fusion vaccine and subsequent enrichment by agonistic 4-1bb selection enhances cytotoxicity, activation and memory cell phenotype. Thus, ex vivo vaccine stimulation and 4-1bb selection presents a novel approach for cell-based immunotherapy for AML.

RRMM and Post-BCMA Treated Subjects from the CC-220-MM-001 Study Show Increased Genomic Aberrations Associated with High-Risk and Significant Dysfunction in CD4+ T-Cell Compartment Compared to NDMM Subjects

Introduction Outcomes for patients with multiple myeloma (MM) have improved significantly through development of novel therapeutics, including immunomodulatory agents (IMiDs ®), proteasome inhibitors, anti-CD38 monoclonal antibodies and new BMCA targeting T-cell redirecting therapies. While most MM patients respond well to initial therapy, over time their disease relapses, requiring several subsequent lines of treatment. However, how patient tumors and immune profiles evolve over lines of treatment and how this may impact the efficacy of subsequent treatment regimens remains poorly understood. CC-220-MM-001 is a multicohort, phase 1/2 trial (NCT02773030) studying the efficacy of iberdomide (CC-220; a cereblon [CRBN] E3 ligase modulator) as monotherapy, and in combination with other treatments in subjects with newly diagnosed MM (NDMM) or relapsed/refractory MM (RRMM), including patients who have received prior BCMA targeting agents. This study allows uniform comparison of immune and tumor biomarkers across these clinical patient segments. Methods Baseline samples collected in the CC-220-MM-001 study prior to iberdomide treatment included peripheral blood for immunophenotyping, bone marrow biopsies for immunohistochemistry and CD138+ enriched bone marrow aspirates for genomic analysis. Biomarkers were evaluated for differences between NDMM subjects and subjects refractory to IMiD agents, proteasome inhibitors, anti-CD38 antibodies, and BCMA targeting CAR-T and T-cell engager therapies. Results Analysis of immune profiles showed NDMM subjects had a less immunodeficient profile compared to RRMM subjects, particularly in the CD4+ compartment, with significantly more total and naïve CD4+ T-cells (p<0.001) and significantly lower proportion of PD-1+ CD4+ T-cells (p=0.002) and CD4+ Tregs (p=0.005). RRMM subjects had median levels of several immune cells well below the lower limit of normal (LLN) reference range for healthy individuals, including low B cells, NK-cells, and total CD3+ and CD4+ (but not CD8+) T-cells. Median number of CD4+ T-cells was approximately half of the LLN (500 cells/mL) and median ratio of CD4+ to CD8+ T-cells was ~0.75. Phenotypic assessment of immune cells in RRMM subjects showed evidence of immune stimulation with >30% T-cells expressing activation markers (HLA-DR+ and ICOS+) and exhibiting a memory phenotype (CD45RO+). In contrast, a low proportion of pre-treatment T-cells were observed to be in a proliferative state (Ki-67+; median 6.2% of CD3+) despite evidence of activation, and more than 1/3 of both CD4+ and CD8+ cells in RRMM subjects expressed PD-1, together suggesting T-cell dysfunction and/or exhaustion. These results were mostly consistent regardless of prior refractoriness to IMiDs and PIs. Conversely, subjects post anti-CD38 had lower levels of NK and CD38+ T-cells (p<0.001) and subjects post-BCMA T-cell redirecting therapies (n=22) trended to have lower absolute levels of both CD4+ and CD8+ T-cells and increased proportion of T-cells expressing activation markers than other RRMM patient segments. Analysis of the bone marrow compartment showed that while CRBN protein was quantifiably detectable in CD138+ cells in almost all samples, including in subjects coming off IMiD based regimens, 40% of RRMM subjects had evidence of molecular dysregulation of CRBN including, loss of COPS7b/COPS8, high CRBN-del-exon10 expression, CRBN LOH or CRBN mutation. A wide range of CRBN protein levels was observed, however, differences in protein levels did not correlate with refractory status to any therapy. Notably, median CRBN expression levels were 2× higher in NDMM subjects. Prevalence of translocations, hyperdiploidy, CNAs and other mutations in RRMM subjects showed 31% of subjects had KRAS mutations, 28% had Amp1q, 23% were hyperdiploid, 21% had del17p, 12% had t(11;14), 11% had NRAS mutations and 9% had t(4;14). Conclusions These data illustrate that late-line RRMM subjects have appreciable immunosuppression compared to NDMM subjects, with particular dysfunction in the CD4+ helper T-cell compartment, suggesting that the efficacy of immunotherapies in late line myeloma may benefit from combinations with agents that improve CD4+ T-cell function. These data also show enrichment of molecular high-risk segments and CRBN-related genomic aberrations in RRMM subjects in the CC-220-MM-001 study.

Assessment of inter-operator variability in peripheral monocyte subset gating strategy using flow cytometry in patients with suspected acute stroke.

Innovative tools to reliably identify patients with acute stroke are needed. Peripheral monocyte subsets, that is, classical-Mon1, intermediate-Mon2, and non-classical-Mon3, with their activation marker expression analyzed using flow-cytometry (FCM) could be interesting cell biomarker candidates. To assess the inter-operator variability in a new peripheral monocyte subset gating strategy using FCM in patients with suspected acute stroke. In BOOST-study ("Biomarkers-algOrithm-for-strOke-diagnoSis-and Treatment-resistance-prediction," NCT04726839), patients ≥18 years with symptoms suggesting acute stroke within the last 24 h were included. Blood was collected upon admission to emergency unit. FCM analysis was performed using the FACS-CANTO-II® flow-cytometer and Flow-Jo™-software. Analyzed markers were CD45/CD91/CD14/CD16 (monocyte backbone) and CD62L/CD11b/HLA-DR/CD86/CCR2/ICAM-1/CX3CR1/TF (activation markers). Inter-operator agreement (starting from raw-data files) was quantified by the measure distribution and, for each patient, the coefficient of variation (CV). Three operators analyzed 20 patient blood samples. Median inter-operator CVs were below the pre-specified tolerance limits (10% [for Mon1 counts], 20% [Mon2, Mon3 counts], 15% [activation marker median-fluorescence-intensities]). We observed a slight, but systematic, inter-operator effect. Overall, absolute inter-operator differences in fractions of monocyte subsets were <0.03. Our gating strategy allowed monocyte subset gating with an acceptable inter-operator variability. Although low, the inter-operator effect should be considered in monocyte data analysis of BOOST-patients.

EXTH-08. IMMUNOTHERAPEUTIC TARGETING OF FIBROBLAST ACTIVATION PROTEIN (FAP) IN TREATMENT REFRACTORY GLIOBLASTOMA USING NOVEL CAR-T CELL THERAPY

Abstract Glioblastoma (GBM), the most common malignant primary adult brain tumor, is characterized by extensive cellular and genetic heterogeneity. The standard of care therapy and clinical trials have not been successful in improving patients’ survival which underscores an urgent need for developing new effective therapies. In silico and in vitro analysis have revealed high level of Fibroblast Activation Protein (FAP) expression in GBM tissue by multiple cell populations including endothelial cells, fibroblasts, stromal and tumor cells, but not normal brain tissue, making FAP a safe and suitable therapeutic target. As chimeric antigen receptor (CAR) expressing T cells have shown promising results against multiple cancers, we aimed to target FAP in GBM by FAP specific CAR-T cells generated using a novel GMP-ready FAP-CAR construct produced based on a virus-free CAR gene transfer using advanced sleeping beauty transposon technology and pre-clinically test their anti-tumor efficacy. Our data revealed that co-culturing CAR-T cells with FAP+ GBM cells (U87) resulted in increased surface expression of T-cell activation markers. Moreover, FAP CAR-T mediated cytotoxicity against FAP+ GBM cells was also observed in the co-culture of GBM and CAR-T cells. For further validation, the effect of FAP CAR-T cells will be tested on patient-derived GBM organoids. The in vivo efficacy of FAP CAR-T cells is currently under investigation and we anticipate that the treatment of GBM tumor-bearing mice with FAP CAR-Ts results in extended survival and tumor burden reduction. These rigorously obtained data show high level of efficacy for FAP-specific CAR-T cells against GBM suggesting that clinical development of this therapeutic modality can provide a novel therapeutic strategy for GBM patients. Therefore, upon successful completion of the preclinical study, we plan to conduct a phase I dose-escalation trial of autologous FAP-CAR T cells for patients with recurrent Glioblastoma.

The role of charme in the phenotype and function of resident cardiac mesenchymal stromal cells

Abstract Background Charme is a murine long non-coding RNA with specific expression in striated muscles, presenting a human orthologue with 45% identity. Its depletion leads to incomplete muscle differentiation. Charme-/- mice display an altered cardiac phenotype with increased wall thickness and reduced chamber dimensions due to myocyte hyperplasia. Left ventricular dilatation and reduced fractional shortening are detected in aged Charme-/- mice. Embryonic myocardial architecture reveals aberrant compaction and ventricular hypotrabeculation, resembling some congenital cardiomyopathies. Cardiac mesenchymal stromal cells (CMSCs) play key roles in tissue homeostasis and pathophysiology, by maintaining the extracellular matrix and by paracrine action on all myocardial cells. Purpose To elucidate the phenotype, paracrine function, and myofibroblast differentiation capacity of resident CMSCs in the Charme-/- mouse model. Methods CMSCs were isolated from 5-week-old wild-type (WT) and Charme-/- mice by explant culture, pooling at least 4 different hearts per culture. Results Charme-/- CMSCs showed increased features of primitive phenotypes, such as enhanced spontaneous spheroid growth (123,6±11,9 vs 51,0±6,4 spheroids/well; N=8, p&amp;lt;0,0001) and clonogenesis efficiency (2,7±0,5-fold; N=7, p&amp;lt;0,05) compared to WT cells. Charme-/- CMSCs also showed increased migration ability (Charme-/-: 68,5±2,7% vs WT: 80,2±0,7% wound area; N=2). Flow cytometry identified a reduced proportion of lin-/Sca1+/CD90+ primitive mesenchymal cells in Charme-/- versus WT CMSCs (7,4±1,6% vs 56,9±6,5%; N=6, p&amp;lt;0,05). Western blot analysis on Charme-/- whole cardiac tissue showed reduced collagen I and collagen I/III protein ratio compared to WT hearts (0,17±0,03 vs 0,85±0,10 normalized OD; N=4, p&amp;lt;0,005). Stimulation with TGFb-1 resulted in lower expression of fibroblast activation markers compared to WT CMSCs, as assessed by immunofluorescence staining for aSMA (0,49±0,05 vs 0,76±0,10 mean fluorescence intensity; N=6-12, p&amp;lt;0,05) and collagen I/III mRNA expression ratio (1,3±0,1 vs 2,2±0,4 2^-DCt; N=3, p&amp;lt;0,01). The secretome of Charme-/- CMSCs revealed a general depletion in many cardioprotective cytokines, included in the KEGG term "PI3K-Akt signalling pathway" (FDR&amp;lt;0,0005) and classified in Gene Ontology categories of myoblast differentiation and fusion (GO:1901739, GO:1901741, GO:0045663, GO:0045661; FDR&amp;lt;0,05). In line with this, the secretome of TGFb1-stimulated Charme-/- CMSCs was less effective in sustaining cardiomyocyte survival versus the WT CMSC secretome (1,70±0,03 vs 1,90±0,04 normalized OD at 48h; N=5, p&amp;lt;0,005). Conclusions Charme-/- CMSCs show a less mature phenotype associated to reduced collagen I presence in situ, reduced activation and differentiation upon stimulation, and impaired cardioprotective paracrine functions, suggesting a key role of Charme in the physiology of the cardiac stroma, possibly mediating in part the altered cardiac phenotype of Charme-/- mice.

Pro-inflammatory sensitization of platelets after a mild course of COVID-19 infection

Abstract Background Coronavirus disease-2019 (COVID-19) is a viral respiratory illness caused by the severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) which can lead to an increased risk of thromboembolic events but also complications even after recovery from the disease. Multiple factors may enhance the risk of thrombotic events in COVID-19 patients including excessive inflammatory responses and increased platelet activity. To date there are hardly any data on how platelet function is affected after a mild course of infection. Purpose In this study, we investigated whether platelet function is affected after recovery from mild COVID-19 disease. Besides the response of platelets to platelet stimuli, expression of the transporter protein multidrug resistance protein 4 (MRP4) and one of its substrates, the inflammatory lipid mediator sphingosine-1-phosphate (S1P), were measured. Methods Venous blood samples were collected from patients within 2-15 weeks after recovery from a mild SARS-CoV-2 infection (recovered) and matched individuals (controls) after written informed consent. Participants were invited again at 6-9 months after infection to reexamine platelet function. Parameters of platelet aggregation were determined by light transmission aggregometry (LTA) in platelet-rich plasma (PRP). Expression of platelet activation markers were measured by Flow Cytometry (FACS). In addition, concentrations of S1P were determined by LC-MS/MS and MRP4-expression in platelets via Western blotting. Results Within 2-15 weeks after recovery, no alterations in platelet aggregation were observed after stimulation of PRP with various ADP (1, 2, and 10 µM) or collagen (1 and 2.5 µg/mL) concentrations. However, regarding FACS analysis, platelet surface expression of CD62P and PAC1 from convalescents prior activation by ADP (2 µM) and by CRP-XL (0.125 ng/mL) was significantly upregulated in comparison to samples from controls (p&amp;lt;0.05 for both). Intriguingly, S1P levels in platelet-poor plasma (PPP) from COVID-19 convalescents were significantly elevated compared to controls, i.e. 0.75±0.01 vs 0.65±0.02 nmol/mL, respectively (p&amp;lt;0.001). S1P in PRP and serum samples was not altered. Furthermore, platelet MRP4 expression was significantly elevated in COVID-19 convalescents (p&amp;lt;0.05). These differences in S1P and MRP4 levels were only present after 2-15 weeks of recovery, but not 6-9 months after infection. Conclusions While after a mild course of COVID-19 infection robust platelet functions such as aggregation determined by LTA were not affected, subtle differences in platelet activation markers occurred. Enhanced platelet MRP4 expression, which may correlate with the observed elevated S1P in PPP, are in agreement with a pro-inflammatory sensitization of platelets even after a mild COVID-19 infection. The implications of this observation concerning long-term effects of COVID-19 await further studies.

Accelerated arterial thrombus formation in Hutchinson Gilford Progeria Syndrome

Abstract Introduction Arterial thrombosis is an age-associated cause of myocardial infarction and stroke, which are the leading causes of mortality and morbidity worldwide. Hutchinson-Gilford Progeria Syndrome (HGPS) is a rare genetic disorder that is caused by a point mutation in the lamin A gene. It is characterized by progressive premature aging, in which caused a decreased life expectancy. Two most frequent causes of death of children with HGPS are myocardial infarction and ischemic stroke – cardiovascular events that are tightly linked to arterial thrombosis. Despite this fact, the effect of the specific lamin A gene mutation on arterial thrombus formation remains unknown. Methods Transgenic heterozygous LmnaG609G knock-in (HGPS) mice and the corresponding wild-type (WT) littermate controls underwent photochemically-induced carotid artery endothelial injury to trigger thrombosis. Coagulation and fibrinolytic factors were measured in these animals. Ex-vivo platelet activation assay was also performed. Results HGPS mice displayed accelerated thrombus formation as underlined by shortened time to occlusion compared to WT littermates (Figure 1A-B). The level of tissue factor and von Willebrand factors are comparable between groups. No significant differences were found on factors involved in the fibrinolytic system, which was confirmed by the comparable level of D-dimers in both groups. A higher level of thrombin-antithrombin complex was observed, accompanied by lower level of antithrombin. Interestingly, HGPS animals displayed enhanced platelet activation markers expression upon ADP, collagen, and thrombin stimulation compared to WT group, demonstrating a higher platelet reactivity in progeria animals (Figure 1C). Conclusions Our study demonstrated an increased arterial thrombotic response in HGPS mice as compared to WT littermates which is, at least in part, mediated by higher platelet reactivity. This novel observation may provide a mechanistic explanation for the increased incidence of acute cardiovascular events observed in children with HGPS and warrant further clinical investigations also in consideration of available antiplatelet therapies.

Abstract 13851: CAR-T Cells: A Potential Novel Strategy for Mitigating Fibrosis in Duchenne Muscular Dystrophy

Introduction: Chimeric Antigen T (CAR)-T cells have proven effective preclinically for mitigating cardiac fibrosis in hypertensive cardiomyopathy. Hypothesis: We assessed whether this approach could be applied to Duchenne Muscular Dystrophy (DMD) by targeting Fibroblast Activating Protein (FAP)-expressing activated fibroblasts in cardiac and skeletal muscle fibrosis. Methods: A protocol for the lymphodepletion conditioning of mice was developed to optimize the dosing of cyclophosphamide. Next, immune-magnetically selected T cells were retrovirally transduced to target FAP (FAP-CAR) and quality-controlled by co-culture killing assays using FAP-expressing HEK target cells. Finally, lymphodepleted D2. mdx mice were intravenously injected with 10 7 FAP-CAR T cells (n=9) or 10 7 GFP-T cells (n=9) or Bovine Serum Albumin (BSA, n=8). Cardiac and skeletal muscle end points were assessed 2 and 5 weeks after treatment. Results: In vitro , the engineered CAR-T cells expressed activation markers (CD69, PD-1) and released large amounts of granzyme, perforin and interferon γ upon exposure to FAP-expressing target cells. One IP injection of cyclophosphamide (3mg) 4 days before treatment was safe and induced a lymphodepletion which enabled robust in vivo expansion of FAP-CAR T cell assessed by flow cytometry in lymphoid organs and blood: 10 5 , 2.10 6 and 10 7 detected CAR-T cells at day 3, 5 and 7 post-injections, respectively. This was paralleled by a more than a 2-fold decrease in endogenous FAP expression in skeletal muscles, as assessed by PCR at day 5 post-injections, and measurable FAP-CAR levels in the spleen compared with GFP-T cell controls. In vivo , FAP-CAR T cells significantly improved LV function with an EF change from baseline (Mean±SEM) of 33.1% ± 6.7% in FAP-CAR vs. 3.7% ± 6.4% and -9.6% ± 7.9% in GFP-T and BSA ( p &lt;0.037 and p &lt;0.005, respectively) at 2 weeks. The benefit was maintained at 5 weeks post-treatment. Several markers of fibrosis, particularly collagens 1 and 3, were also down-regulated in heart and muscles. Conclusions: FAP-CAR-T cells might represent a new therapeutic option for mitigating fibrosis in DMD, likely in conjunction with approaches aimed at addressing the root cause of the disease through a re-expression of a functional dystrophin.