Fibroblast Heterogeneity and Immunosuppressive Environment in Human Breast Cancer

Carcinoma-associated fibroblasts (CAF) are key players in the tumor microenvironment. Here, we characterize four CAF subsets in breast cancer with distinct properties and levels of activation. Two myofibroblastic subsets (CAF-S1, CAF-S4) accumulate differentially in triple-negative breast cancers (TNBC). CAF-S1 fibroblasts promote an immunosuppressive environment through a multi-step mechanism. By secreting CXCL12, CAF-S1 attracts CD4⁺CD25⁺ T lymphocytes and retains them by OX40L, PD-L2, and JAM2. Moreover, CAF-S1 increases T lymphocyte survival and promotes their differentiation into CD25^HighFOXP3^High, through B7H3, CD73, and DPP4. Finally, in contrast to CAF-S4, CAF-S1 enhances the regulatory T cell capacity to inhibit T effector proliferation. These data are consistent with FOXP3+ T lymphocyte accumulation in CAF-S1-enriched TNBC and show how a CAF subset contributes to immunosuppression.

Regulatory T Cells in Skin Facilitate Epithelial Stem Cell Differentiation

The maintenance of tissue homeostasis is critically dependent on the function of tissue-resident immune cells and the differentiation capacity of tissue-resident stem cells (SCs). How immune cells influence the function of SCs is largely unknown. Regulatory T cells (Tregs) in skin preferentially localize to hair follicles (HFs), which house a major subset of skin SCs (HFSCs). Here, we mechanistically dissect the role of Tregs in HF and HFSC biology. Lineage-specific cell depletion revealed that Tregs promote HF regeneration by augmenting HFSC proliferation and differentiation. Transcriptional and phenotypic profiling of T_regs and HFSCs revealed that skin-resident Tregs preferentially express high levels of the Notch ligand family member, Jagged 1 (Jag1). Expression of Jag1 on Tregs facilitated HFSC function and efficient HF regeneration. Taken together, our work demonstrates that Tregs in skin play a major role in HF biology by promoting the function of HFSCs.

Lactic acid promotes PD-1 expression in regulatory T cells in highly glycolytic tumor microenvironments

The balance of programmed death-1 (PD-1)-expressing CD8⁺ T cells and regulatory T (Treg) cells in the tumor microenvironment (TME) determines the clinical efficacy of PD-1 blockade therapy through the competition of their reactivation. However, factors that determine this balance remain unknown. Here, we show that Treg cells gain higher PD-1 expression than effector T cells in highly glycolytic tumors, including MYC-amplified tumors and liver tumors. Under low-glucose environments via glucose consumption by tumor cells, Treg cells actively absorbed lactic acid (LA) through monocarboxylate transporter 1 (MCT1), promoting NFAT1 translocation into the nucleus, thereby enhancing the expression of PD-1, whereas PD-1 expression by effector T cells was dampened. PD-1 blockade invigorated the PD-1-expressing Treg cells, resulting in treatment failure. We propose that LA in the highly glycolytic TME is an active checkpoint for the function of Treg cells in the TME via upregulation of PD-1 expression.

Monocyte-Macrophages and T Cells in Atherosclerosis

Atherosclerosis is an arterial disease process characterized by the focal subendothelial accumulation of apolipoprotein-B-containing lipoproteins, immune and vascular wall cells, and extracellular matrix. The lipoproteins acquire features of damage-associated molecular patterns and trigger first an innate immune response, dominated by monocyte-macrophages, and then an adaptive immune response. These inflammatory responses often become chronic and non-resolving and can lead to arterial damage and thrombosis-induced organ infarction. The innate immune response is regulated at various stages, from hematopoiesis to monocyte changes and macrophage activation. The adaptive immune response is regulated primarily by mechanisms that affect the balance between regulatory and effector T cells. Mechanisms related to cellular cholesterol, phenotypic plasticity, metabolism, and aging play key roles in affecting these responses. Herein, we review select topics that shed light on these processes and suggest new treatment strategies.

Caloric Restriction Mimetics Enhance Anticancer Immunosurveillance

Caloric restriction mimetics (CRMs) mimic the biochemical effects of nutrient deprivation by reducing lysine acetylation of cellular proteins, thus triggering autophagy. Treatment with the CRM hydroxycitrate, an inhibitor of ATP citrate lyase, induced the depletion of regulatory T cells (which dampen anticancer immunity) from autophagy-competent, but not autophagy-deficient, mutant KRAS-induced lung cancers in mice, thereby improving anticancer immunosurveillance and reducing tumor mass. Short-term fasting or treatment with several chemically unrelated autophagy-inducing CRMs, including hydroxycitrate and spermidine, improved the inhibition of tumor growth by chemotherapy in vivo. This effect was only observed for autophagy-competent tumors, depended on the presence of T lymphocytes, and was accompanied by the depletion of regulatory T cells from the tumor bed.

Mesothelial cell-derived antigen-presenting cancer-associated fibroblasts induce expansion of regulatory T cells in pancreatic cancer

Recent studies have identified a unique cancer-associated fibroblast (CAF) population termed antigen-presenting CAFs (apCAFs), characterized by the expression of major histocompatibility complex class II molecules, suggesting a function in regulating tumor immunity. Here, by integrating multiple single-cell RNA-sequencing studies and performing robust lineage-tracing assays, we find that apCAFs are derived from mesothelial cells. During pancreatic cancer progression, mesothelial cells form apCAFs by downregulating mesothelial features and gaining fibroblastic features, a process induced by interleukin-1 and transforming growth factor β. apCAFs directly ligate and induce naive CD4+ T cells into regulatory T cells (Tregs) in an antigen-specific manner. Moreover, treatment with an antibody targeting the mesothelial cell marker mesothelin can effectively inhibit mesothelial cell to apCAF transition and Treg formation induced by apCAFs. Taken together, our study elucidates how mesothelial cells may contribute to immune evasion in pancreatic cancer and provides insight on strategies to enhance cancer immune therapy.

HIF-1α Is a Metabolic Switch between Glycolytic-Driven Migration and Oxidative Phosphorylation-Driven Immunosuppression of Tregs in Glioblastoma

The mechanisms by which regulatory T cells (Tregs) migrate to and function within the hypoxic tumor microenvironment are unclear. Our studies indicate that specific ablation of hypoxia-inducible factor 1α (HIF-1α) in Tregs results in enhanced CD8+ T cell suppression versus wild-type Tregs under hypoxia, due to increased pyruvate import into the mitochondria. Importantly, HIF-1α-deficient Tregs are minimally affected by the inhibition of lipid oxidation, a fuel that is critical for Treg metabolism in tumors. Under hypoxia, HIF-1α directs glucose away from mitochondria, leaving Tregs dependent on fatty acids for mitochondrial metabolism within the hypoxic tumor. Indeed, inhibition of lipid oxidation enhances the survival of mice with glioma. Interestingly, HIF-1α-deficient-Treg mice exhibit significantly enhanced animal survival in a murine model of glioma, due to their stymied migratory capacity, explaining their reduced abundance in tumor-bearing mice. Thus HIF-1α acts as a metabolic switch for Tregs between glycolytic-driven migration and oxidative phosphorylation-driven immunosuppression.

TCR Transgenic Mice Reveal Stepwise, Multi-site Acquisition of the Distinctive Fat-Treg Phenotype

Visceral adipose tissue (VAT) hosts a population of regulatory T (Treg) cells, with a unique phenotype, that controls local and systemic inflammation and metabolism. Generation of a T cell receptor transgenic mouse line, wherein VAT Tregs are highly enriched, facilitated study of their provenance, dependencies, and activities. We definitively established a role for T cell receptor specificity, uncovered an unexpected function for the primordial Treg transcription-factor, Foxp3, evidenced a cell-intrinsic role for interleukin-33 receptor, and ordered these dependencies within a coherent scenario. Genesis of the VAT-Treg phenotype entailed a priming step in the spleen, permitting them to exit the lymphoid organs and surveil nonlymphoid tissues, and a final diversification process within VAT, in response to microenvironmental cues. Understanding the principles of tissue-Treg biology is a prerequisite for precision-targeting strategies.

Reprogramming the Local Lymph Node Microenvironment Promotes Tolerance that Is Systemic and Antigen Specific

Many experimental therapies for autoimmune diseases, such as multiple sclerosis (MS), aim to bias T cells toward tolerogenic phenotypes without broad suppression. However, the link between local signal integration in lymph nodes (LNs) and the specificity of systemic tolerance is not well understood. We used intra-LN injection of polymer particles to study tolerance as a function of signals in the LN microenvironment. In a mouse MS model, intra-LN introduction of encapsulated myelin self-antigen and a regulatory signal (rapamycin) permanently reversed paralysis after one treatment during peak disease. Therapeutic effects were myelin specific, required antigen encapsulation, and were less potent without rapamycin. This efficacy was accompanied by local LN reorganization, reduced inflammation, systemic expansion of regulatory T cells, and reduced T cell infiltration to the CNS. Our findings suggest that local control over signaling in distinct LNs can promote cell types and functions that drive tolerance that is systemic but antigen specific.

Differential Roles of IL-2 Signaling in Developing versus Mature Tregs

Although Foxp3⁺ regulatory T cells (Tregs) require interleukin-2 (IL-2) for their development, it has been unclear whether continuing IL-2 signals are needed to maintain lineage stability, survival, and suppressor function in mature Tregs. We generated mice in which CD25, the main ligand-binding subunit of the IL-2 receptor, can be inducibly deleted from Tregs after thymic development. In contrast to Treg development, we find that IL-2 is dispensable for maintaining lineage stability in mature Tregs. Although continuous IL-2 signaling is needed for long-term Treg survival, CD25-deleted Tregs may persist for several weeks in vivo using IL-7. We also observe defects in glycolytic metabolism and suppressor function following CD25 deletion. Thus, unlike developing Tregs in which the primary role of IL-2 is to initiate Foxp3 expression, mature Tregs require continuous IL-2 signaling to maintain survival and suppressor function, but not to maintain lineage stability.

Mitochondrial Oxidative Damage Underlies Regulatory T Cell Defects in Autoimmunity

Regulatory T cells (Tregs) are vital for the maintenance of immune homeostasis, while their dysfunction constitutes a cardinal feature of autoimmunity. Under steady-state conditions, mitochondrial metabolism is critical for Treg function; however, the metabolic adaptations of Tregs during autoimmunity are ill-defined. Herein, we report that elevated mitochondrial oxidative stress and a robust DNA damage response (DDR) associated with cell death occur in Tregs in individuals with autoimmunity. In an experimental autoimmune encephalitis (EAE) mouse model of autoimmunity, we found a Treg dysfunction recapitulating the features of autoimmune Tregs with a prominent mtROS signature. Scavenging of mtROS in Tregs of EAE mice reversed the DDR and prevented Treg death, while attenuating the Th1 and Th17 autoimmune responses. These findings highlight an unrecognized role of mitochondrial oxidative stress in defining Treg fate during autoimmunity, which may facilitate the design of novel immunotherapies for diseases with disturbed immune tolerance.

Mesenchymal Stem and Stromal Cells Harness Macrophage-Derived Amphiregulin to Maintain Tissue Homeostasis

The cross-talk between mesenchymal stem and stromal cells (MSCs) and macrophages is critical for the restoration of tissue homeostasis after injury. Here, we demonstrate a pathway through which MSCs instruct macrophages to resolve inflammation and preserve tissue-specific stem cells, leading to homeostasis in mice with autoimmune uveoretinitis and sterile-injury-induced corneal epithelial stem cell deficiency. Distinct from their conventional role in macrophage reprogramming to anti-inflammatory phenotype by a PGE2-dependent mechanism, MSCs enhance the phagocytic activity of macrophages, which partly depends on the uptake of MSC mitochondria-containing extracellular vesicles. The MSC-primed macrophages increase the secretion of amphiregulin (AREG) in a phagocytosis-dependent manner. AREG is essential for MSC-primed macrophages to suppress immune responses through regulatory T (Treg) cells and to protect corneal epithelial stem cells via apoptosis inhibition and proliferation promotion. Hence, the data reveal that MSCs harness macrophage-derived AREG to maintain tissue homeostasis after injury and provide a therapeutic target in immune-mediated disease and regenerative medicine.

PGE2-EP2/EP4 signaling elicits immunosuppression by driving the mregDC-Treg axis in inflammatory tumor microenvironment

Active inflammation generally promotes immune activation. However, in the tumor microenvironment (TME), active inflammation occurs in parallel with immunosuppression, and both contribute to tumor growth. Why inflammation does not lead to immune activation in TME remains unclear. In this study, using the immune checkpoint inhibitor-insensitive mouse cancer model and single-cell RNA sequencing, we show that PGE₂-EP2/EP4 signaling simultaneously promotes active inflammation by inducing expression of the NF-κB genes in myeloid cells and elicits immunosuppression by driving the mregDC (mature DC enriched in immunoregulatory molecules)-Treg (regulatory T cell) axis for Treg recruitment and activation in the tumor. Importantly, the EP2/EP4 expression level is strongly correlated with the gene signatures of both active inflammation and the mregDC-Treg axis and has significant prognosis value in various human cancers. Thus, PGE₂-EP2/EP4 signaling functions as the key regulatory node linking active inflammation and immunosuppression in TME, which can be targeted by EP2 and EP4 antagonists for cancer therapeutics.

Gene Therapy-Induced Antigen-Specific Tregs Inhibit Neuro-inflammation and Reverse Disease in a Mouse Model of Multiple Sclerosis

The devastating neurodegenerative disease multiple sclerosis (MS) could substantially benefit from an adeno-associated virus (AAV) immunotherapy designed to restore a robust and durable antigen-specific tolerance. However, developing a sufficiently potent and lasting immune-regulatory therapy that can intervene in ongoing disease is a major challenge and has thus been elusive. We addressed this problem by developing a highly effective and robust tolerance-inducing in vivo gene therapy. Using a pre-clinical animal model, we designed a liver-targeting gene transfer vector that expresses full-length myelin oligodendrocyte glycoprotein (MOG) in hepatocytes. We show that by harnessing the tolerogenic nature of the liver, this powerful gene immunotherapy restores immune tolerance by inducing functional MOG-specific regulatory T cells (Tregs) in vivo, independent of major histocompatibility complex (MHC) restrictions. We demonstrate that mice treated prophylactically are protected from developing disease and neurological deficits. More importantly, we demonstrate that when given to mice with preexisting disease, ranging from mild neurological deficits to severe paralysis, the gene immunotherapy abrogated CNS inflammation and significantly reversed clinical symptoms of disease. This specialized approach for inducing antigen-specific immune tolerance has significant therapeutic potential for treating MS and other autoimmune disorders.

Expansion of Human Tregs from Cryopreserved Umbilical Cord Blood for GMP-Compliant Autologous Adoptive Cell Transfer Therapy

Umbilical cord blood is a traditional and convenient source of cells for hematopoietic stem cell transplantation. Thymic regulatory T cells (Tregs) are also present in cord blood, and there is growing interest in the use of autologous Tregs to provide a low-risk, fully human leukocyte antigen (HLA)-matched cell product for treating autoimmune diseases, such as type 1 diabetes. Here, we describe a good manufacturing practice (GMP)-compatible Treg expansion protocol using fluorescence-activated cell sorting, resulting in a mean 2,092-fold expansion of Tregs over a 16-day culture for a median yield of 1.26 × 10⁹ Tregs from single-donor cryopreserved units. The resulting Tregs passed prior clinical trial release criteria for Treg purity and sterility, including additional rigorous assessments of FOXP3 and Helios expression and epigenetic analysis of the FOXP3 Treg-specific demethylated region (TSDR). Compared with expanded adult peripheral blood Tregs, expanded cord blood Tregs remained more naive, as assessed by continued expression of CD45RA, produced reduced IFN-γ following activation, and effectively inhibited responder T cell proliferation. Immunosequencing of the T cell receptor revealed a remarkably diverse receptor repertoire within cord blood Tregs that was maintained following in vitro expansion. These data support the feasibility of generating GMP-compliant Tregs from cord blood for adoptive cell transfer therapies and highlight potential advantages in terms of safety, phenotypic stability, autoantigen specificity, and tissue distribution.

Crohn's Disease Disturbs the Immune Properties of Human Adipose-Derived Stem Cells Related to Inflammasome Activation

Crohn's disease (CD) is characterized by the expansion of mesenteric fat, also known as “creeping fat.” We explored the plasticity and immune properties of adipose-derived stem cells (ASCs) in the context of CD as potential key players in the development of creeping fat. Mesenteric CD-derived ASCs presented a more proliferative, inflammatory, invasive, and phagocytic phenotype than equivalent cells from healthy donors, irrespective of the clinical stage. Remarkably, ASCs from the subcutaneous depot of patients with CD also showed an activated immune response that was associated with a reduction in their immunosuppressive properties. The invasive phenotype of mesenteric CD ASCs was governed by an inflammasome-mediated inflammatory state since blocking inflammasome signaling, mainly the secretion of interleukin-1β, reversed this characteristic. Thus, CD alters the biological functions of ASCs as adipocyte precursors, but also their immune properties. Selection of ASCs with the best immunomodulatory properties is advocated for the success of cell-based therapies.

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ASCs isolated from CD patients are highly proliferative, invasive, and phagocytic

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Proliferative ASCs may be responsible for the development of creeping fat

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ASCs from CD patients have dampened immunosuppressive properties

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Selection of the best immunosuppressive ASCs for cell therapy is advocated

Nemo-like Kinase Drives Foxp3 Stability and Is Critical for Maintenance of Immune Tolerance by Regulatory T Cells

The Foxp3 transcription factor is a crucial determinant of both regulatory T (TREG) cell development and their functional maintenance. Appropriate modulation of tolerogenic immune responses therefore requires the tight regulation of Foxp3 transcriptional output, and this involves both transcriptional and post-translational regulation. Here, we show that during T cell activation, phosphorylation of Foxp3 in TREG cells can be regulated by a TGF-β activated kinase 1 (TAK1)-Nemo-like kinase (NLK) signaling pathway. NLK interacts and phosphorylates Foxp3 in TREG cells, resulting in the stabilization of protein levels by preventing association with the STUB1 E3-ubiquitin protein ligase. Conditional TREG cell NLK-knockout (NLKΔTREG) results in decreased TREG cell-mediated immunosuppression in vivo, and NLK-deficient TREG cell animals develop more severe experimental autoimmune encephalomyelitis. Our data suggest a molecular mechanism, in which stimulation of TCR-mediated signaling can induce a TAK1-NLK pathway to sustain Foxp3 transcriptional activity through the stabilization of protein levels, thereby maintaining TREG cell suppressive function.

Critical Role of Regulatory T Cells in the Latency and Stress-Induced Reactivation of HSV-1

Herpes simplex virus 1 (HSV-1) spreads in populations through a latency entry and reactivation cycle. The role of host immune-suppressive factor regulatory T cells (Treg cells) in controlling latency establishment and reactivation is not completely understood. Here, using an HSV-1 ocular infection murine model, we observe a positive correlation between the level of Treg cells and viral infectivity and demonstrate the requirement for Treg cells in latency establishment. Furthermore, we show that host stress leads to HSV-1 reactivation via increased Treg cell control of CD8⁺ T cells, permitting viral replication under diminished immune surveillance. Together, we propose that Treg cell regulation may serve as a key target for controlling HSV infection.

Maternal diet modulates the infant microbiome and intestinal Flt3L necessary for dendritic cell development and immunity to respiratory infection

Poor maternal diet during pregnancy is a risk factor for severe lower respiratory infections (sLRIs) in the offspring, but the underlying mechanisms remain elusive. Here, we demonstrate that in mice a maternal low-fiber diet (LFD) led to enhanced LRI severity in infants because of delayed plasmacytoid dendritic cell (pDC) recruitment and perturbation of regulatory T cell expansion in the lungs. LFD altered the composition of the maternal milk microbiome and assembling infant gut microbiome. These microbial changes reduced the secretion of the DC growth factor Flt3L by neonatal intestinal epithelial cells and impaired downstream pDC hematopoiesis. Therapy with a propionate-producing bacteria isolated from the milk of high-fiber diet-fed mothers, or supplementation with propionate, conferred protection against sLRI by restoring gut Flt3L expression and pDC hematopoiesis. Our findings identify a microbiome-dependent Flt3L axis in the gut that promotes pDC hematopoiesis in early life and confers disease resistance against sLRIs.

Engineered human cytokine/antibody fusion proteins expand regulatory T cells and confer autoimmune disease protection

Low-dose human interleukin-2 (hIL-2) treatment is used clinically to treat autoimmune disorders due to the cytokine's preferential expansion of immunosuppressive regulatory T cells (Tregs). However, off-target immune cell activation and short serum half-life limit the clinical potential of IL-2 treatment. Recent work showed that complexes comprising hIL-2 and the anti-hIL-2 antibody F5111 overcome these limitations by preferentially stimulating Tregs over immune effector cells. Although promising, therapeutic translation of this approach is complicated by the need to optimize dosing ratios and by the instability of the cytokine/antibody complex. We leverage structural insights to engineer a single-chain hIL-2/F5111 antibody fusion protein, termed F5111 immunocytokine (IC), which potently and selectively activates and expands Tregs. F5111 IC confers protection in mouse models of colitis and checkpoint inhibitor-induced diabetes mellitus. These results provide a roadmap for IC design and establish a Treg-biased immunotherapy that could be clinically translated for autoimmune disease treatment.

Immune disease variants modulate gene expression in regulatory CD4+ T cells

Identifying cellular functions dysregulated by disease-associated variants could implicate novel pathways for drug targeting or modulation in cell therapies. However, follow-up studies can be challenging if disease-relevant cell types are difficult to sample. Variants associated with immune diseases point toward the role of CD4+ regulatory T cells (Treg cells). We mapped genetic regulation (quantitative trait loci [QTL]) of gene expression and chromatin activity in Treg cells, and we identified 133 colocalizing loci with immune disease variants. Colocalizations of immune disease genome-wide association study (GWAS) variants with expression QTLs (eQTLs) controlling the expression of CD28 and STAT5A, involved in Treg cell activation and interleukin-2 (IL-2) signaling, support the contribution of Treg cells to the pathobiology of immune diseases. Finally, we identified seven known drug targets suitable for drug repurposing and suggested 63 targets with drug tractability evidence among the GWAS signals that colocalized with Treg cell QTLs. Our study is the first in-depth characterization of immune disease variant effects on Treg cell gene expression modulation and dysregulation of Treg cell function.

Breast cancer tumor microenvironment affects Treg/IL-17-producing Treg/Th17 cell axis: Molecular and therapeutic perspectives

The tumor microenvironment (TME) comprises a variety of immune cells, among which T cells exert a prominent axial role in tumor development or anti-tumor responses in patients with breast cancer (BC). High or low levels of anti-inflammatory cytokines, such as transforming growth factor β, in the absence or presence of proinflammatory cytokines, such as interleukin-6 (IL-6), delineate the fate of T cells toward either regulatory T (Treg) or T helper 17 (Th17) cells, respectively. The transitional state of RORγt⁺Foxp3⁺ Treg (IL-17-producing Treg) resides in the middle of this reciprocal polarization, which is known as Treg/IL-17-producing Treg/Th17 cell axis. TME secretome, including microRNAs, cytokines, and extracellular vesicles, can significantly affect this axis. Furthermore, immune checkpoint inhibitors may be used to reconstruct immune cells; however, some of these novel therapies may favor tumor development. Therefore, understanding secretory and cell-associated factors involved in their differentiation or polarization and functions may be targeted for BC management. This review discusses microRNAs, cytokines, and extracellular vesicles (as secretome), as well as transcription factors and immune checkpoints (as cell-associated factors), which influence the Treg/IL-17-producing Treg/Th17 cell axis in BC. Furthermore, approved or ongoing clinical trials related to the modulation of this axis in the TME of BC are described to broaden new horizons of promising therapeutic approaches.

Opioid-induced fragile-like regulatory T cells contribute to withdrawal

Dysregulation of the immune system is a cardinal feature of opioid addiction. Here, we characterize the landscape of peripheral immune cells from patients with opioid use disorder and from healthy controls. Opioid-associated blood exhibited an abnormal distribution of immune cells characterized by a significant expansion of fragile-like regulatory T cells (Tregs), which was positively correlated with the withdrawal score. Analogously, opioid-treated mice also showed enhanced Treg-derived interferon-γ (IFN-γ) expression. IFN-γ signaling reshaped synaptic morphology in nucleus accumbens (NAc) neurons, modulating subsequent withdrawal symptoms. We demonstrate that opioids increase the expression of neuron-derived C-C motif chemokine ligand 2 (Ccl2) and disrupted blood-brain barrier (BBB) integrity through the downregulation of astrocyte-derived fatty-acid-binding protein 7 (Fabp7), which both triggered peripheral Treg infiltration into NAc. Our study demonstrates that opioids drive the expansion of fragile-like Tregs and favor peripheral Treg diapedesis across the BBB, which leads to IFN-γ-mediated synaptic instability and subsequent withdrawal symptoms.

Alpha-1 Antitrypsin-Expressing Mesenchymal Stromal Cells Confer a Long-Term Survival Benefit in a Mouse Model of Lethal GvHD

Acute graft-versus-host disease is a frequent complication associated with allogeneic hematopoietic stem cell transplantation. Patients that become refractory to initial steroid treatment have a poor prognosis. apceth-201 consists of human allogeneic mesenchymal stromal cells, engineered by lentiviral transduction to express the protease inhibitor alpha-1 antitrypsin, to augment the anti-inflammatory potential of the mesenchymal stromal cells. We show that apceth-201 mesenchymal stromal cells efficiently suppress T cell proliferation and polarize macrophages to an anti-inflammatory M2 type, in vitro. To assess the in vivo efficacy of apceth-201, it was tested in two different mouse models of acute graft-versus-host disease. Control animals in a humanized model succumbed quickly to disease, whereas median survival was doubled in apceth-201-treated animals. The product was also tested in a graft-versus-host disease model system that closely mimics haploidentical hematopoietic stem cell transplantation, an approach that is now being evaluated for use in the clinic. Control animals succumbed quickly to disease, whereas treatment with apceth-201 resulted in long-term survival of 57% of the animals. Within 25 days after the second injection, clinical scores returned to baseline in responding animals, indicating complete resolution of graft-versus-host disease. These promising data have led to planning of a phase I study using apceth-201.