In vivo depletion of CD4+FOXP3+ Treg cells by the PC61 anti-CD25 monoclonal antibody is mediated by FcgammaRIII+ phagocytes

Melatonin ameliorates necrotizing enterocolitis by preventing Th17/Treg imbalance through activation of the AMPK/SIRT1 pathway

Necrotizing enterocolitis (NEC) is a severe gastrointestinal disease affecting premature infants. Mounting evidence supports the therapeutic effect of melatonin on NEC, although the underlying mechanisms remain unclear. Methods: NEC was induced in 10-day-old C57BL/6 pups via hypoxia and gavage feeding of formula containing enteric bacteria, and then, mice received melatonin, melatonin + recombinant IL-17, melatonin + anti-CD25 monoclonal antibody, melatonin + Ex-527, or melatonin + Compound C treatment. Control mice were left with their dams to breastfeed and vehicle-treated NEC pups were used as controls for treatment. Ileal tissues were collected from mice and analyzed by histopathology, immunoblotting, and flow cytometry. FITC-labeled dextran was administered to all surviving pups to evaluate gut barrier function by fluorometry. We used molecular biology and cell culture approaches to study the related mechanisms in CD4+ T cells from umbilical cord blood. Results: We demonstrated that melatonin treatment ameliorates disease in an NEC mouse model in a manner dependent on improved intestinal Th17/Treg balance. We also showed that melatonin blocks the differentiation of pathogenic Th17 cells and augments the generation of protective Treg cells in vitro. We further demonstrated that the Th17/Treg balance is influenced by melatonin through activation of AMPK in the intestine, in turn promoting SIRT1 activation and stabilization. Conclusions: These results demonstrate that melatonin-induced activation of AMPK/SIRT1 signaling regulates the balance between Th17 and Treg cells and that therapeutic strategies targeting the Th17/Treg balance via the AMPK/SIRT1 pathway might be beneficial for the treatment of NEC.

STAT3 Modulation of Regulatory T Cells in Response to Radiation Therapy in Head and Neck Cancer

BACKGROUND

Radioresistance represents a major problem in the treatment of head and neck cancer (HNC) patients. To improve response, understanding tumor microenvironmental factors that contribute to radiation resistance is important. Regulatory T cells (Tregs) are enriched in numerous cancers and can dampen the response to radiation by creating an immune-inhibitory microenvironment. The purpose of this study was to investigate mechanisms of Treg modulation by radiation in HNC.

METHODS

We utilized an orthotopic mouse model of HNC. Anti-CD25 was used for Treg depletion. Image-guided radiation was delivered to a dose of 10 Gy. Flow cytometry was used to analyze abundance and function of intratumoral immune cells. Enzyme-linked immunosorbent assay was performed to assess secreted factors. For immune-modulating therapies, anti-PD-L1, anti-CTLA-4, and STAT3 antisense oligonucleotide (ASO) were used. All statistical tests were two-sided.

RESULTS

Treatment with anti-CD25 and radiation led to tumor eradication (57.1%, n = 4 of 7 mice), enhanced T-cell cytotoxicity compared with RT alone (CD4 effector T cells [Teff]: RT group mean = 5.37 [ 0.58] vs RT + αCD25 group mean =10.71 [0.67], P = .005; CD8 Teff: RT group mean = 9.98 [0.81] vs RT + αCD25 group mean =16.88 [2.49], P = .01) and induced tumor antigen-specific memory response (100.0%, n = 4 mice). In contrast, radiation alone or when combined with anti-CTLA4 did not lead to durable tumor control (0.0%, n = 7 mice). STAT3 inhibition in combination with radiation, but not as a single agent, improved tumor growth delay, decreased Tregs, myeloid-derived suppressor cells, and M2 macrophages and enhanced effector T cells and M1 macrophages. Experiments in nude mice inhibited the benefit of STAT3 ASO and radiation.

CONCLUSION

We propose that STAT3 inhibition is a viable and potent therapeutic target against Tregs. Our data support the design of clinical trials integrating STAT3 ASO in the standard of care for cancer patients receiving radiation.

Low-dose interleukin-2 reverses behavioral sensitization in multiple mouse models of headache disorders

Headache disorders are highly prevalent and debilitating, with limited treatment options. Previous studies indicate that many proinflammatory immune cells contribute to headache pathophysiology. Given the well-recognized role of regulatory T (Treg) cells in maintaining immune homeostasis, we hypothesized that enhancing Treg function may be effective to treat multiple headache disorders. In a mouse model of chronic migraine, we observed that repeated nitroglycerin (NTG, a reliable trigger of migraine in patients) administration doubled the number of CD3 T cells in the trigeminal ganglia without altering the number of Treg cells, suggesting a deficiency in Treg-mediated immune homeostasis. We treated mice with low-dose interleukin-2 (ld-IL2) to preferentially expand and activate endogenous Treg cells. This not only prevented the development of NTG-induced persistent sensitization but also completely reversed the established facial skin hypersensitivity resulting from repeated NTG administration. The effect of ld-IL2 was independent of mouse sex and/or strain. Importantly, ld-IL2 treatment did not alter basal nociceptive responses, and repeated usage did not induce tolerance. The therapeutic effect of ld-IL2 was abolished by Treg depletion and was recapitulated by Treg adoptive transfer. Furthermore, treating mice with ld-IL2 1 to 7 days after mild traumatic brain injury effectively prevented as well as reversed the development of behaviors related to acute and chronic post-traumatic headache. In a model of medication overuse headache, Ld-IL2 completely reversed the cutaneous hypersensitivity induced by repeated administration of sumatriptan. Collectively, this study identifies ld-IL2 as a promising prophylactic for multiple headache disorders with a mechanism distinct from the existing treatment options.

Regulatory T cells promote remyelination in the murine experimental autoimmune encephalomyelitis model of multiple sclerosis following human neural stem cell transplant

Multiple sclerosis (MS) is a chronic, inflammatory autoimmune disease that affects the central nervous system (CNS) for which there is no cure. In MS, encephalitogenic T cells infiltrate the CNS causing demyelination and neuroinflammation; however, little is known about the role of regulatory T cells (Tregs) in CNS tissue repair. Transplantation of neural stem and progenitor cells (NSCs and NPCs) is a promising therapeutic strategy to promote repair through cell replacement, although recent findings suggest transplanted NSCs also instruct endogenous repair mechanisms. We have recently described that dampened neuroinflammation and increased remyelination is correlated with emergence of Tregs following human NPC transplantation in a murine viral model of immune-mediated demyelination. In the current study we utilized the prototypic murine autoimmune model of demyelination experimental autoimmune encephalomyelitis (EAE) to test the efficacy of hNSC transplantation. Eight-week-old, male EAE mice receiving an intraspinal transplant of hNSCs during the chronic phase of disease displayed remyelination, dampened neuroinflammation, and an increase in CNS CD4⁺CD25⁺FoxP3⁺ regulatory T cells (Tregs). Importantly, ablation of Tregs abrogated histopathological improvement. Tregs are essential for maintenance of T cell homeostasis and prevention of autoimmunity, and an emerging role for Tregs in maintenance of tissue homeostasis through interactions with stem and progenitor cells has recently been suggested. The data presented here provide direct evidence for collaboration between CNS Tregs and hNSCs promoting remyelination.

Use of Tregs as a cell-based therapy via CD39 for benign prostate hyperplasia with inflammation

Benign prostatic hyperplasia (BPH) occurs most commonly among older men, often accompanied by chronic tissue inflammation. Although its aetiology remains unclear, autoimmune dysregulation may contribute to BPH. Regulatory T cells (Tregs) prevent autoimmune responses and maintain immune homeostasis. In this study, we aimed to investigate Tregs frequency, phenotype, and function in BPH patients and to evaluate adoptive transfer Tregs for immunotherapy in mice with BPH via CD39. Prostate specimens and peripheral blood from BPH patients were used to investigate Treg subsets, phenotype and Treg‐associated cytokine production. Sorted CD39^+/− Tregs from healthy mice were adoptively transferred into mice before or after testosterone propionate administration. The Tregs percentage in peripheral blood from BPH patients was attenuated, exhibiting low Foxp3 and CD39 expression with low levels of serum IL‐10, IL‐35 and TGF‐β. Immunohistochemistry revealed Foxp3+ cells were significantly diminished in BPH prostate with severe inflammatory. Although the Tregs subset was comprised of more effector/memory Tregs, CD39 was still down‐regulated on effector/memory Tregs in BPH patients. Before or after testosterone propionate administration, no alterations of BPH symptoms were observed due to CD39‐ Tregs in mice, however, CD39⁺Tregs existed more potency than Tregs to regulate prostatic hyperplasia and inhibit inflammation by decreasing IL‐1β and PSA secretion, and increasing IL‐10 and TGF‐β secretion. Furthermore, adoptive transfer with functional Tregs not only improved prostate hyperplasia but also regulated muscle cell proliferation in bladder. Adoptive transfer with Tregs may provide a novel method for the prevention and treatment of BPH clinically.

Regulatory T cell is critical for interleukin-33-mediated neuroprotection against stroke

Interleukin-33 (IL-33) is known to activate the regulatory T lymphocytes (Tregs), which are negatively correlated with brain damage after ischemic stroke. In this study, we aimed to investigate the role of Tregs in IL-33-mediated neuroprotection and elucidate the underlying mechanisms. In vivo, male C57BL/6 N mice were subjected to 60 min of transient middle cerebral artery occlusion (tMCAO), followed by daily administration of vehicle or IL-33 immediately after injury. Tregs were depleted by intraperitoneal administration of anti-CD25 antibody (anti-CD25Ab). Behavioral changes, brain edema, neuronal injury, Treg percentages, and cytokine expression levels were investigated in each group. In vitro experiments, primary mouse neuronal cells were subjected to oxygen-glucose deprivation (OGD) for 3 h. Vehicle- or drug-conditioned Tregs were applied to the neurons at the time of induction of hypoxia. Neuronal apoptosis and cytokine expression were measured in each group. The results indicate that intraperitoneal administration of anti-CD25Ab reduced CD4 + CD25 + Foxp3+ Tregs, increased infarct volume, enhanced stroke-induced cell death, and decreased sensorimotor functions. Notably, IL-33 increased CD4 + CD25 + Foxp3+ Tregs in the spleen and brain. However, blockading ST2 attenuated these effects of IL-33. The supernatant of the IL-33-treated Treg culture reduced neuronal apoptosis and elevated the production of the Treg cytokines IL-10, IL-35, and transforming growth factor-β (TGF-β). Anti-CD25Ab abrogated the neuroprotective effect of IL-33. Mechanistically, the neuroprotective effects of IL-33 were associated with reduction in apoptosis-related proteins and production of Tregs related cytokines. Overall, these findings showed that IL-33 afforded neuroprotection against ischemic brain injury by enhancing ST2-dependent regulatory T-cell expansion and activation via a mechanism involving anti-apoptosis proteins and cytokines, representing a promising immune modulatory target for the treatment of stroke.

There Is (Scientific) Strength in Numbers: A Comprehensive Quantitation of Fc Gamma Receptor Numbers on Human and Murine Peripheral Blood Leukocytes

Antibodies are essential mediators of immunological defense mechanisms, are clinically used as therapeutic agents, but are also functionally involved in various immune-mediated disorders. Whereas IgG antibodies accomplish some of their biological tasks autonomously, many functions depend on their binding to activating and inhibitory Fcγ receptors (FcγR). From a qualitative point of view expression patterns of FcγR on immunologically relevant cell types are well-characterized both for mice and humans. Surprisingly, however, there is only quite limited information available on actual quantities of FcγR expressed by the different leukocyte populations. In this study we provide a comprehensive data set assessing quantitatively how many individual human and mouse FcγRs are expressed on B cells, NK cells, eosinophils, neutrophils, basophils and both classical, and non-classical monocytes under steady state conditions. Moreover, among human donors we found two groups with different expression levels of the inhibitory FcγRIIb on monocytes which appears to correlate with haplotypes of the activating FcγRIIIa.

CD8+ T cells regulated by CD4+CD25+ regulatory T cells in the early stage exacerbate the development of Dermatophagoides farinae-induced skin lesions via increasing mast cell infiltration in mice

Atopic dermatitis is a chronic inflammatory skin disease associated with CD4⁺ Th2 cell-shifted immune responses. Although the infiltration of skin lesions by CD8⁺ T cells has been recognized, their roles have not been fully defined. In this study, we examined the relationship between CD4⁺ and CD8⁺ cells in antigen-induced skin lesions of mice. BALB/c mice were repeatedly challenged with Dermatophagoides farinae (Der f) applied to the right ear nine times. Pre-treatment with anti-CD4 monoclonal antibody (mAb) during the third to sixth challenges, but not the post-treatment during the sixth to ninth challenges, exacerbated the development of Der f-induced ear swelling; pre-treatment with anti-CD25 mAb, which depletes regulatory T cells (Tregs), also exacerbated the lesions. Furthermore, the number of CD8⁺ T cells in lymph nodes was augmented by these pre-treatments. These findings prompted us to examine the effect of anti-CD8 mAb. Pre-treatment with anti-CD8 mAb, but not post-treatment, strongly inhibited the development of Der f-induced ear swelling; additionally, the epidermal hyperplasia and infiltration of mast cells were inhibited by the pre-treatment. Collectively, we revealed that CD8⁺ T cells regulated by CD4⁺CD25⁺ Tregs in the early stage are key contributors to the development of Der f-induced skin lesions via increasing mast cell infiltration, indicating that CD8⁺ T and Tregs could be potential therapeutic targets for atopic dermatitis.

Regulatory T Cells Promote Apelin-Mediated Sprouting Angiogenesis in Type 2 Diabetes

The role of CD4⁺ T cells in the ischemic tissues of T2D patients remains unclear. Here, we report that T2D patients' vascular density was negatively correlated with the number of infiltrating CD4⁺ T cells after ischemic injury. Th1 was the predominant subset, and Th1-derived IFN-γ and TNF-α directly impaired human angiogenesis. We then blocked CD4⁺ T cell infiltration into the ischemic tissues of both Lepr^db/db and diet-induced obese T2D mice. Genome-wide RNA sequencing shows an increased proliferative and angiogenic capability of diabetic ECs in ischemic tissues. Moreover, wire myography shows enhanced EC function and laser Doppler imaging reveals improved post-ischemic blood reperfusion. Mechanistically, functional revascularization after CD4 coreceptor blockade was mediated by Tregs. Genetic lineage tracing via Cdh5-CreER and Apln-CreER and coculture assays further illustrate that Tregs increased vascular density and induced de novo sprouting angiogenesis in a paracrine manner. Taken together, our results reveal that Th1 impaired while Tregs promoted functional post-ischemic revascularization in obesity and diabetes.

Rat IgG mediated circulatory cell depletion in mice requires mononuclear phagocyte system and is facilitated by complement

Application of exogenous Abs targeting cell surface Ags has been widely used as an experimental approach to induce cell depletion or to inhibit receptor functionality. Moreover, Ab therapy is emerging as one of the mainstream strategies for cancer treatment. Previous studies on the mechanisms of Ab-mediated cell depletion mainly employed Abs from the same species as the research subject. However, there has been a recent trend toward using xenogeneic (cross-species) Abs to achieve cell depletion or block receptor-ligand interactions; with rat Abs used in mice being the most common approach. Considering the molecular differences in Abs from different species, the mechanism(s) of xenogeneic Ab-mediated cell depletion is likely to be different than species-matched Ab supplementation. The current work describes our efforts to identify the mechanism of rat anti-mouse Ly6G (clone: 1A8) mAb mediated depletion of mouse neutrophils. The results showed that neutrophils circulating in the blood but not those in the bone marrow are depleted, and depletion depends on mononuclear phagocyte system, especially liver Kupffer cells that efficiently capture and phagocytize targeted cells. Interestingly, whereas species-matched Ab depletion does not require complement functionality, we found that complement activation significantly facilitates cross-species neutrophil depletion. Finally, we found that some rat mAbs (anti-C5aR, anti-CD11a, anti-CD11b, and anti-VLA4) used to block cell surface receptors also induce cell depletion. Thus, our work strongly recommends controlling for cell depletion effect when using these Abs for receptor blockade purposes.

Cancer-Specific Loss of p53 Leads to a Modulation of Myeloid and T Cell Responses

Loss of p53 function contributes to the development of many cancers. While cell-autonomous consequences of p53 mutation have been studied extensively, the role of p53 in regulating the anti-tumor immune response is still poorly understood. Here, we show that loss of p53 in cancer cells modulates the tumor-immune landscape to circumvent immune destruction. Deletion of p53 promotes the recruitment and instruction of suppressive myeloid CD11b+ cells, in part through increased expression of CXCR3/CCR2-associated chemokines and macrophage colony-stimulating factor (M-CSF), and attenuates the CD4+ T helper 1 (Th1) and CD8+ T cell responses in vivo. p53-null tumors also show an accumulation of suppressive regulatory T (Treg) cells. Finally, we show that two key drivers of tumorigenesis, activation of KRAS and deletion of p53, cooperate to promote immune tolerance.

An intrinsic role of IL-33 in Treg cell-mediated tumor immunoevasion

Regulatory T (T_reg) cells accumulate into tumors hindering the success of cancer immunotherapy. Yet, therapeutic targeting of T_reg cells shows limited efficacy or leads to autoimmunity. The molecular mechanisms that guide T_reg cell stability in tumors, remain elusive. Herein, we identify a cell-intrinsic role of the alarmin IL-33 in the functional stability of T_reg cells. Specifically, IL-33-deficient T_reg cells demonstrated attenuated suppressive properties in vivo and facilitated tumor regression in an ST2 (IL-33 receptor)-independent fashion. Upon activation, Il33^–/– T_reg cells exhibited epigenetic reprogramming with increased chromatin accessibility of the Ifng locus leading to elevated interferon-γ (IFN-γ) production in an NF-κB–T-bet-dependent manner. IFN-γ was essential for T_reg cell defective function since its ablation restored Il33^–/– T_reg cell suppressive properties. Importantly, genetic ablation of Il33 potentiated the therapeutic effect of immunotherapy. Our findings reveal a novel and therapeutically important intrinsic role of IL-33 in T_reg cell stability in cancer.

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.

Tumor microenvironment dictates regulatory T cell phenotype: Upregulated immune checkpoints reinforce suppressive function

Background

Regulatory T (T_reg) cells have an immunosuppressive function in cancer, but the underlying mechanism of immunosuppression in the tumor microenvironment (TME) is unclear.

Methods

We compared the phenotypes of T cell subsets, including T_reg cells, obtained from peripheral blood, malignant effusion, and tumors of 103 cancer patients. Our primary focus was on the expression of immune checkpoint (IC)-molecules, such as programmed death (PD)-1, T-cell immunoglobulin and mucin-domain containing (TIM)-3, T cell Ig and ITIM domain (TIGIT), and cytotoxic T lymphocyte antigen (CTLA)-4, on T_reg cells in paired lymphocytes from blood, peritumoral tissue, and tumors of 12 patients with lung cancer. To identify the immunosuppressive mechanisms acting on tumor-infiltrating T_reg cells, we conducted immunosuppressive functional assays in a mouse model.

Results

CD8⁺, CD4⁺ T cells, and T_reg cells exhibited a gradual upregulation of IC-molecules the closer they were to the tumor. Interestingly, PD-1 expression was more prominent in T_reg cells than in conventional T (T_conv) cells. In lung cancer patients_, higher levels of IC-molecules were expressed on T_reg cells than on T_conv cells, and T_reg cells were also more enriched in the tumor than in the peri-tumor and blood. In a mouse lung cancer model, IC-molecules were also preferentially upregulated on T_reg cells, compared to T_conv cells. PD-1 showed the greatest increase on most cell types, especially T_reg cells, and this increase occurred gradually over time after the cells entered the TME. PD-1 high-expressing tumor-infiltrating T_reg cells displayed potent suppressive activity, which could be partially inhibited with a blocking anti-PD-1 antibody.

Conclusions

We demonstrate that the TME confers a suppressive function on T_reg cells by upregulating IC-molecule expression. Targeting IC-molecules, including PD-1, on T_reg cells may be effective for cancer treatment.

Regulatory T Cells Tailored with pH-Responsive Liposomes Shape an Immuno-Antitumor Milieu against Tumors

Cell-based delivery platforms have received great interest in recent years and have been indicated as a promising strategy for cancer immunotherapy. Despite their wide applications in the clinical and preclinical stages, their concomitant viability and efficacy remain major issues. Herein, a strategy for harnessing regulatory T (Treg) cells is developed as an actively targeting drug-delivery system to transport drug-loaded liposomes to the desired tumor sites via conjugating liposomes on the surface of Treg cells. Under the guidance of tumor-oriented chemokines, liposome-anchored Treg cells can be leveraged to migrate and infiltrate the acidic tumor microenvironment, where pH-sensitive liposomes release the loaded cargos [comprising interleukin-2, programmed cell death ligand 1 antibody (PD-L1), and imiquimod], provoke dramatic dendritic cell maturation, block the PD-1/PD-L1 immune-checkpoint, elevate the frequency of infiltrating CD8⁺ effector T cells, and collectively contribute to potent inhibition of in situ and metastatic tumors. Here, the findings suggest a potential approach that offers a simple, robust, and safe insight into the tuning of Treg cells as an encouraging vector for augmenting cancer immunotherapy.

The Effect of Antibody Fragments on CD25 Targeted Regulatory T Cell Near-Infrared Photoimmunotherapy

Regulatory T (Treg) cells play a major role in immune suppression permitting tumors to evade immune surveillance. Depletion of intratumoral Treg cells can result in tumor regression. However, systemic depletion of Tregs may also induce autoimmune adverse events. Near-infrared photoimmunotherapy (NIR-PIT) is a newly developed cell-specific cancer therapy that locally kills specific cells in the tumor. Antibody-photoabsorber (IRDye700DX) conjugates (APC) are injected and bind to the tumor, and subsequent administration of NIR light to the tumor results in rapid cell death only in targeted cells. CD25-targeted NIR-PIT has been shown to induce spatially selective depletion of tumor-associated Treg cells. In this study, we compared the efficacy of an antibody fragment, anti-CD25-F(ab')₂, and a full antibody, anti-CD25-IgG, as agents for NIR-PIT. Tumor-bearing mice were divided into four groups: (1) no treatment; (2) anti-CD25-IgG-IR700 i.v. only; (3) anti-CD25-F(ab')₂-IR700 i.v. with NIR light exposure; and (4) anti-CD25-IgG-IR700 i.v. with NIR light exposure. Although both CD25-targeted NIR-PITs resulted in significant tumor growth inhibition, the anti-CD25-F(ab')₂-IR700 based NIR-PIT was superior to the anti-CD25-IgG-IR700 NIR-PIT. The anti-CD25-F(ab')₂-IR700 demonstrated faster clearance from the body than the anti-CD25-IgG-IR700. Sustained circulation of anti-CD25-IgG-IR700 may block IL-2 binding on the activated effector T-cells decreasing immune response. In conclusion, anti-CD25-F(ab')₂ based NIR-PIT was more effective in reducing tumor growth than anti-CD25-IgG based NIR-PIT. Absence of the Fc portion of the APC leads to faster clearance and therefore promotes a superior activated T cell response in tumors.

TNFR2 promotes Treg-mediated recovery from neuropathic pain across sexes

Tumor necrosis factor (TNF) is a cytokine that induces signaling via two receptors, TNFR1 and TNFR2. TNF signaling via TNFR1 contributes to development and maintenance of neuropathic pain. Here, we show that TNFR2 is essential for recovery from neuropathic pain across sexes. Treatment of male and female neuropathic mice with a TNFR2 agonist resulted in long-lasting recovery from neuropathic pain. We identified Tregs as the cellular mediator of the analgesic effect of TNFR2. Indeed, TNFR2 agonist administration alleviated peripheral and central inflammation and promoted neuroprotection in a Treg-dependent manner, indicating that TNFR2-dependent modulation of immunity is neuroprotective. We therefore argue that TNFR2 agonists might be a class of nonopioid drugs that can promote long-lasting pain recovery in males and females.

Tumor necrosis factor receptor 2 (TNFR2) is a transmembrane receptor that is linked to immune modulation and tissue regeneration. Here, we show that TNFR2 essentially promotes long-term pain resolution independently of sex. Genetic deletion of TNFR2 resulted in impaired neuronal regeneration and chronic nonresolving pain after chronic constriction injury (CCI). Further, pharmacological activation of TNFR2 using the TNFR2 agonist EHD2-sc-mTNF_R2 in mice with chronic neuropathic pain promoted long-lasting pain recovery. TNFR2 agonist treatment reduced neuronal injury, alleviated peripheral and central inflammation, and promoted repolarization of central nervous system (CNS)-infiltrating myeloid cells into an antiinflammatory/reparative phenotype. Depletion of regulatory T cells (Tregs) delayed spontaneous pain recovery and abolished the therapeutic effect of EHD2-sc-mTNF_R2. This study therefore reveals a function of TNFR2 in neuropathic pain recovery and demonstrates that both TNFR2 signaling and Tregs are essential for pain recovery after CCI. Therefore, therapeutic strategies based on the concept of enhancing TNFR2 signaling could be developed into a nonopioid therapy for the treatment of chronic neuropathic pain.

Fibrogenesis in Chronic DSS Colitis is Not Influenced by Neutralisation of Regulatory T Cells, of Major T Helper Cytokines or Absence of IL-13

Mechanisms underlying fibrogenesis in chronic colitis are largely unknown. There is an urgent need for clinical markers and identification of targets to prevent, treat and limit intestinal fibrosis. This study investigated the contribution of major T cell cytokines and T regulatory cells (Tregs) to inflammation and fibrosis induced in a model of experimental colitis by oral intake of dextran sodium sulphate (DSS) in wild type and IL-13 knock-out C57Bl/6 mice. Inflammation and fibrosis were scored by macroscopic and histological examination and fibrosis was quantified by hydroxyproline. Numbers of Tregs and IFN-γ⁺, IL-13⁺ and IL-17A⁺ CD4⁺ T helper (Th) cells in mesenteric lymph nodes increased during chronic DSS administration and mRNA for IFN-γ and IL-17 in the inflamed colon tissue was upregulated. However, antibody-mediated neutralisation of IFN-γ or IL-17A/F in a therapeutic setting had no effect on chronic intestinal inflammation and fibrosis. Antibody-mediated depletion of Tregs did not enhance fibrosis, nor did IL-13 deficiency have an effect on the fibrotic disease. These data argue against an important contribution of Tregs and of the cytokines IFN-γ, IL-13, IL-17A, IL-17F in the induction and/or control of fibrosis in this Crohn's disease like murine model.

Regulatory T-cells promote pulmonary repair by modulating T helper cell immune responses in lipopolysaccharide-induced acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) induces a strong local infiltration of regulatory T-cells (Tregs) in the lungs. However, at present, there remains a lack of adequate evidence showing the direct effect of Tregs on pulmonary repair and the related mechanisms of ARDS. Therefore, in this project, we studied the impact of Tregs on lipopolysaccharide (LPS)-induced ARDS and pulmonary inflammation. Surprisingly, we found that depletion of Tregs by injection of PC61 anti-CD25 antibody not only interfered with the inflammation resolution, such as inhibited total cell infiltration into the alveolar space, downregulated neutrophils, upregulated macrophages, but also impaired pulmonary epithelium and endothelial cell proliferation. Consistent with the attenuation of pulmonary repair, we found that the Th1 and Th17 immune responses were also impaired in Treg-depleted mice, suggesting that the presence of Tregs is vital for tissue repair, as Tregs modulate and promote the Th immune response in LPS-induced pulmonary inflammation.

In Vivo Generation of Gut-Homing Regulatory T Cells for the Suppression of Colitis

Current therapies for gut inflammation have not reached the desired specificity and are attended by unintended immune suppression. This study aimed to provide evidence for supporting a hypothesis that direct in vivo augmentation of the induction of gut-homing regulatory T (Treg) cells is a strategy of expected specificity for the treatment of chronic intestinal inflammation (e.g., inflammatory bowel disease). We showed that dendritic cells (DCs), engineered to de novo produce high concentrations of both 1,25-dihydroxyvitamin D, the active vitamin D metabolite, and retinoic acid, an active vitamin A metabolite, augmented the induction of T cells that express both the regulatory molecule Foxp3 and the gut-homing receptor CCR9 in vitro and in vivo. In vivo, the newly generated Ag-specific Foxp3⁺ T cells homed to intestines. Additionally, transfer of such engineered DCs robustly suppressed ongoing experimental colitis. Moreover, CD4⁺ T cells from spleens of the mice transferred with the engineered DCs suppressed experimental colitis in syngeneic hosts. The data suggest that the engineered DCs enhance regulatory function in CD4⁺ T cell population in peripheral lymphoid tissues. Finally, we showed that colitis suppression following in vivo transfer of the engineered DCs was significantly reduced when Foxp3⁺ Treg cells were depleted. The data indicate that maximal colitis suppression mediated by the engineered DCs requires Treg cells. Collectively, our data support that DCs de novo overproducing both 1,25-dihydroxyvitamin D and retinoic acid are a promising novel therapy for chronic intestinal inflammation.

Depletion of regulatory T cells in tumors with an anti-CD25 immunotoxin induces CD8 T cell-mediated systemic antitumor immunity

The tumor microenvironment plays a critical role in controlling tumor progression and immune surveillance. We produced an immunotoxin (2E4-PE38) that kills mouse cells expressing CD25 by attaching the Fv portion of monoclonal antibody 2E4 (anti-mouse CD25) to a 38-kDa portion of Pseudomonas exotoxin A. We employed three mouse cancer tumor models (AB1 mesothelioma, 66c14 breast cancer, and CT26M colon cancer). Tumors were implanted at two sites on BALB/c mice. On days 5 and 9, one tumor was directly injected with 2E4-PE38, and the other was not treated; 2E4-PE38 produced complete regressions of 85% of injected AB1 tumors, 100% of 66c14 tumors, and 100% of CT26M tumors. It also produced complete regressions of 77% of uninjected AB1 tumors, 47% of 66c14 tumors, and 92% of CT26M tumors. Mice with complete regressions of 66c14 tumors were immune to rechallenge with 66c14 cells. Mice with complete regressions of AB1 or CT26M tumors developed cross-tumor immunity rejecting both tumor types. Injection of anti-CD25 antibody or a mutant inactive immunotoxin were generally ineffective. Tumors were analyzed 3 days after 2E4-PE38 injection. The number of regulatory T cells (Tregs) was significantly reduced in the injected tumor but not in the spleen. Injected tumors contained an increase in CD8 T cells expressing IFN-γ, the activation markers CD69 and CD25, and macrophages and conventional dendritic cells. Treatment with antibodies to CD8 abolished the antitumor effect. Selective depletion of Tregs in tumors facilitates the development of a CD8 T cell-dependent antitumor effect in three mouse models.

A GMCSF-Neuroantigen Tolerogenic Vaccine Elicits Systemic Lymphocytosis of CD4+ CD25high FOXP3+ Regulatory T Cells in Myelin-Specific TCR Transgenic Mice Contingent Upon Low-Efficiency T Cell Antigen Receptor Recognition

Previous studies showed that single-chain fusion proteins comprised of GM-CSF and major encephalitogenic peptides of myelin, when injected subcutaneously in saline, were potent tolerogenic vaccines that suppressed experimental autoimmune encephalomyelitis (EAE) in rats and mice. These tolerogenic vaccines exhibited dominant suppressive activity in inflammatory environments even when emulsified in Complete Freund's Adjuvant (CFA). The current study provides evidence that the mechanism of tolerance was dependent upon vaccine-induced regulatory CD25⁺ T cells (Tregs), because treatment of mice with the Treg-depleting anti-CD25 mAb PC61 reversed tolerance. To assess tolerogenic mechanisms, we focused on 2D2-FIG mice, which have a transgenic T cell repertoire that recognizes myelin oligodendrocyte glycoprotein peptide MOG35-55 as a low-affinity ligand and the neurofilament medium peptide NFM13-37 as a high-affinity ligand. Notably, a single subcutaneous vaccination of GMCSF-MOG in saline elicited a major population of FOXP3⁺ Tregs that appeared within 3 days, was sustained over several weeks, expressed canonical Treg markers, and was present systemically at high frequencies in the blood, spleen, and lymph nodes. Subcutaneous and intravenous injections of GMCSF-MOG were equally effective for induction of FOXP3⁺ Tregs. Repeated booster vaccinations with GMCSF-MOG elicited FOXP3 expression in over 40% of all circulating T cells. Covalent linkage of GM-CSF with MOG35-55 was required for Treg induction whereas vaccination with GM-CSF and MOG35-55 as separate molecules lacked Treg-inductive activity. GMCSF-MOG elicited high levels of Tregs even when administered in immunogenic adjuvants such as CFA or Alum. Conversely, incorporation of GM-CSF and MOG35-55 as separate molecules in CFA did not support Treg induction. The ability of the vaccine to induce Tregs was dependent upon the efficiency of T cell antigen recognition, because vaccination of 2D2-FIG or OTII-FIG mice with the high-affinity ligands GMCSF-NFM or GMCSF-OVA (Ovalbumin323-339), respectively, did not elicit Tregs. Comparison of 2D2-FIG and 2D2-FIG-Rag1 ^-/- strains revealed that GMCSF-MOG may predominantly drive Treg expansion because the kinetics of vaccine-induced Treg emergence was a function of pre-existing Treg levels. In conclusion, these findings indicate that the antigenic domain of the GMCSF-NAg tolerogenic vaccine is critical in setting the balance between regulatory and conventional T cell responses in both quiescent and inflammatory environments.

The Microbial Metabolite Butyrate Stimulates Bone Formation via T Regulatory Cell-Mediated Regulation of WNT10B Expression

Nutritional supplementation with probiotics can prevent pathologic bone loss. Here we examined the impact of supplementation with Lactobacillus rhamnosus GG (LGG) on bone homeostasis in eugonadic young mice. Micro-computed tomography revealed that LGG increased trabecular bone volume in mice, which was due to increased bone formation. Butyrate produced in the gut following LGG ingestion, or butyrate fed directly to germ-free mice, induced the expansion of intestinal and bone marrow (BM) regulatory T (Treg) cells. Interaction of BM CD8+ T cells with Treg cells resulted in increased secretion of Wnt10b, a bone anabolic Wnt ligand. Mechanistically, Treg cells promoted the assembly of a NFAT1-SMAD3 transcription complex in CD8+ cells, which drove expression of Wnt10b. Reducing Treg cell numbers, or reconstitution of TCRβ-/- mice with CD8+ T cells from Wnt10b-/- mice, prevented butyrate-induced bone formation and bone mass acquisition. Thus, butyrate concentrations regulate bone anabolism via Treg cell-mediated regulation of CD8+ T cell Wnt10b production.

CD25 and TGF-β blockade based on predictive integrated immune ratio inhibits tumor growth in pancreatic cancer

BACKGROUND

The prognosis of pancreatic ductal adenocarcinoma (PDAC) remains poor due to the difficulty of disease diagnosis and therapy. Immunotherapy has had robust performance against several malignancies, including PDAC. In this study, we aim to analyze the expression of CD8 and FoxP3 on T lymphocytes and TGF-β expression in tumor tissues, and then analyze the possible clinical significance of these finding in order to find a novel effective immunotherapy target in PDAC using a murine model.

METHODS

A tissue microarray using patient PDAC samples was stained and analyzed for associations with clinicopathological characteristics. A preclinical murine model administrated with various immunotherapies were analyzed by growth inhibitor, flow cytometry, enzyme-linked immuno sorbent assay and immunohistochemistry.

RESULTS

The infiltrating FoxP3⁺ regulatory T cells (Tregs) in tumor tissues were associated with survival, while CD8⁺ tumor infiltrating lymphocytes (TILs) were not. Considering the drawbacks of these measure alone, the number of CD8⁺ and FoxP3⁺ T cells were combined to create a new estimated value-integrated immune ratio (IIR), which showed excellent validity in survival risk stratification. IIR was further verified as an independent prognostic factor according to multivariate analysis as well as TGF-β expression. Association between TGF-β expression and infiltrating Tregs was also verified. Then, in our preclinical murine model, CD25 and TGF-β combination blockade had a higher tumor growth inhibitor value. This combination therapy significantly depleted periphery and intra-tumor FoxP3⁺ Tregs while increasing intra-tumor CD8⁺ TILs levels compared to controls or anti-TGF-β monotherapy (p < 0.05). Anti-CD25 monotherapy alone also had the ability to deplete periphery and intra-tumor Tregs (p < 0.05). The excretion of intra-tumor IL-10, TGF-β was notably lower but higher IFN-γ excretion in this combination immunotherapy. Such combination immunotherapy was further confirmed to synergize with anti-PD-1 monotherapy to improve tumor growth inhibition and cure rates.

CONCLUSIONS

The combination of CD25, TGF-β and PD-1 blockade plays a potentially effective role in inhibiting tumor formation and progression. Our results also provide a strong rational strategy for use of IIR in future immunotherapy clinical trials.

Quiescent Tissue Stem Cells Evade Immune Surveillance

Stem cells are critical for the maintenance of many tissues, but whether their integrity is maintained in the face of immunity is unclear. Here we found that cycling epithelial stem cells, including Lgr5⁺ intestinal stem cells, as well as ovary and mammary stem cells, were eliminated by activated T cells, but quiescent stem cells in the hair follicle and muscle were resistant to T cell killing. Immune evasion was an intrinsic property of the quiescent stem cells resulting from systemic downregulation of the antigen presentation machinery, including MHC class I and TAP proteins, and is mediated by the transactivator NLRC5. This process was reversed upon stem cell entry into the cell cycle. These studies identify a link between stem cell quiescence, antigen presentation, and immune evasion. As cancer-initiating cells can derive from stem cells, these findings may help explain how the earliest cancer cells evade immune surveillance.

Isolated Schistosoma mansoni eggs prevent allergic airway inflammation

Chronic helminth infection with Schistosoma (S.) mansoni protects against allergic airway inflammation (AAI) in mice and is associated with reduced Th2 responses to inhaled allergens in humans, despite the presence of schistosome‐specific Th2 immunity. Schistosome eggs strongly induce type 2 immunity and allow to study the dynamics of Th2 versus regulatory responses in the absence of worms. Treatment with isolated S. mansoni eggs by i.p. injection prior to induction of AAI to ovalbumin (OVA)/alum led to significantly reduced AAI as assessed by less BAL and lung eosinophilia, less cellular influx into lung tissue, less OVA‐specific Th2 cytokines in lungs and lung‐draining mediastinal lymph nodes and less circulating allergen‐specific IgG1 and IgE antibodies. While OVA‐specific Th2 responses were inhibited, treatment induced a strong systemic Th2 response to the eggs. The protective effect of S. mansoni eggs was unaltered in μMT mice lacking mature (B2) B cells and unaffected by Treg cell depletion using anti‐CD25 blocking antibodies during egg treatment and allergic sensitization. Notably, prophylactic egg treatment resulted in a reduced influx of pro‐inflammatory, monocyte‐derived dendritic cells into lung tissue of allergic mice following challenge. Altogether, S. mansoni eggs can protect against the development of AAI, despite strong egg‐specific Th2 responses.

Indoleamine 2,3-dioxygenase-dependent expansion of T-regulatory cells maintains mucosal healing in ulcerative colitis

BACKGROUND

Dendritic cell (DC)-derived indolamine 2,3-dioxygenase (IDO) degrades tryptophan to kynurenine, which promotes conversion of inflammatory T cells in immunosuppressive regulatory T cells (Tregs). We analyzed the significance of the IDO:Treg axis for inducing and maintaining mucosal healing in ulcerative colitis (UC).

METHODS

Dextran sodium sulphate (DSS)-induced colitis in BALB/c mice (model for mucosal healing) and C57BL/6 mice (model for persistent disease) was used. Serum, fecal samples and colon-infiltrating immune cells of 65 patients with UC with mucosal healing or persistent colitis were analyzed.

RESULTS

Significantly higher serum levels of kynurenine and downregulated inflammatory cytokines were noticed in DSS-treated BALB/c mice compared with C57BL/6 mice. Increased IDO activity and attenuated capacity for antigen presentation and production of inflammatory cytokines, observed in BALB/c DCs, was followed by a significantly lower number of inflammatory T helper 1 (Th1) and Th17 cells and a notably increased number of Tregs in the colons of DSS-treated BALB/c mice. DCs and Tregs were crucially important for the maintenance of mucosal healing since their depletion aggravated colitis. Mucosal healing, followed by an increase in kynurenine and intestinal Tregs, was re-established when BALB/c DCs were transferred into DC-depleted or Treg-depleted DSS-treated BALB/c mice. This phenomenon was completely abrogated by the IDO inhibitor. Significantly higher serum and fecal levels of kynurenine, accompanied by an increased presence of intestinal Tregs, were noticed in patients with UC with mucosal healing and negatively correlated with disease severity, fecal calprotectin, colon-infiltrating interferon γ and interleukin-17-producing cells, serum and fecal levels of inflammatory cytokines.

CONCLUSION

IDO-dependent expansion of endogenous Tregs should be further explored as a new approach for the induction and maintenance of mucosal healing in patients with UC.

Resistance to Radiotherapy and PD-L1 Blockade Is Mediated by TIM-3 Upregulation and Regulatory T-Cell Infiltration

Purpose: Radiotherapy (RT) can transform the immune landscape and render poorly immunogenic tumors sensitive to PD-L1 inhibition. Here, we established that the response to combined RT and PD-L1 inhibition is transient and investigated mechanisms of resistance.Experimental Design: Mechanisms of resistance to RT and PD-L1 blockade were investigated in orthotopic murine head and neck squamous cell carcinoma (HNSCC) tumors using mass cytometry and whole-genome sequencing. Mice were treated with anti-PD-L1 or anti-TIM-3 alone and in combination with and without RT. Tumor growth and survival were assessed. Flow cytometry was used to assess phenotypic and functional changes in intratumoral T-cell populations. Depletion of regulatory T cells (Treg) was performed using anti-CD25 antibody.Results: We show that the immune checkpoint receptor, TIM-3, is upregulated on CD8 T cells and Tregs in tumors treated with RT and PD-L1 blockade. Treatment with anti-TIM-3 concurrently with anti-PD-L1 and RT led to significant tumor growth delay, enhanced T-cell cytotoxicity, decreased Tregs, and improved survival in orthotopic models of HNSCC. Despite this treatment combination, the response was not durable, and analysis of relapsed tumors revealed resurgence of Tregs. Targeted Treg depletion, however, restored antitumor immunity in mice treated with RT and dual immune checkpoint blockade and resulted in tumor rejection and induction of immunologic memory.Conclusions: These data reveal multiple layers of immune regulation that can promote tumorigenesis and the therapeutic potential of sequential targeting to overcome tumor resistance mechanisms. We propose that targeted Treg inhibitors may be critical for achieving durable tumor response with combined radiotherapy and immunotherapy. Clin Cancer Res; 24(21); 5368-80. ©2018 AACR.

TGF-β1 secreted by Tregs in lymph nodes promotes breast cancer malignancy via up-regulation of IL-17RB

Lymph node (LN) metastasis is commonly associated with systemic distant organ metastasis in human breast cancer and is an important prognostic predictor for survival of breast cancer patients. However, whether tumor‐draining LNs (TDLNs) play a significant role in modulating the malignancy of cancer cells for distant metastasis remains controversial. Using a syngeneic mouse mammary tumor model, we found that breast tumor cells derived from TDLN have higher malignancy and removal of TDLNs significantly reduced distant metastasis. Up‐regulation of oncogenic Il‐17rb in cancer cells derived from TDLNs contributes to their malignancy. TGF‐β1 secreted from regulatory T cells (Tregs) in the TDLNs mediated the up‐regulation of Il‐17rb through downstream Smad2/3/4 signaling. These phenotypes can be abolished by TGF‐β1 neutralization or depletion of Tregs. Consistently, clinical data showed that the up‐regulation of IL‐17RB in cancer cells from LN metastases correlated with the increased prevalence of Tregs as well as the aggressive growth of tumors in mouse xenograft assay. Together, these results indicate that Tregs in TDLNs play an important role in modulating the malignancy of breast cancer cells for distant metastasis. Blocking IL‐17RB expression could therefore be a potential approach to curb the process.

Selective FcγR Co-engagement on APCs Modulates the Activity of Therapeutic Antibodies Targeting T Cell Antigens

The co-engagement of fragment crystallizable (Fc) gamma receptors (FcγRs) with the Fc region of recombinant immunoglobulin monoclonal antibodies (mAbs) and its contribution to therapeutic activity has been extensively studied. For example, Fc-FcγR interactions have been shown to be important for mAb-directed effector cell activities, as well as mAb-dependent forward signaling into target cells via receptor clustering. Here we identify a function of mAbs targeting T cell-expressed antigens that involves FcγR co-engagement on antigen-presenting cells (APCs). In the case of mAbs targeting CTLA-4 and TIGIT, the interaction with FcγR on APCs enhanced antigen-specific T cell responses and tumoricidal activity. This mechanism extended to an anti-CD45RB mAb, which led to FcγR-dependent regulatory T cell expansion in mice.

Crosstalk between mesenchymal stem cells and T regulatory cells is crucially important for the attenuation of acute liver injury

One of the therapeutic options for the treatment of fulminant hepatitis is repopulation of intrahepatic regulatory cells because their pool is significantly reduced during acute liver failure. Although it is known that mesenchymal stem cells (MSCs), which have beneficent effects in the therapy of fulminant hepatitis, may promote expansion of regulatory T cells (Tregs) and regulatory B cells (Bregs), the role of these regulatory cells in MSC-mediated attenuation of acute liver injury is unknown. Herewith, we described the molecular mechanisms involved in the crosstalk between MSCs and liver regulatory cells and analyzed the potential of MSC-based therapy for the expansion of intrahepatic regulatory cells in mouse model of acute liver failure. MSC-dependent attenuation of α-galactosylceramide (α-GalCer)-induced acute liver injury in mice was accompanied with an increased presence of interleukin (IL) 10-producing CD4⁺ CD25⁺ forkhead box P3⁺ Tregs and IL10- and transforming growth factor β-producing marginal zone-like Bregs in the liver. Depletion of Bregs did not alter MSC-based alleviation of acute liver failure, whereas depletion of Tregs completely abrogated hepatoprotective effects of MSCs and inhibited their capacity to attenuate hepatotoxicity of liver natural killer T cells (NKTs), indicating that Tregs, and not Bregs, were critically involved in MSC-based modulation of acute liver inflammation. MSCs, in a paracrine, indoleamine 2,3-dioxygenase-dependent manner, significantly increased the capacity of Tregs to produce immunosuppressive IL10 and to suppress hepatotoxicity of liver NKTs. Accordingly, adoptive transfer of MSC-primed Tregs resulted in the complete attenuation of α-GalCer-induced acute liver failure. In conclusion, our findings highlighted the crucial importance of Tregs for MSC-based attenuation of acute liver failure and indicated the significance of MSC-mediated priming of Tregs as a new therapeutic approach in Treg-based therapy of acute liver injury. Liver Transplantation 24 687-702 2018 AASLD.

Peripherally derived T regulatory and γδ T cells have opposing roles in the pathogenesis of intractable pediatric epilepsy

The pathophysiology of drug-resistant pediatric epilepsy is unknown. Flow cytometric analysis of inflammatory leukocytes in resected brain tissues from 29 pediatric patients with genetic (focal cortical dysplasia) or acquired (encephalomalacia) epilepsy demonstrated significant brain infiltration of blood-borne inflammatory myeloid cells and memory CD4+ and CD8+ T cells. Significantly, proinflammatory (IL-17- and GM-CSF-producing) γδ T cells were concentrated in epileptogenic lesions, and their numbers positively correlated with disease severity. Conversely, numbers of regulatory T (T reg) cells inversely correlated with disease severity. Correspondingly, using the kainic acid model of status epilepticus, we show ameliorated seizure activity in both γδ T cell- and IL-17RA-deficient mice and in recipients of T reg cells, whereas T reg cell depletion heightened seizure severity. Moreover, both IL-17 and GM-CSF induced neuronal hyperexcitability in brain slice cultures. These studies support a major pathological role for peripherally derived innate and adaptive proinflammatory immune responses in the pathogenesis of intractable epilepsy and suggest testing of immunomodulatory therapies.

Redirecting TGF-β Signaling through the β-Catenin/Foxo Complex Prevents Kidney Fibrosis

TGF-β is a key profibrotic factor, but targeting TGF-β to prevent fibrosis also abolishes its protective anti-inflammatory effects. Here, we investigated the hypothesis that we can redirect TGF-β signaling by preventing downstream profibrotic interaction of β-catenin with T cell factor (TCF), thereby enhancing the interaction of β-catenin with Foxo, a transcription factor that controls differentiation of TGF-β induced regulatory T cells (iTregs), and thus, enhance anti-inflammatory effects of TGF-β In iTregs derived from EL4 T cells treated with recombinant human TGF-β1 (rhTGF-β1) in vitro, inhibition of β-catenin/TCF transcription with ICG-001 increased Foxp3 expression, interaction of β-catenin and Foxo1, binding of Foxo1 to the Foxp3 promoter, and Foxo transcriptional activity. Moreover, the level of β-catenin expression positively correlated with the level of Foxo1 binding to the Foxp3 promoter and Foxo transcriptional activity. T cell fate mapping in Foxp3gfp Ly5.1/5.2 mice revealed that coadministration of rhTGF-β1 and ICG-001 further enhanced the expansion of iTregs and natural Tregs observed with rhTGF-β1 treatment alone. Coadministration of rhTGF-β1 with ICG-001 also increased the number of Tregs and reduced inflammation and fibrosis in the kidney fibrosis models of unilateral ureteric obstruction and ischemia-reperfusion injury. Notably, ICG-001 prevented the fibrosis in distant organs (lung and liver) caused by rhTGF-β1. Together, our results show that diversion of β-catenin from TCF- to Foxo-mediated transcription inhibits the β-catenin/TCF-mediated profibrotic effects of TGF-β while enhancing the β-catenin/Foxo-mediated anti-inflammatory effects. Targeting β-catenin/Foxo may be a novel therapeutic strategy in the treatment of fibrotic diseases that lead to organ failure.

Immunometabolism and PI(3)K Signaling As a Link between IL-2, Foxp3 Expression, and Suppressor Function in Regulatory T Cells

CD4⁺ Foxp3⁺ regulatory T cells (Tregs) are an essential component of immune homeostasis. Modulation of Treg function has been proposed as a means of treating autoimmune conditions and preventing rejection of organ transplants, although achieving this goal will require a detailed understanding of Treg signaling pathways. Signaling within Tregs is known to differ considerably from that observed in other T cell subsets. Of note, Tregs are the only cell type known to constitutively express CD25, the main ligand-binding subunit of the IL-2 receptor. The PI(3)K/Akt/mTOR cascade constitutes a major signaling pathway downstream of IL-2 and is closely tied to cellular metabolism. Due to increasing recognition of the links between cellular fuel usage and immune cell function, the interplay between IL-2 signaling and Treg metabolism represents an important space for exploration and a potential approach for immunomodulation. Here, we discuss how IL-2 may affect Treg metabolism via PI(3)K signaling, as well as the effects of altered metabolism on Treg lineage stability and suppressor function.

Tolerogenic nanoparticles restore the antitumor activity of recombinant immunotoxins by mitigating immunogenicity

Protein-based drugs are very active in treating cancer, but their efficacy can be limited by the formation of neutralizing antidrug antibodies (ADAs). Recombinant immunotoxins are proteins that are very effective in patients with leukemia, where immunity is suppressed, but induce ADAs, which compromise their activity, in patients with intact immunity. Here we induced a specific, durable, and transferable immune tolerance to recombinant immunotoxins by combining them with nanoparticles containing rapamycin (SVP-R). SVP-R mitigated the formation of inhibitory ADAs in naïve and sensitized mice, resulting in restoration of antitumor activity. The immune tolerance is mediated by colocalization of the SVP-R and immunotoxin to dendritic cells and macrophages in the spleen and is abrogated by depletion of regulatory T cells. Tolerance induced by SVPs was not blocked by checkpoint inhibitors or costimulatory agonist monoclonal antibodies that by themselves enhance ADA formation.

Blockade of TNFR2 signaling enhances the immunotherapeutic effect of CpG ODN in a mouse model of colon cancer

Through the tumor necrosis factor (TNF) receptor type II (TNFR2), TNF preferentially activates, expands, and promotes the phenotypic stability of CD4⁺Foxp3⁺ regulatory T (T_reg) cells. Those T_reg cells that have a high abundance of TNFR2 have the maximal immunosuppressive capacity. We investigated whether targeting TNFR2 could effectively suppress the activity of T_reg cells and consequently enhance the efficacy of cancer immunotherapy. We found that, relative to a suboptimal dose of the immunostimulatory Toll-like receptor 9 ligand CpG oligodeoxynucleotide (ODN), the combination of the suboptimal dose of CpG ODN with the TNFR2-blocking antibody M861 more markedly inhibited the growth of subcutaneously grafted mouse CT26 colon tumor cells. This resulted in markedly fewer TNFR2⁺ T_reg cells and more interferon-γ-positive (IFN-γ⁺) CD8⁺ cytotoxic T lymphocytes infiltrating the tumor and improved long-term tumor-free survival in the mouse cohort. Tumor-free mice were resistant to rechallenge by the same but not unrelated (4T1 breast cancer) cells. Treatment with the combination of TNFR2-blocking antibody and a CD25-targeted antibody also resulted in enhanced inhibition of tumor growth in a syngeneic 4T1 mouse model of breast cancer. Thus, the combination of a TNFR2 inhibitor and an immunotherapeutic stimulant may represent a more effective treatment strategy for various cancers.

Microbiota-activated PPAR-γ signaling inhibits dysbiotic Enterobacteriaceae expansion

Perturbation of the gut-associated microbial community may underlie many human illnesses, but the mechanisms that maintain homeostasis are poorly understood. We found that the depletion of butyrate-producing microbes by antibiotic treatment reduced epithelial signaling through the intracellular butyrate sensor peroxisome proliferator-activated receptor γ (PPAR-γ). Nitrate levels increased in the colonic lumen because epithelial expression of Nos2, the gene encoding inducible nitric oxide synthase, was elevated in the absence of PPAR-γ signaling. Microbiota-induced PPAR-γ signaling also limits the luminal bioavailability of oxygen by driving the energy metabolism of colonic epithelial cells (colonocytes) toward β-oxidation. Therefore, microbiota-activated PPAR-γ signaling is a homeostatic pathway that prevents a dysbiotic expansion of potentially pathogenic Escherichia and Salmonella by reducing the bioavailability of respiratory electron acceptors to Enterobacteriaceae in the lumen of the colon.

Partial CD25 Antagonism Enables Dominance of Antigen-Inducible CD25high FOXP3+ Regulatory T Cells As a Basis for a Regulatory T Cell-Based Adoptive Immunotherapy

FOXP3⁺ regulatory T cells (Tregs) represent a promising platform for effective adoptive immunotherapy of chronic inflammatory disease, including autoimmune diseases such as multiple sclerosis. Successful Treg immunotherapy however requires new technologies to enable long-term expansion of stable, antigen-specific FOXP3⁺ Tregs in cell culture. Antigen-specific activation of naïve T cells in the presence of TGF-β elicits the initial differentiation of the FOXP3⁺ lineage, but these Treg lines lack phenotypic stability and rapidly transition to a conventional T cell (Tcon) phenotype during in vitro propagation. Because Tregs and Tcons differentially express CD25, we hypothesized that anti-CD25 monoclonal antibodies (mAbs) would only partially block IL-2 signaling in CD25^high FOXP3⁺ Tregs while completely blocking IL-2 responses of CD25^{low-intermediate} Tcons to enable preferential outgrowth of Tregs during in vitro propagation. Indeed, murine TGF-β-induced MOG-specific Treg lines from 2D2 transgenic mice that were maintained in IL-2 with the anti-CD25 PC61 mAb rapidly acquired and indefinitely maintained a FOXP3^high phenotype during long-term in vitro propagation (>90% FOXP3⁺ Tregs), whereas parallel cultures lacking PC61 rapidly lost FOXP3. These results pertained to TGF-β-inducible "iTregs" because Tregs from 2D2-FIG Rag1^-/- mice, which lack thymic or natural Tregs, were stabilized by continuous culture in IL-2 and PC61. MOG-specific and polyclonal Tregs upregulated the Treg-associated markers Neuropilin-1 (NRP1) and Helios (IKZF2). Just as PC61 stabilized FOXP3⁺ Tregs during expansion in IL-2, TGF-β fully stabilized FOXP3⁺ Tregs during cellular activation in the presence of dendritic cells and antigen/mitogen. Adoptive transfer of blastogenic CD25^high FOXP3⁺ Tregs from MOG35-55-specific 2D2 TCR transgenic mice suppressed experimental autoimmune encephalomyelitis in pretreatment and therapeutic protocols. In conclusion, low IL-2 concentrations coupled with high PC61 concentrations constrained IL-2 signaling to a low-intensity range that enabled dominant stable outgrowth of suppressive CD25^high FOXP3⁺ Tregs. The ability to indefinitely expand stable Treg lines will provide insight into FOXP3⁺ Treg physiology and will be foundational for Treg-based immunotherapy.

Removal of regulatory T cells prevents secondary chronic infection but increases the mortality of subsequent sub-acute infection in sepsis mice

The immunosuppression following initial septic insult impairs resistance to secondary infection. Modulation of lymphocytes population may help to develop an effective therapeutic strategy. In this study, lipopolysaccharide (LPS)-induced endotoxemia was employed as the initial septic insult. 24 hours later, mice underwent cecal ligation and puncture to induce chronic or sub-acute peritonitis. Potential usefulness of T regs deletion antibody (anti-CD25) in improving LPS-induced immunosuppression and the survival of subsequent different infections were evaluated. LPS injection induced lymphocyte loss and led to decreased IL-6, TNF-α and IFN-γ, and weakened bacteria clearance upon chronic peritonitis at 24 h post-LPS, whereas reconstitution with lymphocytes reversed these changes. LPS-induced T regs expansion contributed to T and NK cells decrease in number and activity during sepsis. Depletion of T regs using anti-CD25 antibodies partly prevented lymphocyte loss and increased the responses of T and NK cells to subsequent stimulation, resulting in significantly increased bacterial clearance and survival in a 2-hit model of chronic peritonitis, but which significantly increased early mortality upon subsequently sub-acute infection. Yet, using lower dosage of anti-CD25 antibodies to moderate down-regulate T regs levels could partly improve bacterial clearance and survival in either chronic or sub-acute infection. These results demonstrate that using anti-CD25 antibodies to deplete T regs can ameliorate immunosuppression through increasing T cells and NK cells responses in sepsis, which is beneficial for preventing subsequently chronic infection, but will probably bring some deleterious effects for subsequent sub-acute infection.

Update on the Protective Role of Regulatory T Cells in Myocardial Infarction: A Promising Therapy to Repair the Heart

Myocardial infarction (MI) remains one of the leading causes of heart failure development and death worldwide. To date, interventional and pharmacological therapies are effective in reducing the onset of heart failure and promoting survival. However, progressive maladaptive remodeling post-MI persists in a large fraction of patients resulting in poor prognosis. Immune cell responses and an inflammatory environment largely contribute to adverse cardiac remodeling post-MI. CD4FOXP3 regulatory T cells (Tregs) are known for their immunosuppressive capacity and have been successfully implemented in multiple preclinical studies of permanent and ischemia-reperfusion MI. In this review, we highlight the important cardioprotective role of Tregs at the cardiac tissue, cellular, and molecular level, as well as the most prominent pharmacological venues that could be used to exploit Tregs as a novel therapeutic intervention to lessen myocardial injury post-MI.

Regulatory T cells are expanded by Teriparatide treatment in humans and mediate intermittent PTH-induced bone anabolism in mice

Teriparatide is a bone anabolic treatment for osteoporosis, modeled in animals by intermittent PTH (iPTH) administration, but the cellular and molecular mechanisms of action of iPTH are largely unknown. Here, we show that Teriparatide and iPTH cause a ~two-threefold increase in the number of regulatory T cells (Tregs) in humans and mice. Attesting in vivo relevance, blockade of the Treg increase in mice prevents the increase in bone formation and trabecular bone volume and structure induced by iPTH Therefore, increasing the number of Tregs is a pivotal mechanism by which iPTH exerts its bone anabolic activity. Increasing Tregs pharmacologically may represent a novel bone anabolic therapy, while iPTH-induced Treg increase may find applications in inflammatory conditions and transplant medicine.

Much More than a Cardiotonic Steroid: Modulation of Inflammation by Ouabain

Since the discovery of ouabain as a cardiotonic steroid hormone present in higher mammals, research about it has progressed rapidly and several of its physiological and pharmacological effects have been described. Ouabain can behave as a stress hormone and adrenal cortex is its main source. Direct effects of ouabain are originated due to the binding to its receptor, the Na⁺/K⁺-ATPase, on target cells. This interaction can promote Na⁺ transport blockade or even activation of signaling transduction pathways (e.g., EGFR/Src-Ras-ERK pathway activation), independent of ion transport. Besides the well-known effect of ouabain on the cardiovascular system and blood pressure control, compelling evidence indicates that ouabain regulates a number of immune functions. Inflammation is a tightly coordinated immunological function that is also affected by ouabain. Indeed, this hormone can modulate many inflammatory events such as cell migration, vascular permeability, and cytokine production. Moreover, ouabain also interferes on neuroinflammation. However, it is not clear how ouabain controls these events. In this brief review, we summarize the updates of ouabain effect on several aspects of peripheral and central inflammation, bringing new insights into ouabain functions on the immune system.

Regulatory T cells impede acute and long-term immunity to blood-stage malaria through CTLA-4

Malaria, caused by the protozoan Plasmodium, is a devastating mosquito-borne disease with the potential to affect nearly half the world's population. Despite mounting substantial T and B cell responses, humans fail to efficiently control blood-stage malaria or develop sterilizing immunity to reinfections. Although forkhead box P3 (FOXP3)⁺CD4⁺ regulatory T (T_reg) cells form a part of these responses, their influence remains disputed and their mode of action is unknown. Here we show that T_reg cells expand in both humans and mice in blood-stage malaria and interfere with conventional T helper cell responses and follicular T helper (T_FH)-B cell interactions in germinal centers. Mechanistically, T_reg cells function in a critical temporal window to impede protective immunity through cytotoxic-T-lymphocyte-associated protein-4 (CTLA-4). Targeting T_reg cells or CTLA-4 in this precise window accelerated parasite clearance and generated species-transcending immunity to blood-stage malaria in mice. Our study uncovers a critical mechanism of immunosuppression associated with blood-stage malaria that delays parasite clearance and prevents development of potent adaptive immunity to reinfection. These data also reveal a temporally discrete and potentially therapeutically amenable functional role for T_reg cells and CTLA-4 in limiting antimalarial immunity.

Blockage of regulatory T cells augments induction of protective immune responses by influenza virus-like particles in aged mice

Elderly humans over 65 years old are at great risk to pathogenesis by influenza virus infection. However, although influenza vaccines provide effective protection in healthy young adults, protection of elderly adults is substantially lower even with a good match between the vaccine and the circulating influenza virus. To gain insight of the underlying mechanism for the reduced immunogenicity of influenza vaccines in the aged population, we investigated immunogenicity of influenza virus-like particle vaccines in aged mice, which represent a useful model for studying aging associated impairment in immune responses. Specifically, we investigated the effect of inhibiting regulatory T cells in aged mice on induction of protective immune responses by influenza vaccines. Our results showed that injecting anti-CD25 antibodies could down-regulate CD25 on the surface of regulatory T cells and significantly increase the levels of antibody responses induced by VLP immunization in aged mice. Further, the profiles of antibody responses were also changed towards Th1 type by regulatory T cell blockage in aged mice. Moreover, aged mice that were treated by anti-CD25 antibodies prior to vaccination were more effectively protected against lethal influenza virus challenge.

Antibody-dependent fragmentation is a newly identified mechanism of cell killing in vivo

The prevailing view is that therapeutic antibodies deplete cells through opsonization and subsequent phagocytosis, complement-dependent lysis or antibody-dependent cellular-cytotoxicity. We used high resolution in vivo imaging to identify a new antibody-dependent cell death pathway where Kupffer cells ripped large fragments off crawling antibody-coated iNKT cells. This antibody-dependent fragmentation process resulted in lethality and depletion of crawling iNKT cells in the liver sinusoids and lung capillaries. iNKT cell depletion was Fcy-receptor dependent and required iNKT cell crawling. Blood, spleen or joint iNKT cells that did not crawl were not depleted. The antibody required high glycosylation for sufficiently strong binding of the iNKT cells to the Fc Receptors on Kupffer cells. Using an acetaminophen overdose model, this approach functionally depleted hepatic iNKT cells and affected the severity of liver injury. This study reveals a new mechanism of antibody-dependent killing in vivo and raises implications for the design of new antibodies for cancer and auto-reactive immune cells.

A Stat6/Pten Axis Links Regulatory T Cells with Adipose Tissue Function

Obesity and type 2 diabetes are associated with metabolic defects and adipose tissue inflammation. Foxp3+ regulatory T cells (Tregs) control tissue homeostasis by counteracting local inflammation. However, if and how T cells interlink environmental influences with adipocyte function remains unknown. Here, we report that enhancing sympathetic tone by cold exposure, beta3-adrenergic receptor (ADRB3) stimulation or a short-term high-calorie diet enhances Treg induction in vitro and in vivo. CD4+ T cell proteomes revealed higher expression of Foxp3 regulatory networks in response to cold or ADRB3 stimulation in vivo reflecting Treg induction. Specifically, Ragulator-interacting protein C17orf59, which limits mTORC1 activity, was upregulated in CD4+ T cells by either ADRB3 stimulation or cold exposure, suggesting contribution to Treg induction. By loss- and gain-of-function studies, including Treg depletion and transfers in vivo, we demonstrated that a T cell-specific Stat6/Pten axis links cold exposure or ADRB3 stimulation with Foxp3+ Treg induction and adipose tissue function. Our findings offer a new mechanistic model in which tissue-specific Tregs maintain adipose tissue function.

Beneficial effects of Galectin-9 on allergen-specific sublingual immunotherapy in a Dermatophagoides farinae-induced mouse model of chronic asthma

BACKGROUND

Allergen-specific sublingual immunotherapy is a potential disease-modifying treatment for allergic asthma. Galectin-9 (Gal-9), a β-galactoside-binding protein with various biologic effects, acts as an immunomodulator in excessive immunologic reactions by expanding regulatory T cells (Treg) and enhancing transforming growth factor (TGF)-β signaling. We investigated the efficacy of sublingually administered Gal-9 as an adjuvant to a specific allergen in a Dermatophagoides farinae (Df)-induced mouse model of chronic asthma.

METHODS

BALB/c mice were intranasally sensitized with Df extract 5 days/week for 5 weeks, and then sublingual Df-allergen extract for 2 weeks (5 days/week). Three days after the final sublingual treatment, mice were intranasally challenged with Df extract. The early asthmatic response (EAR) was evaluated 5 min after the last Df challenge. Airway hyperresponsiveness (AHR) was assayed and bronchoalveolar lavage (BAL) was performed 24 h after the last allergen challenge. Serum IgE and cytokine levels, and number of inflammatory cells in the BAL fluid (BALF) were analyzed.

RESULTS

Sublingual Df treatment in the presence of Gal-9, but not alone, significantly reduced AHR; EAR; number of eosinophils and interleukin-13 in the BALF; and serum IgE levels. BALF TGF-β1 levels were significantly increased in the presence of Gal-9 compared with Df alone. Treg depletion blocked the inhibitory effects of Gal-9 on the EAR, AHR, eosinophilic airway inflammation, and Df-specific serum IgE levels, and suppressed BALF TGF-β1 levels.

CONCLUSIONS

Gal-9 exhibited beneficial effects of sublingual Df allergen-specific immunotherapy in a Df-induced mouse model of chronic asthma, possibly by Gal-9-induced TGF-β1 production in the lung.

A Novel Platform for Immune Tolerance Induction in Hemophilia A Mice

Hemophilia A (HA) is an X-linked bleeding disease caused by factor VIII (FVIII) deficiency. We previously demonstrated that FVIII is produced specifically in liver sinusoid endothelial cells (LSECs) and to some degree in myeloid cells, and thus, in the present work, we seek to restrict the expression of FVIII transgene to these cells using cell-specific promoters. With this approach, we aim to limit immune response in a mouse model by lentiviral vector (LV)-mediated gene therapy encoding FVIII. To increase the target specificity of FVIII expression, we included miRNA target sequences (miRTs) (i.e., miRT-142.3p, miRT-126, and miRT-122) to silence expression in hematopoietic cells, endothelial cells, and hepatocytes, respectively. Notably, we report, for the first time, therapeutic levels of FVIII transgene expression at its natural site of production, which occurred without the formation of neutralizing antibodies (inhibitors). Moreover, inhibitors were eradicated in FVIII pre-immune mice through a regulatory T cell-dependent mechanism. In conclusion, targeting FVIII expression to LSECs and myeloid cells by using LVs with cell-specific promoter minimized off-target expression and immune responses. Therefore, at least for some transgenes, expression at the physiologic site of synthesis can enhance efficacy and safety, resulting in long-term correction of genetic diseases such as HA.