Stability and function of regulatory T cells is maintained by a neuropilin-1-semaphorin-4a axis

Baker's yeast beta glucan supplementation was associated with an improved innate immune mRNA expression response after exercise

Beta glucans are found in many natural sources, however, only Baker's Yeast Beta Glucan (BYBG) has been well documented to have structure-function effects that are associated with improved innate immune response to stressors (e.g., exercise, infection, etc.). The purpose was to identify a BYBG-associated mRNA expression pattern following exercise. Participants gave IRB-approved consent and were randomized to BYBG (Wellmune®; N=9) or Placebo (maltodextrin; N=10) for 6-weeks prior to performing 90 min of whole-body exercise. Paxgene blood samples were collected prior to exercise (PRE), after exercise (POST), two hours after exercise (2H), and four hours after exercise (4H). Total RNA was isolated and analyzed for the expression of 770 innate immune response mRNA (730 mRNA targets; 40 housekeepers/controls; Nanostring nCounter). The raw data were normalized against housekeeping controls and expressed as Log2 fold change from PRE for a given condition. Significance was set at p < 0.05 with adjustments for multiple comparisons and false discovery rate. We identified 47 mRNA whose expression was changed after exercise with BYBG and classified them to four functional pathways: 1) Immune Cell Maturation (8 mRNA), 2) Immune Response and Function (5 mRNA), 3) Pattern Recognition Receptors and DAMP or PAMP Detection (25 mRNA), and 4) Detection and Resolution of Tissue Damage (9 mRNA). The identified mRNA whose expression was altered after exercise with BYBG may represent an innate immune response pattern and supports previous conclusions that BYBG improves immune response to a future sterile inflammation or infection.

Regulatory T Cell Insufficiency in Autoimmune Diabetes Is Driven by Selective Loss of Neuropilin-1 on Intraislet Regulatory T Cells

Approaches to reverse or limit regulatory T cell (Treg) insufficiency are of great interest for development of immunotherapeutic treatments for autoimmune patients, including type 1 diabetes. Treg insufficiency is heavily implicated in the progression of autoimmune diabetes in the NOD mouse model and is characterized by defects in Treg numbers, development, and/or function. Utilizing a Treg-centric screen, we show that intraislet Tregs have a uniquely dysfunctional phenotype, hallmarked by an almost complete lack of neuropilin-1 (Nrp1), a cell surface receptor required to maintain Treg stability. Intraislet Nrp1- Tregs exhibit hallmark features of fragility, including reduced suppressive capacity, decreased CD73 and Helios, and increased Rorγt and Tbet. Intraislet Nrp1- Tregs also exhibit decreased Foxp3 expression on a per cell basis, suggesting that Nrp1 may also be required for long-term Treg stability. Mechanistically, Treg-restricted augmentation of Nrp1 expression limited the onset of autoimmune diabetes in NOD mice suggesting that Nrp1 critically impacts intraislet Treg function. Transcriptional analysis showed that Nrp1 restoration led to an increase in markers and pathways of TCR signaling, survival, and suppression, and when Nrp1 protein expression is examined by cellular indexing of transcriptomes and epitopes by sequencing, significant differences were observed between Nrp1+ and Nrp1- Tregs in all tissues, particularly in markers of Treg fragility. This translated into substantive differences between Nrp1+ and Nrp1- Tregs that afforded the former with a competitive advantage in the islets. Taken together, these data suggest that maintenance of Nrp1 expression and signaling on Tregs limits diabetes onset and may serve as a strategy to combat Treg insufficiency in autoimmune disease.

Transcription factor Ikzf1 associates with Foxp3 to repress gene expression in Treg cells and limit autoimmunity and anti-tumor immunity

The master transcription factor of regulatory T (Treg) cells, forkhead box protein P3 (Foxp3), controls Treg cell function by targeting certain genes for activation or repression, but the specific mechanisms by which it mediates this activation or repression under different conditions remain unclear. We found that Ikzf1 associates with Foxp3 via its exon 5 (IkE5) and that IkE5-deficient Treg cells highly expressed genes that would otherwise be repressed by Foxp3 upon T cell receptor stimulation, including Ifng. Treg-specific IkE5-deletion caused interferon-γ (IFN-γ) overproduction, which destabilized Foxp3 expression and impaired Treg suppressive function, leading to systemic autoimmune disease and strong anti-tumor immunity. Pomalidomide, which degrades IKZF1 and IKZF3, induced IFN-γ overproduction in human Treg cells. Mechanistically, the Foxp3-Ikzf1-Ikzf3 complex competed with epigenetic co-activators, such as p300, for binding to target gene loci via chromatin remodeling. Therefore, the Ikzf1 association with Foxp3 is essential for the gene-repressive function of Foxp3 and could be exploited to treat autoimmune disease and cancer.

Genetic variants associated with immune-mediated liver injury from checkpoint inhibitors

BACKGROUND

The clinical features, liver histology, and genetic variants in 57 patients with moderate to severe immune-mediated liver injury from checkpoint inhibitors (ILICI) are presented.

METHODS

Between 2010 and 2022, 57 high-causality ILICI cases were enrolled in the Drug-Induced Liver Injury Network. HLA and selected candidate gene variants were tested for association with ILICI risk compared to the general population and other DILI controls.

RESULTS

The 57 high-causality cases were attributed to pembrolizumab (16), ipilimumab (15), ipilimumab and nivolumab (13), and other immune checkpoint inhibitors (13) and occurred at a median of 72 days after the first infusion. Median age was 57.8 years, 66% male, and 89% were non-Hispanic Whites. At DILI onset, 53% had hepatocellular, 35% mixed, and 15% cholestatic, with younger patients more likely to have hepatocellular injury. The incidence of ANA, smooth muscle antibody, and elevated IgG levels was low (17%, 23%, and 0%), but corticosteroids were given to 86%. Microgranulomas and hepatic steatosis were seen in 54% and 46% of the 26 liver biopsies, respectively. The HLA alleles associated with autoimmune hepatitis were not over-represented, but 2 host immune response genes (EDIL3 and SAMA5A) and 3 other genes (GABRP, SMAD3, and SLCO1B1) were associated with ILICI (OR: 2.08-2.4, p<0.01).

CONCLUSIONS

ILICI typically arises within 12 weeks of initiating immunotherapy and is self-limited in most cases. Genetic variants involved in host T-cell regulation and drug disposition were identified, implicating these pathways in the pathogenesis of ILICI. If validated, these findings could lead to improved diagnostic instruments and possible treatments for ILICI.

The CCL2-CCR4 axis promotes Regulatory T cell trafficking to canine glioma tissues

PURPOSE

Spontaneously occurring glioma in pet dogs is increasingly recognized as a valuable translational model for human glioblastoma. Canine high-grade glioma and human glioblastomas share many molecular similarities, including the accumulation of immunosuppressive regulatory T cells (Tregs) that inhibit anti-tumor immune responses. Identifying in dog mechanisms responsible for Treg recruitment may afford to target the cellular population driving immunosuppression, the results providing a rationale for translational clinical studies in human patients. Our group has previously identified C-C motif chemokine 2 (CCL2) as a glioma-derived T-reg chemoattractant acting on chemokine receptor 4 (CCR4) in a murine orthotopic glioma model. Recently, we demonstrated a robust increase of CCL2 in the brain tissue of canine patients bearing high-grade glioma.

METHODS

We performed a series of in vitro experiments using canine Tregs and patient-derived canine glioma cell lines (GSC 1110, GSC 0514, J3T-Bg, G06A) to interrogate the CCL2-CCR4 signaling axis in the canine.

RESULTS

We established a flow cytometry gating strategy for identifying and isolating FOXP3+ Tregs in dogs. The canine CD4 + CD25high T-cell population was highly enriched in FOXP3 and CCR4 expression, indicating they are bona fide Tregs. Canine Treg migration was enhanced by CCL2 or by glioma cell line-derived supernatant. Blockade of the CCL2-CCR4 axis significantly reduced migration of canine Tregs. CCL2 mRNA was expressed in all glioma cell lines, and expression increased when exposed to Tregs but not CD4 + helper T-cells.

CONCLUSION

Our study validates CCL2-CCR4 as a bi-directional Treg-glioma immunosuppressive and tumor-promoting axis in canine high-grade glioma.

IL-2/JES6-1 Antibody Complex Expands the Maternal T-Regulatory Cell Pool and Alleviates Fetal Loss in Abortion-Prone Mice

Regulatory T (Treg) cells are essential for immune tolerance of embryo implantation, and insufficient Treg cells are implicated in early pregnancy loss. An abortion-prone mouse model was used to evaluate the utility of IL-2 complexed with JES6-1 anti-IL-2 antibody (IL-2/JES6-1) to boost uterine Treg cells and improve reproductive success. IL-2/JES6-1, but not IL-2/IgG control, administered in the periconception phase to CBA/J females mated with DBA/2 males elicited a greater than twofold increase in the proportion of CD4+ T cells expressing forkhead box P3 (FOXP3), and an increase in the ratio of FOXP3+ Treg cells/FOXP3- T conventional cells, in the uterus and its draining lymph nodes at embryo implantation that was sustained into midgestation. An attenuated phenotype was evident in both thymic-derived and peripheral Treg cells with elevated cytotoxic T-lymphocyte antigen-4, CD25, and FOXP3, indicating improved suppressive function, as well as increased proliferative marker Ki-67. IL-2/JES6-1 treatment reduced fetal loss from 31% to 10%, but this was accompanied by a 6% reduction in late gestation fetal weight, despite comparable placental size and architecture. Similar effects of IL-2/JES6-1 on Treg cells and fetal growth were seen in CBA/J females with healthy pregnancies sired by BALB/c males. These findings show that expanding the uterine Treg cell pool through targeting IL-2 signaling is a strategy worthy of further investigation for mitigating immune-mediated fetal loss.

Neoantigen-specific cytotoxic Tr1 CD4 T cells suppress cancer immunotherapy

CD4+ T cells can either enhance or inhibit tumour immunity. Although regulatory T cells have long been known to impede antitumour responses1-5, other CD4+ T cells have recently been implicated in inhibiting this response6,7. Yet, the nature and function of the latter remain unclear. Here, using vaccines containing MHC class I (MHC-I) neoantigens (neoAgs) and different doses of tumour-derived MHC-II neoAgs, we discovered that whereas the inclusion of vaccines with low doses of MHC-II-restricted peptides (LDVax) promoted tumour rejection, vaccines containing high doses of the same MHC-II neoAgs (HDVax) inhibited rejection. Characterization of the inhibitory cells induced by HDVax identified them as type 1 regulatory T (Tr1) cells expressing IL-10, granzyme B, perforin, CCL5 and LILRB4. Tumour-specific Tr1 cells suppressed tumour rejection induced by anti-PD1, LDVax or adoptively transferred tumour-specific effector T cells. Mechanistically, HDVax-induced Tr1 cells selectively killed MHC-II tumour antigen-presenting type 1 conventional dendritic cells (cDC1s), leading to low numbers of cDC1s in tumours. We then documented modalities to overcome this inhibition, specifically via anti-LILRB4 blockade, using a CD8-directed IL-2 mutein, or targeted loss of cDC2/monocytes. Collectively, these data show that cytotoxic Tr1 cells, which maintain peripheral tolerance, also inhibit antitumour responses and thereby function to impede immune control of cancer.

Fragile Treg cells: Traitors in immune homeostasis?

Regulatory T (Treg) cells play a key role in maintaining immune tolerance and tissue homeostasis. However, in some disease microenvironments, Treg cells exhibit fragility, which manifests as preserved FoxP3 expression accompanied by inflammation and loss of immunosuppression. Fragile Treg cells are formatively, phenotypically and functionally diverse in various diseases, further complicating the role of Treg cells in the immunotherapeutic response and offering novel targets for disease treatment by modulating specific Treg subsets. In this review, we summarize findings on fragile Treg cells to provide a framework for characterizing the formation and role of fragile Treg cells in different diseases, and we discuss how this information may guide the development of more specific Treg-targeted immunotherapies.

IFNγ Production by Functionally Reprogrammed Tregs Promotes Antitumor Efficacy of OX40/CD137 Bispecific Agonist Therapy

Regulatory T cells (Treg) are highly enriched within many tumors and suppress immune responses to cancer. There is intense interest in reprogramming Tregs to contribute to antitumor immunity. OX40 and CD137 are expressed highly on Tregs, activated and memory T cells, and NK cells. In this study, using a novel bispecific antibody targeting mouse OX40 and CD137 (FS120m), we show that OX40/CD137 bispecific agonism induces potent antitumor immunity partially dependent upon IFNγ production by functionally reprogrammed Tregs. Treatment of tumor-bearing animals with OX40/CD137 bispecific agonists reprograms Tregs into both fragile Foxp3+ IFNγ+ Tregs with decreased suppressive function and lineage-instable Foxp3- IFNγ+ ex-Tregs. Treg fragility is partially driven by IFNγ signaling, whereas Treg instability is associated with reduced IL2 responsiveness upon treatment with OX40/CD137 bispecific agonists. Importantly, conditional deletion of Ifng in Foxp3+ Tregs and their progeny partially reverses the antitumor efficacy of OX40/CD137 bispecific agonist therapy, revealing that reprogramming of Tregs into IFNγ-producing cells contributes to the anti-tumor efficacy of OX40/CD137 bispecific agonists. These findings provide insights into mechanisms by which bispecific agonist therapies targeting costimulatory receptors highly expressed by Tregs potentiate antitumor immunity in mouse models.

SIGNIFICANCE

The bispecific antibody FS120, an immunotherapy currently being tested in the clinic, partially functions by inducing anti-tumor activity of Tregs, which results in tumor rejection.

Venetoclax Induces BCL-2-Dependent Treg to TH17 Plasticity to Enhance the Antitumor Efficacy of Anti-PD-1 Checkpoint Blockade

The specific BCL-2 small molecule inhibitor venetoclax induces apoptosis in a wide range of malignancies, which has led to rapid clinical expansion in its use alone and in combination with chemotherapy and immune-based therapies against a myriad of cancer types. While lymphocytes, and T cells in particular, rely heavily on BCL-2 for survival and function, the effects of small molecule blockade of the BCL-2 family on surviving immune cells is not fully understood. We aimed to better understand the effect of systemic treatment with venetoclax on regulatory T cells (Treg), which are relatively resistant to cell death induced by specific drugging of BCL-2 compared to other T cells. We found that BCL-2 blockade altered Treg transcriptional profiles and mediated Treg plasticity toward a TH17-like Treg phenotype, resulting in increased IL17A production in lymphoid organs and within the tumor microenvironment. Aligned with previously described augmented antitumor effects observed when combining venetoclax with anti-PD-1 checkpoint inhibition, we also demonstrated that Treg-specific genetic BCL-2 knockout combined with anti-PD-1 induced tumor regression and conferred overlapping genetic changes with venetoclax-treated Tregs. As long-term combination therapies using venetoclax gain more traction in the clinic, an improved understanding of the immune-modulatory effects caused by venetoclax may allow expansion of its use against malignancies and immune-related diseases.

Impact of LAG-3/FGL1 pathway on immune evasive contexture and clinical outcomes in advanced urothelial carcinoma

BACKGROUND

Anti-programmed death-1 (PD-1)/anti-PD-ligand-1 (PD-L1) pathway inhibition is a standard regimen for advanced urothelial carcinoma (UC); however, its limited efficacy has been reflected in reported medium response rates. This study explored the role of next-generation coinhibitory receptors (IRs; lymphocyte activation gene 3 (LAG-3), T-cell immunoglobulin and mucin domain 3 (TIM-3), and T-cell immunoreceptor with Ig and ITIM domains (TIGIT)) and their ligands (LGs) in the response to PD-(L)1 blockade therapy and the oncological outcomes in patients with UC.

METHODS

We investigated metastatic UC cases who underwent PD-(L)1 therapy (cohort 1: n=348, cohort 2: n=89, and cohort 4: n=29) or advanced UC cases involving surgery (cohort 3: n=293 and cohort 5: n=90). We assessed the mRNA expression profiles and corresponding clinical information regarding IRs and LGs using cohorts 1, 2, and 3. Additionally, we elucidated the spatial features of these targeted markers using multiplex immunohistochemistry (mIHC) on formalin-fixed paraffin-embedded samples from cohorts 4 and 5. Survival, differential expressed gene, and Gene Set Enrichment analyses were performed. For mIHC, quantitative analyses were also performed to correlate immune and tumor cell densities with patient survival.

RESULTS

LAG-3 expression was strongly associated with the responsiveness of PD-(L)1 blockade compared with the expression of TIM-3 and TIGIT. In tumors with high LAG-3 levels, the increased expression of fibrinogen-like protein 1 (FGL1) had a significantly negative effect on the response to PD-(L)1 blockade and overall survival. Moreover, high FGL1 levels were associated with elevated CD4+ regulatory T-cell gene signatures and the upregulation of CD39 and neuropilin-1, with both indicating CD8+ T-cell exhaustion. mIHC analyses revealed that patients with stromal CD8+LAG-3+cellshigh-tumor FGL1+cellshigh exhibited a significant negative correlation with survival rates compared with those with stromal CD8+LAG-3+cellshigh-tumor FGL1+cellslow.

CONCLUSIONS

LAG-3 expression and high FGL1 coexpression are important predictive factors of adverse oncological outcomes related to the presence of immunosuppressive contextures. These findings are hypothesis-generating, warranting further mechanistic and clinical studies aimed to evaluate LAG-3/FGL1 blockade in UC.

SWI/SNF chromatin remodeling factor BAF60b restrains inflammatory diseases by affecting regulatory T cell migration

Regulatory T (Treg) cells play a critical regulatory role in the immune system by suppressing excessive immune responses and maintaining immune balance. The effective migration of Treg cells is crucial for controlling the development and progression of inflammatory diseases. However, the mechanisms responsible for directing Treg cells into the inflammatory tissue remain incompletely elucidated. In this study, we identified BAF60b, a subunit of switch/sucrose nonfermentable (SWI/SNF) chromatin remodeling complexes, as a positive regulator of Treg cell migration that inhibits the progression of inflammation in experimental autoimmune encephalomyelitis (EAE) and colitis animal models. Mechanistically, transcriptome and genome-wide chromatin-landscaped analyses demonstrated that BAF60b interacts with the transcription factor RUNX1 to promote the expression of CCR9 on Treg cells, which in turn affects their ability to migrate to inflammatory tissues. Our work provides insights into the essential role of BAF60b in regulating Treg cell migration and its impact on inflammatory diseases.

PARP11 inhibition inactivates tumor-infiltrating regulatory T cells and improves the efficacy of immunotherapies

Tumor-infiltrating regulatory T cells (TI-Tregs) elicit immunosuppressive effects in the tumor microenvironment (TME) leading to accelerated tumor growth and resistance to immunotherapies against solid tumors. Here, we demonstrate that poly-(ADP-ribose)-polymerase-11 (PARP11) is an essential regulator of immunosuppressive activities of TI-Tregs. Expression of PARP11 correlates with TI-Treg cell numbers and poor responses to immune checkpoint blockade (ICB) in human patients with cancer. Tumor-derived factors including adenosine and prostaglandin E2 induce PARP11 in TI-Tregs. Knockout of PARP11 in the cells of the TME or treatment of tumor-bearing mice with selective PARP11 inhibitor ITK7 inactivates TI-Tregs and reinvigorates anti-tumor immune responses. Accordingly, ITK7 decelerates tumor growth and significantly increases the efficacy of anti-tumor immunotherapies including ICB and adoptive transfer of chimeric antigen receptor (CAR) T cells. These results characterize PARP11 as a key driver of TI-Treg activities and a major regulator of immunosuppressive TME and argue for targeting PARP11 to augment anti-cancer immunotherapies.

Semaphorin 4A Maintains Trophoblastic Function via Activating the STAT3 Pathway

The migration, proliferation, and apoptosis of trophoblastic cells play a crucial role in ensuring the effective preservation of pregnancy at the maternal-fetal interface. Any deviations in the structure and function of these cells might potentially result in the development of numerous pregnancy-related disorders, including missed abortion (MA). This study involved the examination of semaphorin 4A (SEMA4A) expression in missed abortion (n = 18) and normal early pregnancy (n = 18) villus. The findings of this study indicate a statistically significant decrease in the expression of SEMA4A in the villi of individuals diagnosed with missed abortion, as compared to the control group. The results of our vitro study showed that SEMA4A promoted the migration and proliferation of trophoblast cells and inhibited their apoptosis. Subsequent studies have shown that SEMA4A may be involved in regulating p-STAT3/STAT3, MMP9, bcl-2, and BAX levels. In summary, the findings of this study indicate a correlation between the decreased level of SEMA4A in chorionic villi and missed abortion. These results offer novel theoretical insights into the proper implantation and development of SEMA4A embryos at the maternal-fetal interface.

Complex Role of Regulatory T Cells (Tregs) in the Tumor Microenvironment: Their Molecular Mechanisms and Bidirectional Effects on Cancer Progression

Regulatory T cells (Tregs) possess unique immunosuppressive activity among CD4-positive T cells. Tregs are ubiquitously present in mammals and function to calm excessive immune responses, thereby suppressing allergies or autoimmune diseases. On the other hand, due to their immunosuppressive function, Tregs are thought to promote cancer progression. The tumor microenvironment (TME) is a multicellular system composed of many cell types, including tumor cells, infiltrating immune cells, and cancer-associated fibroblasts (CAFs). Within this environment, Tregs are recruited by chemokines and metabolic factors and impede effective anti-tumor responses. However, in some cases, their presence can also improve patient's survival rates. Their functional consequences may vary across tumor types, locations, and stages. An in-depth understanding of the precise roles and mechanisms of actions of Treg is crucial for developing effective treatments, emphasizing the need for further investigation and validation. This review aims to provide a comprehensive overview of the complex and multifaceted roles of Tregs within the TME, elucidating cellular communications, signaling pathways, and their impacts on tumor progression and highlighting their potential anti-tumor mechanisms through interactions with functional molecules.

CXCR3+ effector regulatory T cells associate with disease tolerance during lower respiratory pneumovirus infection

Lifestyle factors like poor maternal diet or antibiotic exposure disrupt early life microbiome assembly in infants, increasing the risk of severe lower respiratory infections (sLRI). Our prior studies in mice indicated that a maternal low-fibre diet (LFD) exacerbates LRI severity in infants by impairing recruitment of plasmacytoid dendritic cells (pDC) and consequently attenuating expansion of lung regulatory T (Treg) cells during pneumonia virus of mice (PVM) infection. Here, we investigated whether maternal dietary fibre intake influences Treg cell phenotypes in the mediastinal lymph nodes (mLN) and lungs of PVM-infected neonatal mice. Using high dimensional flow cytometry, we identified distinct clusters of regulatory T cells (Treg cells), which differed between lungs and mLN during infection, with notably greater effector Treg cell accumulation in the lungs. Compared to high-fibre diet (HFD)-reared pups, frequencies of various effector Treg cell subsets were decreased in the lungs of LFD-reared pups. Particularly, recruitment of chemokine receptor 3 (CXCR3+) expressing Treg cells was attenuated in LFD-reared pups, correlating with lower lung expression of CXCL9 and CXCL10 chemokines. The recruitment of this subset in response to PVM infection was similarly impaired in pDC depleted mice or following anti-CXCR3 treatment, increasing immunopathology in the lungs. In summary, PVM infection leads to the sequential recruitment and expansion of distinct Treg cell subsets to the lungs and mLN. The attenuated recruitment of the CXCR3+ subset in LFD-reared pups increases LRI severity, suggesting that strategies to enhance pDCs or CXCL9/CXCL10 expression will lower immune-mediated pathogenesis.

The CCL2-CCR4 Axis Promotes Regulatory T Cell Trafficking to Canine Glioma Tissues

Purpose

Spontaneously occurring glioma in pet dogs is increasingly recognized as a valuable translational model for human glioblastoma. Canine high grade glioma and human glioblastomas share many molecular similarities, including accumulation of immunosuppressive regulatory T cells (Tregs) that inhibit anti-tumor immune responses. Identifying in dog mechanisms responsible for Treg recruitment may afford targeting the cellular population driving immunosuppression, the results providing a rationale for translational clinical studies in human patients. Our group has previously identified C-C motif chemokine 2 (CCL2) as a glioma-derived T-reg chemoattractant acting on chemokine receptor 4 (CCR4) in a murine orthotopic model of glioma. Recently, we demonstrated a robust increase of CCL2 in the brain tissue of canine patients bearing high-grade glioma.

Methods

We performed a series of in vitro experiments using canine Tregs and patient-derived canine glioma cell lines (GSC 1110, GSC 0514, J3T-Bg, G06A) to interrogate the CCL2-CCR4 signaling axis in the canine.

Results

We established a flow cytometry gating strategy for identification and isolation of FOXP3+ Tregs in dogs. The canine CD4 + CD25high T-cell population was highly enriched in FOXP3 and CCR4 expression, indicating they are bona fide Tregs. Canine Treg migration was enhanced by CCL2 or by glioma cell line-derived supernatant. Blockade of the CCL2-CCR4 axis significantly reduced migration of canine Tregs. CCL2 mRNA was expressed in all glioma cell lines and expression increased when exposed to Tregs but not to CD4 + helper T-cells.

Conclusion

Our study validates CCL2-CCR4 as a bi-directional Treg-glioma immunosuppressive and tumor-promoting axis in canine high-grade glioma.

Immunological nanomaterials to combat cancer metastasis

Metastasis causes greater than 90% of cancer-associated deaths, presenting huge challenges for detection and efficient treatment of cancer due to its high heterogeneity and widespread dissemination to various organs. Therefore, it is imperative to combat cancer metastasis, which is the key to achieving complete cancer eradication. Immunotherapy as a systemic approach has shown promising potential to combat metastasis. However, current clinical immunotherapies are not effective for all patients or all types of cancer metastases owing to insufficient immune responses. In recent years, immunological nanomaterials with intrinsic immunogenicity or immunomodulatory agents with efficient loading have been shown to enhance immune responses to eliminate metastasis. In this review, we would like to summarize various types of immunological nanomaterials against metastasis. Moreover, this review will summarize a series of immunological nanomaterial-mediated immunotherapy strategies to combat metastasis, including immunogenic cell death, regulation of chemokines and cytokines, improving the immunosuppressive tumour microenvironment, activation of the STING pathway, enhancing cytotoxic natural killer cell activity, enhancing antigen presentation of dendritic cells, and enhancing chimeric antigen receptor T cell therapy. Furthermore, the synergistic anti-metastasis strategies based on the combinational use of immunotherapy and other therapeutic modalities will also be introduced. In addition, the nanomaterial-mediated imaging techniques (e.g., optical imaging, magnetic resonance imaging, computed tomography, photoacoustic imaging, surface-enhanced Raman scattering, radionuclide imaging, etc.) for detecting metastasis and monitoring anti-metastasis efficacy are also summarized. Finally, the current challenges and future prospects of immunological nanomaterial-based anti-metastasis are also elucidated with the intention to accelerate its clinical translation.

Treg-Derived Extracellular Vesicles: Roles in Diseases and Theranostics

Regulatory T cells (Tregs), a subset of CD4+ T cells, are indispensable in maintaining immune self-tolerance and have been utilized in various diseases. Treg-derived extracellular vesicles (Treg-EVs) have been discovered to play an important role in the mechanism of Treg functions. As cell-derived membranous particles, EVs carry multiple bioactive substances that possess tremendous potential for theranostics. Treg-EVs are involved in numerous physiological and pathological processes, carrying proteins and miRNAs inherited from the parental cells. To comprehensively understand the function of Treg-EVs, here we reviewed the classification of Treg-EVs, the active molecules in Treg-EVs, their various applications in diseases, and the existing challenges for Treg-EVs based theranostics. This Review aims to clarify the feasibility and potential of Treg-EVs in diseases and theranostics, facilitating further research and application of Treg-EVs.

Neuropilin-1high monocytes protect against neonatal inflammation

Neonates are susceptible to inflammatory disorders such as necrotizing enterocolitis (NEC) due to their immature immune system. The timely appearance of regulatory immune cells in early life contributes to the control of inflammation in neonates, yet the underlying mechanisms of which remain poorly understood. In this study, we identified a subset of neonatal monocytes characterized by high levels of neuropilin-1 (Nrp1), termed Nrp1high monocytes. Compared with their Nrp1low counterparts, Nrp1high monocytes displayed potent immunosuppressive activity. Nrp1 deficiency in myeloid cells aggravated the severity of NEC, whereas adoptive transfer of Nrp1high monocytes led to remission of NEC. Mechanistic studies showed that Nrp1, by binding to its ligand Sema4a, induced intracellular p38-MAPK/mTOR signaling and activated the transcription factor KLF4. KLF4 transactivated Nos2 and enhanced the production of nitric oxide (NO), a key mediator of immunosuppression in monocytes. These findings reveal an important immunosuppressive axis in neonatal monocytes and provide a potential therapeutic strategy for treating inflammatory disorders in neonates.

Converting "cold" to "hot": epigenetics strategies to improve immune therapy effect by regulating tumor-associated immune suppressive cells

Significant developments in cancer treatment have been made since the advent of immune therapies. However, there are still some patients with malignant tumors who do not benefit from immunotherapy. Tumors without immunogenicity are called "cold" tumors which are unresponsive to immunotherapy, and the opposite are "hot" tumors. Immune suppressive cells (ISCs) refer to cells which can inhibit the immune response such as tumor-associated macrophages (TAMs), myeloid-derived suppressor cells (MDSCs), regulatory T (Treg) cells and so on. The more ISCs infiltrated, the weaker the immunogenicity of the tumor, showing the characteristics of "cold" tumor. The dysfunction of ISCs in the tumor microenvironment (TME) may play essential roles in insensitive therapeutic reaction. Previous studies have found that epigenetic mechanisms play an important role in the regulation of ISCs. Regulating ISCs may be a new approach to transforming "cold" tumors into "hot" tumors. Here, we focused on the function of ISCs in the TME and discussed how epigenetics is involved in regulating ISCs. In addition, we summarized the mechanisms by which the epigenetic drugs convert immunotherapy-insensitive tumors into immunotherapy-sensitive tumors which would be an innovative tendency for future immunotherapy in "cold" tumor.

Targeting CXCR4 impaired T regulatory function through PTEN in renal cancer patients

BACKGROUND

Tregs trafficking is controlled by CXCR4. In Renal Cell Carcinoma (RCC), the effect of the new CXCR4 antagonist, R54, was explored in peripheral blood (PB)-Tregs isolated from primary RCC patients.

METHODS

PB-Tregs were isolated from 77 RCC patients and 38 healthy donors (HDs). CFSE-T effector-Tregs suppression assay, IL-35, IFN-γ, IL-10, TGF-β1 secretion, and Nrp-1+Tregs frequency were evaluated. Tregs were characterised for CTLA-4, PD-1, CD40L, PTEN, CD25, TGF-β1, FOXP3, DNMT1 transcriptional profile. PTEN-pAKT signalling was evaluated in the presence of R54 and/or triciribine (TCB), an AKT inhibitor. Methylation of TSDR (Treg-Specific-Demethylated-Region) was conducted.

RESULTS

R54 impaired PB-RCC-Tregs function, reduced Nrp-1+Tregs frequency, the release of IL-35, IL-10, and TGF-β1, while increased IFN-γ Teff-secretion. The CXCR4 ligand, CXCL12, recruited CD25+PTEN+Tregs in RCC while R54 significantly reduced it. IL-2/PMA activates Tregs reducing pAKT+Tregs while R54 increases it. The AKT inhibitor, TCB, prevented the increase in pAKT+Tregs R54-mediated. Moreover, R54 significantly reduced FOXP3-TSDR demethylation with DNMT1 and FOXP3 downregulation.

CONCLUSION

R54 impairs Tregs function in primary RCC patients targeting PTEN/PI3K/AKT pathway, reducing TSDR demethylation and FOXP3 and DNMT1 expression. Thus, CXCR4 targeting is a strategy to inhibit Tregs activity in the RCC tumour microenvironment.

NRP1 downregulation correlates with enhanced ILC2 responses during IL-33 challenge

Group 2 innate lymphoid cells (ILC2s) play critical roles in driving the pathogenesis of allergic airway inflammation. The mechanisms underlying the regulation of ILC2s remain to be fully understood. Here, we identified neuropilin-1 (NRP1) as a surface marker of ILC2s in response to IL-33 stimulation. NRP1 was abundantly expressed in ILC2s from lung under steady state, which was significantly reduced upon IL-33 stimulation. ILC2s with high expression of NRP1 (NRP1high) displayed lower response to IL-33, as compared with NRP1low ILC2s. Transcriptional profiling and flow cytometric analysis showed that downregulation of AKT-mTOR signalling participated in the diminished functionality of NRP1high ILC2s. These observations revealed a potential role of NRP1 in ILC2s responses under allergic inflammatory condition.

Targeting CD44 and other pleiotropic co-receptors as a means for broad inhibition of tumor growth and metastasis

Although progress has been made in the treatment of cancer, particularly for the four major types of cancers affecting the lungs, colon, breast and prostate, resistance to cancer treatment often emerges upon inhibition of major signaling pathways, which leads to the activation of additional pathways as a last-resort survival mechanism by the cancer cells. This signaling plasticity provides cancer cells with a level of operational freedom, reducing treatment efficacy. Plasticity is a characteristic of cancer cells that are not only able to switch signaling pathways but also from one cellular state (differentiated cells to stem cells or vice versa) to another. It seems implausible that the inhibition of one or a few signaling pathways of heterogeneous and plastic tumors can sustain a durable effect. We propose that inhibiting molecules with pleiotropic functions such as cell surface co-receptors can be a key to preventing therapy escape instead of targeting bona fide receptors. Therefore, we ask the question whether co-receptors often considered as "accessory molecules" are an overlooked key to control cancer cell behavior.

Semaphorins in tumor microenvironment: Biological mechanisms and therapeutic progress

Hallmark features of the tumor microenvironment include immune cells, stromal cells, blood vessels, and extracellular matrix (ECM), providing a conducive environment for the growth and survival of tumors. Recent advances in the understanding of cancer biology have highlighted the functional role of semaphorins (SEMAs). SEMAs are a large and diverse family of widely expressed secreted and membrane-binding proteins, which were initially implicated in axon guidance and neural development. However, it is now clear that they are widely expressed beyond the nervous system and participate in regulating immune responses and cancer progression. In fact, accumulating evidence disclosed that different SEMAs can either stimulate or restrict tumor progression, some of which act as important regulators of tumor angiogenesis. Conversely, limited information is known about the functional relevance of SEMA signals in TME. In this setting, we systematically elaborate the role SEMAs and their major receptors played in characterized components of TME. Furthermore, we provide a convergent view of current SEMAs pharmacological progress in clinical treatment and also put forward their potential application value and clinical prospects in the future.

Decoding the potential role of regulatory T cells in sepsis-induced immunosuppression

Sepsis, a multiorgan dysfunction with high incidence and mortality, is caused by an imbalanced host-to-infection immune response. Organ-support therapy improves the early survival rate of sepsis patients. In the long term, those who survive the "cytokine storm" and its secondary damage usually show higher susceptibility to secondary infections and sepsis-induced immunosuppression, in which regulatory T cells (Tregs) are evidenced to play an essential role. However, the potential role and mechanism of Tregs in sepsis-induced immunosuppression remains elusive. In this review, we elucidate the role of different functional subpopulations of Tregs during sepsis and then review the mechanism of sepsis-induced immunosuppression from the aspects of regulatory characteristics, epigenetic modification, and immunometabolism of Tregs. Thoroughly understanding how Tregs impact the immune system during sepsis may shed light on preclinical research and help improve the translational value of sepsis immunotherapy.

Regulatory T cells suppress myeloma-specific immunity during autologous stem cell mobilization and transplantation

ABSTRACT

Autologous stem cell transplantation (ASCT) is the standard of care consolidation therapy for eligible patients with myeloma but most patients eventually progress, an event associated with features of immune escape. Novel approaches to enhance antimyeloma immunity after ASCT represent a major unmet need. Here, we demonstrate that patient-mobilized stem cell grafts contain high numbers of effector CD8 T cells and immunosuppressive regulatory T cells (Tregs). We showed that bone marrow (BM)-residing T cells are efficiently mobilized during stem cell mobilization (SCM) and hypothesized that mobilized and highly suppressive BM-derived Tregs might limit antimyeloma immunity during SCM. Thus, we performed ASCT in a preclinical myeloma model with or without stringent Treg depletion during SCM. Treg depletion generated SCM grafts containing polyfunctional CD8 T effector memory cells, which dramatically enhanced myeloma control after ASCT. Thus, we explored clinically tractable translational approaches to mimic this scenario. Antibody-based approaches resulted in only partial Treg depletion and were inadequate to recapitulate this effect. In contrast, a synthetic interleukin-2 (IL-2)/IL-15 mimetic that stimulates the IL-2 receptor on CD8 T cells without binding to the high-affinity IL-2Ra used by Tregs efficiently expanded polyfunctional CD8 T cells in mobilized grafts and protected recipients from myeloma progression after ASCT. We confirmed that Treg depletion during stem cell mobilization can mitigate constraints on tumor immunity and result in profound myeloma control after ASCT. Direct and selective cytokine signaling of CD8 T cells can recapitulate this effect and represent a clinically testable strategy to improve responses after ASCT.

Semmaphorin 3 A causes immune suppression by inducing cytoskeletal paralysis in tumour-specific CD8+ T cells

Semaphorin-3A (SEMA3A) functions as a chemorepulsive signal during development and can affect T cells by altering their filamentous actin (F-actin) cytoskeleton. The exact extent of these effects on tumour-specific T cells are not completely understood. Here we demonstrate that Neuropilin-1 (NRP1) and Plexin-A1 and Plexin-A4 are upregulated on stimulated CD8+ T cells, allowing tumour-derived SEMA3A to inhibit T cell migration and assembly of the immunological synapse. Deletion of NRP1 in both CD4+ and CD8+ T cells enhance CD8+ T-cell infiltration into tumours and restricted tumour growth in animal models. Conversely, over-expression of SEMA3A inhibit CD8+ T-cell infiltration. We further show that SEMA3A affects CD8+ T cell F-actin, leading to inhibition of immune synapse formation and motility. Examining a clear cell renal cell carcinoma patient cohort, we find that SEMA3A expression is associated with reduced survival, and that T-cells appear trapped in SEMA3A rich regions. Our study establishes SEMA3A as an inhibitor of effector CD8+ T cell tumour infiltration, suggesting that blocking NRP1 could improve T cell function in tumours.

High sensitivity of host Helios+/Neuropilin-1+ Treg to pretransplant conditioning hampers development of OX40bright/integrin-β7+ regulatory cells in acute gastrointestinal GvHD

This study sought to compare the behavior of Treg subsets displaying different coexpression patterns of Neuropilin-1 (Nrp1) and Helios, under the influence of gut stress unrelated to hematopoietic stem cell transplantation, pretransplantation conditioning, and posttransplant gastrointestinal acute graft versus host disease (GI-aGvHD). Host CD4+/CD25hi/Foxp3+ Treg cells, identified by flow cytometry, were isolated from various tissues of mice affected by these stressors. Expression of CD25, CTLA-4, CD39, OX40, integrin-β7, LAG3, TGFβ/LAP, granzyme-A, -B, and interleukin-10 was compared in four Treg subsets displaying Helios or Nrp1 only, both or none. Fluorescence-activated cell sorter-sorted Treg subsets, displaying markers affected in a conditioning- and GI-aGVHD-restricted manner, were further investigated by transcriptome profiling and T-cell suppression assays. We found that conditioning by irradiation greatly diminished the relative frequency of Helios+/Nrp1+ Treg, shifting the balance toward Helios-/Nrp1- Treg in the host. Upregulation of integrin-β7 and OX40 occurred in GI-aGvHD-dependent manner in Helios+/Nrp1+ cells but not in Helios-/Nrp1- Treg. Sorted Treg subsets, confirmed to overexpress Nrp1, Helios, OX40, or integrin-β7, displayed superior immunosuppressive activity and enrichment in activation-related messenger RNA transcripts. Our data suggest that conditioning-induced shrinkage of the Nrp1+/Helios+ Treg subset may contribute to the development of GI-GvHD by impairing gut homing and decreasing the efficiency of Treg-mediated immunosuppression.

Potential anti-tumor effects of regulatory T cells in the tumor microenvironment: a review

Regulatory T cells (Tregs) expressing the transcription factor FoxP3 are essential for maintaining immunological balance and are a significant component of the immunosuppressive tumor microenvironment (TME). Single-cell RNA sequencing (ScRNA-seq) technology has shown that Tregs exhibit significant plasticity and functional diversity in various tumors within the TME. This results in Tregs playing a dual role in the TME, which is not always centered around supporting tumor progression as typically believed. Abundant data confirms the anti-tumor activities of Tregs and their correlation with enhanced patient prognosis in specific types of malignancies. In this review, we summarize the potential anti-tumor actions of Tregs, including suppressing tumor-promoting inflammatory responses and boosting anti-tumor immunity. In addition, this study outlines the spatial and temporal variations in Tregs function to emphasize that their predictive significance in malignancies may change. It is essential to comprehend the functional diversity and potential anti-tumor effects of Tregs to improve tumor therapy strategies.

Mediator complex subunit 1 architects a tumorigenic Treg cell program independent of inflammation

While immunotherapy has revolutionized cancer treatment, its safety has been hampered by immunotherapy-related adverse events. Unexpectedly, we show that Mediator complex subunit 1 (MED1) is required for T regulatory (Treg) cell function specifically in the tumor microenvironment. Treg cell-specific MED1 deletion does not predispose mice to autoimmunity or excessive inflammation. In contrast, MED1 is required for Treg cell promotion of tumor growth because MED1 is required for the terminal differentiation of effector Treg cells in the tumor. Suppression of these terminally differentiated Treg cells is sufficient for eliciting antitumor immunity. Both human and murine Treg cells experience divergent paths of differentiation in tumors and matched tissues with non-malignant inflammation. Collectively, we identify a pathway promoting the differentiation of a Treg cell effector subset specific to tumors and demonstrate that suppression of a subset of Treg cells is sufficient for promoting antitumor immunity in the absence of autoimmune consequences.

Targeting JMJD1C to selectively disrupt tumor Treg cell fitness enhances antitumor immunity

Regulatory T (Treg) cells are critical for immune tolerance but also form a barrier to antitumor immunity. As therapeutic strategies involving Treg cell depletion are limited by concurrent autoimmune disorders, identification of intratumoral Treg cell-specific regulatory mechanisms is needed for selective targeting. Epigenetic modulators can be targeted with small compounds, but intratumoral Treg cell-specific epigenetic regulators have been unexplored. Here, we show that JMJD1C, a histone demethylase upregulated by cytokines in the tumor microenvironment, is essential for tumor Treg cell fitness but dispensable for systemic immune homeostasis. JMJD1C deletion enhanced AKT signals in a manner dependent on histone H3 lysine 9 dimethylation (H3K9me2) demethylase and STAT3 signals independently of H3K9me2 demethylase, leading to robust interferon-γ production and tumor Treg cell fragility. We have also developed an oral JMJD1C inhibitor that suppresses tumor growth by targeting intratumoral Treg cells. Overall, this study identifies JMJD1C as an epigenetic hub that can integrate signals to establish tumor Treg cell fitness, and we present a specific JMJD1C inhibitor that can target tumor Treg cells without affecting systemic immune homeostasis.

Immunotherapy Innovations in the Fight against Osteosarcoma: Emerging Strategies and Promising Progress

Immunosuppressive elements within the tumor microenvironment are the primary drivers of tumorigenesis and malignant advancement. The presence, as well as the crosstalk between myeloid-derived suppressor cells (MDSCs), osteosarcoma-associated macrophages (OS-Ms), regulatory T cells (Tregs), and endothelial cells (ECs) with osteosarcoma cells cause the poor prognosis of OS. In addition, the consequent immunosuppressive factors favor the loss of treatment potential. Nanoparticles offer a means to dynamically and locally manipulate immuno-nanoparticles, which present a promising strategy for transforming OS-TME. Additionally, chimeric antigen receptor (CAR) technology is effective in combating OS. This review summarizes the essential mechanisms of immunosuppressive cells in the OS-TME and the current immune-associated strategies. The last part highlights the limitations of existing therapies and offers insights into future research directions.

The impact of Foxp3+ regulatory T-cells on CD8+ T-cell dysfunction in tumour microenvironments and responses to immune checkpoint inhibitors

Immune checkpoint inhibitors (ICIs) have been a breakthrough in cancer therapy, inducing durable remissions in responding patients. However, they are associated with variable outcomes, spanning from disease hyperprogression to complete responses with the onset of immune-related adverse events. The consequences of checkpoint inhibition on Foxp3+ regulatory T (Treg ) cells remain unclear but could provide key insights into these variable outcomes. In this review, we first cover the mechanisms that underlie the development of hot and cold tumour microenvironments, which determine the efficacy of immunotherapy. We then outline how differences in tumour-intrinsic immunogenicity, T-cell trafficking, local metabolic environments and inhibitory checkpoint signalling differentially impair CD8+ T-cell function in tumour microenvironments, all the while promoting Treg -cell suppressive activity. Finally, we focus on the mechanisms that enable the induction of polyfunctional CD8+ T-cells upon checkpoint blockade and discuss the role of ICI-induced Treg -cell reactivation in acquired resistance to treatment.

Deficiency of inflammation-sensing protein neuropilin-2 in myeloid-derived macrophages exacerbates colitis via NF-κB activation

Neuropilin-2 (NRP2) is a multifunctional protein engaged in the regulation of angiogenesis, lymphangiogenesis, axon guidance, and tumor metastasis, but its function in colitis remains unclear. Here, we found that NRP2 was an inflammation-sensing protein rapidly and dramatically induced in myeloid cells, especially in macrophages, under inflammatory contexts. NRP2 deficiency in myeloid cells exacerbated dextran sulfate sodium salt-induced experimental colitis by promoting polarization of M1 macrophages and colon injury. Mechanistically, NRP2 could be induced via NF-κB activation by TNF-α in macrophages, but exerted an inhibitory effect on NF-κB signaling, forming a negative feedback loop with NF-κB to sense and alleviate inflammation. Deletion of NRP2 in macrophages broke this negative feedback circuit, leading to NF-κB overactivation, inflammatory exacerbation, and more severe colitis. Collectively, these findings reveal inflammation restriction as a role for NRP2 in macrophages under inflammation contexts and suggest that NRP2 in macrophages may relieve inflammation in inflammatory bowel disease. © 2023 The Pathological Society of Great Britain and Ireland.

The Role of Protein Methyltransferases in Immunity

The immune system protects our body from bacteria, viruses, and toxins and removes malignant cells. Activation of immune cells requires the onset of a network of important signaling proteins. Methylation of these proteins affects their structure and biological function. Under stimulation, T cells, B cells, and other immune cells undergo activation, development, proliferation, differentiation, and manufacture of cytokines and antibodies. Methyltransferases alter the above processes and lead to diverse outcomes depending on the degree and type of methylation. In the previous two decades, methyltransferases have been reported to mediate a great variety of immune stages. Elucidating the roles of methylation in immunity not only contributes to understanding the immune mechanism but is helpful in the development of new immunotherapeutic strategies. Hence, we review herein the studies on methylation in immunity, aiming to provide ideas for new approaches.

Regulatory T Cells for Control of Autoimmunity

Regulatory T (Treg) cells, which specifically express the master transcription factor FoxP3, are indispensable for the maintenance of immunological self-tolerance and homeostasis. Their functional or numerical anomalies can be causative of autoimmune and other inflammatory diseases. Recent advances in the research of the cellular and molecular basis of how Treg cells develop, exert suppression, and maintain their function have enabled devising various ways for controlling physiological and pathological immune responses by targeting Treg cells. It is now envisaged that Treg cells as a "living drug" are able to achieve antigen-specific immune suppression of various immune responses and reestablish immunological self-tolerance in the clinic.

New Promising Routes in Peptic Ulcers: Toll-like Receptors and Semaphorins

Peptic ulcers (PU) are one of the commonest yet problematic diseases found to be existing in the majority of the population. Today, drugs from a wide range of therapeutic classes are available for the management of the disease. Still, the complications of the condition are difficult to tackle and the side effect profile is quite a concern. The literature indicates that Toll-like receptors (TLRs) and Semaphorins (SEMAs) have been under study for their various pharmacological actions over the past few decades. Both these signalling pathways are found to regulate immunological and inflammatory responses. Moreover, receptors and signalling molecules from the family of TLRs and SEMAs are found to have bacterial recognition and antibacterial properties which are essential in eradicating Helicobacter pylori (H. pylori), one of the major causative agents of PU. Our understanding of SEMAs, a class of proteins involved in cell signalling, is relatively less developed compared to TLRs, another class of proteins involved in the immune response. SEMAs and TLRs play different roles in biological processes, with SEMAs primarily involved in guiding cell migration and axon guidance during development, while TLRs are responsible for recognizing pathogens and initiating an immune response. Here, in this review, we will discuss in detail the signalling cascade of TLRs and SEMAs and thereby understand its association with PU for future therapeutic targeting. The review also aims at providing an overview of the study that has been into exploring the role of these signalling pathways in the management of PU.

Treg plasticity and human diseases

INTRODUCTION

As a subset of CD4+ T cells, regulatory T cells (Tregs) with the characteristic expression of transcription factor FOXP3 play a key role in maintaining self-tolerance and regulating immune responses. However, in some inflammatory circumstances, Tregs can express cytokines of other T help (Th) cells by internal reprogramming, which is called Treg plasticity. These reprogrammed Tregs with impaired suppressive ability contribute to the progression of diseases by secreting pro-inflammatory cytokines. However, in the tumor microenvironment (TME), such changes in phenotype rarely occur in Tregs, on the contrary, Tregs usually display a stronger suppressive function and inhibit anti-tumor immunity. It is important to understand the mechanisms of Treg plasticity in inflammatory diseases and cancers.

OBJECTIVES

In this review, we summarize the characteristics of different Th-like Tregs and discuss the potential mechanisms of these changes in phenotype. Furthermore, we summarize the Treg plasticity in human diseases and discuss the effects of these changes in phenotype on disease progression, as well as the potential application of drugs or reagents that regulate Treg plasticity in human diseases.

CONCLUSIONS

Treg plasticity is associated with inflammatory diseases and cancers. Regulating Treg plasticity is a promising direction for the treatment of inflammatory diseases and cancers.

Immunoregulation: the interplay between metabolism and redox homeostasis

Regulatory T cells are fundamental for the induction and maintenance of immune homeostasis, with their dysfunction resulting in uncontrolled immune responses and tissue destruction predisposing to autoimmunity, transplant rejection and several inflammatory and metabolic disorders. Recent discoveries have demonstrated that metabolic processes and mitochondrial function are critical for the appropriate functioning of these cells in health, with their metabolic adaptation, influenced by microenvironmental factors, seen in several pathological processes. Upon activation regulatory T cells rearrange their oxidation-reduction (redox) system, which in turn supports their metabolic reprogramming, adding a layer of complexity to our understanding of cellular metabolism. Here we review the literature surrounding redox homeostasis and metabolism of regulatory T cells to highlight new mechanistic insights of these interlinked pathways in immune regulation.

Activation of the aryl hydrocarbon receptor inhibits neuropilin-1 upregulation on IL-2-responding CD4+ T cells

Neuropilin-1 (Nrp1), a transmembrane protein expressed on CD4+ T cells, is mostly studied in the context of regulatory T cell (Treg) function. More recently, there is increasing evidence that Nrp1 is also highly expressed on activated effector T cells and that increases in these Nrp1-expressing CD4+ T cells correspond with immunopathology across several T cell-dependent disease models. Thus, Nrp1 may be implicated in the identification and function of immunopathologic T cells. Nrp1 downregulation in CD4+ T cells is one of the strongest transcriptional changes in response to immunoregulatory compounds that act though the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor. To better understand the link between AhR and Nrp1 expression on CD4+ T cells, Nrp1 expression was assessed in vivo and in vitro following AhR ligand treatment. In the current study, we identified that the percentage of Nrp1 expressing CD4+ T cells increases over the course of activation and proliferation in vivo. The actively dividing Nrp1+Foxp3- cells express the classic effector phenotype of CD44hiCD45RBlo, and the increase in Nrp1+Foxp3- cells is prevented by AhR activation. In contrast, Nrp1 expression is not modulated by AhR activation in non-proliferating CD4+ T cells. The downregulation of Nrp1 on CD4+ T cells was recapitulated in vitro in cells isolated from C57BL/6 and NOD (non-obese diabetic) mice. CD4+Foxp3- cells expressing CD25, stimulated with IL-2, or differentiated into Th1 cells, were particularly sensitive to AhR-mediated inhibition of Nrp1 upregulation. IL-2 was necessary for AhR-dependent downregulation of Nrp1 expression both in vitro and in vivo. Collectively, the data demonstrate that Nrp1 is a CD4+ T cell activation marker and that regulation of Nrp1 could be a previously undescribed mechanism by which AhR ligands modulate effector CD4+ T cell responses.

Targeting neuropilin-1 abolishes anti-PD-1-upregulated regulatory T cells and synergizes with 4-1BB agonist for liver cancer treatment

BACKGROUND AIMS

Regulatory T cells (Tregs) are an obstacle to PD-1 blockade-mediated antitumor efficacy. However, the behaviors of Tregs response to anti-PD-1 in HCC and the characteristics of Tregs tissue adaptation from peripheral lymphoid tissues to the tumor are still unclear.

APPROACH RESULTS

Here, we determine that PD-1 monotherapy potentially augments the accumulation of tumor CD4 + Tregs. Mechanistically, anti-PD-1 mediates Tregs proliferation in lymphoid tissues rather than in the tumor. Increased peripheral Tregs burden replenishes intratumoral Tregs, raising the ratio of intratumoral CD4 + Tregs to CD8 + T cells. Subsequently, single-cell transcriptomics revealed that neuropilin-1 (Nrp-1) supports Tregs migration behavior, and the genes of Crem and Tnfrsf9 regulate the behaviors of the terminal suppressive Tregs. Nrp-1 + 4-1BB - Tregs stepwise develop to the Nrp-1 - 4-1BB + Tregs from lymphoid tissues into the tumor. Moreover, Treg-restricted Nrp1 depletion abolishes anti-PD-1-upregulated intratumoral Tregs burden and synergizes with the 4-1BB agonist to enhance the antitumor response. Finally, a combination of the Nrp-1 inhibitor and the 4-1BB agonist in humanized HCC models showed a favorable and safe outcome and evoked the antitumor effect of the PD-1 blockade.

CONCLUSION

Our findings elucidate the potential mechanism of anti-PD-1-mediated intratumoral Tregs accumulation in HCC and uncover the tissue adaptation characteristics of Tregs and identify the therapeutic potential of targeting Nrp-1 and 4-1BB for reprogramming the HCC microenvironment.

Is neuropilin-1 the neuroimmune initiator of multi-system hyperinflammation in COVID-19?

A major immunopathological feature of Coronavirus disease-2019 (COVID-19) is excessive inflammation in the form of "cytokine storm". The storm is characterized by injurious levels of cytokines which form a complicated network damaging different organs, including the lungs and the brain. The main starter of "cytokine network" hyperactivation in COVID-19 has not been discovered yet. Neuropilins (NRPs) are transmembrane proteins that act as neuronal guidance and angiogenesis modulators. The crucial function of NRPs in forming the nervous and vascular systems has been well-studied. NRP1 and NRP2 are the two identified homologs of NRP. NRP1 has been shown as a viral entry pathway for SARS-CoV2, which facilitates neuroinvasion by the virus within the central or peripheral nervous systems. These molecules directly interact with various COVID-19-related molecules, such as specific regions of the spike protein (major immune element of SARS-CoV2), vascular endothelial growth factor (VEGF) receptors, VEGFR1/2, and ANGPTL4 (regulator of vessel permeability and integrity). NRPs mainly play a role in hyperinflammatory injury of the CNS and lungs, and also the liver, kidney, pancreas, and heart in COVID-19 patients. New findings have suggested NRPs good candidates for pharmacotherapy of COVID-19. However, therapeutic targeting of NRP1 in COVID-19 is still in the preclinical phase. This review presents the implications of NRP1 in multi-organ inflammation-induced injury by SARS-CoV2 and provides insights for NRP1-targeting treatments for COVID-19 patients.

Neuropilin-1 identifies a subset of highly activated CD8+ T cells during parasitic and viral infections

Neuropilin-1 (Nrp-1) expression on CD8+ T cells has been identified in tumor-infiltrating lymphocytes and in persistent murine gamma-herpes virus infections, where it interferes with the development of long-lived memory T cell responses. In parasitic and acute viral infections, the role of Nrp-1 expression on CD8+ T cells remains unclear. Here, we demonstrate a strong induction of Nrp-1 expression on CD8+ T cells in Plasmodium berghei ANKA (PbA)-infected mice that correlated with neurological deficits of experimental cerebral malaria (ECM). Likewise, the frequency of Nrp-1+CD8+ T cells was significantly elevated and correlated with liver damage in the acute phase of lymphocytic choriomeningitis virus (LCMV) infection. Transcriptomic and flow cytometric analyses revealed a highly activated phenotype of Nrp-1+CD8+ T cells from infected mice. Correspondingly, in vitro experiments showed rapid induction of Nrp-1 expression on CD8+ T cells after stimulation in conjunction with increased expression of activation-associated molecules. Strikingly, T cell-specific Nrp-1 ablation resulted in reduced numbers of activated T cells in the brain of PbA-infected mice as well as in spleen and liver of LCMV-infected mice and alleviated the severity of ECM and LCMV-induced liver pathology. Mechanistically, we identified reduced blood-brain barrier leakage associated with reduced parasite sequestration in the brain of PbA-infected mice with T cell-specific Nrp-1 deficiency. In conclusion, Nrp-1 expression on CD8+ T cells represents a very early activation marker that exacerbates deleterious CD8+ T cell responses during both, parasitic PbA and acute LCMV infections.

TRIM11 attenuates Treg cell differentiation by p62-selective autophagic degradation of AIM2

Ubiquitination is an important protein modification that regulates diverse biological processes, including CD4+ T cell differentiation and functions. However, the function of most E3 ubiquitin ligases in CD4+ T cell differentiation and CD4+ T cell-mediated pathological diseases remains unclear. In this study, we find that tripartite motif-containing motif 11 (TRIM11) specifically negatively regulates regulatory T (Treg) cell differentiation in CD4+ T cells and promotes autoimmune disease development in an AIM2-dependent manner. Mechanistically, TRIM11 interacts with absent in melanoma 2 (AIM2) and promotes the selective autophagic degradation of AIM2 by inducing AIM2 ubiquitination and binding to p62 in CD4+ T cells. AIM2 attenuates AKT and FOXO1 phosphorylation, MYC signaling, and glycolysis, thereby promoting the stability of Treg cells during experimental autoimmune encephalomyelitis (EAE). Our findings suggest that TRIM11 serves as a potential target for immunotherapeutic intervention for dysregulated immune responses that lead to autoimmunity and cancers.

Exploring the dual role of B cells in solid tumors: implications for head and neck squamous cell carcinoma

In the tumor milieu of head and neck squamous cell carcinoma (HNSCC), distinct B cell subpopulations are present, which exert either pro- or anti-tumor activities. Multiple factors, including hypoxia, cytokines, interactions with tumor cells, and other immune infiltrating lymphocytes (TILs), alter the equilibrium between the dual roles of B cells leading to cancerogenesis. Certain B cell subsets in the tumor microenvironment (TME) exhibit immunosuppressive function. These cells are known as regulatory B (Breg) cells. Breg cells suppress immune responses by secreting a series of immunosuppressive cytokines, including IL-10, IL-35, TGF-β, granzyme B, and adenosine or dampen effector TILs by intercellular contacts. Multiple Breg phenotypes have been discovered in human and mouse cancer models. However, when compartmentalized within a tertiary lymphoid structure (TLS), B cells predominantly play anti-tumor effects. A mature TLS contains a CD20+ B cell zone with several important types of B cells, including germinal-center like B cells, antibody-secreting plasma cells, and memory B cells. They kill tumor cells via antibody-dependent cytotoxicity and phagocytosis, and local complement activation effects. TLSs are also privileged sites for local T and B cell coordination and activation. Nonetheless, in some cases, TLSs may serve as a niche for hidden tumor cells and indicate a bad prognosis. Thus, TIL-B cells exhibit bidirectional immune-modulatory activity and are responsive to a variety of immunotherapies. In this review, we discuss the functional distinctions between immunosuppressive Breg cells and immunogenic effector B cells that mature within TLSs with the focus on tumors of HNSCC patients. Additionally, we review contemporary immunotherapies that aim to target TIL-B cells. For the development of innovative therapeutic approaches to complement T-cell-based immunotherapy, a full understanding of either effector B cells or Breg cells is necessary.

An oncolytic virus-delivered TGFβ inhibitor overcomes the immunosuppressive tumor microenvironment

While checkpoint blockade immunotherapies have widespread success, they rely on a responsive immune infiltrate; as such, treatments enhancing immune infiltration and preventing immunosuppression are of critical need. We previously generated αPD-1 resistant variants of the murine HNSCC model MEER. While entirely αPD-1 resistant, these tumors regress after single dose of oncolytic vaccinia virus (VV). We then generated a VV-resistant MEER line to dissect the immunologic features of sensitive and resistant tumors. While treatment of both tumor types induced immune infiltration and IFNγ, we found a defining feature of resistance was elevation of immunosuppressive cytokines like TGFβ, which blunted IFNγ signaling, especially in regulatory T cells. We engineered VV to express a genetically encoded TGFβRII inhibitor. Inhibitor-expressing VV produced regressions in resistant tumor models and showed impressive synergy with checkpoint blockade. Importantly, tumor-specific, viral delivery of TGFβ inhibition had no toxicities associated with systemic TGFβ/TGFβR inhibition. Our data suggest that aside from stimulating immune infiltration, oncolytic viruses are attractive means to deliver agents to limit immunosuppression in cancer.

Biological and Clinical Implications of the Vascular Endothelial Growth Factor Coreceptor Neuropilin-1 in Human Immunodeficiency Virus

Plasma vascular endothelial growth factor (VEGF) coreceptor neuropilin-1 (NRP-1) had the largest association with coronary plaque in the Randomized Trial to Prevent Vascular Events in HIV (REPRIEVE) proteomics analysis. With little known about NRP-1 in people with human immunodeficiency virus (PWH), we explored its relation to other proteins in REPRIEVE and validated our findings through a Centers for AIDS Research Network of Integrated Clinical Systems (CNICS) case-cohort study by assessing its relation to host factors and incident cardiovascular disease and cancer. Within REPRIEVE, NRP-1 was associated with proteins involved in angiogenesis, signal transduction, immunoregulation, and cell migration/adhesion. Within CNICS, NRP-1 was associated with key host factors, including older age and male sex. NRP-1 was associated with an increased hazard of multiple cancers but a decreased prostate cancer risk. Finally, NRP-1 was most strongly associated with mortality and type 2 myocardial infarction. These data suggest that NRP-1 is part of a clinically relevant immunoregulatory pathway related to multiple comorbidities in PWH. Clinical Trials Registration. NCT02344290.

"IL-2 immunotherapy for targeting regulatory T cells in autoimmunity"

FOXP3+ regulatory T cells (Treg) are indispensable for immune homoeostasis and for the prevention of autoimmune diseases. Interleukin-2 (IL-2) signalling is critical in all aspects of Treg biology. Consequences of defective IL-2 signalling are insufficient numbers or dysfunction of Treg and hence autoimmune disorders in human and mouse. The restoration and maintenance of immune homoeostasis remain central therapeutic aims in the field of autoimmunity. Historically, broadly immunosuppressive drugs with serious side-effects have been used for the treatment of autoimmune diseases or prevention of organ-transplant rejection. More recently, ex vivo expanded or in vivo stimulated Treg have been shown to induce effective tolerance in clinical trials supporting the clinical benefit of targeting natural immunosuppressive mechanisms. Given the central role of exogenous IL-2 in Treg homoeostasis, a new and promising focus in drug development are IL-2-based approaches for in vivo targeted expansion of Treg or for enhancement of their suppressive activity. In this review, we summarise the role of IL-2 in Treg biology and consequences of dysfunctional IL-2 signalling pathways. We then examine evidence of efficacy of IL-2-based biological drugs targeting Treg with specific focus on therapeutic candidates in clinical trials and discuss their limitations.

Activation of the aryl hydrocarbon receptor inhibits neuropilin-1 upregulation on IL-2 responding CD4 + T cells

Neuropilin-1 (Nrp1), a transmembrane protein expressed on CD4 + T cells, is mostly studied in the context of regulatory T cell (Treg) function. More recently, there is increasing evidence that Nrp1 is also highly expressed on activated effector T cells and that increases in these Nrp1-expressing CD4 + T cells correspond with immunopathology across several T cell-dependent disease models. Thus, Nrp1 may be implicated in the identification and function of immunopathologic T cells. Nrp1 downregulation in CD4 + T cells is one of the strongest transcriptional changes in response to immunoregulatory compounds that act though the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor. To better understand the link between AhR and Nrp1 expression on CD4 + T cells, Nrp1 expression was assessed in vivo and in vitro following AhR ligand treatment. In the current study, we identified that the percentage of Nrp1 expressing CD4 + T cells increases over the course of activation and proliferation in vivo . The actively dividing Nrp1 + Foxp3 - cells express the classic effector phenotype of CD44 hi CD45RB lo , and the increase in Nrp1 + Foxp3 - cells is prevented by AhR activation. In contrast, Nrp1 expression is not modulated by AhR activation in non-proliferating CD4 + T cells. The downregulation of Nrp1 on CD4 + T cells was recapitulated in vitro in cells isolated from C57BL/6 and NOD (non-obese diabetic) mice. CD4 + Foxp3 - cells expressing CD25, stimulated with IL-2, or differentiated into Th1 cells, were particularly sensitive to AhR-mediated inhibition of Nrp1 upregulation. IL-2 was necessary for AhR-dependent downregulation of Nrp1 expression both in vitro and in vivo . Collectively, the data demonstrate that Nrp1 is a CD4 + T cell activation marker and that regulation of Nrp1 could be a previously undescribed mechanism by which AhR ligands modulate effector CD4 + T cell responses.