CTLA-4 co-receptor impacts on the function of Treg and CD8+ T-cell subsets

Dual Checkpoint Aptamer Immunotherapy: Unveiling Tailored Cancer Treatment Targeting CTLA-4 and NKG2A

Recent strides in immunotherapy have illuminated the crucial role of CTLA-4 and PD-1/PD-L1 pathways in contemporary oncology, presenting both promises and challenges in response rates and adverse effects. This study employs a computational biology tool (in silico approach) to craft aptamers capable of binding to dual receptors, namely, inhibitory CTLA4 and NKG2A, thereby unleashing both T and NK cells and enhancing CD8+ T and NK cell functions for tumor cell lysis. Computational analysis highlighted AYA22T-R2-13 with HADDOCK scores of -78.2 ± 10.2 (with CTLA4), -60.0 ± 4.2 (with NKG2A), and -77.5 ± 5.6 (with CD94/NKG2A). Confirmation of aptamer binding to targeted proteins was attained via ELISA and flow cytometry methods. In vitro biological functionality was assessed using lactate dehydrogenase (LDH) cytotoxicity assay. Direct and competitive assays using ELISA and flow cytometry demonstrated the selective binding of AYA22T-R2-13 to CTLA4 and NKG2A proteins, as well as to the cell surface receptors of IL-2-stimulated T cells and NK cells. This binding was inhibited in the presence of competition from CTLA4 or NKG2A proteins. Remarkably, the blockade of CTLA4 or NKG2A by AYA22T-R2-13 augmented human CD8 T cell- and NK cell-mediated tumor cell lysis in vitro. Our findings highlight the precise binding specificity of AYA22T-R2-13 for CTLA4-B7-1/B7-2 (CD80/CD86) or CD94/NKG2A-HLA-E interactions, positioning it as a valuable tool for immune checkpoint blockade aptamer research in murine tumor models. These in vitro studies establish a promising foundation for further enhancing binding capacity and establishing efficacy and safety in animal models. Consequently, our results underscore the potential of AYA22T-R2-13 in cancer immunotherapy, offering high specificity, low toxicity, and the potential for cost-effective production.

Tryptophan Metabolism in Obesity: The Indoleamine 2,3-Dioxygenase-1 Activity and Therapeutic Options

Obesity activates both innate and adaptive immune responses in adipose tissue. Adipose tissue macrophages are functional antigen-presenting cells that promote the proliferation of interferon-gamma (IFN-γ)-producing cluster of differentiation (CD)4+ T cells in adipose tissue of obese subjects. The increased formation of neopterin and degradation of tryptophan may result in decreased T-cell responsiveness and lead to immunodeficiency. The activity of inducible indoleamine 2,3-dioxygenase-1 (IDO1) plays a major role in pro-inflammatory, IFN-γ-dominated settings. The expression of several kynurenine pathway enzyme genes is significantly increased in obesity. IDO1 in obesity shifts tryptophan metabolism from serotonin and melatonin synthesis to the formation of kynurenines and increases the ratio of kynurenine to tryptophan as well as with neopterin production. Reduction in serotonin (5-hydroxytryptamine; 5-HT) production provokes satiety dysregulation that leads to increased caloric uptake and obesity. According to the monoamine-deficiency hypothesis, a deficiency of cerebral serotonin is involved in neuropsychiatric symptomatology of depression, mania, and psychosis. Indeed, bipolar disorder (BD) and related cognitive deficits are accompanied by a higher prevalence of overweight and obesity. Furthermore, the accumulation of amyloid-β in Alzheimer's disease brains has several toxic effects as well as IDO induction. Hence, abdominal obesity is associated with vascular endothelial dysfunction. kynurenines and their ratios are prognostic parameters in coronary artery disease. Increased kynurenine/tryptophan ratio correlates with increased intima-media thickness and represents advanced atherosclerosis. However, after bariatric surgery, weight reduction does not lead to the normalization of IDO1 activity and atherosclerosis. IDO1 is involved in the mechanisms of immune tolerance and in the concept of tumor immuno-editing process in cancer development. Serum IDO1 activity is still used as a parameter in cancer development and growth. IDO-producing tumors show a high total IDO immunostaining score, and thus, using IDO inhibitors, such as Epacadostat, Navoximod, and L isomer of 1-methyl-tryptophan, seems an important modality for cancer treatment. There is an inverse correlation between serum folate concentration and body mass index, thus folate deficiency leads to hyperhomocysteinemia-induced oxidative stress. Immune checkpoint blockade targeting cytotoxic T-lymphocyte-associated protein-4 synergizes with imatinib, which is an inhibitor of mitochondrial folate-mediated one-carbon (1C) metabolism. Antitumor effects of imatinib are enhanced by increasing T-cell effector function in the presence of IDO inhibition. Combining IDO targeting with chemotherapy, radiotherapy and/or immunotherapy, may be an effective tool against a wide range of malignancies. However, there are some controversial results regarding the efficacy of IDO1 inhibitors in cancer treatment.

Immune checkpoint therapy for solid tumours: clinical dilemmas and future trends

Immune-checkpoint inhibitors (ICBs), in addition to targeting CTLA-4, PD-1, and PD-L1, novel targeting LAG-3 drugs have also been approved in clinical application. With the widespread use of the drug, we must deeply analyze the dilemma of the agents and seek a breakthrough in the treatment prospect. Over the past decades, these agents have demonstrated dramatic efficacy, especially in patients with melanoma and non-small cell lung cancer (NSCLC). Nonetheless, in the field of a broad concept of solid tumours, non-specific indications, inseparable immune response and side effects, unconfirmed progressive disease, and complex regulatory networks of immune resistance are four barriers that limit its widespread application. Fortunately, the successful clinical trials of novel ICB agents and combination therapies, the advent of the era of oncolytic virus gene editing, and the breakthrough of the technical barriers of mRNA vaccines and nano-delivery systems have made remarkable breakthroughs currently. In this review, we enumerate the mechanisms of each immune checkpoint targets, associations between ICB with tumour mutation burden, key immune regulatory or resistance signalling pathways, the specific clinical evidence of the efficacy of classical targets and new targets among different tumour types and put forward dialectical thoughts on drug safety. Finally, we discuss the importance of accurate triage of ICB based on recent advances in predictive biomarkers and diagnostic testing techniques.

Optimal timing of steroid initiation in response to CTLA-4 antibody in metastatic cancer: A mathematical model

Immune checkpoint inhibitors, introduced in recent years, have revolutionized the treatment of many cancers. However, the toxicity associated with this therapy may cause severe adverse events. In the case of advanced lung cancer or metastatic melanoma, a significant number (10%) of patients treated with CTLA-4 inhibitor incur damage to the pituitary gland. In order to reduce the risk of hypophysitis and other severe adverse events, steroids may be combined with CTLA-4 inhibitor; they reduce toxicity, but they also diminish the anti-cancer effect of the immunotherapy. This trade-off between tumor reduction and the risk of severe adverse events poses the following question: What is the optimal time to initiate treatment with steroid. We address this question with a mathematical model from which we can also evaluate the comparative benefits of each schedule of steroid administration. In particular, we conclude that treatment with steroid should not begin too early, but also not very late, after immunotherapy began; more precisely, it should start as soon as tumor volume, under the effect of CTLA-4 inhibitor alone, begins to decrease. We can also compare the benefits of short term treatment of steroid at high doses to a longer term treatment with lower doses.

Pharmacological Treatments Available for Immune-Checkpoint-Inhibitor-Induced Colitis

Immune checkpoint inhibitor treatment has shown revolutionary therapeutic effects in various carcinomas. However, immune-related adverse events (irAE) following this treatment can sometimes lead to treatment discontinuation. One such frequently encountered adverse event is immune-related colitis (irAE colitis). Corticosteroids (CS) are the first-line treatment for irAE colitis, but we often encounter CS-refractory or -resistant cases. The application of multiple biologics has been proposed as a therapy to be administered after CS treatment; however, the efficacy and safety of biologics for patients with irAE colitis who do not respond to CS have not been established. This review summarizes the treatment regimens available for irAE colitis, focusing on the mechanism of action of corticosteroids, infliximab, vedolizumab, and other drugs.

Combination therapy for mCRPC with immune checkpoint inhibitors, ADT and vaccine: A mathematical model

Metastatic castration resistant prostate cancer (mCRPC) is commonly treated by androgen deprivation therapy (ADT) in combination with chemotherapy. Immune therapy by checkpoint inhibitors, has become a powerful new tool in the treatment of melanoma and lung cancer, and it is currently being used in clinical trials in other cancers, including mCRPC. However, so far, clinical trials with PD-1 and CTLA-4 inhibitors have been disappointing. In the present paper we develop a mathematical model to assess the efficacy of any combination of ADT with cancer vaccine, PD-1 inhibitor, and CTLA-4 inhibitor. The model is represented by a system of partial differential equations (PDEs) for cells, cytokines and drugs whose density/concentration evolves in time within the tumor. Efficacy of treatment is determined by the reduction in tumor volume at the endpoint of treatment. In mice experiments with ADT and various combinations of PD-1 and CTLA-4 inhibitors, tumor volume at day 30 was always larger than the initial tumor. Our model, however, shows that we can decrease tumor volume with large enough dose; for example, with 10 fold increase in the dose of anti-PD-1, initial tumor volume will decrease by 60%. Although the treatment with ADT in combination with PD-1 inhibitor or CTLA-4 inhibitor has been disappointing in clinical trials, our simulations suggest that, disregarding negative effects, combinations of ADT with checkpoint inhibitors can be effective in reducing tumor volume if larger doses are used. This points to the need for determining the optimal combination and amounts of dose for individual patients.

CHI3L1 enhances melanoma lung metastasis via regulation of T cell co-stimulators and CTLA-4/B7 axis

ICOS/ICOSL and CD28/B7-1/B7-2 are T cell co-stimulators and CTLA-4 is an immune checkpoint inhibitor that play critical roles in the pathogenesis of neoplasia. Chitinase 3-like-1 (CHI3L1) is induced in many cancers where it portends a poor prognosis and contributes to tumor metastasis. Here we demonstrate that CHI3L1 inhibits the expression of ICOS, ICOSL and CD28 while stimulating CTLA-4 and the B7 moieties in melanoma lung metastasis. We also demonstrate that RIG-like helicase innate immune activation augments T cell co-stimulation, inhibits CTLA-4 and suppresses pulmonary metastasis. At least additive antitumor responses were seen in melanoma lung metastasis treated with anti-CTLA-4 and anti-CHI3L1 antibodies in combination. Synergistic cytotoxic T cell-induced tumor cell death and the heightened induction of the tumor suppressor PTEN were seen in co-cultures of T and tumor cells treated with bispecific antibodies that target both CHI3L1 and CTLA-4. Thus, CHI3L1 contributes to pulmonary metastasis by inhibiting T cell co-stimulation and stimulating CTLA-4. The simultaneous targeting of CHI3L1 and the CTLA-4 axis with individual and, more powerfully with bispecific antibodies, represent promising therapeutic strategies for pulmonary metastasis.

Microbeam Radiotherapy-A Novel Therapeutic Approach to Overcome Radioresistance and Enhance Anti-Tumour Response in Melanoma

Melanoma is the deadliest type of skin cancer, due to its invasiveness and limited treatment efficacy. The main therapy for primary melanoma and solitary organ metastases is wide excision. Adjuvant therapy, such as chemotherapy and targeted therapies are mainly used for disseminated disease. Radiotherapy (RT) is a powerful treatment option used in more than 50% of cancer patients, however, conventional RT alone is unable to eradicate melanoma. Its general radioresistance is attributed to overexpression of repair genes in combination with cascades of biochemical repair mechanisms. A novel sophisticated technique based on synchrotron-generated, spatially fractionated RT, called Microbeam Radiation Therapy (MRT), has been shown to overcome these treatment limitations by allowing increased dose delivery. With MRT, a collimator subdivides the homogeneous radiation field into an array of co-planar, high-dose microbeams that are tens of micrometres wide and spaced a few hundred micrometres apart. Different preclinical models demonstrated that MRT has the potential to completely ablate tumours, or significantly improve tumour control while dramatically reducing normal tissue toxicity. Here, we discuss the role of conventional RT-induced immunity and the potential for MRT to enhance local and systemic anti-tumour immune responses. Comparative gene expression analysis from preclinical tumour models indicated a specific gene signature for an 'MRT-induced immune effect'. This focused review highlights the potential of MRT to overcome the inherent radioresistance of melanoma which could be further enhanced for future clinical use with combined treatment strategies, in particular, immunotherapy.

Single-cell transcriptome analysis identifies skin-specific T-cell responses in systemic sclerosis

OBJECTIVES

Although T cells have been implicated in the pathogenesis of systemic sclerosis (SSc), a comprehensive study of T-cell-mediated immune responses in the affected skin of patients with progressive SSc is lacking. Droplet-based single-cell transcriptome analysis of SSc skin biopsies opens avenues for dissecting patient-specific T-cell heterogeneity, providing a basis for identifying novel gene expression related to functional pathways associated with severity of SSc skin disease.

METHODS

Single-cell RNA sequencing was performed by droplet-based sequencing (10x Genomics), focusing on 3729 CD3⁺ lymphocytes (867 cells from normal and 2862 cells from SSc skin samples) from skin biopsies of 27 patients with active SSc and 10 healthy donors. Confocal immunofluorescence microscopy of progressive SSc skin samples validated transcriptional results and visualised spatial localisations of T-cell subsets.

RESULTS

We identified several subsets of recirculating and tissue-resident T cells in healthy and SSc skin that were associated with distinct signalling pathways. While most clusters shared a common gene expression signature between patients and controls, we identified a unique cluster of recirculating CXCL13⁺ T cells in SSc skin which expressed a T helper follicular-like gene expression signature and that appears to be poised to promote B-cell responses within the inflamed skin of patients.

CONCLUSIONS

Current available therapies to reverse or even slow progression of SSc lead to broad killing of immune cells and consequent toxicities, including death. Identifying the precise immune mechanism(s) driving SSc pathogenesis could lead to innovative therapies that selectively target the aberrant immune response, resulting in better efficacy and less toxicity.

CD80 Expression on Tumor Cells Alters Tumor Microenvironment and Efficacy of Cancer Immunotherapy by CTLA-4 Blockade

Cluster of differentiation (CD) 80 is mainly expressed in immune cells but can also be found in several types of cancer cells. This molecule may either activate or inhibit immune reactions. Here, we determined the immunosuppressive role of CD80 in the tumor microenvironment by CRISPR/Cas9-mediated deactivation of the corresponding gene in the mouse oncogenic TC-1 cell line. The tumor cells with deactivated CD80 (TC-1/dCD80-1) were more immunogenic than parental cells and induced tumors that gained sensitivity to cytotoxic T-lymphocyte antigen 4 (CTLA-4) blockade, as compared with the TC-1 cells. In vivo depletion experiments showed that the deactivation of CD80 switched the pro-tumorigenic effect of macrophages observed in TC-1-induced tumors into an anti-tumorigenic effect in TC-1/dCD80-1 tumors and induced the pro-tumorigenic activity of CD4⁺ cells. Moreover, the frequency of lymphoid and myeloid cells and the CTLA-4 expression by T helper (Th)17 cells were increased in TC-1/dCD80-1- compared with that in the TC-1-induced tumors. CTLA-4 blockade downregulated the frequencies of most immune cell types and upregulated the frequency of M2 macrophages in the TC-1 tumors, while it increased the frequency of lymphoid cells in TC-1/dCD80-1-induced tumors. Furthermore, the anti-CTLA-4 therapy enhanced the frequency of CD8⁺ T cells as well as CD4⁺ T cells, especially for a Th1 subset. Regulatory T cells (Treg) formed the most abundant CD4⁺ T cell subset in untreated tumors. The anti-CTLA-4 treatment downregulated the frequency of Treg cells with limited immunosuppressive potential in the TC-1 tumors, whereas it enriched this type of Treg cells and decreased the Treg cells with high immunosuppressive potential in TC-1/dCD80-1-induced tumors. The immunosuppressive role of tumor-cell-expressed CD80 should be considered in research into biomarkers for the prediction of cancer patients' sensitivity to immune checkpoint inhibitors and for the development of a tumor-cell-specific CD80 blockade.

An overview of the published and running randomized phase 3 clinical results of radiotherapy in combination with immunotherapy

Several studies have established that radiotherapy (RT) in combination with immunotherapy (IO) has a strong synergistic effect. RT changes the tumor microenvironment, generates local inflammation reactions, and enhances immunostimulatory effects, which are able to assist IO with improving local and systemic tumor control. In several pre-clinical reports, RT in combination with IO reveals regression of tumors locally (irradiated sites) and systemically (non-irradiated sites). Several clinical trials are currently running, mostly as phase I and II studies. This article provides an overview of the randomized, prospective reported and recruiting phase 3 clinical trials of RT in combination with IO. To date, three phase 3 trials have been published on RT and sequential IO with variable results, ranging from no significant difference (Kwon et al., START) to absolute differences in overall survival of 13.5% after 3 years (PACIFIC), respectively. No phase 3 randomized trials have been published on the simultaneous combination of RT with IO. Thirty trials are presently under way, and still recruiting patients to quantify the response to RT with IO. These studies fall into three categories of research interests: (I) to discover an enhancement effect of IO as induction therapy with RT; (II) to determine the additional effect of concurrent IO on the local effect of RT; and (III) to determine the additional effect of adjuvant or consolidation IO on the local effect of RT. Most of the ongoing studies are a combination of these interests, with 15 trials evaluating the concurrent RT+IO with IO consolidation strategy. The results in coming years will provide more insights in the role of RT as an activator of the immune system, the effect of IO as local sensitizer of RT, the optimal sequencing of IO with RT, and the total RT doses needed to obtain the optimal local and systemic effect.

Immunotherapy as sensitizer for local radiotherapy

The purpose of this report was to systematically review the radiation enhancement factor (REF) effects of immunotherapy on radiotherapy (RT) to the local tumor in comparison with other traditional radiation sensitizers such as cisplatin. PubMed and Medline databases were searched until February 2019. Reports with abscopal effect in the results were excluded. Graphs of the selected papers were digitized using Plot Digitizer (Sourceforge.net) in order to calculate the tumor growth delay (TGD) caused by immunotherapy. To enable comparison between different studies,the TGD were used to define the REF between RT versus the RT/immunotherapy combination. Thirty-two preclinical papers, and nine clinical series were selected. Different mouse models were exposed to RT doses ranging from 1 to 10 fractions of 1.8 to 20 Gray (Gy) per fraction. Endpoints were heterogeneous, ranging from regression to complete local response. No randomized clinical studies were identified. The median preclinical REF effect of different immunotherapy was varying from 1.7 to 9.1. There was no relationship observed either with subclasses of immunotherapy orRT doses. In the clinical studies, RT doses ranged from 1 to 37 fractions of 1.8 to 24 Gy per fraction. Most clinical trials used ipilimumab and interleukin-2. Local control rate in the clinical series ranged from 66% to 100%. A strong REF of immunotherapy (1.7 to 9.1) was observed, this being higher than traditionally sensitizers such as cisplatin (1.1). This result implies that for the same RT dose, a higher local control was achieved with a combination of immunotherapy and RT in preclinical settings. This study therefore supports the use of combined RT and immunotherapy to improve local tumor control in clinical settings without exacerbation of toxicities.

Recovery of CD226-TIGIT+FoxP3+ and CD226-TIGIT-FoxP3+ regulatory T cells contributes to clinical remission from active stage in ulcerative colitis patients

PURPOSE

Ulcerative colitis (UC) is a chronic inflammatory immune-related disease. Imbalance between pathogenic cells and immunosuppressive cells is associated with disease activity of UC. Regulatory T cells (Tregs) are critical for this immune homeostasis. However, the clinical significance of CD226 and TIGIT expressions on FoxP3⁺Tregs in UC remains unclear.

METHODS

Comprehensive analyses of CD226 and TIGIT expressions on FoxP3⁺Tregs were performed by flow cytometry in 72 UC patients and 35 healthy controls, and ten active UC patients achieving remission after treatment with 5-aminosalicylic acid were followed up. Expressions of β7, α4 and αE on FoxP3⁺Tregs were analyzed. Clinical indicators were retrospectively acquired and serum cytokines were detected using ELISA, and their correlations with FoxP3⁺Treg subsets were conducted.

RESULTS

In active UC, levels of FoxP3⁺Tregs and CD226^-FoxP3⁺Tregs regardless of TIGIT expression were significantly decreased while percentages of CD226⁺TIGIT^-FoxP3⁺Tregs and CD226⁺TIGIT⁺FoxP3⁺Tregs were obviously increased. The expressions of β7, α4β7 and αEβ7 in FoxP3⁺Tregs, CD226^-TIGIT⁺FoxP3⁺Tregs and CD226^-TIGIT^-FoxP3⁺Tregs were significantly elevated in active UC. Furthermore, inverse correlations were found between FoxP3⁺Tregs, CD226^-TIGIT⁺FoxP3⁺Tregs, CD226^-TIGIT^-FoxP3⁺Tregs and serum CRP, as well as Mayo scores. IL-10 was reduced and positively correlated with CD226^-TIGIT⁺FoxP3⁺Tregs and CD226^-TIGIT^-FoxP3⁺Tregs while IL-12 was increased and negatively correlated with CD226^-TIGIT⁺FoxP3⁺Tregs and CD226^-TIGIT^-FoxP3⁺Tregs in active UC. In follow-up patients, the levels of FoxP3⁺Tregs, CD226^-TIGIT⁺FoxP3⁺Tregs and CD226^-TIGIT^-FoxP3⁺Tregs and serum IL-10 levels were significantly recovered when achieving remission after treatment.

CONCLUSIONS

Lack of CD226 expression on FoxP3⁺Tregs regardless of TIGIT expression may play an important role in exhibiting their suppressive function and preventing from disease activity in UC.

Immunophenotype of T Cells Expressing Programmed Death-1 and Cytotoxic T Cell Antigen-4 in Early Lung Cancer: Local vs. Systemic Immune Response

The overexpression of programmed death-1 (PD-1) and cytotoxic T cell antigen 4 (CTLA-4) receptors on T cells are among the major mechanisms of tumor immunoevasion. However, the expression pattern of these receptors on T cell subpopulations of a different activation status and at different sites is poorly characterized. Thus, we analyzed the expression of PD-1 and CTLA-4 on the naïve, activated, memory, and activated memory T cells. Bronchoalveolar lavage fluid (BALF) from the lung affected by lung cancer (clBALF), the opposite ‘healthy’ lung (hlBALF), and peripheral blood (PB) samples were collected from 32 patients. The cells were analyzed by multiparameter flow cytometry. The proportion of memory, activated, and activated memory CD8+ cells with the expression of PD-1 and CTLA-4 were elevated in the clBALF when compared to the hlBALF (insignificantly), but these proportions were significantly higher in the BALF when compared with the PB. The proportions of PD-1+ and CTLA-4+ T cells were elevated in the squamous cell carcinoma when compared to the adenocarcinoma patients. Also, the expression of PD-1 and CTLA-4 on T cells from the BALF was significantly higher than from PB. We report for the first time the differential expression of checkpoint molecules on CD4+ and CD8+ lymphocytes at a different stage of activation in the local environment of lung cancer. Moreover, the circulating T cells have a distinct expression of these receptors, which suggests their poor utility as biomarkers for immunotherapy.

Immune Dysregulation in Cancer Patients Undergoing Immune Checkpoint Inhibitor Treatment and Potential Predictive Strategies for Future Clinical Practice

Realization of the full potential of immune checkpoint inhibitor-targeted onco-immunotherapy is largely dependent on overcoming the obstacles presented by the resistance of some cancers, as well as on reducing the high frequency of immune-related adverse events (IRAEs) associated with this type of immunotherapy. With the exception of combining therapeutic monoclonal antibodies, which target different types of immune checkpoint inhibitory molecules, progress in respect of improving therapeutic efficacy has been somewhat limited to date. Likewise, the identification of strategies to predict and monitor the development of IRAEs has also met with limited success due, at least in part, to lack of insight into mechanisms of immunopathogenesis. Accordingly, considerable effort is currently being devoted to the identification and evaluation of strategies which address both of these concerns and it is these issues which represent the major focus of the current review, particularly those which may be predictive of development of IRAEs. Following an introductory section, this review briefly covers those immune checkpoint inhibitors currently approved for clinical application, as well as more recently identified immune checkpoint inhibitory molecules, which may serve as future therapeutic targets. The remaining and more extensive sections represent overviews of: (i) putative strategies which may improve the therapeutic efficacy of immune checkpoint inhibitors; (ii) recent insights into the immunopathogenesis of IRAEs, most prominently enterocolitis; and (iii) strategies, mostly unexplored, which may be predictive of development of IRAEs.

Quantitative and qualitative analysis of regulatory T cells in B cell chronic lymphocytic leukemia

Accumulated data indicate a significant role of T cell dysfunction in the pathogenesis of chronic lymphocytic leukemia. In CLL, regulatory T cells are significantly higher and show lower apoptotic levels compared to healthy donors. We demonstrate that CLL derived CD4⁺CD25^-CD127^- and CD4⁺CD25^lowCD127^- subpopulations share a common immunophenotypic profile with conventional Tregs and are associated with advanced stage disease. We further provide evidence that the increased number of Tregs contributes indirectly to the proliferation of the CLL clone, by suppressing the proliferation of Teffs which in turn suppress CLL cells. These data are further supported by our observations that CLL derived Tregs appear rather incapable of inducing apoptosis of both normal B cells and CLL cells, in contrast to normal Tregs, suggesting an immunoediting effect of CLL cells on Tregs which negatively affects the functionality of the latter and contributes to the failure of Tregs in CLL to efficiently eliminate the abnormal clone.

Preclinical Rationale and Clinical Considerations for Radiotherapy Plus Immunotherapy: Going Beyond Local Control

The use of radiation for cancer therapy has expanded and sparked interest in possible synergistic effects by combining it with current immunotherapies. In this review, we present a case of a patient who responded to programmed cell death 1 (PD1) blockade and radiation therapy and discuss possible mechanisms. We provide background on the blockade of the cytotoxic T-lymphocyte antigen 4 (CTLA-4) and PD1 checkpoints and highlight future immune-based therapies that may synergize with radiation, including cytosine-phosphate-guanine vaccines, OX40 agonists, CD40 agonists, regulatory T-cell depletion, and metabolic "rewiring" of cancer cells. Clinical considerations are noted for combining radiation with immunotherapies to extend the benefit of immunotherapy to more patients. New trials are needed to appropriately investigate the best sequencing and radiation dose to prime an immune response and to identify predictive biomarkers of such responses.

Elevated regulatory T cells, surface and intracellular CTLA-4 expression and interleukin-17 in the lung cancer microenvironment in humans

Regulatory T cells (Tregs) play an important role in the suppression of the immune response in lung cancer. Cytotoxic T-lymphocyte antigen 4 (CTLA-4) expressed on T lymphocytes is capable of downregulating cytotoxic T cells and is constitutively expressed on Tregs. Little is known about the population of Tregs with two forms of CTLA-4: surface (s) and intracellular (in) in the lung cancer environment. Th17 cells defined by production of IL-17 have pleiotropic functions in anticancer immune response. Our aim was to detect the elements of immune response regulation in lung cancer in three compartments: by analysis of bronchoalveolar lavage fluid (BALF) from the lung affected by cancer (clBALF), healthy symmetrical lung (hlBALF) and peripheral blood (PB) from the same patient. A total of 54 samples were collected. Tregs, (s)CTLA-4, (in)CTLA-4 were detected by flow cytometry with antibodies against CD4, CD25, Foxp3, CD127, CTLA-4, and concentration of IL-17 was estimated by ELISA. We observed a significantly higher proportion of Tregs in clBALF than in hlBALF or PB (8.5 vs. 5.0 vs. 5.1%, respectively, p < 0.05). The median proportion of (in)CTLA-4+ Tregs was higher in clBALF than in hlBALF or PB (89.0, 81.5, 56.0%, p < 0.05). IL-17 concentration was the highest in clBALF-6.6 pg/ml. We observed a significant correlation between the proportion of Tregs and (in)CTLA-4+ Tregs with IL-17A concentration in clBALF. We confirmed significant differences in the proportion of regulatory elements between cancerous lung and healthy lung and PB and the usefulness of BALF analysis in evaluation of immune response regulation in local lung cancer environment.

Lin28b Regulates Fetal Regulatory T Cell Differentiation through Modulation of TGF-β Signaling

Immune tolerance between the fetus and mother represents an active process by which the developing fetus must not mount immune responses to noninherited Ags on chimeric maternal cells that reside in fetal tissue. This is, in part, mediated by the suppressive influence of CD4⁺FOXP3⁺CD25⁺ regulatory T cells (Tregs). Fetal secondary lymphoid organs have an increased frequency of Tregs and, as compared with adult T cells, fetal naive CD4⁺ T cells exhibit a strong predisposition to differentiate into Tregs when stimulated. This effect is mediated by the TCR and TGF-β pathways, and fetal T cells show significantly increased Treg differentiation in response to anti-CD3 and TGF-β stimulation. Naive fetal T cells also exhibit increased signaling through the TGF-β pathway, with these cells demonstrating increased expression of the signaling mediators TGF-βRI, TGF-βRIII, and SMAD2, and higher levels of SMAD2/SMAD3 phosphorylation. Increased fetal Treg differentiation is mediated by the RNA-binding protein Lin28b, which is overexpressed in fetal T cells as compared with adult cells. When Lin28b expression is decreased in naive fetal T cells, they exhibit decreased Treg differentiation that is associated with decreased TGF-β signaling and lowered expression of TGF-βRI, TGF-βRIII, and SMAD2. Lin28b regulates the maturation of let-7 microRNAs, and these TGF-β signaling mediators are let-7 targets. We hypothesize that loss of Lin28b expression in fetal T cells leads to increased mature let-7, which causes decreased expression of TGF-βRI, TGF-βRIII, and SMAD2 proteins. A reduction in TGF-β signaling leads to reduced Treg numbers.

Feeding a diet devoid of choline to lactating rodents restricts growth and lymphocyte development in offspring

The nutrient choline is necessary for membrane synthesis and methyl donation, with increased requirements during lactation. The majority of immune development occurs postnatally, but the importance of choline supply for immune development during this critical period is unknown. The objective of this study was to determine the importance of maternal supply of choline during suckling on immune function in their offspring among rodents. At parturition, Sprague-Dawley dams were randomised to either a choline-devoid (ChD; n 7) or choline-sufficient (ChS, 1 g/kg choline; n 10) diet with their offspring euthanised at 3 weeks of age. In a second experiment, offspring were weaned to a ChS diet until 10 weeks of age (ChD-ChS, n 5 and ChS-ChS, n 9). Splenocytes were isolated, and parameters of immune function were measured. The ChD offspring received less choline in breast milk and had lower final body and organ weight compared with ChS offspring (P<0·05), but this effect disappeared by week 10 with choline supplementation from weaning. ChD offspring had a higher proportion of T cells expressing activation markers (CD71 or CD28) and a lower proportion of total B cells (CD45RA+) and responded less to T cell stimulation (lower stimulation index and less IFN-γ production) ex vivo (P<0·05). ChD-ChS offspring had a lower proportion of total and activated CD4+ T cells, and produced less IL-6 after mitogen stimulation compared with cells from ChS-ChS (P<0·05). Our study suggests that choline is required in the suckling diet to facilitate immune development, and choline deprivation during this critical period has lasting effects on T cell function later in life.

Current status of checkpoint inhibitors in lymphoma

Cancer immunotherapy is evolving very fast. With understanding of tumor and immune system interactions, two pathways have been identified through which tumor cells evade and escape immune system. Blocking these pathways by monoclonal antibodies has shown promising results in wide variety of tumors. The treatment of lymphomas have been evolving with various new molecules ranging from monoclonal antibodies, antibody–drug conjugates to small molecule inhibitors. Here, we review the activity of immune checkpoint inhibitors in various lymphomas. These agents have shown very promising activity in Hodgkin lymphoma and other B-cell lymphomas in early-phase clinical trials.

ICAM-1-dependent homotypic aggregates regulate CD8 T cell effector function and differentiation during T cell activation

A hallmark of T cell activation in vitro and in vivo is the clustering of T cells with each other via interaction of the LFA-1 integrin with ICAM-1. The functional significance of these homotypic aggregates in regulating T cell function remains unknown. We used an APC-free in vitro activation system to demonstrate that stimulation of purified naive CD8 T cells results in enhanced expression of ICAM-1 on T cells that is sustained by the inflammatory cytokine IL-12 and associated with robust T cell aggregates. ICAM-1-deficient CD8 T cells proliferate normally but demonstrate a striking failure to aggregate. Interestingly, loss of ICAM-1 expression results in elevated levels of IFN-γ and granzyme B, as well as enhanced cytotoxicity. Similar results were obtained when anti-LFA-1 Ab was used to block the clustering of wild-type T cells. ICAM-1 ligation is not required for IFN-γ regulation, as clustering of ICAM-1-deficient CD8 T cells with wild-type T cells reduces IFN-γ expression. Analysis using a fluorescent reporter that monitors TCR signal strength indicates that T cell clustering limits T cell exposure to Ag during activation. Furthermore, T cell clustering promotes the upregulation of the CTLA-4 inhibitory receptor and the downregulation of eomesodermin, which controls effector molecule expression. Activation of ICAM-1-deficient CD8 T cells in vivo results in an enhanced percentage of KLRG-1(+) T cells indicative of short-lived effectors. These results suggest that T cell clustering represents a mechanism that allows continued proliferation but regulates T cell effector function and differentiation.

Maintenance immunosuppression in renal transplantation

The need to maintain allograft recipients on immunosuppression is nearly universal. Immunosuppressive agents used in organ transplantation target one or more steps of the host alloimmune response, specifically processes related to CD4-positive T lymphocytes. Calcineurin-inhibitor based steroid-containing regimens have been the mainstay of maintenance immunosuppression over the last two decades. Newer agents have shown efficacy in this role in recent trials with comparable allograft and patient outcomes. These agents have permitted calcineurin-inhibitor minimization and steroid-sparing strategies in selected groups of patients.

Cytokine profile, proliferation and phosphorylation of ERK1/2 and Akt in circulating mononuclear cells from individuals during the chronic intestinal phase of Schistosomiasis mansoni infection

Background

The immune response to Schistosoma mansoni is characterized by a granulomatous reaction around the parasite eggs that are trapped in the host liver, and this reaction modulates the immune response during the chronic phase of the disease. The typical peripheral blood mononuclear cell (PBMC) response of patients during the chronic intestinal phase of infection is characterized by a decreased response to an S. mansoni soluble egg antigen. To obtain a greater understanding of Schistosoma infections, this study investigated the effects of the soluble egg antigen (SEA) and soluble adult worm antigen (SWAP) of S. mansoni on cellular proliferation, cytokine production, and ERK1/2 and Akt phosphorylation in PBMCs from infected (XTO) and egg-negative (NI) individuals living in the same endemic area.

Methods

The activation status was evaluated by cell immunophenotypic staining (cytometry). The cell proliferation assay was by CFSE method. Cytokine detection assay (Th1 and Th2) was by Cytometric Bead and Array phosphorylation status was by ELISA.

Results

The XTO, NI and BD (blood donor) individuals from an area not endemic for schistosomiasis were compared. The CD4⁺ T lymphocyte proliferation rate was lower in the XTO group, but not the NI group, after SEA stimulation compared to the BD group. The CD8⁺ T cell proliferation rate was lower in the XTO group in the unstimulated cultures and after both SEA and SWAP stimulation compared to the BD group. Cytokine analysis after either SEA or SWAP stimulation showed a balanced cytokine pattern in the XTO and NI groups. ERK1/2 and Akt phosphorylation were only marginally detected in all groups; however, a decrease in ERK 1/2 phosphorylation was observed in the SWAP-stimulated XTO group compared to both the NI and BD groups.

Conclusions

The data indicate that SEA-stimulated CD4⁺ T cells from infected patients have a lower proliferation rate than the same cells from the NI group. Furthermore, we observed that SWAP stimulation influences ERK1/2 phosphorylation in the XTO group.

Biomarkers on melanoma patient T cells associated with ipilimumab treatment

Background

Ipilimumab induces long-lasting clinical responses in a minority of patients with metastatic melanoma. To better understand the mechanism(s) of action and to identify novel biomarkers associated with the clinical benefit and toxicity of ipilimumab, baseline characteristics and changes in CD4⁺ and CD8⁺ T cells from melanoma patients receiving ipilimumab were characterized by gene profiling and flow cytometry.

Methods

Microarray analysis of flow-cytometry purified CD4⁺ and CD8⁺ T cells was employed to assess gene profiling changes induced by ipilimumab. Selected molecules were further investigated by flow cytometry on pre, 3-month and 6-month post-treatment specimens.

Results

Ipilimumab up-regulated Ki67 and ICOS on CD4⁺ and CD8⁺ cells at both 3- and 6-month post ipilimumab (p ≤ 0.001), decreased CCR7 and CD25 on CD8⁺ at 3-month post ipilimumab (p ≤ 0.02), and increased Gata3 in CD4⁺ and CD8⁺ cells at 6-month post ipilimumab (p ≤ 0.001). Increased EOMES⁺CD8⁺, GranzymeB⁺EOMES⁺CD8⁺ and decreased Ki67⁺EOMES⁺CD4⁺ T cells at 6 months were significantly associated with relapse (all p ≤ 0.03). Decreased Ki67⁺CD8⁺ T cells were significantly associated with the development of irAE (p = 0.02). At baseline, low Ki67⁺EOMES⁺CD8⁺ T cells were associated with relapse (p ≤ 0.001), and low Ki67⁺EOMES⁺CD4⁺ T cells were associated with irAE (p ≤ 0.008).

Conclusions

Up-regulation of proliferation and activation signals in CD4⁺ and CD8⁺ T cells were pharmacodynamic markers for ipilimumab. Ki67⁺EOMES⁺CD8⁺ and Ki67⁺EOMES⁺CD4⁺T cells at baseline merit further testing as biomarkers associated with outcome and irAEs, respectively.

Epicutaneous immunization with DNP-BSA induces CD4+ CD25+ Treg cells that inhibit Tc1-mediated CS

As we have shown previously that protein antigen applied epicutaneously (EC) in mice inhibits TNP-specific Th1-mediated contact sensitivity (CS), we postulated that the maneuver of EC immunization might also suppress Tc1-dependent CS response. Here we showed that EC immunization of normal mice with 2,4-dinitrophenylated bovine serum albumin (DNP-BSA) applied on the skin in the form of a patch induces a state of subsequent unresponsiveness due to regulatory T cells (Treg) that inhibited sensitization and elicitation of effector T-cell responses. Suppression is transferable in vivo by TCRαβ(+) CD4(+) CD25(+) lymphocytes harvested from lymph nodes (LNs) of skin-patched animals. Flow cytometry revealed that EC immunization with DNP-BSA increased TCRαβ(+) CD4(+) CD25(+) FoxP3(+) lymphocytes in subcutaneous LNs, suggesting that observed suppression was mediated by Treg cells. Further, in vitro experiments showed that EC immunization with DNP-BSA prior to 1-fluoro-2,4-dinitrobenzen sensitization suppressed LN cell proliferation and inhibited production of TNF-α, IL-12 and IFN-γ. Using a transwell system or anti-CTLA-4 mAb, we found that EC induced suppression required direct Treg-effector cell contact and is CTLA-4-dependent.

Abdominal γ-radiation induces an accumulation of function-impaired regulatory T cells in the small intestine

PURPOSE

To assess the frequency and the functional characteristics of one major component of immune tolerance, the CD4(+)FoxP3(+) regulatory T cells (Tregs) in a mouse model of abdominal irradiation.

METHODS AND MATERIALS

Mice were exposed to a single abdominal dose of γ-radiation (10 Gy). We evaluated small intestine Treg infiltration by Foxp3 immunostaining and the functional suppressive activity of Tregs isolated from mesenteric lymph nodes.

RESULTS

Foxp3 immunostaining showed that radiation induced a long-term infiltration of the intestine by Tregs (levels 5.5 times greater than in controls). Co-culture of Tregs from mesenteric lymph nodes with CD4(+) effector cells showed that the Tregs had lost their suppressive function. This loss was associated with a significant decrease in the levels of Foxp3, TGF-β, and CTLA-4 mRNA, all required for optimal Treg function. At Day 90 after irradiation, Tregs regained their suppressive activity as forkhead box P3 (Foxp3), transforming growth factor beta (TGF-β), and cytotoxic T-lymphocyte antigen 4 (CTLA-4) expression returned to normal. Analysis of the secretory function of mesenteric lymph node Tregs, activated in vitro with anti-CD3/anti-CD28 Abs, showed that this dysfunction was independent of a defect in interleukin-10 secretion.

CONCLUSION

Radiation caused a long-term accumulation of function-impaired Foxp3(+)CD4(+) Tregs in the intestine. Our study provides new insights into how radiation affects the immune tolerance in peripheral tissues.

Foxp3-transduced polyclonal regulatory T cells suppress NK cell functions in a TGF-beta dependent manner

CD4(+)CD25(+) regulatory T cells (Treg) are a unique population of T cells that maintain immune tolerance and are essential in host suppression of autoimmune diseases. Natural killer (NK) cells are an important component of the innate immune system and respond to insults. Recent studies demonstrate that NK cells may play a vital role during the onset and progression of certain autoimmune diseases. The decreased or abolished regulation by Treg cells on NK cells may lead to the abnormal autoimmune response. The purpose of this study was to investigate the suppressive effect of Foxp3-transduced CD4(+) T cells on NK cell functions, and thus to present a possible method for managing NK cell-related autoimmune abnormalities. This study showed that forced Foxp3 expression in polyclonal CD4(+) T cells could obtain Treg cells phenotype, including specifically expressing CD25, transforming growth factor (TGF-beta) and CTLA-4. Since NK cells have two major immunological properties--cytotoxicity and cytokine production, we observed that transduction-induced Treg cells decreased NK cell cytotoxicity obviously, and dramatically downregulated the interferon-gamma secretion of NK cell responding to IL-12 stimulation. Moreover, it was found that cell-cell interaction was essential for suppression of NK cell functions, and TGF-beta played a vital role in the inhibition process. These results indicate that the forced Foxp3 expression in polyclonal CD4(+) T cells could induce Treg cells and potentially inhibit NK cell functions.

Co-expression of TNFR2 and CD25 identifies more of the functional CD4+FOXP3+ regulatory T cells in human peripheral blood

Previously, we found that co-expression of CD25 and TNFR2 identified the most suppressive subset of mouse Treg. In this study, we report that human peripheral blood (PB) FOXP3(+) cells present in CD25(high), CD25(low) and even CD25(-) subsets of CD4(+) cells expressed high levels of TNFR2. Consequently, TNFR2-expressing CD4(+)CD25(+) Treg included all of the FOXP3(+) cells present in the CD4(+)CD25(high) subset as well as a substantial proportion of the FOXP3(+) cells present in the CD4(+)CD25(low) subset. Flow cytometric analysis of PB identified five-fold more Treg, determined by FOXP3 expression, in the CD4(+)CD25(+)TNFR2(+) subset than in the CD4(+)CD25(high) subset. In addition, similar levels of FOXP3(+) cells were identified in both the CD4(+)CD25(+)TNFR2(+) and CD4(+)CD25(+)CD127(low/-) subsets. Furthermore, the CD4(+)CD25(+)TNFR2(+) subset expressed high levels of CTLA-4, CD45RO, CCR4 and low levels of CD45RA and CD127, a phenotype characteristic of Treg. Upon TCR stimulation, human PB CD4(+)CD25(+)TNFR2(+) cells were anergic and markedly inhibited the proliferation and cytokine production of co-cultured T-responder cells. In contrast, CD4(+)CD25(+)TNFR2(-) and CD4(+)CD25(-)TNFR2(+) T cells did not show inhibitory activity. As some non-Treg express TNFR2, the combination of CD25 and TNFR2 must be used to identify a larger population of human Treg, a population that may prove to be of diagnostic and therapeutic benefit in cancer and autoimmune diseases.