CD152 (CTLA-4) regulates effector functions of CD8+ T lymphocytes by repressing Eomesodermin

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.

The role of the Immune System in the Development of Endometriosis

Endometriosis is a chronic disease that affects about 10% of women of reproductive age. It can contribute to pelvic pain, infertility or other conditions such as asthma, cardiovascular disease, breast or ovarian cancer. Research has shown that one of the conditions for the development of endometrial lesions is the dysfunction of the immune system. It appears that immune cells, such as neutrophils, macrophages, NK cells and dendritic cells, may play a specific role in the angiogenesis, growth and invasion of endometriosis cells. Immune cells secrete cytokines and defensins that also affect the endometriosis environment. This review discusses the various components of the immune system that are involved in the formation of endometrial lesions in women.

HLA-G and CD152 Expression Levels Encourage the Use of Umbilical Cord Tissue-Derived Mesenchymal Stromal Cells as an Alternative for Immunosuppressive Therapy

Mesenchymal stromal cells (MSCs) have been used in immunosuppressive therapy due to their therapeutic effects, with the HLA-G molecule seeming to play a fundamental role. This work evaluated alternative MSC sources to bone marrow (BM), namely, umbilical cord tissue (UC), adipose tissue (AD) and dental pulp tissue (DP), and the influence of interferon-γ (IFN-γ) and hypoxia on the cultivation of these cells for use in immunosuppression therapies. Expression of costimulatory markers CD40, CD80 and CD86 and immunosuppressive molecules CD152 and HLA-G was analyzed. Lymphocyte inhibition assays were also performed. Sequencing of the HLA-G gene from exons 1 to 5 was performed using next-generation sequencing to determine the presence of alleles. UC-derived MSCs (UCMSCs) expressed higher CD152 and HLA-G1 under standard cultivation. UCMSCs and DP-derived MSCs (DPSCs) secreted similar levels of HLA-G5. All MSC sources inhibited the proliferation of peripheral blood mononuclear cells (PBMCs); growth under regular versus hypoxic conditions resulted in similar levels of inhibition. When IFN-γ was added, PBMC growth was inhibited to a lesser extent by UCMSCs. The HLA-G*01:04:01:01 allele appears to generate a more efficient MSC response in inhibiting lymphocyte proliferation. However, the strength of this conclusion was limited by the small sample size. UCMSCs are an excellent alternative to BM in immunosuppressive therapy: they express high concentrations of inhibitory molecules and can be cultivated without stimuli, which minimizes cost.

The Current Landscape of NKT Cell Immunotherapy and the Hills Ahead

Simple Summary

Natural killer T (NKT) cells are a subset of lipid-reactive T cells that enhance anti-tumor immunity. While preclinical studies have shown NKT cell immunotherapy to be safe and effective, clinical studies lack predictable therapeutic efficacy and no approved treatments exist. In this review, we outline the current strategies, challenges, and outlook for NKT cell immunotherapy.

Abstract

NKT cells are a specialized subset of lipid-reactive T lymphocytes that play direct and indirect roles in immunosurveillance and anti-tumor immunity. Preclinical studies have shown that NKT cell activation via delivery of exogenous glycolipids elicits a significant anti-tumor immune response. Furthermore, infiltration of NKT cells is associated with a good prognosis in several cancers. In this review, we aim to summarize the role of NKT cells in cancer as well as the current strategies and status of NKT cell immunotherapy. This review also examines challenges and future directions for improving the therapy.

EOMES and IL-10 regulate antitumor activity of T regulatory type 1 CD4+ T cells in chronic lymphocytic leukemia

The transcription factor eomesodermin (EOMES) promotes interleukin (IL)-10 expression in CD4+ T cells, which has been linked to immunosuppressive and cytotoxic activities. We detected cytotoxic, programmed cell death protein-1 (PD-1) and EOMES co-expressing CD4+ T cells in lymph nodes (LNs) of patients with chronic lymphocytic leukemia (CLL) or diffuse large B-cell lymphoma. Transcriptome and flow cytometry analyses revealed that EOMES does not only drive IL-10 expression, but rather controls a unique transcriptional signature in CD4+ T cells, that is enriched in genes typical for T regulatory type 1 (TR1) cells. The TR1 cell identity of these CD4+ T cells was supported by their expression of interferon gamma and IL-10, as well as inhibitory receptors including PD-1. TR1 cells with cytotoxic capacity accumulate also in Eµ-TCL1 mice that develop CLL-like disease. Whereas wild-type CD4+ T cells control TCL1 leukemia development after adoptive transfer in leukopenic Rag2-/- mice, EOMES-deficient CD4+ T cells failed to do so. We further show that TR1 cell-mediated control of TCL1 leukemia requires IL-10 receptor (IL-10R) signaling, as Il10rb-deficient CD4+ T cells showed impaired antileukemia activity. Altogether, our data demonstrate that EOMES is indispensable for the development of IL-10-expressing, cytotoxic TR1 cells, which accumulate in LNs of CLL patients and control TCL1 leukemia in mice in an IL-10R-dependent manner.

Impairments in Peripheral Blood T Effector and T Regulatory Lymphocytes in Bipolar Disorder Are Associated with Staging of Illness and Anti-cytomegalovirus IgG Levels

There is now evidence that, based on cytokine profiles, bipolar disorder (BD) is accompanied by simultaneous activation of the immune-inflammatory response system (IRS) and the compensatory immune-regulatory system (CIRS), and that both components may be associated with the staging of illness. Nevertheless, no BD studies have evaluated the IRS/CIRS ratio using CD (cluster of differentiation) molecules expressed by peripheral blood activated T effector (Teff) and T regulatory (Treg) subpopulations. This study examined Teff/Treg subsets both before and after ex vivo anti-CD3/CD28 stimulation using flow cytometric immunophenotyping in 25 symptomatic remitted BD patients and 21 healthy controls and assessed human cytomegalovirus (HCMV)-specific IgG antibodies. BD is associated with a significantly lowered frequency of unstimulated CD3 + CD8 + CD71+ and CD4 + CD25 + FOXP3 and increased CD4 + CD25 + FOXP3 + CD152+ frequencies and with lowered stimulated frequencies of CD3 + CD8 + CD71+, CD4 + CD25 + FOXP3 + CD152+, and CD4 + CD25 + FOXP3 + GARP cells and, consequently, by an increased stimulated Teff/Treg ratio. Moreover, the number of manic, but not hypomanic or depressive episodes, is significantly and negatively associated with the stimulated proportions of CD3 + CD4 + CD154+, and CD69+ and CD71+ expression on CD4+ and CD8+ cells, while duration of illness (≥ 10 years) is accompanied by a depleted frequency of stimulated CD152+ Treg, and CD154+ and CD71+ CD4+ T cells. BD and anti-human cytomegalovirus (HCMV) IgG levels significantly interact to decrease the expression of CD4 + CD25 + FOXP+GARP T phenotypes. In conclusion, in BD patients, immune injuries, staging, and HCMV seropositivity interact and cause CIRS dysfunctions and exaggerated IRS responses, which play a key role in parainflammation and neuroaffective toxicity. HCMV seropositivity contributes to an immune-risk phenotype in BD.

What did we learn from CTLA-4 insufficiency on the human immune system?

Cytotoxic-T-lymphocyte-antigen-4 (CTLA-4) is a negative immune regulator constitutively expressed on regulatory T (Treg) cells and upregulated on activated T cells. CTLA-4 inhibits T cell activation by various suppressive functions including competition with CD28, regulation of the inhibitory function of Treg cells, such as transendocytosis, and the control of adhesion and motility. Intrinsic CTLA-4 signaling has been controversially discussed, but so far no distinct signaling pathway has been identified. The CTLA-4-mediated Treg suppression plays an important role in the maintenance of peripheral tolerance and the prevention of autoimmune diseases. Human CTLA-4 insufficiency is caused by heterozygous germline mutations in CTLA4 and characterized by a complex immune dysregulation syndrome. Clinical studies on CTLA4 mutation carriers showed a reduced penetrance and variable expressivity, suggesting modifying factor(s). One hundred and forty-eight CTLA4 mutation carriers have been reported; patients showed hypogammaglobulinemia, recurrent infectious diseases, various autoimmune diseases, and lymphocytic infiltration into multiple organs. The CTLA-4 expression level in Treg cells was reduced, while the frequency of Treg cells was increased in CTLA-4-insufficient patients. The transendocytosis assay is a specific functional test for the assessment of newly identified CTLA4 gene variants. Immunoglobulin substitution, corticosteroids, immunosuppressive therapy, and targeted therapy such as with CTLA-4 fusion proteins and mechanistic target of rapamycin (mTOR) inhibitors were applied; patients with life-threatening, treatment-resistant symptoms underwent hematopoietic stem cell transplantation. The fact that in humans CTLA-4 insufficiency causes severe disease taught us that the amount of CTLA-4 molecules present in/on T cells matters for immune homeostasis. However, whether the pathology-causing activated T lymphocytes in CTLA-4-insufficient patients are antigen-specific is an unsolved question. CTLA-4, in addition, has a role in autoimmune diseases and cancer. Anti-CTLA-4 drugs are employed as checkpoint inhibitors to target various forms of cancer. Thus, clinical research on human CTLA-4 insufficiency might provide us a deeper understanding of the mechanism(s) of the CTLA-4 molecule and immune dysregulation disorders.

Blocking TGF-β Signaling To Enhance The Efficacy Of Immune Checkpoint Inhibitor

During malignant transformation, a growing body of mutations accumulate in cancer cells which not only drive cancer progression but also endow cancer cells with high immunogenicity. However, because one or multiple steps in cancer-immunity cycle are impaired, anti-cancer immune response is too weak to effectively clear cancer cells. Therefore, how to restore robust immune response to malignant cells is a hot research topic in cancer therapeutics field. In the last decade, based on the deeper understanding of cancer immunity, great signs of progress have been made in cancer immunotherapies especially immune checkpoint inhibitors (ICIs). ICIs could block negative immune co-stimulatory pathways and reactivate tumor-infiltrating lymphocytes (TILs) from exhausted status. ICIs exhibit potent anti-cancer effect and have been approved for the treatment of numerous cancer types. Parallel with durable and effective tumor control, the actual response rate of ICIs is unsatisfactory. Although a subset of patients benefit from ICIs treatment, a large proportion of patients show primary or acquired resistance. Previously intensive studies indicated that the efficacy of ICIs was determined by a series of factors including tumor mutation burden, programmed death ligand-1 (PD-L1) expression, and TILs status. Recently, it was reported that transforming growth factor-beta (TGF-β) signaling pathway participated in cancer immune escape and ICI resistance. Concurrent TGF-β blockade might be a feasible strategy to enhance the efficacy of immunotherapy and relieve ICI resistance. In this mini-review, we summarized the latest understanding of TGF-β signaling pathway and cancer immunity. Besides, we highlighted the synergistic effect of TGF-β blockade and ICIs.

Association of increased eomesodermin, BCL6, and granzyme B expression with major clinical manifestations of Hashimoto's thyroiditis - an observational study

PURPOSE

Studies of cytotoxic T cells and their respective lineage master regulators have been limited in Hashimoto's thyroiditis (HT). It is unclear whether their transcriptomes are changed in HT patients and how these changes are associated with the thyroid damage, major clinical manifestations, and disease progression.

METHODS

We explored the gene expression patterns of selected transcription factors [eomesodermin (EOMES), BACH2, BCL6, TCF1] and cytolytic molecules [granzyme B (GZMB)] in peripheral blood (PB) T cells of 10 healthy controls and 30 HT patients of various subtypes (hypothyroid, untreated HT; L-thyroxine (T4)-treated HT, and spontaneously euthyroid HT) using real-time quantitative PCR.

RESULTS

EOMES (Mann-Whitney P = 0.044), GZMB (P = 0.028), and BCL6 mRNA (P = 0.001) were overrepresented in PB T cells from HT and showed levels varying by age, thyroid volume and disease severity. BCL6 transcripts were predominantly enriched in severely affected, hypothyroid cases, both on and off LT4. Increased EOMES RNA expression was associated with advancing age, lower thyroid volumes and higher peak adjusted TSH levels over the course of the disease. The body mass-adjusted, steady-state maintenance dose of LT4 increased with GZMB and BCL6 levels in PB T cells of hypothyroid cases, mostly postmenopausal women having long-standing, non-goitrous and atrophic disease form.

CONCLUSIONS

Our exploratory results suggest a role for GZMB, EOMES, and BCL6 in the context of HT, thyroid injury, and aggressive/advanced disease forms. Functions enriched within differentially expressed transcripts could be an important new target in understanding the pathogenesis of HT.

CTLA-4-mediated posttranslational modifications direct cytotoxic T-lymphocyte differentiation

The blockade of inhibitory receptors such as CTLA-4 (CD152) is being used as immune-checkpoint therapy, offering a powerful strategy to restore effective immune responses against tumors. To determine signal components that are induced under the control of CTLA-4 we analyzed activated murine CD8⁺ T cells by quantitative proteomics. Accurate mass spectrometry revealed that CTLA-4 engagement led to central changes in the phosphorylation of proteins involved in T-cell differentiation. Beside other targets, we discovered a CTLA-4-mediated induction of the translational inhibitor programmed cell death-4 (PDCD4) as a result of FoxO1 nuclear re-localization. PDCD4 further bound a distinct set of mRNAs including Glutaminase, which points out a critical role for CTLA-4 in CD8⁺ T-cell metabolism. Consequently, PDCD4-deficient cytotoxic T-lymphocytes (CTLs) expressed increased amounts of otherwise repressed effector molecules and ultimately led to superior control of tumor growth in vivo. These findings reveal a novel CTLA-4-mediated pathway to attenuate CTLs and indicate the importance of post-transcriptional mechanisms in the regulation of anti-tumor immune responses.

The differentiation and plasticity of Tc17 cells are regulated by CTLA-4-mediated effects on STATs

As the blockade of inhibitory surface-molecules such as CTLA-4 on T cells has led to recent advances in antitumor immune therapy, there is great interest in identifying novel mechanisms of action of CD8⁺ T cells to evoke effective cytotoxic antitumor responses. Using in vitro and in vivo models, we investigated the molecular pathways underlying the CTLA-4-mediated differentiation of IL-17-producing CD8⁺ T cells (Tc17 cells) that strongly impairs cytotoxicity. Our studies demonstrate that Tc17 cells lacking CTLA-4 signaling have limited production of STAT3-target gene products such as IL-17, IL-21, IL-23R and RORγt. Upon re-stimulation with IL-12, these cells display fast downregulation of Tc17 hallmarks and acquire Tc1 characteristics such as IFNγ and TNF-α co-expression, which is known to correlate with tumor control. Indeed, upon adoptive transfer, these cells were highly efficient in the antigen-specific rejection of established OVA-expressing B16 melanoma in vivo. Mechanistically, in primary and re-stimulated Tc17 cells, STAT3 binding to the IL-17 promoter was strongly augmented by CTLA-4, associated with less binding of STAT5 and reduced relative activation of STAT1 which is known to block STAT3 activity. Inhibiting CTLA-4-induced STAT3 activity reverses enhancement of signature Tc17 gene products, rendering Tc17 cells susceptible to conversion to Tc1-like cells with enhanced cytotoxic potential. Thus, CTLA-4 critically shapes the characteristics of Tc17 cells by regulating relative STAT3 activation, which provides new perspectives to enhance cytotoxicity of antitumor responses.

Eomesodermin(lo) CTLA4(hi) Alloreactive CD8+ Memory T Cells Are Associated With Prolonged Renal Transplant Survival Induced by Regulatory Dendritic Cell Infusion in CTLA4 Immunoglobulin-Treated Nonhuman Primates

BACKGROUND

Memory T cells (Tmem), particularly those resistant to costimulation blockade (CB), are a major barrier to transplant tolerance. The transcription factor Eomesodermin (Eomes) is critical for Tmem development and maintenance, but its expression by alloactivated T cells has not been examined in nonhuman primates.

METHODS

We evaluated Eomes and coinhibitory cytotoxic T lymphocyte antigen-4 (CTLA4) expression by alloactivated rhesus monkey T cells in the presence of CTLA4 immunoglobulin, both in vitro and in renal allograft recipients treated with CTLA4Ig, with or without regulatory dendritic cell (DCreg) infusion.

RESULTS

In normal monkeys, CD8+ T cells expressed significantly more Eomes than CD4+ T cells. By contrast, CD8+ T cells displayed minimal CTLA4. Among T cell subsets, central Tmem (Tcm) expressed the highest levels of Eomes. Notably, Eomes(lo)CTLA4(hi) cells displayed higher levels of CD25 and Foxp3 than Eomes(hi)CTLA4(lo) CD8+ T cells. After allostimulation, distinct proliferating Eomes(lo)CTLA4(hi) and Eomes(hi)CTLA4(lo) CD8+ T cell populations were identified, with a high proportion of Tcm being Eomes(lo)CTLA4(hi). CB with CTLA4Ig during allostimulation of CD8+ T cells reduced CTLA4 but not Eomes expression, significantly reducing Eomes(lo)CTLA4(hi) cells. After transplantation with CB and rapamycin, donor-reactive Eomes(lo)CTLA4(hi) CD8+ T cells were reduced. However, in monkeys also given DCreg, absolute numbers of these cells were elevated significantly.

CONCLUSIONS

Low Eomes and high CTLA4 expression by donor-reactive CD8+ Tmem is associated with prolonged renal allograft survival induced by DCreg infusion in CTLA4Ig-treated monkeys. Prolonged allograft survival associated with DCreg infusion may be related to maintenance of donor-reactive Eomes(lo)CTLA4(hi) Tcm.

Ipilimumab reshapes T cell memory subsets in melanoma patients with clinical response

PURPOSE

Therapy targeting CTLA-4 immune checkpoint provides increased survival in patients with advanced melanoma. However, immunotherapy is frequently associated with delayed and heterogeneous clinical responses and it is important to identify prognostic immunological correlates of clinical endpoints.

EXPERIMENTAL DESIGN

77 patients with stage III/IV melanoma were treated with ipilimumab alone every 3 weeks, during 9 weeks. Blood samples were collected at the baseline and before each dose for in depth immune monitoring.

RESULTS

The median follow-up was 28 mo with a median survival of 7 mo. Survival and clinical benefit were significantly improved when absolute lymphocyte count at the baseline was above 1 × 10(9)/L. Notably, ipilimumab had a global effect on memory T cells, with an early increase of central and effector subsets in patients with disease control. By contrast, percentages of stem cell memory T cells (TSCM) gradually decreased despite stable absolute counts and sustained proliferation, suggesting a process of differentiation. Higher proportions of eomes(+) and Ki-67(+) T cells were observed, with enhanced skin homing potential and induction of cytotoxic markers.

CONCLUSION

These results suggest that CTLA-4 blockade is able to reshape the memory subset with the potential involvement of Eomes and memory subsets including TSCM.

Checkpoint blockade immunotherapy relies on T-bet but not Eomes to induce effector function in tumor-infiltrating CD8+ T cells

Coinhibitory receptor blockade is a promising strategy to boost T-cell immunity against a variety of human cancers. However, many patients still do not benefit from this treatment, and responders often experience immune-related toxicities. These issues highlight the need for advanced mechanistic understanding to improve patient outcomes and uncover clinically relevant biomarkers of treatment efficacy. However, the T-cell-intrinsic signaling pathways engaged during checkpoint blockade treatment are not well defined, particularly for combination approaches. Using a murine model to study how effector CD8(+) T-cell responses to tumors may be enhanced in a tolerizing environment, we identified a critical role for the T-box transcription factor T-bet. Combination blockade of CTLA-4, PD-1, and LAG-3 induced T-bet expression in responding tumor/self-reactive CD8(+) T cells. Eradication of established leukemia using this immunotherapy regimen depended on T-bet induction, which was required for IFNγ production and cytotoxicity by tumor-infiltrating T cells, and for efficient trafficking to disseminated tumor sites. These data provide new insight into the success of checkpoint blockade for cancer immunotherapy, revealing T-bet as a key transcriptional regulator of tumor-reactive CD8(+) T-cell effector differentiation under otherwise tolerizing conditions.

CTLA-4 (CD152) enhances the Tc17 differentiation program

Although CD8(+) T cells that produce IL-17 (Tc17 cells) have been linked to host defense, Tc17 cells show reduced cytotoxic activity, which is the characteristic function of CD8(+) T cells. Here, we show that CTLA-4 enhances the frequency of IL-17 in CD8(+) T cells, indicating that CTLA-4 (CD152) specifically promotes Tc17 differentiation. Simultaneous stimulation of CTLA-4(+/+) and CTLA-4(-/-) T cells in cocultures and agonistic CTLA-4 stimulation unambiguously revealed a cell-intrinsic mechanism for IL-17 control by CTLA-4. The quality of CTLA-4-induced Tc17 cells was tested in vivo, utilizing infection with the facultative intracellular bacterium Listeria monocytogenes (LM). Unlike CTLA-4(+/+) Tc17 cells, CTLA-4(-/-) were nearly as efficient as Tc1 CTLA-4(+/+) cells in LM clearance. Additionally, adoptively transferred CTLA-4(-/-) Tc17 cells expressed granzyme B after rechallenge, and produced Tc1 cytokines such as IFN-γ and TNF-α, which strongly correlate with bacterial clearance. CTLA-4(+/+) Tc17 cells demonstrated a high-quality Tc17 differentiation program ex vivo, which was also evident in isolated IL-17-secreting Tc17 cells, with CTLA-4-mediated enhanced upregulation of Tc17-related molecules such as IL-17A, RORγt, and IRF-4. Our results show that CTLA-4 promotes Tc17 differentiation that results in robust Tc17 responses. Its inactivation might therefore represent a central therapeutic target to enhance clearance of infection.

Eomesodermin is required for antitumor immunity mediated by 4-1BB-agonist immunotherapy

CD8⁺ T cells in progressing tumors frequently fail to mount an effective antitumor response often in association with the expression of inhibitory receptors, including programmed cell death-1 (PD-1) and lymphocyte-activation gene 3 (Lag3). Using a lymphoma tumor model, we demonstrate that tumor-infiltrating CD8⁺ T cells from growing tumors co-express inhibitory receptors and co-stimulatory receptors, including 4-1BB (TNFRSF9) as well as high levels of 2 transcription factors, Eomesodermin (Eomes) and T-bet (Tbx21), critical determinants of CD8⁺ T cell fate. Immunotherapy with an agonistic anti-4–1-BB antibody altered the ratio of Eomes to T-bet expression in tumor-infiltrating CD8⁺ T cells by increasing Eomes and decreasing T-bet expression. 4-1BB-agonist immunotherapy was also associated with downregulated expression of the inhibitory receptors PD-1 and Lag3 on tumor-infiltrating CD8⁺ T cells, a molecular phenotype associated with subsequent attenuation of tumor growth. Furthermore, 4-1BB-agonist immunotherapy failed to effect tumor progression in mice with Eomes deficient T cells. However, upon resumption of tumor growth, tumor-infiltrating CD8⁺ T cells from treated animals continued to express high levels of Eomes as well as elevated levels of the inhibitory receptors PD-1 and Lag3. Our data suggest that tumor-infiltrating CD8⁺ T cells are poised between activation and inhibition as dictated by expression of both co-stimulatory receptors and inhibitory receptors and demonstrate that T cell expression of Eomes is necessary, but not sufficient, for efficacious 4-1BB-agonist-mediated immunotherapy.

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.

Technical Advance: Fluorescent reporter reveals insights into eomesodermin biology in cytotoxic lymphocytes

The T-box transcription factor Eomes is expressed in cytotoxic immune cells and plays an important role in development, maintenance, and function of these cell types. Identification and separation of cells with differential Eomes expression would allow for better understanding of the transcriptional program governing these cytotoxic lymphocytes. Here, we report the use of an Eomes(gfp)-targeted mouse allele that displays robust fidelity to Eomes protein expression in NK and T cells. Use of this reporter mouse revealed that Eomes expression in antiviral effector cells did not correlate with enhanced cytotoxicity but rather was associated with more efficient central memory differentiation. Weakening of reporter activity in Eomes-deficient CD8(+) T cells revealed a critical role for Eomes protein in maintaining central memory cells that have activated the Eomes locus. Characterization of reporter activity in NK lineage cells also permitted identification of a novel intermediate of NK cell maturation. Thus, the murine Eomes(gfp)-targeted allele provides a novel opportunity to explore Eomes biology in cytotoxic lymphocytes.

Suppressing T cell motility induced by anti-CTLA-4 monotherapy improves antitumor effects

A promising strategy for cancer immunotherapy is to disrupt key pathways regulating immune tolerance, such as cytotoxic T lymphocyte-associated protein 4 (CTLA-4). However, the determinants of response to anti-CTLA-4 mAb treatment remain incompletely understood. In murine models, anti-CTLA-4 mAbs alone fail to induce effective immune responses to poorly immunogenic tumors but are successful when combined with additional interventions, including local ionizing radiation (IR) therapy. We employed an established model based on control of a mouse carcinoma cell line to study endogenous tumor-infiltrating CD8+ T lymphocytes (TILs) following treatment with the anti-CTLA-4 mAb 9H10. Alone, 9H10 monotherapy reversed the arrest of TILs with carcinoma cells in vivo. In contrast, the combination of 9H10 and IR restored MHC class I-dependent arrest. After implantation, the carcinoma cells had reduced expression of retinoic acid early inducible-1 (RAE-1), a ligand for natural killer cell group 2D (NKG2D) receptor. We found that RAE-1 expression was induced by IR in vivo and that anti-NKG2D mAb blocked the TIL arrest induced by IR/9H10 combination therapy. These results demonstrate that anti-CTLA-4 mAb therapy induces motility of TIL and that NKG2D ligation offsets this effect to enhance TILs arrest and antitumor activity.

Activation of the Hippo pathway by CTLA-4 regulates the expression of Blimp-1 in the CD8+ T cell

During the primary response, the commitment of the CD8(+) T cell to Blimp-1 expression and the terminal differentiation that Blimp-1 induces must be timed so as not to impair the process of clonal expansion. We determined whether the Hippo pathway, which links cell-cell contact to differentiation in other cell lineages, controls Blimp-1 expression. Activating the CD8(+) T cell with antigen and IL-2 causes expression of the core Hippo pathway components, including the pivotal transcriptional cofactor Yap. Contact between activated CD8(+) T cells induces Hippo pathway-mediated Yap degradation and Blimp-1 expression; a Hippo-resistant, stable form of Yap suppresses Blimp-1 expression. Cytotoxic T lymphocyte antigen 4 (CTLA-4) and CD80 comprise the receptor-ligand pair that mediates contact-dependent Hippo pathway activation. In vivo, CD8(+) T cells expressing Hippo resistant-Yap or lacking CTLA-4 have diminished expression of the senescence marker, KLRG1, during a viral infection. The CTLA-4/Hippo pathway/Blimp-1 system may couple terminal differentiation of CD8(+) T cell with the magnitude of clonal expansion.

Associations between cytotoxic T lymphocyte-associated antigen-4 polymorphisms and serum tumor necrosis factor-α and interferon-γ levels in patients with chronic hepatitis B virus infection

BACKGROUND

Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) polymorphism, which may affect host immune response including cytokines production, is thought to be associated with hepatitis B virus (HBV) infection. This study investigated the associations between CTLA4 polymorphism and serum tumor necrosis factor (TNF)-α and interferon (IFN)-γ levels in patients with chronic HBV infection.

METHODS

CTLA4 promoter -318C/T and exon 1 +49A/G polymorphisms and serum TNF-α and IFN-γ levels were determined in 172 patients with chronic HBV infection and 145 healthy controls.

RESULTS

The genotype of CTLA4 -318C/T polymorphism had no association to TNF-α and IFN-γ levels. Serum levels of TNF-α and IFN-γ in chronic HBV patients with +49GG genotype were lower than those with +49AG genotype (p = 0.030 and p = 0.042, respectively), and haplotypes -318C + 49A and -318C + 49G seemed to have no significant effects on TNF-α and IFN-γ levels.

CONCLUSIONS

CTLA4 +49GG genotype was associated to lower TNF-α and IFN-γ levels in patients with chronic HBV infection but this association was diminished by haplotype formation with -318C/T alleles, indicating that the influence of CTLA4 -318C/T and +49A/G polymorphisms on the susceptibility and disease progress of chronic HBV infection may not be effectuated by affecting TNF-α and IFN-γ secretion.

Investigation of cytotoxic T-lymphocyte-associated protein 4 gene polymorphisms in symptomatic gallstone disease

Gallstone disease (GSD), which is increasingly prevalent in Taiwan, develops through a complex process involving genetic, environmental, and immune factors. Cytotoxic T-lymphocyte-associated protein 4 (CTLA4) limits T-cell proliferation. The present study looked for associations between symptomatic GSD and polymorphisms of the CTLA4 gene. For this case-control cross-sectional study among Taiwanese, 275 patients with symptomatic GSD and 852 controls were enrolled. Genotyping of CTLA4-318 C/T, +49 A/G, and CT60 A/G single nucleotide polymorphisms (SNPs) was performed by polymerase chain reaction-restriction fragment length polymorphism. The genotype, allele, carrier, and haplotype frequencies were calculated by direct counting or with Haploview 4.1 software. Genotype, allele, carrier, and haplotype frequencies of the CTLA4 SNPs studied were equally distributed in symptomatic GSD patients and controls. No significant associations between symptomatic GSD and these 3 SNPs were observed. Our data suggest that CTLA4-318 C/T, +49 A/G, and CT60 A/G SNPs do not confer increased susceptibility to symptomatic GSD.

Memories that last forever: strategies for optimizing vaccine T-cell memory

For acute self-limiting infections a vaccine is successful if it elicits memory at least as good as the natural experience; however, for persistent and chronic infections such as HIV, hepatitis C virus (HCV), human papillomavirus (HPV), and human herpes viruses, this paradigm is not applicable. At best, during persistent virus infection the person must be able to maintain the integrity of the immune system in equilibrium with controlling replicating virus. New vaccine strategies are required that elicit both potent high-avidity CD8(+) T-cell effector/memory and central memory responses that can clear the nidus of initial virus-infected cells at mucosal surfaces to prevent mucosal transmission or significantly curtail development of disease. The objective of an HIV-1 T-cell vaccine is to generate functional CD8(+) effector memory cells at mucosal portals of virus entry to prevent viral transmission. In addition, long-lived CD8(+) and CD4(+) central memory cells circulating through secondary lymphoid organs and resident in bone marrow, respectively, are needed to provide a concerted second wave of defense that can contain virus at mucosal surfaces and prevent systemic dissemination. Further understanding of factors which can influence long-lived effector and central memory cell differentiation will significantly contribute to development of effective T-cell vaccines. In this review we will focus on discussing mechanisms involved in T-cell memory and provide promising new approaches toward expanding current vaccine strategies to enhance antiviral memory.

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

CTLA-4 has potent regulatory effects on the threshold of T-cell signalling and, in the process, guards against the development of hyper-proliferation and autoimmunity. Despite this, the role of CTLA-4 on specific T-cell subsets has been unclear. Such studies could shed light on both the function of CTLA-4, and on the contribution of the subsets to the disease phenotype of the Ctla4(-/-) mouse. Recently, a role for this co-receptor in the function of Treg has been outlined and, in this issue of the European Journal of Immunology, the selective targeting of the T-box transcription factor Eomes by CTLA-4 in the regulation of CD8(+) cytolytic T-cell (CTL) effector function is shown. Together, these papers shed light on the role of CTLA-4 in different T-cell subsets.