Function Of Cytotoxic T Lymphocyte Antigen-4 Research Articles

Abstract 665: Correlation between a CTLA-4 single nucleotide polymorphism and high response to anti-PD1/PDL1 immunotherapy in advanced non small cell lung cancer

Abstract Blockade of the immune checkpoint protein Programmed Cell Death Protein-1 or its ligand (PD-1 and PD-L1, respectively) allows durable cancer control in a proportion of patients with non-small cell lung cancer (NSCLC). However, a substantial proportion of patients have suboptimal outcomes and variability in response remains incompletely understood. Immune-related adverse events (irAEs) correlate with survival for single agent anti-PD1/PD-L1 therapy in NSCLC, suggesting benefits of systemic immune activation. Similarly, combined pharmacological blockade of a second checkpoint, such as Cytotoxic T-lymphocyte Antigen-4 (CTLA-4), with PD-1 gives heightened immune activation, resulting in both improved cancer outcomes and more irAEs. Inherited heterozygosity for single nucleotide polymorphisms (SNPs) within and surrounding CTLA-4 is associated with autoimmune disease, including autoimmune thyroid disease, rheumatoid arthritis (RA) and Type 1 diabetes (T1D). Many of these autoimmune diseases are clinically and pathologically indistinguishable from anti-CTLA4-induced irAEs, suggesting equivalence of pharmacological and genetic blockade of the gene. We hypothesised that SNPs impacting CTLA-4 function would be enriched in a cohort of NSCLC patients exhibiting exceptional response to single-agent anti-PD1. For the purposes of this analysis, exceptional response was defined as progression free survival of at least 2 years and one or more irAE of CTCAE grade 2 or higher. We performed whole genome sequencing (Illumina HiSeq X Ten) on germline DNA from 35 prospectively recruited patients meeting these criteria from a treatment pool of over 700 patients. In these individuals, frequency of a curated list of SNPs located within a 200 kilobase region encompassing CTLA-4 was analysed and compared to patients with lung cancer within the Pan-Cancer Analysis of Whole Genomes (PCAWG) and to cancer- and dementia-free elderly individuals in the Medical Genome Reference Bank (MGRB). Using linear regression analysis, we identified several non-coding SNPs enriched within the exceptional responders compared with control populations. One SNP was present in 15.7% of exceptional responders; twice the frequency of comparable cases within PCAWG and almost four times more than MGRB, remaining statistically significant following rigorous adjustment. This non-coding SNP is reported to exhibit differential enhancer activity and has been associated with RA and T1D. Its enrichment within the exceptional responders suggests that the altered CTLA-4 function may cooperate with blockade of PD-1 to confer higher immune response. This common variant may provide a biomarker for single agent anti-PD1 treatment or a potential therapeutic target. Pre-clinical analyses and validation within an independent cohort are underway. Citation Format: India A. Allen, Amanda Russell, Katherine J. Jackson, Timothy Peters, Greg Gibson, Anthony M. Joshua, Christopher C. Goodnow, Deborah L. Burnett, Megan B. Barnet. Correlation between a CTLA-4 single nucleotide polymorphism and high response to anti-PD1/PDL1 immunotherapy in advanced non small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 665.

Altered frequency and function of spleen CTLA-4+Tim-3+ T cells are associated with miscarriage†.

Normal pregnancy is associated with several immune adaptations in both systemic and local maternal-fetal interface to allow the growth of semi-allogeneic conceptus. A failure in maternal immune tolerance to the fetus may result in abnormal pregnancies, such as recurrent spontaneous abortion. The regulation of T-cell homeostasis during pregnancy has important implications for maternal tolerance and immunity. Cytotoxic T-lymphocyte antigen-4 (CTLA-4) and T-cell immunoglobulin mucin-3 (Tim-3) are important negative immune regulatory molecules involved in viral persistence and tumor metastasis. Here we described the lower frequency of splenic T cells co-expressing CTLA-4 and Tim-3 accompanied by higher levels of proinflammatory but lower anti-inflammatory cytokines production in abortion-prone mouse model. Blockade of CTLA-4 and Tim-3 pathways leaded to the dysfunction of splenic T cells. By the higher expression during normal pregnancy, CTLA-4 and Tim-3 co-expression on splenic T cells linked to immunosuppressive phenotype. As the spleen is an important site for peripheral immune activation, our data suggest potential noninvasive biomarkers and therapeutic targets for miscarriage.

The expression of mCTLA-4 in skin lesion inversely correlates with the severity of psoriasis

BackgroundPsoriasis is a chronic inflammatory disease characterized by epidermal hyperplasia and increased T cell infiltration. Cytotoxic T lymphocyte antigen-4 (CTLA-4) is a key factor that affects T cell function and immune response. However, whether the expression of CTLA-4 affects the severity of psoriasis is still unknown. ObjectiveThe aim of the project was to investigate the correlation between the expression of CTLA-4 and the severity of psoriasis. MethodsThe plasma soluble CTLA-4 levels and membrane CTLA-4 expression were measured by enzyme-linked immunosorbent assay and immunohistochemistry analysis in mild, moderate and severe psoriasis patients, respectively. Imiquimod-induced mouse model of psoriasis was treated with CTLA-4 immunoglobulin fusion protein (CTLA-4 Ig) or anti-CTLA-4 antibody. Epidermal thickness and infiltrating CD3+ T cell counts were evaluated. ResultsThe plasma soluble CTLA-4 levels had no significant difference among mild, moderate, and severe patients (p > 0.05). However, the membrane CTLA-4 expression in skin was significantly higher in mild psoriasis patients compared to moderate and severe psoriasis patients (17652.86 ± 18095.66 vs 6901.36 ± 4400.77 vs 3970.24 ± 5509.15, p < 0.001). Furthermore, in imiquimod-induced mouse model of psoriasis, the results showed that mimicking CTLA-4 function improved the skin phenotype and reduced epidermal thickness (172.87 ± 28.25 vs 245.87 ± 36.61 μm, n = 6, p < 0.01) as well as infiltrating CD3+ T cell counts (5.09 ± 3.45 vs 13.45 ± 4.70, p < 0.01) compared to control group. However, blocking CTLA-4 function aggregated the skin phenotype including enhanced epidermal thickness and infiltrating CD3+ T cell counts compared to control group. ConclusionThese results indicated that the expression of mCTLA-4 in skin lesion inversely correlated with the severity of psoriasis and CTLA-4 might play a critical role in the disease severity of psoriasis.

Cytotoxic T-lymphocyte Antigen-4 Binding to SHP2 Interacting Transmembrane Adapter Protein by Phosphorylation in T-Cell

Purpose: To investigate potential cytotoxic T-lymphocyte antigen-4 (CTLA-4) binding partners and assess whether potential binding partners affect the full function of CTLA-4. . Methods: The down-regulation effects of CTLA-4 and SIT were assessed by culturing CD3 stimulated T-cells. CTLA-4 and SIT proteins were measured by immunoblot analysis and production of interlukin-2 transcription activity evaluated by luciferase assay. Results: CTLA-4 inhibited the interlukin-2 production capacity of CD3-stimulated T cells. CTLA-4 interaction with SHP2 interacting transmembrane adapter protein (SIT) in the down-regulation of the transcription of Interulin-2 required CTLA-4 binding to SIT tyrosine motifs. The SIT tyrosine mutants were significantly lower (25 – 75 %) after phosphorylation compared with WT-SIT (transfected cells, p < 0.05) and untreated control. The remaining 90 % phosphorylation in the F188ANS mutant can be explained by phosphorylation of other tyrosines in the sequence of SIT (p < 0.05). For interukin-2 transcription, F188ANS single mutant and double F148SEV mutant, increased NF-AT activity by 35 % compared with the wild type (p < 0.05). Conclusion: The findings imply that SIT transmembrane adaptor (SIT) protein, binds to CTLA-4 and thus potentiates the inhibitory role of this co-receptor. This phenomenon may lead to the development of new treatment strategies for autoimmune diseases and graft rejection. Keywords: Cytotoxic T-lymphocyte antigen-4, Interleukin-2, Nuclear factor of activated T-cells/Activator protein-1, SHP2 interacting transmembrane adapter protein, Autoimmune diseases, Graft rejection

Deletion of CTLA-4 on regulatory T cells during adulthood leads to resistance to autoimmunity.

Cytotoxic T lymphocyte antigen-4 (CTLA-4) is an essential negative regulator of T cell responses. Germline Ctla4 deficiency is lethal, making investigation of the function of CTLA-4 on mature T cells challenging. To elucidate the function of CTLA-4 on mature T cells, we have conditionally ablated Ctla4 in adult mice. We show that, in contrast to germline knockout mice, deletion of Ctla4 during adulthood does not precipitate systemic autoimmunity, but surprisingly confers protection from experimental autoimmune encephalomyelitis (EAE) and does not lead to increased resistance to MC38 tumors. Deletion of Ctla4 during adulthood was accompanied by activation and expansion of both conventional CD4(+)Foxp3(-) (T conv) and regulatory Foxp3(+) (T reg cells) T cell subsets; however, deletion of CTLA-4 on T reg cells was necessary and sufficient for protection from EAE. CTLA-4 deleted T reg cells remained functionally suppressive. Deletion of Ctla4 on T reg cells alone or on all adult T cells led to major changes in the Ctla4 sufficient T conv cell compartment, including up-regulation of immunoinhibitory molecules IL-10, LAG-3 and PD-1, thereby providing a compensatory immunosuppressive mechanism. Collectively, our findings point to a profound role for CTLA-4 on T reg cells in limiting their peripheral expansion and activation, thereby regulating the phenotype and function of T conv cells.

Mechanisms of tolerance

Mechanisms of tolerance

Dual function of CTLA-4 in regulatory T cells and conventional T cells to prevent multiorgan autoimmunity

Cytotoxic T lymphocyte antigen-4 (CTLA-4) is an inhibitory receptor on T cells essential for maintaining T cell homeostasis and tolerance to self. Mice lacking CTLA-4 develop an early onset, fatal breakdown in T cell tolerance. Whether this autoimmune disease occurs because of the loss of CTLA-4 function in regulatory T cells, conventional T cells, or both is unclear. We show here that lack of CTLA-4 in regulatory T cells leads to aberrant activation and expansion of conventional T cells. However, CTLA-4 expression in conventional T cells prevents aberrantly activated T cells from infiltrating and fatally damaging nonlymphoid tissues. These results demonstrate that CTLA-4 has a dual function in maintaining T cell tolerance: CTLA-4 in regulatory T cells inhibits inappropriate naïve T cell activation and CTLA-4 in conventional T cells prevents the harmful accumulation of self-reactive pathogenic T cells in vital organs.

Ipilimumab: controversies in its development, utility and autoimmune adverse events.

A promising new class of anti-cancer drugs includes antibodies that mediate immune regulatory effects. It has become very clear over the last decade that different types of immune cells and different pathways serve to suppress anti-cancer immunity, particularly in the microenvironment of the tumor. The first examples of immune modulating antibodies are those directed against cytotoxic T lymphocyte antigen-4 (CTLA-4), a molecule present on activated T cells. Human antibodies that abrogate the function of CTLA-4 have been tested in the clinic and found to have clinical activity against melanoma. In this review, we discuss some of the controversies surrounding the potential clinical utility of one of those antibodies, ipilimumab, formerly MDX-010, from Medarex and Bristol Myers Squibb. The optimal dose and schedule of ipilimumab was derived in multiple clinical trials whose latest results are described below. Favorable survival in patients with stage IV melanoma were observed that appear to be associated with unique side effects of the drug called "immune-related adverse events". The management of these side effects is described, and the unusual kinetics of anti-tumor response with ipilimumab as well as a newly proposed schema for assessing anti-tumor responses in patients receiving biologic compounds like ipilimumab, which may supercede RECIST or WHO criteria, are addressed.

CTLA‐4 gene promoter and exon 1 polymorphisms in Iranian patients with gastric and colorectal cancers

Cytotoxic T-lymphocyte antigen-4 (CTLA-4) is a potent immunoregulatory molecule that suppresses antitumor response by down-regulating T-cell activation. Effects of several polymorphisms in CTLA-4 on CTLA-4 expression and function have been previously documented. The aim of this study was to investigate the putative effect of CTLA-4 polymorphisms on susceptibility to gastric and colorectal cancers in an Iranian population. A total of 155 patients (109 with colorectal cancer and 46 with gastric cancer) and 190 age- and sex-matched healthy controls were evaluated. Genotyping of -1722T/C, -1661A/G, and +49A/G were performed by PCR restriction fragment length polymorphism methods and of -318C/T by a PCR amplification refractory mutation system technique. No statistically significant differences were found in the genotype distribution and allele frequencies among patients and controls. Haplotype analysis demonstrated that the TACG haplotype (-1722T, -1661A, -318C, +49G) frequency was significant increased in patients with colorectal cancer (P = 0.009) and gastric cancer (P = 0.006) in comparison to the control group. In contrast, the TACA haplotype frequency was significantly decreased in patients with colorectal cancer (P = 0.02) and not significantly decreased in patients with gastric cancer (P = 0.13) compared to the control group. A positive association between CTLA-4 TACG haplotype and gastric and colorectal cancers was found in an Iranian population. A protective role for TACA haplotype is postulated.

CTLA-4 up-regulation of lymphocyte function-associated antigen 1 adhesion and clustering as an alternate basis for coreceptor function

Although cytotoxic T lymphocyte antigen-4 (CTLA-4) negatively regulates T cell activation, the full range of functions mediated by this coreceptor has yet to be established. In this study, we report the surprising finding that CTLA-4 engagement by soluble antibody or CD80 potently up-regulates lymphocyte function-associated antigen 1 (LFA-1) adhesion to intercellular adhesion molecule-1 (ICAM-1) and receptor clustering concurrent with IL-2 inhibition. This effect was also observed with CTLA-4 ligation and not with other coreceptors. T cell antigen receptor (TcR)-induced lymphocyte function-associated antigen 1 function was also dependent on CTLA-4 expression as observed with reduced adhesion/clustering on CTLA-4(-/-) primary T cells. CTLA-4 up-regulated adhesion was mediated by regulator for cell adhesion and polarization type 1 (Rap-1) as shown by anti-CTLA-4-induced Rap-1 activation as well as Rap-1-N17 blockade and Rap-1-V12 mimicry of adhesion/clustering. Our findings identify a potent role for CTLA-4 in directing integrin adhesion and provide an alternate mechanism to account for aspects of CTLA-4 function in T cell immunity.

In vivo overexpression of CTLA‐4 suppresses lymphoproliferative diseases and thymic negative selection

Cytotoxic T lymphocyte antigen-4 (CTLA-4) induces major inhibitory signals for T cell activation. From analyses of TCR-transgenic (Tg) CTLA-4-deficient mice, it has been believed that CTLA-4 does not affect thymocyte development. To focus upon the in vivo function of CTLA-4 in thymocyte development from a different aspect, we have established Tg mice expressing either full-length CTLA-4 (FL-Tg) or a mutant CTLA-4 lacking the cytoplasmic region (truncated, TR-Tg), and analyzed thymocyte development. TR-T cells express much higher CTLA-4 on the cell surface than FL-T cells, in which most CTLA-4 was localized in intracellular vesicles. While CTLA-4-/- mice exhibit lymphoproliferative disease, neither of the Tg mice with CTLA-4-/- background developed the disorder. Although the development of thymocytes appeared normal in both Tg mice, in vivo depletion of double-positive thymocytes by injection of anti-CD3 Ab as well as the elimination of minor lymphocyte-stimulating antigen-reactive thymocytes were impaired in FL-Tg mice but not in TR-Tg mice. Functionally, cross-linking of CTLA-4 on thymocytes from FL-Tg mice, but not from TR-Tg mice, inhibited proliferation. These results reveal a potential role of CTLA-4, through its cytoplasmic domain, in the negative selection of thymocytes and in the prevention of lymphoproliferative disease.