Role Of Cytotoxic T Lymphocyte Antigen-4 Research Articles

Specific CD8(+) T cell response immunotherapy for hepatocellular carcinoma and viral hepatitis.

Hepatocellular carcinoma (HCC), chronic hepatitis B (CHB) and chronic hepatitis C (CHC) are characterized by exhaustion of the specific CD8(+) T cell response. This process involves enhancement of negative co-stimulatory molecules, such as programmed cell death protein-1 (PD-1), cytotoxic T-lymphocyte antigen-4 (CTLA-4), 2B4, Tim-3, CD160 and LAG-3, which is linked to intrahepatic overexpression of some of the cognate ligands, such as PD-L1, on antigen presenting cells and thereby favouring a tolerogenic environment. Therapies that disrupt these negative signalling mechanisms represent promising therapeutic tools with the potential to restore reactivity of the specific CD8(+) T cell response. In this review we discuss the impressive in vitro and in vivo results that have been recently achieved in HCC, CHB and CHC by blocking these negative receptors with monoclonal antibodies against these immune checkpoint modulators. The article mainly focuses on the role of CTLA-4 and PD-1 blocking monoclonal antibodies, the first ones to have reached clinical practice. The humanized monoclonal antibodies against CTLA-4 (tremelimumab and ipilimumab) and PD-1 (nivolumab and pembrolizumab) have yielded good results in testing of HCC and chronic viral hepatitis patients. Trelimumab, in particular, has shown a significant increase in the time to progression in HCC, while nivolumab has shown a remarkable effect on hepatitis C viral load reduction. The research on the role of ipilimumab, nivolumab and pembrolizumab on HCC is currently underway.

Effect of cytotoxic T-lymphocyte antigen-4, TNF-alpha polymorphisms on osteosarcoma: evidences from a meta-analysis.

Previous studies have investigated the role of cytotoxic T-lymphocyte antigen-4 (CTLA-4) and tumor necrosis factor-alpha (TNF-α) in carcinogenesis of osteosarcoma, but their results were inconsistent. We aimed to clarify the associations between CTLA-4, TNF-α polymorphism and osteosarcoma risk by using meta-analysis. We searched relevant studies without language restriction in PubMed, EMbase, Cochrane Library, Google Scholar databases, Chinese National Knowledge Infrastructure (CNKI) and conference literature in humans published prior to March 2013. The strengths of the associations between genetic variants and osteosarcoma risk were estimated by odds ratio (OR) with 95% confidence interval (95% CI). A total of seven studies with 1,198 osteosarcoma patients and 1,493 controls were selected. Four studies were eligible for CTLA-4 (1,003 osteosarcoma and 1,162 controls), and three studies for TNF-α (195 osteosarcoma and 331 controls). Pooled results showed that rs231775 polymorphism of CTLA-4 was associated with osteosarcoma risk (GG vs. AA: OR=1.63, 95% CI=1.24-2.13; GG + GA vs. AA: OR=1.56, 95% CI=1.21-2.01; AA + GA vs. GG: OR=0.83, 95% CI=0.71-0.97; G vs. A: OR=1.21, 95% CI=1.08-1.36). No significant heterogeneity was observed across the studies. No significant associations were found between rs5742909 polymorphism of CTLA-4 or rs1800629 polymorphism of TNF-α and osteosarcoma risk. These results suggest that the rs231775 polymorphism of CTLA-4 may play an important role in carcinogenesis of osteosarcoma.

The CTLA-4 +49GG genotype is associated with susceptibility for nephrotic kidney diseases

The pathogenesis of primary nephrotic kidney diseases is not completely understood. As T-cell involvement is suspected, cytotoxic T-lymphocyte antigen 4 (CTLA-4) expressed on activated T cells could play a role in the immune response. Single-nucleotide polymorphisms (SNPs) in the CTLA-4 gene are associated with several autoimmune-related diseases. Our goal was to study the occurrence of the SNPs -318C/T, +49A/G and CT60 on the CTLA-4 gene in healthy blood donors (N = 156) compared with nephrotic patients with biopsy-proven minimal-change disease (MCD, N = 160), focal segmental glomerulosclerosis (FSGS, N = 159) and membranous nephropathy (MN, N = 185). Odds ratios (ORs) with 95% confidence intervals (95% CIs) were calculated to estimate the strength of the association. The +49GG genotype was significantly (P < 0.001) associated with the risk for MCD, FSGS and MN (AA versus GG: OR = 3.403, 95% CI = 1.748-6.622, OR = 3.846, 95% CI = 1.945-7.604 and OR = 2.381, 95% CI = 1.257-4.511, respectively). No further significant associations, neither with the heterozygous genotype of +49A/G nor for the -318C/T or CT60 SNP, were detected. The +49GG genotype of the +49A/G SNP in the CTLA-4 gene is associated with the risk for MCD, FSGS and MN, suggesting a possible role for CTLA-4 in a proposed common final pathway in the pathogenesis of primary nephrotic kidney diseases.

Ligation of CTLA-4 to the TCR inhibits T cell activation and directs differentiation into Foxp3+ regulatory T cells (72.2)

Abstract ABSTRACT Crosslinking of ligand-engaged cytotoxic T lymphocyte antigen-4 (CTLA-4) to the T cell receptor (TCR) during the early phase of T cell activation attenuates TCR signaling, leading to T cell inhibition. To promote this event, a bispecific fusion protein comprising a mutant mouse CD80 (CD80w88a) and lymphocyte activation antigen-3 (LAG-3) was engineered to concurrently engage CTLA-4 and crosslink it to the TCR. Crosslinking is expected to attain via ligation of CTLA-4 first to MHC II and then indirectly to the TCR, generating a CTLA-4-MHC II-TCR tri-molecular complex that forms between T cells and antigen-presenting cells (APCs) during T cell activation. Treating T cells with this bispecific fusion protein inhibited T cell activation. In addition, it induced the production of IL-10 and TGF- β and attenuated AKT and mTOR signaling. Intriguingly, treatment with the bispecific fusion protein also directed early T cell differentiation into Foxp3+ regulatory T cells (Tregs). This process was dependent on the endogenous production of TGF- β. Thus, bispecific fusion proteins that engage CTLA-4 and co-ligate it to the TCR during the early phase of T cell activation can negatively regulate the T cell response. Bispecific biologics with such dual functions may therefore represent a novel class of therapeutics for immune modulation. The findings presented here also reveal a potential new role for CTLA-4 in Treg differentiation.

Ligation of Cytotoxic T Lymphocyte Antigen-4 to T Cell Receptor Inhibits T Cell Activation and Directs Differentiation into Foxp3+ Regulatory T Cells

Cross-linking of ligand-engaged cytotoxic T lymphocyte antigen-4 (CTLA-4) to the T cell receptor (TCR) during the early phase of T cell activation attenuates TCR signaling, leading to T cell inhibition. To promote this event, a bispecific fusion protein comprising a mutant mouse CD80 (CD80w88a) and lymphocyte activation antigen-3 was engineered to concurrently engage CTLA-4 and cross-link it to the TCR. Cross-linking is expected to be attained via ligation of CTLA-4 first to MHCII and then indirectly to the TCR, generating a CTLA-4-MHCII-TCR trimolecular complex that forms between T cells and antigen-presenting cells during T cell activation. Treating T cells with this bispecific fusion protein inhibited T cell activation. In addition, it induced the production of IL-10 and TGF-β and attenuated AKT and mTOR signaling. Intriguingly, treatment with the bispecific fusion protein also directed early T cell differentiation into Foxp3-positive regulatory T cells (Tregs). This process was dependent on the endogenous production of TGF-β. Thus, bispecific fusion proteins that engage CTLA-4 and co-ligate it to the TCR during the early phase of T cell activation can negatively regulate the T cell response. Bispecific biologics with such dual functions may therefore represent a novel class of therapeutics for immune modulation. These findings presented here also reveal a potential new role for CTLA-4 in Treg differentiation.

Immune regulation by CTLA‐4—relevance to autoimmune diabetes in a transgenic mouse model

The importance of cytotoxic T lymphocyte antigen-4 (CTLA-4) in immune regulation is unquestioned, yet a precise understanding of which cells express it, and how it mediates immune inhibitory function, is lacking. Regulatory T cells are known to constitutively express CTLA-4 intracellularly, whereas conventional T cells require activation to trigger CTLA-4 expression. However comparative analysis of CTLA-4 trafficking in regulatory and conventional subsets has not been performed. Here we assess CTLA-4 expression in antigen-specific conventional and regulatory cells responding to immunizing antigen in vivo and analyse the membrane trafficking of CTLA-4 using an in vitro recycling assay. We assess the expression of CTLA-4 on Treg infiltrating the pancreas in the DO11×RIP-mOVA diabetes model and the role of CTLA-4 in Treg function. Regulatory T cells show an enhanced capacity to traffic CTLA-4 following stimulation compared with conventional T cells. Treg infiltrating the pancreas in DO11×RIP-mOVA mice show high expression of CTLA-4. Furthermore CTLA-4-deficient Treg fail to control diabetes in an adoptive transfer model of diabetes, even in situations where they outnumber the disease-inducing conventional T cells. These data show that not only do regulatory T cells express higher levels of intracellular CTLA-4 than conventional T cells, but they also show an increased capacity to traffic CTLA-4 to the cell surface following stimulation. CTLA-4 is strongly upregulated in regulatory T cells infiltrating the target tissue in a mouse model of type 1 diabetes and expression of this protein is critical for effective regulation.

Prokaryotic expression of woodchuck cytotoxic T lymphocyte antigen 4 (wCTLA-4) and preparation of polyclonal antibody to wCTLA-4

Cytotoxic T lymphocyte antigen 4 (CTLA-4) is an inhibitory T cell receptor predominately expressed on activated T cells and plays an important role in regulation of specific T cell responses to viral infection. The woodchuck model is an informative animal model for hepatitis B virus (HBV) infection. In this study, the extracellular region of woodchuck CTLA-4 (wCTLA-4) was cloned and the fusion protein of GST-wCTLA-4 was expressed and purified. Polyclonal antibody against GST-wCTLA-4 (anti-GST-wCTLA-4) was prepared. The full length wCTLA-4 protein expressed in transfected baby hamster kidney cells was detected by anti-GST-wCTLA-4 in western blot analysis and immunofluorescence staining. Anti-GST-wCTLA-4 provides a useful tool to study the role of CTLA-4 in T-cell response in the woodchuck model. Further, the blocking of CTLA-4 with anti-GST-wCTLA-4, as a novel therapy approach for chronic hepatitis B virus infection, could be studied in woodchuck model now.

CTLA-4 Is a Direct Target of Wnt/β-Catenin Signaling and Is Expressed in Human Melanoma Tumors

Our goal was to identify genes regulated by Wnt/beta-catenin signaling in melanoma cells, as this pathway has been implicated in melanocyte development and in melanoma biology. We therefore undertook transcriptional profiling of UACC 1273 human melanoma cells following treatment with recombinant Wnt-3a and found that cytotoxic T-lymphocyte antigen-4 (CTLA-4) was the most highly induced gene. We observed CTLA-4 expression in human epidermal melanocytes and in patient-derived primary melanoma tumors and found that Wnt/beta-catenin signaling elevates CTLA-4 expression in two cultured melanoma cell lines. CTLA-4 is likely a direct target of Wnt/beta-catenin signaling, as the beta-catenin responsiveness of a 1.7 kb region of the CTLA-4 promoter requires a T-cell factor-1/lymphoid enhancing factor-1 consensus site present at -114 to -119 bp from the transcriptional start site. These findings are the initial demonstration that CTLA-4 is a direct target of Wnt/beta-catenin signaling and the first report of its expression in primary melanoma tumors and melanocytes. Given the described role of CTLA-4 in inhibiting the immune response, these findings may shed light on the role of Wnt/beta catenin signaling in melanoma and on the mechanism of action of human anti-CTLA-4 antibody, currently in phase III clinical trials for the treatment of melanoma.