Immune Regulatory 1 Cells: A Novel and Potent Subset of Human T Regulatory Cells

A subset of T regulatory cells (Tregs), identified by TIRC7 (T cell immune response cDNA 7) expression is designated as Immune Regulatory 1 Cells (IR1 cells). TIRC7 is an immune checkpoint inhibitor, co-localized with the T- cell receptor, HLA-DR and CTLA-4 during T-cell activation, which delivers regulatory signals via binding to its ligand, HLA-DR α2 domain. IR1 cells express FOXP3, and multiple other markers associated with immune suppression. They constitute as much as 10% of Tregs. IR1 cells strongly inhibit proliferation in mixed lymphocyte reactions, where they express high levels of IL-10. Ex vivo expansion of Tregs over 2 weeks in the presence of an agonist TIRC7 antibody disproportionately expands the IR1 Treg subset, while maintaining high expression of suppressive markers including CD39, IL-10, LAP and GARP. Ex vivo expanded IR1 cells are a potent, homogeneous, stable set of suppressor Tregs with the potential to modulate immune dysregulation. The characteristics of IR1 cells suggest a therapeutic advantage over polyclonal Tregs for therapeutic interventions. Early restoration of immune homeostasis using IR1 cells has the potential to fundamentally alter the natural history of conditions characterized by abnormalities in the T regulatory cell compartment.

Randomized phase II trial of the carboxylesterase (CES)-converted novel drug EDO-S7.1 in patients (pts) with advanced biliary tract cancers (BTC)

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Background: The novel drug EDO-S7.1 (CAP7.1) is converted to active etoposide by CES allowing administration of higher doses, reducing resistance, and permitting treatment of advanced tumors. Methods: The primary objective was to compare disease control rate (DCR) in 22 pts with unresectable BTC randomized 1:1 to 3-week cycles of EDO-S7.1 (200 or 150mg/m2; iv) given on days (d) 1–5, or best supportive care (BSC) until progression (assessed every 4 weeks). Secondary objectives were progression-free survival (PFS), time to treatment failure (TTF), overall survival (OS) and safety. BSC pts could crossover to EDO-S7.1 upon progression. Results: DCR favored EDO-S7.1 (55.6% [CI 21.2, 86.3] vs BSC (20.0% [2.5, 55.6]; treatment difference –12.80, 72.39). More EDO-S7.1 treated pts achieved sustainable stable disease (SD) or partial response (PR) vs BSC. Progressive disease occurred in 40% EDO-S7.1 vs 70% BSC pts. Three pts (30%) who progressed on BSC achieved SD following crossover to EDO-S7.1, and one pt (10%) PR (total: 40.0% [12.2, 73.8]) vs two pts with SD following BSC (20.0% [2.5, 55.6]; treatment difference –0.17, 0.57; p=0.0786). Median PFS was 103d with EDO-S7.1 vs 39d with BSC (p=0.006), and median TTF 92d vs 39d, respectively (p=0.006). Median OS was 227d with EDO-S7.1 vs 162d with BSC (p=0.088), and estimated 1-year OS 44% vs 11.3%, respectively. EDO-S7.1 had significant efficacy in pts with metastatic disease (p=0.029) or without prior surgery (p=0.032). Seven pts were eligible for exploratory analysis of tumor CES via immunohistochemistry. 4/7 pts had CES+ tumors and longer median PFS (195d [163, 233]) and OS (302d [214, 838]) vs pts with CES– tumors (46d [46, 83] and 83d [43, 319], respectively). The most common drug-related adverse events (G3–4) (%) were leukopenia 65 (26.1), neutropenia 78.3 (56.5), thrombocytopenia 56.5 (17.4), anemia 52.2 (17.4), alopecia 34.4 (0), fatigue 26.1 (0), and abdominal pain 30.4 (0). Conclusions: EDO-S7.1 demonstrated efficacy in pts with advanced BTC and may provide a new biomarker-guided therapeutic option with stratification by intra-tumor CES assessment. These findings will be explored in a larger patient cohort. Clinical trial information: NCT02094560.

First-in-man dose escalation and pharmacokinetic study of CAP7.1, a novel prodrug of etoposide, in adults with refractory solid tumours

AIM

An open-label, phase I dose-escalation trial was performed in adult patients with various solid cancers to identify the maximum tolerated dose (MTD), to assess the safety, pharmacokinetic profile and anti-tumour activity of the new prodrug CAP7.1. The prodrug is converted to its active moiety etoposide via carboxylesterases in selective cells leading to a better tolerability and higher efficacy in therapeutic resistance cells and children with refractory neuroblastoma.

PATIENTS AND METHODS

Eligible adult patients with advanced, refractory, solid malignancies received CAP7.1 as intravenous infusion on 5 consecutive days. Doses were escalated in four cohorts consisting of three to six patients, with a starting dose of 45 mg/m²/day. Treatment cycles were repeated in 21-day intervals in the absence of disease progression and prohibitive toxicity. The safety, pharmacokinetics and efficacy were evaluated, and the MTD and dose-limiting toxicity (DLT) were determined.

RESULTS

Nineteen patients were assigned to four CAP7.1 dose cohorts (45, 90, 150 and 200 mg/m²/day). CAP7.1 was well tolerated. Haematotoxicity was observed at the two highest dose levels including three DLTs (two febrile neutropenia and one sepsis) only and were reversible with adequate therapy. No organ toxicity was observed. Non-haematological toxicities (mild-moderate) consist mainly of nausea, fatigue, vomiting, pyrexia and alopecia. One partial response and 11 stable diseases were observed as supporting signs of efficacy.

CONCLUSION

MTD of CAP7.1 was reached at the dose of 200 mg/m². A favourable safety profile and initial anti-tumour efficacy of CAP7.1 in therapeutic refractory tumours warrant further evaluation in clinical studies.

Randomized, multicenter phase II trial of CAP7.1 in patients with advanced biliary tract cancers

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Background: Non-resectable biliary tract cancers (BTC) have poor prognosis, but are chemosensitive. CAP7.1 is a new chemical entity that releases etoposide in the presence of carboxylesterases, leading to higher intra-tumor etoposide (E) with improved safety and efficacy. Methods: The primary objective of this trial is to determine the rate of disease control (DCR) (stable disease, SD; partial response, PR and complete response, CR) according to Recist 1.1. of CAP7.1 in patients (pts) with BTC. Secondary objectives are progression free survival (PFS), overall survival (OS) and safety. Pts with adenocarcinoma arising from bile ducts or gallbladder were randomized (1:1) to either CAP7.1 or best supportive care (BSC) group (institutional palliative treatment). Pts in CAP7.1 arm subjected to a 3-week cyle (cy) with CAP7.1 on days 1-5 in 3-week cy was given with either 200 or 150mg/m2. until progression. At progression BSC pts were allowed to cross over to CAP7.1. Safety was assessed with CTCAE v 3.0 and efficacy after 2 cy of treatment. 18 /50 pts (9 in each study arm) finalized 1st stage and analyzed for efficacy and safety. Results: DCR in the CAP7.1 arm was 56%, with 5/9 of pts with SD (including tumor shrinkages), while all pts in the BSC arm progressed. The median PFS time was 3.5 months (95% CI, 1.9 to 8.4 months) in the CAP7.1 arm. 5 pts crossed over to the CAP7.1 arm. 2/3 pts continued CAP7.1 treatment up to 5 and 8 cycles as SD, respectively, while one pts achieved PR. The median OS time from first treatment with CAP7.1 was 5.9 months (95% CI, 2.6 to 15.3 months) over all evaluable pts, including BSC after crossing to CAP7.1. Commonly observed drug related adverse events (AE) are hematoxicity/myeolosuppression, various events of infection, alopecia, fatigue, nausea and abdominal pain, which were in general well managed. G3-4 neutropenia occurred in 4/10 pt at a dose of 150 mg/m²/d and in 6/11 pts at 200 mg/ m2/d; uncomplicated g 3-4 thrombocytopenia occurred in 2/11 pt at 200 and in 1/10 at 150 mg/ m2/d. Non-hematological AE were mainly mild or moderate e.g. abdominal pain and alopecia as most frequent AEs. Conclusions: CAP7.1 showed promising activity in therapy refractory advanced BTC patients.

TIRC7 and HLA-DR axis contributes to inflammation in multiple sclerosis

BACKGROUND AND OBJECTIVE

Interactions between TIRC7 (a novel seven-transmembrane receptor on activated lymphocytes) and its ligand HLA-DR might be involved in the inflammatory process in multiple sclerosis (MS).

METHODS

Methods comprised immunohistochemistry and microscopy on archival MS autopsies, proliferation-, cytokine-, and surface-staining assays using peripheral blood lymphocytes (PBLs) from MS patients and an in vitro model.

RESULTS

TIRC7 was expressed in brain-infiltrating lymphocytes and strongly correlated with disease activity in MS. TIRC7 expression was reduced in T cells and induced in B cells in PBLs obtained from MS patients. After ex vivo activation, T cell expression of TIRC7 was restored in patients with active MS disease. The interaction of TIRC7(+) T lymphocytes with cells expressing HLA-DR on their surface led to T cell proliferation and activation whereas an anti-TIRC7 mAb preventing interactions with its ligand inhibited proliferation and Th1 and Th17 cytokine expression in T cells obtained from MS patients and in myelin basic protein-specific T cell clone.

CONCLUSION

Our findings suggest that TIRC7 is involved in inflammation in MS and anti-TIRC7 mAb can prevent immune activation via selective inhibition of Th1- and Th17-associated cytokine expression. This targeting approach may become a novel treatment option for MS.

Adiponectin is a negative regulator of antigen-activated T cells

Adiponectin (APN), a cytokine constitutively produced in fat tissue, has been shown to exert anti-inflammatory effects in various disease models. While the influence of APN on monocytic cells has been extensively studied in vitro, little is known about its role in T cells. In this study, we show that while <10% of human peripheral blood T cells express adiponectin receptors (AdipoRs) on their surface, most T cells store AdipoRs in intracellular compartments. AdipoRs colocalized with immune regulatory molecules CTLA-4 and TIRC7 within clathrin-coated vesicles. After stimulation, the expression of adiponectin receptor 1 (AdipoR1) and AdipoR2 was upregulated on the surface of antigen-specific T cells, as determined by tetramer or CD137 staining, and AdipoR1 and AdipoR2 coexpressed with CTLA-4. Addition of APN resulted in a significant diminution of antigen-specific T-cell expansion. Mechanistically, APN enhanced apoptosis and inhibited proliferation of antigen-specific T-cell lines. Further, APN directly inhibited cytokine production in response to antigen stimulation. In line with the in vitro data, APN-deficient (knockout, KO) mice had higher frequencies of CD137(+) T cells upon Coxsackie B virus infection. Altogether, our data suggest that APN is a novel negative T-cell regulator. In contrast to the CTLA-4 ligand B7 only expressed on APCs, APN is abundant in human plasma.

Donor age intensifies the early immune response after transplantation

Increasing donor age is associated with reduced graft function. We wondered if donor age may not only affect intrinsic function but also alter the immune response of the recipient. Kidneys from young and old F-344 rats (3 vs 18 months) were transplanted into bilaterally nephrectomized young Lewis recipients and compared with age-matched controls (follow-up: 6 months). Renal function and structural changes were assessed serially in both native kidneys and allografts. Host alloreactivity, graft-infiltrating cells, and their inflammatory products were determined at intervals to examine the correlation of immune response and donor age. Functional and structural deterioration had advanced significantly in older allografts compared with age-matched native controls, whereas differences between young allografts and native controls of similar age were only minor. Changes in grafts from elderly rats were associated with a more intense host immune response early post-transplant (up to 1 month) reflected by significantly higher numbers of peripheral T and B cells, increased T-cell alloreactivity and modified cytokine patterns associated with elevated frequencies of intragraft dendritic cells, B cells, and CD31+ cells. By 6 months, recipients of young donor grafts produced comparable or more intense alloantigen-specific immune responses. Older donor grafts elicit a stronger immune response in the early period after transplantation.

Antibody targeting of TIRC7 results in significant therapeutic effects on collagen-induced arthritis in mice

TIRC7 is a cell surface molecule which is expressed in T and B lymphocytes and negatively regulates their function. Anti-TIRC7 specific monoclonal antibody (mAb) inhibited T cell memory response to recall antigens. Up-regulation of TIRC7 on lymphocytes from joint tissue of patients with Rheumatoid Arthritis (RA) and mice with collagen induced arthritis (CIA) suggested TIRC7 as a novel target to promote anti-inflammatory reaction. Anti-TIRC7 mAb administration significantly inhibited the induction and progression of CIA and the anti-collagen IgG1 and IgG2a antibody response. Combination therapy of anti-TIRC7 mAb and soluble TNF-alpha receptor demonstrated an increased inhibitory effect over the single compounds on CIA. The results demonstrate the therapeutic potential of TIRC7 targeting with mAb in diseases associated with exaggerated T and B cell responses.

Specific regulation of T helper cell 1-mediated murine colitis by CEACAM1

Carcinoembryonic antigen-related cellular adhesion molecule 1 (CEACAM1) is a cell surface molecule that has been proposed to negatively regulate T cell function. We have shown that CEACAM1 is associated with specific regulation of T helper cell (Th)1 pathways, T-bet–mediated Th1 cytokine signaling, and Th1-mediated immunopathology in vivo. Mice treated with anti–mouse CEACAM1-specific monoclonal antibody (mAb) CC1 during the effector phase exhibited a reduced severity of trinitrobenzene sulfonic acid colitis in association with decreased interferon (IFN)-γ production. Although oxazolone colitis has been reported as Th2 mediated, mice treated with the CC1 mAb or a CEACAM1-Fc chimeric protein exhibited a reduced severity of colitis in association with a significant reduction of IFN-γ and T-bet activation, whereas signal transducer and activator of antigen 4 activation was unaffected. Both interleukin-4 and IFN-γ gene–deficient mice exhibited less severe colitis induction by oxazolone. Direct ligation of T cells in vitro with the murine hepatitis virus spike protein, a natural ligand for the N-domain of CEACAM1, inhibited the differentiation of naive cells into Th1 but not Th2 cells and activation of Th1 but not Th2 cytokine production. These results indicate that CEACAM1 isoforms are a novel class of activation-induced cell surface molecules on T cells that function in the specific regulation of Th1-mediated inflammation such as that associated with inflammatory bowel disease.

Carcinoembryonic antigen-related cellular adhesion molecule 1 isoforms alternatively inhibit and costimulate human T cell function

Carcinoembryonic Ag-related cellular adhesion molecule 1 (CEACAM1) represents a group of transmembrane protein isoforms that consist of variable numbers of extracellular Ig-like domains together with either a long cytoplasmic (cyt) tail containing two immunoreceptor tyrosine-based inhibitory motifs or a unique short cyt tail. Although CEACAM1 has been reported to be expressed on the surface of T lymphocytes upon activation, its roles in T cell regulation are controversial due to the lack of functional characterization of each individual CEACAM1 isoform. We thus cotransfected Jurkat T cells with CEACAM1 isoform-encoding constructs and an IL-2 promoter-bearing plasmid or a small interference RNA targeting src homology domain 2 containing phosphatase 1. In a luciferase reporter assay and through measurements of cytokine secretion (IL-2, IL-4, and IFN-gamma), CEACAM1 containing either a long or a short cyt tail inhibited or costimulated, respectively, TCR/CD3 complex plus CD28 mediated activation with the inhibitory functions of the long cyt tail dominating. The inhibitory function of CEACAM1, was dependent upon src homology domain 2 containing phosphatase 1 activity, required both tyrosine residues within the immunoreceptor tyrosine-based inhibitory motif domains of the cyt tail and was mediated through the mitogen-activated protein kinase pathway. CEACAM1-mediated inhibition could be functionally reconstituted by incubation of PBMC with either a CEACAM1-specific mAb or CEACAM1-Fc fusion protein in the presence of an allogeneic or mitogenic stimulus, respectively. These studies indicate that the long and short cyt tails of CEACAM1 serve as inhibitory and costimulatory receptors, respectively, in T cell regulation.

Monoclonal antibody specific for TIRC7 induces donor-specific anergy and prevents rejection of cardiac allografts in mice

T cell immune response c-DNA (TIRC7) is up-regulated during the early stages of T-cell activation in response to alloantigens. In this study, we analyzed the effects of newly developed monoclonal antibodies (mAb) against TIRC7 in acute cardiac allograft rejection. Fully vascularized heterotopic allogeneic heart transplantation was performed in mice across a full-mismatch barrier (C57Bl/10 into CBA). Recipients received seven injections (day 0-7) of a novel anti-TIRC7 mAb or remained untreated. Graft survival, histology and ex vivo lymphocyte functions were tested. Targeting of TIRC7 with an anti-TIRC7 mAb diminishes lymphocyte infiltration into grafts resulting in delay of morphological graft damage and prolongation of allograft survival. The lymphocytes from anti-TIRC7 mAb-treated animals exhibit hypo-responsiveness without evidence of lymphocyte depletion against the donor allo-antigens. Proliferation and expression of interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) were down-regulated while interleukin-4 (IL-4) and IL-10 expression were spared. Moreover, anti-TIRC7 mAb enhanced up-regulation of CTLA-4 expression but suppressed up-regulation of CD25 on stimulated lymphocytes in vitro and in vivo. Ligation of TIRC7 has important effects on the regulation of co-stimulatory signaling pathways associated with suppressing of T-cell activation. Targeting of TIRC7 may therefore provide a novel therapeutic approach for modulating T cell immune responses during organ transplantation.

Regulation of human intestinal intraepithelial lymphocyte cytolytic function by biliary glycoprotein (CD66a)

Human small intestinal intraepithelial lymphocytes (iIEL) are a unique population of CD8alphabeta+ TCR-alphabeta+ but CD28- T lymphocytes that may function in intestinal epithelial cell immunosurveillance. In an attempt to define novel cell surface molecules involved in iIEL function, we raised several mAbs against activated iIELs derived from the small intestine that recognized an Ag on activated, but not resting, iIELs. Using expression cloning and binding studies with Fc fusion proteins and transfectants, the cognate Ag of these mAbs was identified as the N domain of biliary glycoprotein (CD66a), a carcinoembryonic Ag-related molecule that contains an immune receptor tyrosine-based inhibitory motif. Functionally, these mAbs inhibited the anti-CD3-directed and lymphokine-activated killer activity of the P815 cell line by iIELs derived from the human small intestine. These studies indicate that the expression of biliary glycoprotein on activated human iIELs and, potentially, other mucosal T lymphocytes is involved in the down-regulation of cytolytic function.

Regulation of Human Intestinal Intraepithelial Lymphocyte Cytolytic Function by Biliary Glycoprotein (CD66a)

Human small intestinal intraepithelial lymphocytes (iIEL) are a unique population of CD8αβ+ TCR-αβ+ but CD28− T lymphocytes that may function in intestinal epithelial cell immunosurveillance. In an attempt to define novel cell surface molecules involved in iIEL function, we raised several mAbs against activated iIELs derived from the small intestine that recognized an Ag on activated, but not resting, iIELs. Using expression cloning and binding studies with Fc fusion proteins and transfectants, the cognate Ag of these mAbs was identified as the N domain of biliary glycoprotein (CD66a), a carcinoembryonic Ag-related molecule that contains an immune receptor tyrosine-based inhibitory motif. Functionally, these mAbs inhibited the anti-CD3-directed and lymphokine-activated killer activity of the P815 cell line by iIELs derived from the human small intestine. These studies indicate that the expression of biliary glycoprotein on activated human iIELs and, potentially, other mucosal T lymphocytes is involved in the down-regulation of cytolytic function.

Genomic organization of the gene coding for TIRC7, a novel membrane protein essential for T cell activation

A novel human membrane protein, TIRC7, was recently identified and demonstrated to be essential in T cell activation. Here we report on the genomic organization of the TIRC7 gene, which is composed of 15 exons and spans 7.9 kb. The seven predicted transmembrane-spanning domains of the TIRC7 protein coincide well with exon-intron boundaries. TIRC7 and OC116, a recently described putative subunit of the vacuolar proton pump that was demonstrated to be expressed in an osteoclastoma tumor as well as in a human pancreatic adenocarcinoma cell line, are demonstrated to be alternative transcripts of the same gene. OC116 consists of 20 exons with the last 14 introns and exons being identical with those of TIRC7. The chromosomal locus for both transcripts was identified on chromosome 11q13.4-q13.5. In human alloactivated T lymphocytes, mRNA expression of TIRC7, but not OC116, is demonstrated, indicating that OC116 is not involved in regular T cell proliferation.

The human homolog of Drosophila cornichon protein is differentially expressed in alloactivated T-cells

To identify novel genes induced in the early stage of T-cell activation, mRNA expression in alloactivated human lymphocytes was examined. Differential display-reverse transcription PCR analysis revealed a 207-bp cDNA fragment which was upregulated 24 h after allostimulation of a human T-cell line. The corresponding complete 1396 bp cDNA, named TGAM77, encodes a predicted 134 amino acid protein which shares 63% homology with the cornichon (cni) protein of Drosophila melanogaster. Upregulation of TGAM77 mRNA in the early phase of T-cell activation was confirmed by Northern blot and RT-PCR analysis of activated human lymphocytes. TGAM77 mRNA is expressed in a variety of human tissues with various expression levels. In analogy to cni which is involved in an epidermal growth factor-like signaling pathway inducing cellular asymmetry in Drosophila oogenesis, TGAM77 might function in similar signaling establishing vectorial re-localization and concentration of signaling events in T-cell activation.

Prevention of acute allograft rejection by antibody targeting of TIRC7, a novel T cell membrane protein

A novel 75 kDa membrane protein, TIRC7, is described that exhibits a central role in T cell activation in vitro and in vivo. Modulation of TIRC7-mediated signals with specific anti-TIRC7 antibodies in vitro efficiently prevents human T cell proliferation and IL-2 secretion. Moreover, anti-TIRC7 antibodies specifically inhibit type 1 subset specific IFN-gamma expression but spare the type 2 cytokine IL-4. Diminished proliferation but not IFN-gamma secretion is reversible by exogenous rIL-2. An anti-TIRC7 antibody that cross-reacts with the 75 kDa rat homolog exhibits inhibition of rat alloimmune response in vitro and significantly prolongs kidney allograft survival in vivo. Targeting of TIRC7 may provide a novel therapeutic approach for modulation of the immune response.

Differential display cloning of a novel human histone deacetylase (HDAC3) cDNA from PHA-activated immune cells

The nucleosomal histones can be modified through reversible acetylation by histone acetyltransferases (HATs) and deacetylases (HDACs). HATs induce nucleosomal relaxation and allow DNA-binding by transcriptional activators. HDACs from corepressor complexes which negatively regulate cell growth. However, the HDAC inhibitors butyrate and Trichostatin A block T cell proliferation, suggesting that not all effects of HDACs lead to repression. Using mRNA differential display and 5'RACE we isolated human HDAC3, a novel gene that is upregulated in PHA-activated T cell clones. HDAC3 is homologous to other human HDACs and yeast RPD3. In peripheral blood mononuclear cells (PBMCs), activation by PHA, PMA and alpha-CD3 increased HDAC mRNA but no effect was seen with IFN-gamma, LPS, or IL-4. In contrast, GMCSF downregulated PBMC levels of HDAC3 mRNA. All HDACs were found to be ubiquitously expressed in immune and non-immune tissues. In human myeloid leukemia THP-1 cells, HDAC3 transfection resulted in increased size, aberrant nuclear morphology and cell cycle G2/M cell accumulation. Functional activity of the expressed HDAC3 protein was confirmed in alpha-HDAC3 antibody immunoprecipitates by a histone deacetylase assay. Our study suggests the participation of HDACs in cell cycle progression and activation.

[Immunoglobulin therapy for systemic lupus erythematosus]

A 25-year-old patient with lupus erythematosus was admitted with myositis and erythema of the skin under chloroquine therapy. After improvement of clinical symptoms with cyclophosphamide and prednisolone he was again progredient with myositis. The changing of therapy to methotrexate showed a hepatotoxic side effect with elevated liver enzymes. Under subsequent therapy with azathioprine and prednisolone he developed leukopenia and sepsis. Because of persistent erythema of the skin under therapy with different immunosuppressives we performed a therapy with high-dose intravenous immunoglobulins. After application of immunoglobulins we observed an improvement of the erythema after 10 days, which was persistent after dose reduction for about 4 months.