Effects of high-dose oral insulin on immune responses in children at high risk for type 1 diabetes: the Pre-POINT randomized clinical trial.

IMPORTANCE: Exposing the oral mucosa to antigen may stimulate immune tolerance. It is unknown whether treatment with oral insulin can induce a tolerogenic immune response in children genetically susceptible to type 1 diabetes. OBJECTIVE: To assess the immune responses and adverse events associated with orally administered insulin in autoantibody-negative, genetically at-risk children. DESIGN, SETTING, AND PARTICIPANTS: The Pre-POINT study, a double-blind, placebo-controlled, dose-escalation, phase 1/2 clinical pilot study performed between 2009 and 2013 in Germany, Austria, the United States, and the United Kingdom and enrolling 25 islet autoantibody-negative children aged 2 to 7 years with a family history of type 1 diabetes and susceptible human leukocyte antigen class II genotypes. Follow-up was completed in August 2013. INTERVENTIONS: Children were randomized to receive oral insulin (n = 15) or placebo (n = 10) once daily for 3 to 18 months. Nine children received insulin with dose escalations from 2.5 to 7.5 mg (n = 3), 2.5 to 22.5 mg (n = 3), or 7.5 to 67.5 mg (n = 3) after 6 months; 6 children only received doses of 22.5 mg (n = 3) or 67.5 mg (n = 3). MAIN OUTCOMES AND MEASURES: An immune response to insulin, measured as serum IgG and saliva IgA binding to insulin, and CD4+ T-cell proliferative responses to insulin. RESULTS: Increases in IgG binding to insulin, saliva IgA binding to insulin, or CD4+ T-cell proliferative responses to insulin were observed in 2 of 10 (20% [95% CI, 0.1%-45%]) placebo-treated children and in 1 of 6 (16.7% [95% CI, 0.1%-46%]) children treated with 2.5 mg of insulin, 1 of 6 (16.7%[ 95% CI, 0.1%-46%]) treated with 7.5 mg, 2 of 6 (33.3% [95% CI, 0.1%-71%]) treated with 22.5 mg, and 5 of 6 (83.3% [ 95% CI, 53%-99.9%]) treated with 67.5 mg (P = .02). Insulin-responsive T cells displayed regulatory T-cell features after oral insulin treatment. No hypoglycemia, IgE responses to insulin, autoantibodies to glutamic acid decarboxylase or insulinoma-associated antigen 2, or diabetes were observed. Adverse events were reported in 12 insulin-treated children (67 events) and 10 placebo-treated children (35 events). CONCLUSIONS AND RELEVANCE: In this pilot study of children at high risk for type 1 diabetes, daily oral administration of 67.5 mg of insulin, compared with placebo, resulted in an immune response without hypoglycemia. These findings support the need for a phase 3 trial to determine whether oral insulin can prevent islet autoimmunity and diabetes in such children. TRIAL REGISTRATION: isrctn.org Identifier: ISRCTN76104595.

Adoptive transfer of allogeneic regulatory T cells into patients with chronic graft-versus-host disease.

BACKGROUND AIMS: Mouse models indicate that adoptive transfer of regulatory T cells (Treg) may suppress graft-versus-host-disease (GvHD) while preserving graft-versus-leukemia reactions. We aimed to develop a protocol for the efficient isolation and in vitro expansion of donor-derived Treg and to establish the proof-of-concept for the clinical application of ex vivo-generated Treg preparations in five patients with otherwise treatment-refractory chronic GvHD (cGvHD). METHODS: Allogeneic Treg were isolated from unstimulated leukapheresis products of the corresponding human leukocyte antigen-matched donors by use of clinical-grade magnetic-activated bead sorting. To increase the amount and purity, Treg were cultivated for 7-12 days and infused after a median time of 35 months after allogeneic hematopoietic cell transplantation. RESULTS: Final products contained Treg with a median purity of 84.1% CD4(+)CD25(high)CD127(low)FOXP3(+)of CD45(+) cells and a mean quantity of 2.4 × 10(6) Treg per kg body wt. All isolated cell products showed in vitro suppressive activity. On transfusion, two of five patients showed a clinical response with improvement of cGvHD symptoms. The other three patients showed stable cGvHD symptoms for up to 21 months. In four of five patients, increased counts of Treg were detectable on Treg transfusion, immunosuppressive treatment could be reduced and suppression of CD69 activation marker expression on T-effector cells was observed. However, one patient had development of malignant melanoma and another patient had Bowen skin cancer 4 months and 11 months after Treg transfusion, respectively. CONCLUSIONS: We demonstrate a feasible and reproducible approach of isolating functional Treg in high quantity and purity for clinical application and show opportunities and risks of adoptive Treg transfer into patients with cGvHD.

IL-7 abrogates suppressive activity of human CD4+CD25+FOXP3+ regulatory T cells and allows expansion of alloreactive and autoreactive T cells.

CD4(+)CD25(+)FOXP3(+) regulatory T cells (Tregs) control the activation and expansion of alloreactive and autoreactive T cell clones. Because uncontrolled activation and expansion of autoreactive T cells occur in an IL-7-rich environment, we explored the possibility that IL-7 may affect the function of Treg. We show that the functional high-affinity IL-7R is expressed on both naive and memory Tregs, and exposure to IL-7 results in STAT-5 phosphorylation. Naive, but not memory, Tregs proliferated greatly and acquired a memory phenotype in the setting of a suppression assay when IL-7 was present. Importantly, the presence of IL-7 abrogated the capacity of Tregs to suppress proliferation of conventional T cells in response to TCR activators, including alloantigens and autoantigens. Removal of IL-7 restored the suppressive function of Tregs. Preblocking of the IL-7R on the Tregs also restored suppressor function, indicating that IL-7 directly affected Treg function. Thus, prolonged periods of homeostatic expansion can temporarily release natural regulatory brakes on T cells, thereby providing an additional mechanism for activating and expanding alloreactive and autoreactive T cells.

Retargeting of human regulatory T cells by single-chain bispecific antibodies.

Bispecific Abs hold great potential for immunotherapy of malignant diseases. Because the first components of this new drug class are now entering clinical trials, all aspects of their mode of action should be well understood. Several studies proved that CD8(+) and CD4(+) effector T cells can be successfully redirected and activated against tumor cells by bispecific Abs both in vitro and in vivo. To our knowledge, this study provides the first evidence that bispecific Abs can also redirect and activate regulatory T cells against a surface Ag, independently of their TCR specificity. After cross-linking, via a bispecific Ab, redirected regulatory T cells upregulate the activation markers CD69 and CD25, as well as regulatory T cell-associated markers, like CTLA-4 and FOXP3. The activated regulatory T cells secrete the immunosuppressive cytokine IL-10, but, in contrast to CD8(+) and CD4(+) effector T cells, almost no inflammatory cytokines. In addition, the redirected regulatory T cells are able to suppress effector functions of activated autologous CD4(+) T cells both in vitro and in vivo. Therefore, the potential risk for activation of regulatory T cells should be taken into consideration when bispecific Abs are applied for the treatment of malignant diseases. In contrast, an Ag/tissue-specific redirection of regulatory T cells with bispecific Abs holds great potential for the treatment of autoimmune diseases and graft rejection.

DLC1 interacts with 14-3-3 proteins to inhibit RhoGAP activity and block nucleocytoplasmic shuttling.

Deleted in liver cancer 1 (DLC1) is a Rho-GTPase-activating protein (GAP) that is downregulated in various tumor types. In vitro, DLC1 specifically inactivates the small GTPases RhoA, RhoB and RhoC through its GAP domain and this appears to contribute to its tumor suppressor function in vivo. Molecular mechanisms that control DLC1 activity have not so far been investigated. Here, we show that phorbol-ester-induced activation of protein kinase C and protein kinase D stimulates association of DLC1 with the phosphoserine/phosphothreonine-binding 14-3-3 adaptor proteins via recognition motifs that involve Ser327 and Ser431. Association with 14-3-3 proteins inhibits DLC1 GAP activity and facilitates signaling by active Rho. We further show that treatment of cells with phorbol ester or coexpression of 14-3-3 proteins, blocks DLC1 nucleocytoplasmic shuttling, probably by masking a previously unrecognized nuclear localization sequence. The binding to 14-3-3 proteins is thus a newly discovered mechanism by which DLC1 activity is regulated and compartmentalized.

Identification of human reductases that activate the dinitrobenzamide mustard prodrug PR-104A: a role for NADPH:cytochrome P450 oxidoreductase under hypoxia.

Hypoxia is a common trait found in many solid tumours and thus represents a therapeutic target with considerable potential. PR-104, a hypoxia-activated prodrug currently in clinical trial, is a water-soluble phosphate ester which is converted in vivo to the corresponding alcohol, PR-104A. This 3,5-dinitrobenzamide-2-nitrogen mustard is activated by reduction to the corresponding 5-hydroxylamine (PR-104H) and 5-amine (PR-104M) in hypoxic cells. The clinical effectiveness of PR-104 will depend in part on the expression of reductases within tumours that can effect this reduction. Here, we evaluate the roles of NADPH:cytochrome P450 oxidoreductase (CYPOR; E.C.1.6.2.4) and NAD(P)H:quinone oxidoreductase (NQO1; E.C.1.6.99.2) as candidate PR-104A reductases. A weak correlation was observed between NQO1 activity and aerobic cytotoxicity in a panel of eight tumour cell lines. However, overexpression of human NQO1 did not increase cytotoxicity of PR-104A or the formation of PR-104H/M, showing that PR-104A is not a substrate for NQO1. Overexpression of human CYPOR did, however, increase the hypoxic cytotoxicity of PR-104A, and its metabolism to PR-104H and PR-104M, demonstrating it to be a PR-104A reductase. To assess the contribution of CYPOR to overall activation of PR-104A in hypoxic SiHa cells, a combination of siRNA transfection and antisense expression were used to suppress CYPOR protein by 91% (+/-3%), a phenotype which conferred 45% (+/-7%) decrease in cytotoxic potency of PR-104A. Regression analysis of all CYPOR depletion data was found to correlate with cytoprotection and metabolism (p<0.001). Residual PR-104A reductase activity could be inhibited by the flavoprotein inhibitor diphenyliodonium. We conclude that CYPOR is an important PR-104A reductase, but that other flavoenzymes also contribute to its activation in hypoxic SiHa cells.