CD3-specific antibodies: a portal to the treatment of autoimmunity

The SCHOOL of nature: III. From mechanistic understanding to novel therapies

Protein-protein interactions play a central role in biological processes and thus represent an appealing target for innovative drug design and development. They can be targeted by small molecule inhibitors, modulatory peptides and peptidomimetics, which represent a superior alternative to protein therapeutics that carry many disadvantages. Considering that transmembrane signal transduction is an attractive process to therapeutically control multiple diseases, it is fundamentally and clinically important to mechanistically understand how signal transduction occurs. Uncovering specific protein-protein interactions critical for signal transduction, a general platform for receptor-mediated signaling, the signaling chain homooligomerization (SCHOOL) platform, suggests these interactions as universal therapeutic targets. Within the platform, the general principles of signaling are similar for a variety of functionally unrelated receptors. This suggests that global therapeutic strategies targeting key protein-protein interactions involved in receptor triggering and transmembrane signal transduction may be used to treat a diverse set of diseases. This also assumes that clinical knowledge and therapeutic strategies can be transferred between seemingly disparate disorders, such as T cell-mediated skin diseases and platelet disorders or combined to develop novel pharmacological approaches. Intriguingly, human viruses use the SCHOOL-like strategies to modulate and/or escape the host immune response. These viral mechanisms are highly optimized over the millennia, and the lessons learned from viral pathogenesis can be used practically for rational drug design. Proof of the SCHOOL concept in the development of novel therapies for atopic dermatitis, rheumatoid arthritis, cancer, platelet disorders and other multiple indications with unmet needs opens new horizons in therapeutics.

Activating and inhibitory Fcgamma receptors in immunotherapy: being the actor or being the target

Membrane Fcgamma receptors (FcgammaRs) can act either as potent activators of effector cell functions or as inhibitors of receptor-mediated cell activation following engagement by IgG antibodies bound to their target molecules. The remarkable ability of activating FcgammaRs to trigger antibody-dependent cellular cytotoxicity, cytokine release and phagocytosis/endocytosis followed by antigen presentation has stimulated the development of a number of therapeutic monoclonal antibodies whose Fc regions have been engineered to optimize their effector functions, mostly their killing activities. Conversely, the demonstration that inhibitory FcgammaRs can block or downmodulate effector functions has led to the concept that targeting these receptors is of interest in a number of pathologies. The use of bispecific antibodies leading to the crosslinking of FcgammaRIIB with activating receptors could induce immunomodulation in autoimmune or allergic diseases. Alternatively, the use of cytotoxic/antagonist anti-FcgammaRIIB antibodies could kill FcgammaRIIB-positive tumor cells or prevent the downmodulation of activating receptors. Thus, antibodies engineered to preferentially target activating or inhibitory FcgammaRs are currently being designed for therapeutic use.

Adaptive immune regulation of glial homeostasis as an immunization strategy for neurodegenerative diseases

Neurodegenerative diseases, notably Alzheimer's and Parkinson's diseases, are amongst the most devastating disorders afflicting the elderly. Currently, no curative treatments or treatments that interdict disease progression exist. Over the past decade, immunization strategies have been proposed to combat disease progression. Such strategies induce humoral immune responses against misfolded protein aggregates to facilitate their clearance. Robust adaptive immunity against misfolded proteins, however, accelerates disease progression, precipitated by induced effector T cell responses that lead to encephalitis and neuronal death. Since then, mechanisms that attenuate such adaptive neurotoxic immune responses have been sought. We propose that shifting the balance between effector and regulatory T cell activity can attenuate neurotoxic inflammatory events. This review summarizes advances in immune regulation to achieve a homeostatic glial response for therapeutic gain. Promising new ways to optimize immunization schemes and measure their clinical efficacy are also discussed.

Genetics, pathogenesis and clinical interventions in type 1 diabetes

Type 1 diabetes is an autoimmune disorder afflicting millions of people worldwide. Once diagnosed, patients require lifelong insulin treatment and can experience numerous disease-associated complications. The last decade has seen tremendous advances in elucidating the causes and treatment of the disease based on extensive research both in rodent models of spontaneous diabetes and in humans. Integrating these advances has led to the recognition that the balance between regulatory and effector T cells determines disease risk, timing of disease activation, and disease tempo. Here we describe current progress, the challenges ahead and the new interventions that are being tested to address the unmet need for preventative or curative therapies.

New therapeutic strategies targeting transmembrane signal transduction in the immune system

Single-chain receptors and multi-chain immune recognition receptors (SRs and MIRRs, respectively) represent families of structurally related but functionally different surface receptors expressed on different cells. In contrast to SRs, a distinctive and common structural characteristic of MIRR family members is that the extracellular recognition domains and intracellular signaling domains are located on separate subunits. How extracellular ligand binding triggers MIRRs and initiates intracellular signal transduction processes is not clear. A novel model of immune signaling, the Signaling Chain HOmoOLigomerization (SCHOOL) model, suggests that the homooligomerization of receptor intracellular signaling domains represents a necessary and sufficient condition for receptor triggering. In this review, I demonstrate striking similarities between a consensus model of SR signaling and the SCHOOL model of MIRR signaling and show how these models, together with the lessons learned from viral pathogenesis, provide a molecular basis for novel pharmacological approaches targeting inter- and intrareceptor transmembrane interactions as universal therapeutic targets for a diverse variety of immune and other disorders.

Four-year metabolic outcome of a randomised controlled CD3-antibody trial in recent-onset type 1 diabetic patients depends on their age and baseline residual beta cell mass

AIMS/HYPOTHESIS

The aim of the study was to examine the 48 month outcome of treating recent-onset type 1 diabetic patients for 6 days with humanised CD3-antibody, ChAglyCD3.

METHODS

Eighty patients, aged 12-39 years, were recruited for a phase 2 multicentre trial and randomised to placebo (n=40) or ChAglyCD3 (n=40) treatment by a third party member; participants and care-givers were blinded. The change in insulin dose (U kg(-1)day(-1)) over 48 months was chosen as primary endpoint and compared in 31 placebo-and 33 ChAglyCD3-treated patients. Adverse events were followed in 35 and 38 patients, respectively.

RESULTS

Treatment with ChAglyCD3 delayed the rise in insulin requirements of patients with recent-onset diabetes and reduced its amplitude over 48 months (+0.09 vs +0.32 U kg(-1)day(-1) in the placebo group). Using multivariate analysis this effect was correlated with higher baseline residual beta cell function and a younger age. It was associated with better outcome variables in subgroups selected according to these variables. In the ChAglyCD3 subgroup with higher initial beta cell function, 0/11 patients became C-peptide-negative over 48 months vs 4/9 in the corresponding placebo subgroup. In the subgroup aged <27 years old, antibody treatment preserved initial beta cell function for 36 months (vs >80% decline within 24 months in the placebo subgroup <27 years old), resulted in lower HbA1c concentrations and tended to reduce glycaemic variability (p=0.08). No longterm adverse events were observed.

CONCLUSIONS/INTERPRETATION

A 6 day ChAglyCD3 treatment can suppress the rise in insulin requirements of recent-onset type 1 diabetic patients over 48 months, depending on their age and initial residual beta cell function. In younger patients this effect is associated with reduced deterioration of metabolic variables. These observations help to define inclusion criteria for prevention trials.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00627146

FUNDING

Center grants from the Juvenile Diabetes Research Foundation (4-2001-434, 4-2005-1327) and grants from the Belgian Fund for Scientific Research-Flanders and from Brussels Free University-VUB.

Immune therapy for type 1 diabetes mellitus-what is unique about anti-CD3 antibodies?

Type 1 diabetes mellitus (T1DM) is a prototypic organ-specific autoimmune disease that results from selective destruction of insulin-secreting beta-cells by immune-mediated inflammation (insulitis), that is, the infiltration of pancreatic islets by autoreactive CD4(+) and CD8(+) T lymphocytes. Current treatment is substitutive-chronic use of exogenous insulin-which, in spite of considerable advances, is still associated with constraints and lack of effectiveness over the long-term in relation to the prevention of vascular and neurological complications. Finding a cure for T1DM is an important medical health challenge, as the disease's incidence is steadily increasing in industrialized countries and projections of future prevalence are alarming. Crucially, as T1DM mainly affects children and young adults, any candidate immune therapy must be safe and avoid chronic use of immunosuppressants that promote sustained depression of immune responses. The ideal approach would, therefore, involve induction or, in the case of established T1DM, restoration of immune tolerance to target autoantigens. This Review presents, in particular, two strategies that are still in clinical development but hold great promise. These strategies are focused on the use of candidate autoantigens and anti-CD3 monoclonal antibodies.

Targeting of IL-2 receptor with a caspase fusion protein disrupts autoimmunity in prediabetic and diabetic NOD mice

AIMS/HYPOTHESIS

Interruption of IL-2 signalling is an attractive therapeutic target in autoimmune disorders. In this study we evaluated the effect of a fusion protein composed of IL-2 and caspase-3 (IL2-cas) on NOD mice, as compared with disease induction by cyclophosphamide.

METHODS

IL2-cas was assessed in NOD mice at various ages and in conjunction with cyclophosphamide administration. The effect of IL2-cas on diabetogenic cells was evaluated in adoptive transfer experiments and in cell suspension in vitro.

RESULTS

IL2-cas induced apoptosis in T cells expressing the alpha chain of the IL-2 receptor (cluster of differentiation [CD]25) in vitro, with superior survival of T cells expressing CD4 and forkhead box P3 (FOXP3). The fusion protein decreased mixed lymphocyte reactivity, and pretreatment with IL2-cas decreased the efficacy of adoptive transfer of diabetes into NOD severe combined immunodeficiency mice. Administration of one dose of IL2-cas decreased the incidence of diabetes in NOD mice, showing a superior beneficial effect when administered at young age, and effectively blocked induction of hyperglycaemia by cyclophosphamide, reducing the severity of islet inflammation. Administration of IL2-cas caused an acute increase in CD25(-)FOXP3(+) T cells in the lymph nodes, pancreas and thymus in NOD mice, with similar effects in wild-type mice. Administration of IL2-cas after onset of hyperglycaemia resulted in superior survival.

CONCLUSIONS/INTERPRETATION

Targeted elimination of cells expressing the IL-2 receptor by this fusion protein disrupts the autoimmune pathogenesis in prediabetic and diabetic NOD mice, despite depletion of CD25(+) regulatory T cells. Furthermore, this particular fusion protein is permissive to the development of FOXP3(+) T cells that might contribute to protracted protection from the progression of insulitis and overt hyperglycaemia.

Converting human pluripotent stem cells into beta-cells: recent advances and future challenges

PURPOSE OF REVIEW

The transplantation of insulin-producing beta-cells derived from human embryonic stem cells and induced pluripotent stem cells (collectively termed pluripotent stem cells or PSCs) holds great promise for therapy of diabetes mellitus. The purpose of this review is to summarize recent advances in this area, emphasizing the importance of studies of endocrine pancreas development in efforts to direct PSC differentiation into endocrine cells, as well as to outline the major challenges remaining before transplantation of PSC-derived beta-cells can become a reality.

RECENT FINDINGS

Although several protocols to generate glucose-responsive pancreatic beta-cells in vitro have been described, the most successful approaches are those that most closely mimic embryonic development of the endocrine pancreas. Until recently, cells generated by these methods have exhibited immature pancreatic endocrine phenotypes. However, protocols that generate more functional beta-like cells have now been described. In addition, small molecules are being used to improve protocols to direct differentiation of PSCs into endoderm and pancreatic lineages.

SUMMARY

Advances over the last decade suggest that generating functional beta-cells from human PSCs is achievable. However, there are aspects of beta-cell development that are not well understood and are hampering generation of PSC-derived beta-cells. In particular, the signaling pathways that instruct endocrine progenitor cells to differentiate into mature and functional beta-cells are poorly understood. Other significant obstacles remain, including the need for safe and cost-effective differentiation methods for large-scale generation of transplantation quality beta-cells, methods to prevent immune rejection of grafted tissues, and amelioration of the risks of tumorigenesis.

Partial and transient modulation of the CD3-T-cell receptor complex, elicited by low-dose regimens of monoclonal anti-CD3, is sufficient to induce disease remission in non-obese diabetic mice

It has been established that a total of 250 microg of monoclonal anti-mouse CD3 F(ab')(2) fragments, administered daily (50 microg per dose), induces remission of diabetes in the non-obese diabetic (NOD) mouse model of autoimmune diabetes by preventing beta cells from undergoing further autoimmune attack. We evaluated lower-dose regimens of monoclonal anti-CD3 F(ab')(2) in diabetic NOD mice for their efficacy and associated pharmacodynamic (PD) effects, including CD3-T-cell receptor (TCR) complex modulation, complete blood counts and proportions of circulating CD4(+), CD8(+) and CD4(+) FoxP3(+) T cells. Four doses of 2 microg (total dose 8 microg) induced 53% remission of diabetes, similarly to the 250 microg dose regimen, whereas four doses of 1 microg induced only 16% remission. While the 250 microg dose regimen produced nearly complete and sustained modulation of the CD3 -TCR complex, lower doses, spaced 3 days apart, which induced similar remission rates, elicited patterns of transient and partial modulation. In treated mice, the proportions of circulating CD4(+) and CD8(+) T cells decreased, whereas the proportions of CD4(+) FoxP3(+) T cells increased; these effects were transient. Mice with greater residual beta-cell function, estimated using blood glucose and C-peptide levels at the initiation of treatment, were more likely to enter remission than mice with more advanced disease. Thus, lower doses of monoclonal anti-CD3 that produced only partial and transient modulation of the CD3-TCR complex induced remission rates comparable to higher doses of monoclonal anti-CD3. Accordingly, in a clinical setting, lower-dose regimens may be efficacious and may also improve the safety profile of therapy with monoclonal anti-CD3, potentially including reductions in cytokine release-related syndromes and maintenance of pathogen-specific immunosurveillance during treatment.

New insights into T cell biology and T cell-directed therapy for autoimmunity, inflammation, and immunosuppression

T cell-directed therapies have become mainstays in the management of various autoimmune diseases and organ transplantation. The understanding of T cell biology has expanded greatly since the development of most agents currently in use. Here we discuss important recent discoveries pertaining to T helper cell differentiation, lineage commitment, and function. Within this context, we examine existing T cell-directed therapies, including new agents being evaluated in clinical and preclinical studies. We also use recent findings to speculate on novel targets.

Successes and disappointments with clinical islet transplantation

Transplantation of pancreatic islets is considered a therapeutic option for patients with type 1 diabetes mellitus who have life-threatening hypoglycaemic episodes. After the procedure, a decrease in the frequency and severity of hypoglycaemic episodes and sustained graft function as indicated by detectable levels of C-peptide can be seen in the majority of patients. However, true insulin independence, if achieved, usually lasts for at most a few years. Apart from the low insulin independence rates, reasons for concern regarding this procedure are the side effects of the immunosuppressive therapy, allo-immunization, and the high costs. Moreover, whether islet transplantation prevents the progression of diabetic micro- and macrovascular complications is largely unknown. Areas of current research include the development of less toxic immunosuppressive regimens, the control of the inflammatory reaction immediately after transplantation, the identification of the optimal anatomical site for islet infusion, and the possibility to encapsulate transplanted islets to protect them from the allo-immune response. At present, pancreatic islet transplantation is still an experimental procedure, which is only indicated for a highly selected group of type 1 diabetic patients with life-threatening hypoglycaemic episodes.

Construction of human antibody gene libraries and selection of antibodies by phage display

Recombinant antibodies as therapeutics offer new opportunities for the treatment of many tumor diseases. To date, 18 antibody-based drugs are approved for cancer treatment and hundreds of anti-tumor antibodies are under development. The first clinically approved antibodies were of murine origin or human-mouse chimeric. However, since murine antibody domains are immunogenic in human patients and could result in human anti-mouse antibody (HAMA) responses, currently mainly humanized and fully human antibodies are developed for therapeutic applications.Here, in vitro antibody selection technologies directly allow the selection of human antibodies and the corresponding genes from human antibody gene libraries. Antibody phage display is the most common way to generate human antibodies and has already yielded thousands of recombinant antibodies for research, diagnostics and therapy. Here, we describe methods for the construction of human scFv gene libraries and the antibody selection.

[Toxic effects and use of therapeutic monoclonal antibodies]

The extensive use of therapeutic monoclonal antibodies in clinic has shown that toxic effects may occur in patients. Examples such as muromonab (anti-CD3) and recently TGN1412 (anti-CD28) clearly establish that prediction of toxic effects for these targeted therapies is still complex. These undesirable effects can be classified in four categories: cytokine release syndrome, auto-immune diseases, organ toxicity and opportunistic infections. Immunogenicity, which is highly variable depending on the degree of humanization, could also potentially lead to adverse effects due to immune-complexes formation. The recent accident observed with the anti-CD28 TGN1412 has led to the conclusion that the relative confidence in the safety of monoclonal antibodies should be revised. In addition, the prediction of non-clinical models is rather limited and extrapolation of animal results to the human situation should be performed with caution. A better knowledge of the cellular target of the antibodies and of their mechanisms of action and the identification of risk factors (immune cell activation, wide expression of the target...) should improve the clinical safety of these products. .

[From the ancient serotherapy to naked antibodies: a century of successful targeted therapies]

Monoclonal antibodies and molecular engineering have renewed the ancient serotherapy, multiplying the possibilities of therapeutic interventions and providing many new clinical successes! Standing back about this history allows us to better understand the evolution of concepts underlying the therapeutic use of antibodies, as well as the maturation of the tool itself. The different principles of therapeutic targeting will be successively tackled, from their sometimes hundred year-old conception until the most recent clinical developments: antibodies neutralizing toxins and soluble antigens, anti-microbial antibodies, cytotoxic antibodies, tumour-specific antibodies, cell function -modifying antibodies, etc. This overview will finally offer the opportunity to introduce a new pharmacological classification of the entire class of unconjugated -therapeutic antibodies.

An alpha-galactosylceramide C20:2 N-acyl variant enhances anti-inflammatory and regulatory T cell-independent responses that prevent type 1 diabetes

Protection from type 1 diabetes (T1D), a T helper type 1 (Th1)-mediated disease, is achievable in non-obese diabetic (NOD) mice by treatment with alpha-galactosylceramide (alpha-GalCer) glycolipids that stimulate CD1d-restricted invariant natural killer T (iNK T) cells. While we have reported previously that the C20:2 N-acyl variant of alpha-GalCer elicits a Th2-biased cytokine response and protects NOD mice from T1D more effectively than a form of alpha-GalCer that induces mixed Th1 and Th2 responses, it remained to determine whether this protection is accompanied by heightened anti-inflammatory responses. We show that treatment of NOD mice with C20:2 diminished the activation of 'inflammatory' interleukin (IL)-12 producing CD11c(high)CD8+ myeloid dendritic cells (mDCs) and augmented the function of 'tolerogenic' DCs more effectively than treatment with the prototypical iNKT cell activator KRN7000 (alpha-GalCer C26:0) that induces Th1- and Th2-type responses. These findings correlate with a reduced capacity of C20:2 to sustain the early transactivation of T, B and NK cells. They may also explain our observation that C20:2 activated iNK T cells depend less than KRN7000 activated iNK T cells upon regulation by regulatory T cells for cytokine secretion and protection from T1D. The enhanced anti-inflammatory properties of C20:2 relative to KRN7000 suggest that C20:2 should be evaluated further as a drug to induce iNK T cell-mediated protection from T1D in humans.

Prevention of type 1 diabetes

Prevention of loss of beta cells in type 1 diabetes is a major goal of current research. Knowledge of the genetic susceptibility, increasing ability to predict who may be at risk, recognition of the potential clinical impact of residual insulin secretion after diagnosis, and development of new immunomodulatory agents have supported an increasing number of clinical trials to prevent beta-cell loss. Interventions can be targeted at 3 stages: before the development of autoimmunity (primary prevention), after autoimmunity is recognized (secondary prevention), or after diagnosis when significant numbers of beta cells remain (tertiary prevention). Thus far, several agents show promise when given shortly after diagnosis, but no interventions before diagnosis have shown benefit. Knowledge in this area has grown quickly in recent years and will continue to grow rapidly with several international collaborative efforts underway.

Immune tolerance induction by integrating innate and adaptive immune regulators

A diversity of immune tolerance mechanisms have evolved to protect normal tissues from immune damage. Immune regulatory cells are critical contributors to peripheral tolerance. These regulatory cells, exemplified by the CD4(+)Foxp3(+) regulatory T (Treg) cells and a recently identified population named myeloid-derived suppressor cells (MDSCs), regulate immune responses and limiting immune-mediated pathology. In a chronic inflammatory setting, such as allograft-directed immunity, there may be a dynamic "cross-talk" between the innate and adaptive immunomodulatory mechanisms for an integrated control of immune damage. CTLA4-B7-based interaction between the two branches may function as a molecular "bridge" to facilitate such "cross-talk." Understanding the interplays among Treg cells, innate suppressors, and pathogenic effector T (Teff) cells will be critical in the future to assist in the development of therapeutic strategies to enhance and synergize physiological immunosuppressive elements in the innate and adaptive immune system. Successful development of localized strategies of regulatory cell therapies could circumvent the requirement for very high number of cells and decrease the risks associated with systemic immunosuppression. To realize the potential of innate and adaptive immune regulators for the still elusive goal of immune tolerance induction, adoptive cell therapies may also need to be coupled with agents enhancing endogenous tolerance mechanisms.

Regulatory T cells and inhibitory cytokines in autoimmunity

Foxp3(+) regulatory T cells (T(regs)) contribute significantly to the maintenance of peripheral tolerance, but they ultimately fail in autoimmune diseases. The events that lead to T(reg) failure in controlling autoreactive effector T cells (T(effs)) during autoimmunity are not completely understood. In this review, we discuss possible mechanisms for this subversion as they relate to type 1 diabetes (T1D) and multiple sclerosis (MS). Recent studies emphasize firstly, the role of inflammatory cytokines, such as IL-6, in inhibiting or subverting T(reg) function; secondly, the issue of T(reg) plasticity; thirdly, the possible resistance of autoimmune T cells to T(reg)-mediated control; and fourthly, T(reg)-associated inhibitory cytokines TGFbeta, IL-10 and IL-35 in facilitating T(reg) suppressive activity and promoting T(reg) generation. These recent advances place a large emphasis on the local tissue specific inflammatory environment as it relates to T(reg) function and disease development.

Novel targeted therapies for autoimmunity

The emergence of new targeted therapies is rapidly improving the treatment of autoimmune disease. These drugs have been variably designed to deplete specific T and B cell subsets, interrupt receptor-ligand interactions, and inhibit the activity of inflammatory mediators relevant to immune function. Abatacept, a co-stimulatory blocker, and rituximab, a B cell depleting antibody, are among the approved therapies seeking new indications, while the newer therapies include Fc receptor-non-binding CD3-specific antibodies, IL-12/23 antibodies, an IL-6 receptor antagonist, a sphingosine-1-phosphate agonist, and small molecule inhibitors of intracellular protein kinases. Antigen-specific therapies are in their infancy, but the latest results administering glutamic acid dehydrogenase peptide to type 1 diabetics are promising. In the future, treatment strategies may increasingly explore the use of drug combinations acting at multiple sites of aberrant immunoregulation to achieve disease quiescence and immune tolerance.

Strategies to prevent type 1 diabetes

Type 1 diabetes is a chronic autoimmune condition resulting from T cell-mediated destruction of the insulin-producing cells in the islets of Langerhans. Its primary cause remains unknown, but it has been established that the clinical presentation is preceded by a long prodrome. This enables individuals at high risk of disease to be identified and offers the possibility of intervention to prevent clinical disease. Many groups are working in this field, concentrating on manipulation of environmental exposures that are potential triggers of autoimmunity and on immunomodulation strategies that aim to prevent destruction of beta-cells. Some interventions have shown promising results in early trials, but effective disease prevention remains elusive. This article reviews current progress in the field.

Prerequisites for cytokine measurements in clinical trials with multiplex immunoassays

Background

Growing knowledge about cellular interactions in the immune system, including the central role of cytokine networks, has lead to new treatments using monoclonal antibodies that block specific components of the immune system. Systemic cytokine concentrations can serve as surrogate outcome parameters of these interventions to study inflammatory pathways operative in patients in vivo. This is now possible due to novel technologies such as multiplex immunoassays (MIA) that allows detection of multiple cytokines in a single sample. However, apparently trivial underappreciated processes, (sample handling and storage, interference of endogenous plasma proteins) can greatly impact the reliability and reproducibility of cytokine detection.

Therefore we set out to investigate several processes that might impact cytokine profiles such as blood collecting tubes, duration of storage, and number of freeze thawing cycles.

Results

Since under physiological conditions cytokine concentrations normally are low or undetectable we spiked cytokines in the various plasma and serum samples. Overall recoveries ranged between 80-120%. Long time storage showed cytokines are stable for a period up to 2 years of storage at -80°C. After 4 years several cytokines (IL-1α, IL-1β, IL-10, IL-15 and CXCL8) degraded up to 75% or less of baseline values. Furthermore we show that only 2 out of 15 cytokines remained stable after several freeze-thawing cycles. We also demonstrate implementation of an internal control for multiplex cytokine immunoassays.

Conclusion

All together we show parameters which are essential for measurement of cytokines in the context of clinical trials.

Regulatory T cells and autoimmunity

PURPOSE OF REVIEW

The identification of regulatory T cells (Tregs) as regulators of immunological self-tolerance has stimulated tremendous interest in the field. Over the past 12 months, new studies have added greatly to our understanding of the role of Tregs in autoimmune disease, details of which are presented here.

RECENT FINDINGS

In this review, the mechanism of action of Tregs, their antigen specificity and their frequency and function in different autoimmune diseases is explored. Currently available data on the role of transforming growth factor-beta, the reciprocal relationship between Tregs and Th17 cells, Treg markers, and current therapeutic approaches are evaluated. Other regulatory cells, which have been recently identified to play a significant role in autoimmunity, are described.

SUMMARY

Increasing insights into understanding the complex mechanisms of action of Tregs have already led to exciting therapeutic advances. This review provides an in-depth analysis of recent advances in the field of Tregs in autoimmunity. It highlights targets for future immunomodulatory therapy that may treat and potentially cure autoimmune disease, and it identifies areas for future research.

Progress towards the clinical use of CD3 monoclonal antibodies in the treatment of autoimmunity

PURPOSE OF REVIEW

A major problem in the field of clinical transplantation, as well as in autoimmunity, is that conventional treatments rely on chronic immunosuppression that is not specific for the antigens involved and that increases the risk of infections and tumours. A major need and challenge is, therefore, to achieve 'operational tolerance', namely an inhibition of pathogenic responses in the absence of chronic immunosuppression.

RECENT FINDINGS

Here we review data showing that monoclonal antibodies to the CD3 complex, the signal transducing element of the T cell receptor, promote immune tolerance. This strategy has been the matter of extensive experimental studies in models of autoimmunity and has recently led to a successful clinical translation.

SUMMARY

Results from controlled trials in autoimmune insulin-dependent diabetes showed that CD3 monoclonal antibodies afford long-term effects following a short administration. The present challenge is to build on these results, first, to set the use of CD3 monoclonal antibodies as an established therapy in well selected subsets of patients with autoimmunity, and second, given the similarities of immune mechanisms underlying T cell-mediated autoimmune diseases and allograft rejection, to address if and how this therapeutic strategy could be extended to organ transplantation in the not-too-distant future.

Oral administration of OKT3 monoclonal antibody to human subjects induces a dose-dependent immunologic effect in T cells and dendritic cells

INTRODUCTION

Parenteral OKT3 is used to treat transplant rejection and a humanized anti-CD3 Mab has shown positive clinical effects in new onset diabetes. Oral administration of anti-CD3 has not been tested in humans, but suppresses autoimmunity in animal models. Beta-glucosylceramide enhances NKT cell and regulatory T cell activity and enhances the effects of oral anti-CD3 in animals.

MATERIALS AND METHODS

Fifteen healthy volunteers (three per group) received orally administered OKT3 over a dose range of 0.2 to 5.0 mg daily with or without beta-glucosylceramide 7.5 mg for 5 days. Safety and immune parameters were measured on days 5, 10, and 30.

RESULTS AND DISCUSSION

Oral OKT3 enhanced T cell proliferation, suppressed Th1 and Th17 responses by 43% and 41%, respectively, increased TGF-beta/IL-10 expression and decreased IL-23/IL-6 expression by dendritic cells, and affected the IgG repertoire as measured by antigen arrays. Co-administration of oral beta-glucosylceramide induced similar effects. No side effects were observed and no subjects developed human anti-mouse antibodies.

CONCLUSION

These findings demonstrate that oral anti-CD3 monoclonal antibody is safe and biologically active in humans and presents a new avenue for the treatment of autoimmune diseases.

The molecular mechanisms of immunomodulation and tolerance induction to factor VIII

Successful factor (F) VIII replacement therapy in hemophilia A patients is confounded by the generation of inhibitory anti-FVIII antibodies (Ab) in 25-30% of treated patients. These antibodies, termed 'inhibitors', significantly increase morbidity within the hemophilia population and lower the quality of life for these patients. For the past 30 years, immune tolerance induction (ITI) has been the standard therapy to elicit immunological tolerance to FVIII in the clinic. ITI works well in approximately 75% of patients, but it is expensive, can take years to show effect and is in many cases practically challenging. Therefore, new immunological tolerance induction strategies are now being designed and tested in hemophilia A animal models. This review attempts to provide a comprehensive description, at both the cellular and molecular levels, of these novel advances in tolerance induction and immunomodulation of FVIII. We begin by briefly reviewing why and how the immune system generates a protective response against exogenous FVIII. This leads to a discussion of the latest advances in FVIII tolerance/immunomodulation technology. These advances include interesting methodologies to induce B cell specific tolerance in FVIII primed humans and animals, as well as newer T cell-specific therapies that modify and/or block co-stimulation. We also discuss methods to manipulate FVIII loading of antigen-presenting cells.

Retuning the immune system: the future of type 1 diabetes therapy?

Strategies that restore immune tolerance are attracting growing interest in their potential to advance the treatment of type 1 diabetes beyond lifelong insulin therapy.

Opposing effects of TGF-beta and IL-15 cytokines control the number of short-lived effector CD8+ T cells

An effective immune response against infectious agents involves massive expansion of CD8(+) T cells. Once the infection is cleared, the majority of these effector cells die through unknown mechanisms. How is expansion controlled to maximize pathogen clearance and minimize immunopathology? We found, after Listeria infection, plasma transforming growth factor beta (TGF-beta) titers increased concomitant with the expansion of effector CD8(+) T cells. Blocking TGF-beta signaling did not affect effector function of CD8(+) T cells. However, TGF-beta controlled effector cell number by lowering Bcl-2 amounts and selectively promoting the apoptosis of short-lived effector cells. TGF-beta-mediated apoptosis of this effector subpopulation occurred during clonal expansion and contraction, whereas interleukin-15 (IL-15) promoted their survival only during contraction. We demonstrate that the number of effector CD8(+) T cells is tightly controlled by multiple extrinsic signals throughout effector differentiation; this plasticity should be exploited during vaccine design and immunotherapy against tumors and autoimmune diseases.

Normalization of obesity-associated insulin resistance through immunotherapy

Progressive obesity and its associated metabolic syndromes represent a globally growing challenge, yet mechanistic understanding and current therapeutics are unsatisfactory. We discovered that CD4+ T-lymphocytes, resident in visceral adipose tissue (VAT), control insulin-resistance in diet-induced obese (DIO) mice and likely humans. DIO VAT-associated T cells display biased TCR-Vα repertoires suggesting antigen-specific expansion. CD4+ T-lymphocyte control of glucose homeostasis is compromised in DIO when VAT accumulates pathogenic IFNγ-secreting Th1 cells, overwhelming static numbers of Th2 (CD4+GATA-3+) and regulatory Foxp3+ T cells. CD4+ T cell transfer into DIO, lymphocyte-free RAG^null mice reversed weight gain and insulin resistance predominately through Th2 cells. Brief systemic treatment with αCD3 antibody or its F(ab′)₂ fragment, restores the Th1/Foxp3+ balance and reverses insulin resistance for months, despite continuing high-fat diet. The progression of obesity-associated metabolic abnormalities is physiologically under CD4+ T cell control, with expansion of adipose tissue-resident T cells that can be manipulated by immunotherapy.

Novel humanized anti-CD3 antibodies induce a predominantly immunoregulatory profile in human peripheral blood mononuclear cells

Strategies to minimize the immunogenicity and toxicity of murine anti-CD3 antibodies (e.g. OKT3) are of special interest for organ transplantation and for the treatment of autoimmune diseases. In the present work, we have developed two humanized anti-CD3 antibodies. These molecules were shown to bind to human CD3, though less efficiently, and display less mitogenic activity than OKT3. These results prompted us to investigate whether this reduced mitogenic potential was associated with the development of anti-inflammatory properties. Indeed, in peripheral blood mononuclear cells (PBMCs), the humanized antibody versions induced a predominantly anti-inflammatory cytokine profile, in contrast with the pro-inflammatory profile induced by OKT3. Neither OKT3 nor the humanized versions induced the expression of IL-4, IL-2 or TGF-beta. Both humanized antibodies induced significantly lower production of IFN-gamma and IL-5 and slightly higher production of IL-10 than OKT3. This immunomodulatory profile was most evident by the 80-fold higher ratio of IL-10/IFN-gamma production in PBMCs cultured in the presence of the humanized antibodies, compared to those stimulated with OKT3. Furthermore, these humanized anti-CD3 antibodies induced a late FOXP3 gene expression while OKT3 led to a more transient expression of FOXP3. Taken our results, we suggest that these humanized anti-CD3 antibodies may promote the development of T cells with immunoregulatory activity.

Lethal effect of CD3-specific antibody in mice deficient in TGF-beta1 by uncontrolled flu-like syndrome

CD3-specific Ab therapy results in a transient, self-limiting, cytokine-associated, flu-like syndrome in experimental animals and in patients, but the underlying mechanism for this spontaneous resolution remains elusive. By using an in vivo model of CD3-specific Ab-induced flu-like syndrome, we show in this paper that a single injection of sublethal dose of the Ab killed all TGF-beta1(-/-) mice. The death of TGF-beta1(-/-) mice was associated with occurrence of this uncontrolled flu-like syndrome, as demonstrated by a sustained storm of systemic inflammatory TNF and IFN-gamma cytokines. We present evidence that deficiency of professional phagocytes to produce TGF-beta1 after apoptotic T cell clearance may be responsible, together with hypersensitivity of T cells to both activation and apoptosis, for the uncontrolled inflammation. These findings indicate a key role for TGF-beta1 and phagocytes in protecting the recipients from lethal inflammation and resolving the flu-like syndrome after CD3-specific Ab treatment. The study may also provide a novel molecular mechanism explaining the early death in TGF-beta1(-/-) mice.

Mouse Models for Type 1 Diabetes

Our understanding of the genetics, aetiology and pathogenesis of Type 1 Diabetes (T1D) was propelled by the discovery of animal models of T1D in the late 1970s and early 1980s, particularly the non-obese diabetic (NOD) mouse. Since then, transgenic and gene-targeting technologies allowed the generation of many models with reduced genetic and pathogenic complexity. These models allowed researchers to zoom in on specific aspects of this complex disease. In this review, we provide an overview of currently available mouse models for T1D.

Advances in Type 1 diabetes therapeutics: immunomodulation and beta-cell salvage

Refinements in our understanding of the pathogenic mechanisms of Type 1 diabetes from studies of animal models and clinical observation have led to new clinical trials to prevent disease progression and restore the loss of beta-cells that defines the disease. Antigen-specific agents have shown initial promise and non-antigen-specific agents now have improved safety compared with older agents. In addition, preclinical studies with other agents have shown efficacy. Ultimately, a combination of immunologic and cellular therapies may be needed to restore metabolic control. Agents that augment recovery of dysfunctional beta-cells, and other compounds that may be able to induce beta-cell replication, are logical additions once immune tolerance is achieved.

Stem cells to pancreatic beta-cells: new sources for diabetes cell therapy

The number of patients worldwide suffering from the chronic disease diabetes mellitus is growing at an alarming rate. Insulin-secreting beta-cells in the islet of Langerhans are damaged to different extents in diabetic patients, either through an autoimmune reaction present in type 1 diabetic patients or through inherent changes within beta-cells that affect their function in patients suffering from type 2 diabetes. Cell replacement strategies via islet transplantation offer potential therapeutic options for diabetic patients. However, the discrepancy between the limited number of donor islets and the high number of patients who could benefit from such a treatment reflects the dire need for renewable sources of high-quality beta-cells. Human embryonic stem cells (hESCs) are capable of self-renewal and can differentiate into components of all three germ layers, including all pancreatic lineages. The ability to differentiate hESCs into beta-cells highlights a promising strategy to meet the shortage of beta-cells. Here, we review the different approaches that have been used to direct differentiation of hESCs into pancreatic and beta-cells. We will focus on recent progress in the understanding of signaling pathways and transcription factors during embryonic pancreas development and how this knowledge has helped to improve the methodology for high-efficiency beta-cell differentiation in vitro.

T cell-mediated immunoregulation in the gastrointestinal tract

In the intestinal tract, only a single layer of epithelial cells separates innate and adaptive immune effector cells from a vast amount of antigens. Here, the immune system faces a considerable challenge in tolerating commensal flora and dietary antigens while preventing the dissemination of potential pathogens. Failure to tightly control immune reactions may result in detrimental inflammation. In this respect, 'conventional' regulatory CD4(+) T cells, including naturally occurring and adaptive CD4(+) CD25(+) Foxp3(+) T cells, Th3 and Tr1 cells, have recently been the focus of considerable attention. However, regulatory mechanisms in the intestinal mucosa are highly complex, including adaptations of nonhaematopoietic cells and innate immune cells as well as the presence of unconventional T cells with regulatory properties such as resident TCRgammadelta or TCRalphabeta CD8(+) intraepithelial lymphocytes. This review aims to summarize the currently available knowledge on conventional and unconventional regulatory T cell subsets (Tregs), with special emphasis on clinical data and the potential role or malfunctioning of Tregs in four major human gastrointestinal diseases, i.e. inflammatory bowel diseases, coeliac disease, food allergy and colorectal cancer. We conclude that the clinical data confirms some but not all of the findings derived from experimental animal models.

Rapamycin prevents and breaks the anti-CD3-induced tolerance in NOD mice

OBJECTIVE

Non-Fc-binding anti-CD3-specific antibodies represent a promising therapy for preserving C-peptide production in subjects with recent-onset type 1 diabetes. However, the mechanisms by which anti-CD3 exerts its beneficial effect are still poorly understood, and it is questionable whether this therapeutic approach will prove durable with regard to its ability to impart metabolic preservation without additional actions designed to maintain immunological tolerance. We used the NOD mouse model to test whether rapamycin, a compound well-known for its immunomodulatory activity in mice and humans, could increase the therapeutic effectiveness of anti-CD3 treatment in type 1 diabetes.

RESEARCH DESIGN AND METHODS

Rapamycin was administered to diabetic NOD mice simultaneously with anti-CD3 or to NOD mice cured by anti-CD3 therapy. The ability of this combined therapy to revert type 1 diabetes and maintain a state of long-term tolerance was monitored and compared with that of anti-CD3 therapy alone.

RESULTS

Rapamycin inhibited the ability of anti-CD3 to revert disease without affecting the frequency/phenotype of T-cells. Rapamycin also reinstated diabetes in mice whose disease was previously reversed by anti-CD3. Withdrawal of rapamycin in these latter animals promptly restored a normoglycemic state.

CONCLUSIONS

Our findings indicate that, when combined with anti-CD3, rapamycin exerts a detrimental effect on the disease outcome in NOD mice for as long as it is administered. These results suggest strong caution with regard to combining these treatments in type 1 diabetic patients.

Parameters influencing antigen-specific immunotherapy for Type 1 diabetes

Type 1 diabetes (T1D) is a T cell-mediated autoimmune disease in which the insulin producing beta cells are destroyed. Antigen-based immunotherapy provides an approach to selectively tolerize pathogenic beta cell-specific T cells, while leaving the remainder of the immune system intact. In this article, we discuss our group's experience in defining the parameters that impact the efficacy of beta cell antigen "vaccination" for the prevention and treatment of T1D.

Apotopes and the biliary specificity of primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is characterized by antimitochondrial antibodies (AMAs), directed to the E2 component of the pyruvate dehydrogenase complex (PDC-E2). Notwithstanding the presence of mitochondria in virtually all nucleated cells, the destruction in PBC is limited to small intrahepatic bile ducts. The reasons for this tissue specificity remain unknown, although biliary epithelial cells (BECs) uniquely preserve the PDC-E2 epitope following apoptosis. Notably, PBC recurs in an allogeneic transplanted liver, suggesting generic rather than host PBC-specific susceptibility of BEC. We used cultured human intrahepatic BECs (HIBECs) and other well-characterized cell lines, including, HeLa, CaCo-2 cells, and nontransformed human keratinocytes and bronchial epithelial cells, to determine the integrity and specific localization of PDC-E2 during induced apoptosis. All cell lines, both before and after apoptosis, were tested with sera from patients with PBC (n = 30), other autoimmune liver and rheumatic diseases (n = 20), and healthy individuals (n = 20) as well as with a mouse monoclonal antibody against PDC-E2 and AMA with an immunoglobulin A isotype. PDC-E2 was found to localize unmodified within apoptotic blebs of HIBECs, but not within blebs of various other cell lineages studied. The fact that AMA-containing sera reacted with PDC-E2 on apoptotic BECs without a requirement for permeabilization suggests that the autoantigen is accessible to the immune system during apoptosis.

CONCLUSION

Our data indicate that the tissue (cholangiocyte) specificity of the autoimmune injury in PBC is a consequence of the unique characteristics of HIBECs during apoptosis and can be explained by exposure to the immune system of intact immunoreactive PDC-E2 within apoptotic blebs.

Prevention of allograft rejection by amplification of Foxp3(+)CD4(+)CD25(+) regulatory T cells

CD4(+)CD25(+) T cells were identified originally as potent suppressors of autoimmunity and were later termed "natural regulatory T cells" or nTreg cells. Subsequently, a transcription factor called forkhead box protein 3 (Foxp3) was identified to be a critical regulator for Treg differentiation and function. Foxp3(+)CD4(+)CD25(+) Treg cells have been increasingly documented to suppress allograft rejection and to mediate allograft tolerance in transplantation. In this article, the authors review current approaches for amplification of allo-specific Foxp3(+)CD4(+)CD25(+) Treg cells for prevention of allograft rejection and induction of allo-specific transplant tolerance.

Tolerance-inducing immunosuppressive strategies in clinical transplantation: an overview

The significant development of immunosuppressive drug therapies within the past 20 years has had a major impact on the outcome of clinical solid organ transplantation, mainly by decreasing the incidence of acute rejection episodes and improving short-term patient and graft survival. However, long-term results remain relatively disappointing because of chronic allograft dysfunction and patient morbidity or mortality, which is often related to the adverse effects of immunosuppressive treatment. Thus, the induction of specific immunological tolerance of the recipient towards the allograft remains an important objective in transplantation. In this article, we first briefly describe the mechanisms of allograft rejection and immune tolerance. We then review in detail current tolerogenic strategies that could promote central or peripheral tolerance, highlighting the promises as well as the remaining challenges in clinical transplantation. The induction of haematopoietic mixed chimerism could be an approach to induce robust central tolerance, and we describe recent encouraging reports of end-stage kidney disease patients, without concomitant malignancy, who have undergone combined bone marrow and kidney transplantation. We discuss current studies suggesting that, while promoting peripheral transplantation tolerance in preclinical models, induction protocols based on lymphocyte depletion (polyclonal antithymocyte globulins, alemtuzumab) or co-stimulatory blockade (belatacept) should, at the current stage, be considered more as drug-minimization rather than tolerance-inducing strategies. Thus, a better understanding of the mechanisms that promote peripheral tolerance has led to newer approaches and the investigation of individualized donor-specific cellular therapies based on manipulated recipient regulatory T cells.

Anti-CD3 prevents factor VIII inhibitor development in hemophilia A mice by a regulatory CD4+CD25+-dependent mechanism and by shifting cytokine production to favor a Th1 response

Non–Fc-receptor binding anti-CD3 Ab therapy, in the setting of several different autoimmune disorders, can induce antigen-specific and long-lasting immunologic tolerance. Because factor VIII (FVIII) inhibitor formation is the most serious treatment-related complication for hemophilia A patients, we tested the efficacy of anti-CD3 to prevent FVIII inhibitor formation in hemophilia A BALB/c and C57BL/6 mice. A short course of low-dose anti-CD3 significantly increased expression of CD25 and the proportion of CD4+CD25+ regulatory T cells in the spleen and potently prevented the production of inhibitory and non-neutralizing anti-FVIII antibodies in both strains of mouse. Depleting the CD4+CD25+ cells during anti-CD3 therapy completely ablated tolerance to FVIII. Further phenotypic characterization of regulatory cells in tolerant mice showed a consistently higher number of CD4+GITR+ and CD4+FoxP3+ cells in both strains of mice. In addition, in tolerant C57BL/6 mice we observed an increase in CD4+CD25+CTLA-4+ and CD4+CD25+mTGF-β1+ cells. Finally, in vitro cytokine profiling demonstrated that splenocytes from tolerant BALB/c and C57BL/6 were polarized toward a Th1-immune response. Taken together, these findings indicate that anti-CD3 induces tolerance to FVIII and that the mechanism(s) regulating this response almost certainly occurs through the generation of several distinct regulatory T-cell lineages and by influencing cytokine production and profile.