Use of monoclonal antibodies to T-cell subsets for immunologic monitoring and treatment in recipients of renal allografts

Animal models for transplant immunology: bridging bench to bedside

The progress of transplantation has been propelled forward by animal experiments. Animal models have not only provided opportunities to understand complex immune mechanisms in transplantation but also served as a platform to assess therapeutic interventions. While small animals have been instrumental in uncovering new therapeutic concepts related to immunosuppression and immune tolerance, the progression to human trials has largely been driven by studies in large animals. Recent research has begun to explore the potential of porcine organs to address the shortage of available organs. The consistent progress in transplant immunology research can be attributed to a thorough understanding of animal models. This review provides a comprehensive overview of the available animal models, detailing their modifications, strengths, and weaknesses, as well as their historical applications, to aid researchers in selecting the most suitable model for their specific research needs.

TCF1highPD-1+Ly108+CD8+ T Cells Are Associated with Graft Preservation in Sensitized Mice Treated with Non-Fc Receptor-Binding CD3 Antibodies

The non-Fc-binding anti-CD3 Ab [anti-CD3F(ab')2] can induce graft acceptance depending on the therapeutic window in a rodent heart transplant model. The delayed protocol allows for early graft infiltration of lymphocytes, which may behave in an inhibitory manner. We investigated the most effective protocol for anti-CD3F(ab')2 in sensitized conditions to confirm the evidence for clinical application. C57BL/6 mice were sensitized with BALB/c tail skin grafts and transplanted with BALB/c heart grafts at 8-12 wk after sensitization. Fifty micrograms of anti-CD3F(ab')2 was administered daily for 5 consecutive days on days 1-5 (day 1 protocol) or days 3-7 (delayed protocol). In nonsensitized mice, the delayed protocol significantly prolonged graft survival after transplantation from BALB/c to naive B6 (median survival time [MST], >100 d). In contrast, the delayed protocol was unable to prevent graft rejection in sensitized mice (MST, 5 d). A significantly increased percentage of granzyme B+ CD8+ T cells was observed in the graft on day 3 posttransplantation in sensitized conditions. Further, the day 1 protocol significantly prolonged graft survival (MST, 18 d), even in sensitized conditions. Day 1 treatment significantly increased the percentage of Foxp3+CD25+CD4+ T cells and phenotypically changed CD8+ T cells in the graft (i.e., caused a significant increase in the proportion of Ly108+TCF1highPD-1+CD8+ T cells). In conclusion, different timings of delayed anti-CD3F(ab')2 treatment promoted allograft preservation in association with phenotypic changes in CD4+ and CD8+ T cells in the graft under sensitized conditions.

Paul Russell: the transcendentalist surgeon of America

I first met Dr. Russell in the Fall of 2000 at the Massachusetts General Hospital (MGH). I entered the Russell-Round-Room which was packed with surgeons and physicians of MGH, among whom there was no shortage of self-esteem. I came across a handsome man, full of vigor and competence, standing still for nearly two hours in the corner of the room near the blackboard. He was remarkably attentive to the questions, for which he had very concise responses. He was soft-spoken with an inviting smile, and had a welcoming, modest air about him. Despite his remarkable academic achievements, he was strikingly unassuming and serene -- features likely ingrained in his very nature.

Teplizumab: type 1 diabetes mellitus preventable?

Type 1 diabetes mellitus (T1DM) is an autoimmune condition driven by T lymphocytes that specifically declines the function of beta cells of pancreas. Immunological treatments aim to stop this decline in β-cell function thus preventing TIDM. Although TIDM occur at any age, it is one of the most common chronic disorders in children. T1DM accounts for 5 to 10% of all cases of diabetes amounting 21-42 million affected persons. Teplizumab is a novel drug recently approved by the US FDA for the treatment of T1DM. This drug reduces abnormal glucose tolerance who are at high risk for developing T1DM and have antibodies suggesting an immunological attack on their pancreas. A 14-day infusion of the drug prevents T cells' attack of the insulin-producing cells of the pancreas. Adverse events due to teplizumab reported so far mild and of limited duration. This review gives an overview of the preclinical and clinical research on teplizumab for their role in new-onset T1DM.

100 years post-insulin: immunotherapy as the next frontier in type 1 diabetes

Type 1 diabetes (T1D) is an autoimmune disease characterised by T cell-mediated destruction of the insulin-producing β cells in the pancreas. Similar to other autoimmune diseases, the incidence of T1D is increasing globally. The discovery of insulin 100 years ago dramatically changed the outlook for people with T1D, preventing this from being a fatal condition. As we celebrate the centenary of this milestone, therapeutic options for T1D are once more at a turning point. Years of effort directed at developing immunotherapies are finally starting to pay off, with signs of progress in new onset and even preventative settings. Here, we review a selection of immunotherapies that have shown promise in preserving β cell function and highlight future considerations for immunotherapy in the T1D setting.

L’immunologie : les bases pour comprendre les traitements actuels et à venir

Le système immunitaire intègre un ensemble d’acteurs essentiellement présents dans les organes lymphoides et les tissus qui analysent les modifications avec notre interface essentiellement extérieure. Les acteurs sont aussi bien cellulaires : les cellules de l’immunité acquise lymphocytes T et B qu’innée et de type innée associé à des facteurs diffusibles qu’il s’agisse de cytokines et d’anticorps. Ce système présente des différences de fonctionnement dans les différents tissus et sous l’influence des agressions. Le cancer étant en l’espèce, un type particulier d’agression. L’immunologie est une science en mouvement qui évolue en continu. Les espoirs portés par elle sont justifiés mais les bases fondamentales encore en construction. Les nouvelles thérapies qui ont fait leurs preuves dans les dix années passées le démontrent. Les premières vagues portent sur la cosignalisation, les cellules de type CAR-T et les anticorps bispécifiques. Nous allons essayer de nous projeter sur les étapes suivantes avec les attentes portant sur la cytokine, la vaccination, les modifications du micro-environnement tumoral et les cellules innées et de type innée.

© 2020 SPLF. Publié par Elsevier Masson SAS. Tous droits réservés.

History of organ transplantation and the development of key immunosuppressants

The history of organ transplantation is limited to the last century. To overcome the barrier of the host immune system, which results in transplant rejection, the pioneers of transplantation achieved their first success by performing a kidney transplantation between identical twins. This achievement led the transplant clinicians to perform transplantations with immunological barriers present. Strategies such as whole-body irradiation combined with steroids yielded success in kidney transplantation between non-identical twins and siblings. However, owing to the toxicity related to irradiation, the paradigm shifted to the use of immunosuppressants. Azathioprine, steroids, and anti-lymphocyte globulin became the first multiple immunosuppressive regimens. With the introduction of cyclosporine, the 1-year survival rate increased by more than 80%. Cyclosporine, azathioprine, and steroids became the new standard maintenance regimens until the introduction of tacrolimus and mycophenolate mofetil, which replaced cyclosporine and azathioprine, respectively. The most recent change in immunosuppressants was the development of monoclonal antibodies with specific binding sites, such as CD20 (rituximab) and CD25 (basiliximab). With the innovation of molecular engineering and new insights into the costimulatory pathways, new molecules are under investigation in the field of transplantation.

Immunomodulatory Nanosystems

Immunotherapy has emerged as an effective strategy for the prevention and treatment of a variety of diseases, including cancer, infectious diseases, inflammatory diseases, and autoimmune diseases. Immunomodulatory nanosystems can readily improve the therapeutic effects and simultaneously overcome many obstacles facing the treatment method, such as inadequate immune stimulation, off-target side effects, and bioactivity loss of immune agents during circulation. In recent years, researchers have continuously developed nanomaterials with new structures, properties, and functions. This Review provides the most recent advances of nanotechnology for immunostimulation and immunosuppression. In cancer immunotherapy, nanosystems play an essential role in immune cell activation and tumor microenvironment modulation, as well as combination with other antitumor approaches. In infectious diseases, many encouraging outcomes from using nanomaterial vaccines against viral and bacterial infections have been reported. In addition, nanoparticles also potentiate the effects of immunosuppressive immune cells for the treatment of inflammatory and autoimmune diseases. Finally, the challenges and prospects of applying nanotechnology to modulate immunotherapy are discussed.

Outcomes of Canakinumab Treatment in Recipients of Kidney Transplant With Familial Mediterranean Fever: A Case Series

Familial Mediterranean fever (FMF) is an important and preventable cause of chronic kidney disease due to secondary amyloidosis. Although colchicine is the first-line therapy in patients with FMF with 60% to 65% complete remission rates, 5% to 10% of patients are colchicine-resistant and 5% to 10% of them are intolerant to the therapy. Anti-interleukin-1 agents, such as anakinra and canakinumab, are safe and efficient therapeutic options in patients with colchicine resistance or intolerance. However, the data on management of these targeted agents is limited in recipients of kidney transplant (RKT). In this case series, we aim to share our experience on canakinumab therapy of 4 RKTs with FMF-related amyloidosis, who were followed up in our clinic between 2010 and 2017. All of the 4 patients with end-stage renal disease were colchicine- resistant and on other alternative therapies, which provided poor disease control. For efficient control of secondary amyloidosis, canakinumab therapy was initiated in 1 of the patients before the renal transplant, and for the remaining patients after renal transplant. Any serious adverse effect, development of proteinuria, or graft dysfunction has not been observed in any of the patients. Under the canakinumab treatment, complete clinical responses, prevent typical familial Mediterranean fever attacks with fever and arthritis and abdominal pain, normalized serum amyloid A and C-reactive protein levels were achieved in all patients. Canakinumab treatment is a safe and effective therapeutic option for RKTs with FMF who are resistant or intolerant to colchicine and anakinra.

Targeted delivery of immune therapeutics to lymph nodes prolongs cardiac allograft survival

The targeted delivery of therapeutic drugs to lymph nodes (LNs) provides an unprecedented opportunity to improve the outcomes of transplantation and immune-mediated diseases. The high endothelial venule is a specialized segment of LN vasculature that uniquely expresses peripheral node addressin (PNAd) molecules. PNAd is recognized by MECA79 mAb. We previously generated a MECA79 mAb-coated microparticle (MP) that carries tacrolimus. Although this MP trafficked to LNs, it demonstrated limited therapeutic efficacy in our transplant model. Here, we have synthesized a nanoparticle (NP) as a carrier of anti-CD3, and optimized the conjugation strategy to coat the NP surface with MECA79 mAb (MECA79-anti-CD3-NP) to enhance LN accumulation. As compared with nonconjugated NPs, a significantly higher quantity of MECA79-NPs accumulated in the draining lymph node (DLN). Many MECA79-NPs underwent internalization by T cells and dendritic cells within the LNs. Short-term treatment of murine cardiac allograft recipients with MECA79-anti-CD3-NP resulted in significantly prolonged allograft survival in comparison with the control groups. Prolonged graft survival following treatment with MECA79-anti-CD3-NP was characterized by a significant increase in intragraft and DLN Treg populations. Treg depletion abrogated the prolongation of heart allograft survival. We believe this targeted approach of drug delivery could redefine the methods of administering immune therapeutics in transplantation.

Camelid Single-Domain Antibodies: Historical Perspective and Future Outlook

Tremendous effort has been expended over the past two and a half decades to understand many aspects of camelid heavy chain antibodies, from their biology, evolution, and immunogenetics to their potential applications in various fields of research and medicine. In this article, I present a historical perspective on the development of camelid single-domain antibodies (sdAbs or V_HHs, also widely known as nanobodies) since their discovery and discuss the advantages and disadvantages of these unique molecules in various areas of research, industry, and medicine. Commercialization of camelid sdAbs exploded in 2001 with a flurry of patents issued to the Vrije Universiteit Brussel (VUB) and later taken on by the Vlaams Interuniversitair Instituut voor Biotechnologie (VIB) and, after 2002, the VIB-founded spin-off company, Ablynx. While entrepreneurial spirit has certainly catalyzed the exploration of nanobodies as marketable products, IP restrictions may be partially responsible for the relatively long time span between the discovery of these biomolecules and their entry into the pharmaceutical market. It is now anticipated that the first V_HH-based antibody drug, Caplacizumab, a bivalent anti-vWF antibody for treating rare blood clotting disorders, may be approved and commercialized in 2018 or shortly thereafter. This elusive first approval, along with the expiry of key patents, may substantially alter the scientific and biomedical landscape surrounding camelid sdAbs and pave the way for their emergence as mainstream biotherapeutics.

Inhibition of T cell-mediated inflammation in uveitis by a novel anti-CD3 antibody

Background

A novel anti-mouse CD3ε antibody, Dow2, recognizes mouse CD3ε without activating T cells and suppresses T-cell activation. The purpose of this study was to determine whether Dow2 can inhibit T cells in uveitis.

Methods

Experimental autoimmune uveitis (EAU) was induced in mice by immunization with retinal peptides, followed by administration of Dow2. Inflammation was evaluated by color fundus photography, optical coherence tomography, fluorescein angiography, and histology. Intraocular cells from EAU mice were used to examine the effect of Dow2 on retinal antigen-specific T cells. The effects of Dow2, conventional CD3ε antibodies, and isotype control immunoglobulin G (IgG) on splenic T cells were compared by assessing cell proliferation by the mixed lymphocyte reaction assay, inflammatory cytokine production by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry, and gene expression by quantitative reverse-transcription polymerase chain reaction (RT-PCR). T-cell subpopulations were characterized by flow cytometry to evaluate the expression of CD4, CD8, CD44, CD62L, and Foxp3.

Results

Dow2 significantly reduced T-cell activation and counteracted activation associated with anti-CD3ε antibodies. Unlike conventional CD3ε antibodies, Dow2 treatment did not upregulate T helper (Th)1-/Th17-associated gene expression and cytokine production in splenic T cells. Interferon (IFN)-γ production by retinal antigen-specific T cells was also significantly reduced. Ocular inflammation was significantly reduced in Dow2-treated EAU mice compared to control EAU mice, with fewer T cells infiltrating into the retinas of Dow2-treated EAU mice. In immunohistochemistry, Th1 and Th17 cells invaded the retina in control EAU mice but not Dow2-treated EAU mice. No effects on peripheral T-cell numbers were observed following systemic administration of Dow2.

Conclusion

The novel anti-CD3 antibody Dow2 can inhibit T cell-mediated inflammation in uveitis models. Thus, inhibition of T-cell activation by anti-CD3 therapy with this new antibody may protect uveitis patients from severe ocular inflammation.

Antibody mimicry, receptors and clinical applications

This review focuses on the concept of antibodies acting as receptor agonists and antagonists, and on the potential relevance of this notion in applied medicine. Antibodies are composed of three functional units: two antigen-binding fragments (Fabs) that confer antigen specificity and one constant fragment (Fc) linking antibodies to immune effector functions. The proof-of-concept that large amounts of highly specific and homogeneous antibodies could be produced was provided in 1975 by César Milstein and Georges Köhler. These monoclonal antibody (mAb) reagents started a revolution in medical research, diagnostics, and clinical applications. Alongside diagnostic applications, mAbs were successfully used in vivo: (i) to bind (neutralize/antagonize) antigens expressed on the surface of tumor cells; (ii) to activate immune effector mechanisms; (iii) to crosslink plasma membrane receptors and hence activate therapeutic signaling pathways; and lastly, (iv) the technique was expanded to produce bispecific mAbs, which can bind two different antigens while retaining the ability to activate immune effector functions. The abilities of mAbs to bind, transduce signals, and exert immunostimulatory agonistic capacities are the central issues of this review. The starting point is that some mAbs operate as molecular agonists, substituting for the natural ligand of the receptor. Our analysis is restricted to mAbs that act as receptor agonist/antagonists by either mimicking ligand binding, or through allosteric modulation mediated by binding sites that are topographically distinct from the orthosteric binding site. Functional considerations based on the agonistic stimulation of human CD38 by specific mAbs as surrogate ligands are described as examples of the features of such molecules.

Bacterial production and structure-functional validation of a recombinant antigen-binding fragment (Fab) of an anti-cancer therapeutic antibody targeting epidermal growth factor receptor

Fragment engineering of monoclonal antibodies (mAbs) has emerged as an excellent paradigm to develop highly efficient therapeutic and/or diagnostic agents. Engineered mAb fragments can be economically produced in bacterial systems using recombinant DNA technologies. In this work, we established recombinant production in Escherichia coli for monovalent antigen-binding fragment (Fab) adopted from a clinically used anticancer mAB drug cetuximab targeting epidermal growth factor receptor (EGFR). Recombinant DNA constructs were designed to express both polypeptide chains comprising Fab in a single vector and to secrete them to bacterial periplasmic space for efficient folding. Particularly, a C-terminal engineering to confer an interchain disulfide bond appeared to be able to enhance its heterodimeric integrity and EGFR-binding activity. Conformational relevance of the purified final product was validated by mass spectrometry and crystal structure at 1.9 Å resolution. Finally, our recombinant cetuximab-Fab was found to have strong binding affinity to EGFR overexpressed in human squamous carcinoma model (A431) cells. Its binding ability was comparable to that of cetuximab. Its EGFR-binding affinity was estimated at approximately 0.7 nM of Kd in vitro, which was quite stronger than the binding affinity of natural ligand EGF. Hence, the results validate that our construction could serve as an efficient platform to produce a recombinant cetuximab-Fab with a retained antigen-binding functionality.

Treatment of new onset type 1 diabetes with teplizumab: successes and pitfalls in development

INTRODUCTION

Type 1 diabetes is an organ-specific autoimmune disease, characterized by selective destruction of insulin-producing pancreatic β-cells by T-cell-mediated inflammation. Beginning with studies of cyclosporin A in the 1980s, but with more activity in the past decade, there have been a number of clinical trials to test whether immunotherapies can arrest the decline in C-peptide, which is associated with progression of type 1 diabetes leading to the metabolic instability that characterizes the disease. One of the most promising agents, teplizumab , is an FcR-nonbinding anti-CD3 monoclonal antibody that has been tested in Phase II - III clinical trials and was shown to preserve the C-peptide levels and reduce the need for exogenous insulin.

AREAS COVERED

In this review, we discuss the recent update on clinical data obtained from trials of teplizumab in type 1 diabetes, the drug's postulated mechanism of action and the identification of responders to therapy. We highlight the results of recent trials as well as the lessons that have been learned from the clinical trials involving selection of end points and the inclusion of diverse study populations.

EXPERT OPINION

Teplizumab has been shown to preserve β cell function in patients; however, it does not represent a 'cure' for patients, and its efficacy does entail a significant advance in arresting the progression of the disease toward complete insulin deficiency and reliance on exogenous insulin.

Biotherapies targeting T and B cells: from immune suppression to immune tolerance

The field of immunotherapy has undergone a major rejuvenation with the development of monoclonal antibodies and fusion proteins targeting specialized receptors of T and B lymphocytes or cytokines relevant for the differentiation of these cells. This review will focus on autoimmunity, probably the field that benefited most from these new biological therapies that very significantly impacted the modalities of patient's care. The aim is to present the agents which constitute major disease modifying drugs for the treatment of chronic invalidating autoimmune diseases. In doing so, we shall distinguish between agents that globally depress immune responses and those that may selectively target the harmful autoimmune response over long-term while preserving the capacity of the host to react normally to exogenous antigens, in other words, agents promoting 'operational tolerance'.

Apoptotic cell-linked immunoregulation: implications for promoting immune tolerance in transplantation

The induction of alloantigen-specific immune tolerance is the "Holy-Grail" in transplantation. Although it had been previously demonstrated that transient depletion of T cells through apoptosis could lead to long-term immune tolerance, the underlying mechanism responsible for this tolerance induction and maintenance was unknown. In this short article, a novel mechanism for long-term immune tolerance via transient T cell apoptosis will be discussed, based on our recent findings in a CD3-specific antibody treatment-induced immune tolerance mouse model. Transforming growth factor-β, which is produced by immature dendritic cells whilst they phagocytose apoptotic T cells and by macrophages, plays an important role in initiating long-term immune tolerance. A possible model of how allospecific-immune tolerance can be induced in order to prevent allograft rejection in transplantation will be also proposed.

A Murine Viral Outgrowth Assay to Detect Residual HIV Type 1 in Patients With Undetectable Viral Loads

BACKGROUND

Sensitive assays are needed for detection of residual human immunodeficiency virus (HIV) in patients with undetectable plasma viral loads to determine whether eradication strategies are effective. The gold standard quantitative viral outgrowth assay (QVOA) underestimates the magnitude of the viral reservoir. We sought to determine whether xenograft of leukocytes from HIV type 1 (HIV)-infected patients with undetectable plasma viral loads into immunocompromised mice would result in viral amplification.

METHODS

Peripheral blood mononuclear cells or purified CD4(+) T cells from HIV or simian immunodeficiency virus (SIV)-infected subjects with undetectable plasma viral loads were adoptively transferred into NOD.Cg-Prkdc(scid)Il2rg(tm1Wjl)/SzJ (NSG) mice. The mice were monitored for viremia following depletion of human CD8(+) T cells to minimize antiviral activity. In some cases, humanized mice were also treated with activating anti-CD3 antibody.

RESULTS

With this murine viral outgrowth assay (MVOA), we successfully amplified replication-competent HIV or SIV from all subjects tested, including 5 HIV-positive patients receiving suppressive antiretroviral therapy (ART) and 6 elite controllers or suppressors who were maintaining undetectable viral loads without ART, including an elite suppressor from whom we were unable to recover virus by QVOA.

CONCLUSIONS

Our results suggest that the MVOA has the potential to serve as a powerful tool to identify residual HIV in patients with undetectable viral loads.

From monoclonal antibodies to chimeric antigen receptors for the treatment of human malignancies

Monoclonal antibodies (mAbs) and their directly derived cell-based application known as chimeric antigen receptors (CARs) ensue from the need to develop novel therapeutic strategies that retain high anti-tumor activity, but carry reduced toxicity compared to conventional chemo- and radiotherapies. In this concise review article, we will summarize the application of antibodies designed to target antigens expressed by tumor cells, and the transition from these antibodies to the generation of CARs.

A putative OTU domain-containing protein 1 deubiquitinating enzyme is differentially expressed in thyroid cancer and identifies less-aggressive tumours

Background:

This study aimed to identify novel biomarkers for thyroid carcinoma diagnosis and prognosis.

Methods:

We have constructed a human single-chain variable fragment (scFv) antibody library that was selected against tumour thyroid cells using the BRASIL method (biopanning and rapid analysis of selective interactive ligands) and phage display technology.

Results:

One highly reactive clone, scFv-C1, with specific binding to papillary thyroid tumour proteins was confirmed by ELISA, which was further tested against a tissue microarray that comprised of 229 thyroid tissues, including: 110 carcinomas (38 papillary thyroid carcinomas (PTCs), 42 follicular carcinomas, 30 follicular variants of PTC), 18 normal thyroid tissues, 49 nodular goitres (NG) and 52 follicular adenomas. The scFv-C1 was able to distinguish carcinomas from benign lesions (P=0.0001) and reacted preferentially against T1 and T2 tumour stages (P=0.0108). We have further identified an OTU domain-containing protein 1, DUBA-7 deubiquitinating enzyme as the scFv-binding antigen using two-dimensional polyacrylamide gel electrophoresis and mass spectrometry.

Conclusions:

The strategy of screening and identifying a cell-surface-binding antibody against thyroid tissues was highly effective and resulted in a useful biomarker that recognises malignancy among thyroid nodules and may help identify lower-risk cases that can benefit from less-aggressive management.

Delayed anti-CD3 therapy in a mouse heart transplant model induced tolerance and long-term survival of allograft: achieving tolerance

Goto R, You S, Zaitsu M, Chatenoud L, Wood KJ. Delayed anti-CD3 therapy results in depletion of alloreactive T cells and the dominance of Foxp3(+) CD4(+) graft infiltrating cells. Am. J. Transplant. 13(7), 1655-1664 (2013). Humanized Fc receptor nonbinding anti-CD3 monoclonal antibodies have been tested in patients with autoimmune diseases with the goal of inducing immune tolerance. However, the timing of drug administration may be an important determinant of the biologic effects, since not all T cells are equally affected, and there may be different subsets of cells involved during the evolution of immune responses. The study by Goto et al. showed that delayed administration of anti-CD3 therapy was more effective in depleting alloreactive T cells than administration at the time of transplant, and resulted in long-term survival of the graft by promoting infiltration of CD4 Tregs into the graft.

New generation CD3 monoclonal antibodies: are we ready to have them back in clinical transplantation?

PURPOSE OF REVIEW

The continuing problem of late graft loss and immunosuppressive drug toxicity forces us to explore new treatments for the induction of transplant tolerance. Monoclonal antibodies targeting molecules implicated in lymphocyte activation, in particular CD3/TCR, constitute a promising strategy.

RECENT FINDINGS

Promising results were obtained from the use of antibodies targeting CD3/TCR, coreceptors or costimulatory pathways as tolerance-promoting tools in experimental transplantation. These antibodies do not uniformly depress the immune system but act in an antigen-specific manner by preferentially targeting effector T cells while preserving regulatory T cells. However, translation to the clinic proved to be more difficult than expected. New generation CD3 antibodies, currently used in phase II/III trials in autoimmunity, constitute a promising approach as, beside their immunosuppressive effect, they also express potent tolerogenic capacities. Importantly, CD3 therapy is effective especially when applied in primed hosts, highlighting the importance of the therapeutic window for tolerance induction.

SUMMARY

Further investigations are required for adapting to the clinic monoclonal antibodies as substitutes for current immunosuppression. Our aim is to show that development of new therapeutic strategies/molecules may come from transversal-type research, in particular from experience in autoimmunity, as immune responses leading to autoimmunity and graft rejection involve similar pathways.

Modulation of the human T cell response by a novel non-mitogenic anti-CD3 antibody

The agonistic anti-human CD3ε antibody (Ab), OKT3, has been used to control acute transplant rejection. The in vivo administration of OKT3 was previously shown to induce the partial depletion of T cells and unresponsiveness (anergy) in the remaining CD4⁺ T cells. However, this therapy is also associated with the systemic release of several cytokines, which leads to a series of adverse side effects. We established a novel anti-human CD3ε Ab, 20-2b2, which recognized a close, but different determinant on the CD3ε molecule from that recognized by OKT3. 20-2b2 was non-mitogenic for human CD4⁺ T cells, could inhibit the activation of T cells in vitro, and induced T cell anergy in in vivo experiments using humanized mice. Cytokine release in humanized mice induced by the administration of 20-2b2 was significantly less than that induced by OKT3. Our results indicated that the CD3ε molecule is still an attractive, effective, and useful target for the modulation of T cell responses. The establishment of other Abs that recognize CD3ε, even though the determinant recognized by those Abs may be close to or different from that recognized by OKT3, may represent a novel approach for the development of safer Ab therapies using anti-CD3 Abs, in addition to the modification of OKT3 in terms of the induction of cytokine production.

Flow cytometry and solid organ transplantation: a perfect match

In the field of transplantation, flow cytometry serves a well-established role in pre-transplant crossmatching and monitoring immune reconstitution following hematopoietic stem cell transplantation. The capabilities of flow cytometers have continuously expanded and this combined with more detailed knowledge of the constituents of the immune system, their function and interaction and newly developed reagents to study these parameters have led to additional utility of flow cytometry-based analyses, particularly in the post-transplant setting. This review discusses the impact of flow cytometry on managing alloantigen reactions, monitoring opportunistic infections and graft rejection and gauging immunosuppression in the context of solid organ transplantation.

Historical overview of transplantation

Except for legends and claims of miracles, most histories of transplantation cover only the last 60 years because there were no earlier successes. However, the story of even this era has been documented in such rich detail that a full account would fill several volumes. Thus, this brief summary must be limited to highly selected "landmarks." Some landmarks had an immediate impact, but the importance of others went unrecognized for decades. Some findings that deserved landmark status were overlooked or forgotten, whereas others of no biological significance had major impact. Placing these events in perspective is challenging. Several of transplantation's pioneers are still alive, and most of the others are within living memory. Virtually all of them have produced their own accounts. For the most part, they agree on what the "landmarks" are, but their differences in emphasis and perspective make an interesting story.

CD3 monoclonal antibodies: a first step towards operational immune tolerance in the clinic

Type 1 diabetes (T1D) is a prototypic organ-specific autoimmune disease resulting from the selective destruction of insulin-secreting β-cells within the pancreatic islets of Langerhans. It is caused by an immune-mediated inflammation, involving autoreactive CD4⁺ and CD8⁺ T lymphocytes that infiltrate the islets and initiate insulitis. The use of exogenous insulin is the current standard treatment. However, in spite of significant advances, this therapy is still associated with major constraints, including risk of hypoglycemia and severe degenerative complications. As T1D mainly affects children and young adults, any candidate immune therapy must be safe, and it must avoid a sustained depression of immune responses with all its attendant problems of recurrent infection and drug toxicity. In this context, inducing or restoring immune tolerance to target autoantigens would be the ideal approach. We refer to immune tolerance here as the selective damping of the damaging autoimmune response following a short treatment, while keeping intact the capacity of the host to respond normally to exogenous antigens. The therapeutic approach we discuss in this article originates from attempts to induce tolerance both to soluble antigens and tissue antigens (i.e. alloantigens and autoantigens) by using biological agents that selectively interfere with lymphocyte activation, namely polyclonal and monoclonal anti-T cell antibodies. The challenged dogma was that, in an adult-primed immune system, it was not possible to restore self-tolerance therapeutically without the use of exogenous autoantigen administration. The reality has been that, in diabetes, endogenous host autoantigen can fulfill this role because a significant amount of functioning β-cells remains, even at the time of established hyperglycemia. Experimental results obtained in the 1990s showed that a short-term CD3 antibody treatment in recently diagnosed diabetic non-obese diabetic (NOD) mice induced permanent remission of the disease by restoring self-tolerance. Based on these findings, phase I, II, and III trials were conducted using two distinct humanized Fc-mutated antibodies to human CD3, namely ChAglyCD3 (otelixizumab) and OKT3γ1 Ala-Ala (teplizumab). Overall, when dosing was adequate, the results demonstrated that CD3 antibodies preserved β-cell function very efficiently, maintaining significantly high levels of endogenous insulin secretion in treated patients for up to 24 months after treatment. These data provided the first proof of concept for a long-term therapeutic effect in T1D following a short course administration of a therapeutic agent. Our aim is to review these data and to discuss them in the context of the pitfalls linked to pharmaceutical development, especially in the context of pediatric patients, as in autoimmune diabetes.

Modulatory effect of insulin on T cell receptor mediated calcium signaling is blunted in long lasting type 1 diabetes mellitus

Insulin significantly influences Ca(2+) signals evoked by various stimulants. In type 1 recent onset diabetes mellitus the proliferative response of T cells is significantly decreased. The number of clinical trials exploring the role of anti-CD3 monoclonal antibodies (mAb) as a therapeutic agent in recent onset diabetes mellitus type 1 is increasing last years. Therefore, a better understanding of the interplay between T cell receptor (TCR) dependent Ca(2+) increase, and insulin is of vital clinical significance. The aim of the study was to assess the effect of insulin on TCR evoked Ca(2+) responses in T lymphocytes obtained from healthy volunteers and patients suffering from long lasting diabetes mellitus type 1. Analysis was performed with use of the flow cytometer. We demonstrated that T cells ability to mobilize Ca(2+) was significantly reduced in long lasting diabetes mellitus type 1. Ca(2+) decrease achieved by the long term incubation with anti-CD3 mAb in T cells from healthy volunteers was restored by insulin. Strong interrelationship between baseline Ca(2+) level and plateau phase response to TCR stimulation was observed in the cytoplasm of cells pre-incubated with insulin from both healthy subjects and diabetic patients (r = 0.95, p < 0.0001 and r = 0.94, p < 0.0001, respectively). We postulate the existence of the interplay between TCR mediated activation and insulin. The TCR-insulin interplay is blunted in long lasting diabetes mellitus type 1. These observations may have an important implication for future therapeutic options in diabetes.

Anti-CD3ε mAb improves thymic architecture and prevents autoimmune manifestations in a mouse model of Omenn syndrome: therapeutic implications

Omenn syndrome (OS) is an atypical primary immunodeficiency characterized by severe autoimmunity because of activated T cells infiltrating target organs. The impaired recombinase activity in OS severely affects expression of the pre-T-cell receptor complex in immature thymocytes, which is crucial for an efficient development of the thymic epithelial component. Anti-CD3ε monoclonal antibody (mAb) treatment in RAG2(-/-) mice was previously shown to mimic pre-TCR signaling promoting thymic expansion. Here we show the effect of anti-CD3ε mAb administration in the RAG2(R229Q) mouse model, which closely recapitulates human OS. These animals, in spite of the inability to induce the autoimmune regulator, displayed a significant amelioration in thymic epithelial compartment and an important reduction of peripheral T-cell activation and tissue infiltration. Furthermore, by injecting a high number of RAG2(R229Q) progenitors into RAG2(-/-) animals previously conditioned with anti-CD3ε mAb, we detected autoimmune regulator expression together with the absence of peripheral immunopathology. These observations indicate that improving epithelial thymic function might ameliorate the detrimental behavior of the cell-autonomous RAG defect. Our data provide important therapeutic proof of concept for future clinical applications of anti-CD3ε mAb treatment in severe combined immunodeficiency forms characterized by poor thymus function and autoimmunity.

Antibody phage display libraries: contributions to oncology

Since the advent of phage display technology, dating back to 1985, antibody libraries displayed on filamentous phage surfaces have been used to identify specific binders for many different purposes, including the recognition of tumors. Phage display represents a high-throughput technique for screening billions of random fusion antibodies against virtually any target on the surface or inside cancer cells, or even soluble markers found in patient serum. Many phage display derived binders targeting important tumor markers have been identified. Selection directed to tumoral cells’ surfaces lead to the identification of unknown tumoral markers. Also the improvement of methods that require smaller amounts of cells has opened the possibility to use this approach on patient samples. Robust techniques combining an antibody library displayed on the phage surface and protein microarray allowed the identification of auto antibodies recognized by patient sera. Many Ab molecules directly or indirectly targeting angiogenesis have been identified, and one of them, ramucirumab, has been tested in 27 phase I–III clinical trials in a broad array of cancers. Examples of such antibodies will be discussed here with emphasis on those used as probes for molecular imaging and other clinical trials.

Biologics in organ transplantation

The last two decades have witnessed a pandemic in antibody development, with over 600 entering clinical studies and a total of 28 approved by the FDA and European Union. The incorporation of biologics in transplantation has made a significant impact on allograft survival. Herein, we review the armamentarium of clinical and preclinical biologics used for organ transplantation--with the exception of belatacept--from depleting and IL-2R targeting induction agents to costimulation blockade, B-cell therapeutics, BAFF and complement inhibition, anti-adhesion, and anti-cytokine approaches. While individual agents may be insufficient for tolerance induction, they provide possibilities for reduction of steroid or calcineurin inhibitor use, alternatives to rejection episodes refractory to conventional therapies, and specialized immunosuppression for highly sensitized patients.

Current status of immunosuppressive agents for solid organ transplantation in children

Immunosuppression after organ transplantation is complex and ever evolving. Over the past two decades, newer immunosuppressive agents have been introduced with an aim to provide better patient and graft survival. Improved therapeutic strategies have been developed offering the option to use combinations of drugs with non-overlapping toxicities. There are, however, only a few clinical studies with robust data to rationalize the use of these agents in children. This review will discuss the newer immunosuppressive agents used for solid organ transplant, their current status in post-transplant management and prevention of allograft rejection.

Otelixizumab in the treatment of Type 1 diabetes mellitus

Anti-CD3 antibodies have been demonstrated in both animal and human studies to be able to reverse autoimmune diseases; for example Type 1 diabetes. Not only does treatment with anti-CD3 antibodies result in the removal of pathogenic T cells but evidence suggests that a state of operational tolerance can be induced through the effects on regulatory T cells. The clinical use of anti-CD3 antibodies has been hampered by their safety profile. However, the introduction of humanized, nonmitogenic, aglycosylated anti-CD3 antibodies, such as otelixizumab, and promising results reported in newly-diagnosed patients with Type 1 diabetes, have renewed the interest for these antibodies in the treatment of autoimmune diseases.

Therapeutic potential of Tregs to treat rheumatoid arthritis

There is accumulating evidence for regulatory T cell defects in rheumatoid arthritis and that some biologic interventions, in particular anti-TNF, can target this population. Despite the challenges in defining regulatory T cells in patients, there are a number of approaches currently being developed to utilise their potent immunosuppressive properties. Through genetic manipulation Tregs can be generated ex vivo or in vivo that target antigens present in the inflamed joint. Here we discuss these approaches, their refinement to restore tolerance in patients with rheumatoid arthritis, and strategies to prevent their conversion towards a Th17 phenotype.

Teplizumab therapy for type 1 diabetes

IMPORTANCE OF THE FIELD

Type 1 diabetes mellitus (T1D) is a T-cell mediated autoimmune disease with selective destruction of beta cells. Immunological interventions are directed at arresting the loss of beta-cell function with the promise that this will make it easier for patients to control their glucose levels.

AREAS COVERED IN THIS REVIEW

This review provides a summary of the preclinical and clinical research published between 1992 and 2009 using teplizumab and other anti-CD3 antibodies to arrest the loss of beta-cell function in new onset T1D. Data from animal and human studies on the probable mechanism of action of teplizumab are also reviewed.

WHAT THE READER WILL GAIN

A broad perspective on the use of teplizumab in inducing disease specific tolerance.

TAKE HOME MESSAGE

In Phase I/II randomized control trials, in patients with new onset T1D, teplizumab slowed the rate of loss of beta-cell function over 2 years of follow-up. Treated patients had better glycemic control and lower insulin requirements. Adverse events so far are mild and of limited duration. Phase III clinical trials are underway to confirm these results and to determine if two courses of drug have greater efficacy in arresting loss of beta-cell function.

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.

Organ transplantation: modulation of T-cell activation pathways initiated by cell surface receptors to suppress graft rejection

T-cell activation depends upon two types of signals: a T-cell-receptor-mediated antigen-specific signal and several non-antigen-specific ones provided by the engagement of costimulatory and/or inhibitory T-cell surface molecules. In clinical transplantation, T-cell costimulatory/inhibitory molecules are involved in determining cytokine production, vascular endothelial cell damage, and induction of transplant rejection. Several of the latest new immunotherapeutic strategies being currently developed to control graft rejection aim at inhibiting alloreactive T-cell function by regulating activating and costimulatory/inhibitory signals to T cells. This article describes the recent development and potential application of these therapies in experimental and pre-clinical transplantation.

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.

Anti-CD3 mAbs for treatment of type 1 diabetes

The use of anti-CD3 monoclonal antibodies (mAbs) has moved from the bench to the bedside. The experience with the anti-human CD3 mAb OKT3 for treatment of transplant rejection identified limitations that were largely overcome with the creation of humanized non-FcR binding antibodies: Teplizumab, Otelixizumab and Visilizumab. Preclinical studies showed the ability of the drugs to reverse hyperglycaemia in diabetic non-obese diabetic (NOD) mice providing rationale for clinical trials with the agents. The former two drugs have been tested in subjects with new onset type 1 diabetes. They have both shown, in randomized clinical trials, an ability to reduce the loss of insulin production over the first 2 years of the disease. In addition, the need for exogenous insulin to maintain glucose control has been reduced. However, these agents alone do not restore normal glucose control, and future approaches will likely require combinations of agents with complementary immune or metabolic activity.

Cell type-specific targeting with surface-engineered lentiviral vectors co-displaying OKT3 antibody and fusogenic molecule

PURPOSE

The purpose of this study was to investigate the potential of a T-cell-related targeting method using a lentiviral vector-based gene delivery system.

MATERIALS AND METHODS

A lentiviral vector system was constructed by co-incorporating an anti-CD3 antibody (OKT3) and a fusogen into individual viral particles. The incorporation of OKT3 and fusogen was analyzed using confocal microscopy and the in vitro transduction efficiency was evaluated using flow cytometry. Blocking reagents (ammonium chloride (NH(4)Cl) and soluble OKT3 antibody) were added into vector supernatants during transduction to study the mechanism of this two-molecule targeting strategy. To demonstrate the ability of targeted transduction in vivo, Jurkat.CD3 cells were xenografted subcutaneously into the right flank of each mouse and the lentiviral vector was injected subcutaneously on both sides of each mouse 8 h post-injection. Subsequently, the reporter gene (firefly luciferase) expression was monitored using a noninvasive bioluminescence imaging system.

RESULTS

By co-displaying OKT3 and fusogen on the single lentiviral surface, we could achieve targeted delivery of genes to CD3-positive T-cells both in vitro and in vivo.

CONCLUSIONS

These results suggest the potential utility of this engineered lentiviral system as a new tool for cell type-directed gene delivery.