FcR Interactions Do Not Play a Major Role in Inhibition of Experimental Autoimmune Encephalomyelitis by Anti-CD154 Monoclonal Antibodies

Recognizing Complexity of CD8 T Cells in Transplantation

The major role of CD8+ T cells in clinical and experimental transplantation is well documented and acknowledged. Nevertheless, the precise impact of CD8+ T cells on graft tissue injury is not completely understood, thus impeding the development of specific treatment strategies. The goal of this overview is to consider the biology and functions of CD8+ T cells in the context of experimental and clinical allotransplantation, with special emphasis on how this cell subset is affected by currently available and emerging therapies.

The CD40-CD40L Dyad in Experimental Autoimmune Encephalomyelitis and Multiple Sclerosis

The CD40-CD40L dyad is an immune checkpoint regulator that promotes both innate and adaptive immune responses and has therefore an essential role in the development of inflammatory diseases, including multiple sclerosis (MS). In MS, CD40 and CD40L are expressed on immune cells present in blood and lymphoid organs, affected resident central nervous system (CNS) cells, and inflammatory cells that have infiltrated the CNS. CD40-CD40L interactions fuel the inflammatory response underlying MS, and both genetic deficiency and antibody-mediated inhibition of the CD40-CD40L dyad reduce disease severity in experimental autoimmune encephalomyelitis (EAE). Both proteins are therefore attractive therapeutic candidates to modulate aberrant inflammatory responses in MS. Here, we discuss the genetic, experimental and clinical studies on the role of CD40 and CD40L interactions in EAE and MS and we explore novel approaches to therapeutically target this dyad to combat neuroinflammatory diseases.

Monoclonal Antibodies in Preclinical EAE Models of Multiple Sclerosis: A Systematic Review

Monoclonal antibodies (mAb) are promising therapeutics in multiple sclerosis and multiple new candidates have been developed, hence increasing the need for some agreement for preclinical mAb studies. We systematically analyzed publications of experimental autoimmune encephalomyelitis (EAE) studies showing effects of monoclonal antibodies. A PubMed search retrieved 570 records, out of which 122 studies with 253 experiments were eligible based on experimental design, number of animals and presentation of time courses of EAE scores. Analysis of EAE models, treatment schedules, single and total doses, routes of administration, and onset of treatment from pre-immunization up to 35 days after immunization revealed high heterogeneity. Total doses ranged from 0.1 to 360 mg/kg for observation times of up to 35 days after immunization. About half of experiments (142/253) used total doses of 10-70 mg/kg. Employing this range, we tested anti-Itga4 as a reference mAb at varying schedules and got no, mild or substantial EAE-score reductions, depending on the mouse strain and onset of the treatment. The result agrees with the range of outcomes achieved in 10 reported anti-Itga4 experiments. Studies comparing low and high doses of various mAbs or early vs. late onset of treatment did not reveal dose-effect or timing-effect associations, with a tendency towards better outcomes with preventive treatments starting within the first week after immunization. The systematic comparison allows for extraction of some "common" design characteristics, which may be helpful to further assess the efficacy of mAbs and role of specific targets in preclinical models of multiple sclerosis.

Expression, purification and biological characterization of the extracellular domain of CD40 from Pichia pastoris

BACKGROUND

CD40, also called Bp50, is a novel member of the TNF receptor superfamily. Based on its important role in multiple physiological and pathological processes, the CD40 signaling pathway has become a vital target for treating transplantation, autoimmune diseases and cancers. This study generated a protein fragment that disrupts this signaling pathway.

RESULTS

A DNA fragment encoding the extracellular domain of CD40 (CD40-N) has been codon-optimized and cloned into pPIC9K to create a Pichia pastoris expression and secretion strain. SDS-PAGE and Western blotting assays using the culture media from methanol-induced expression strains showed that recombinant CD40-N, a 27 kDa glycosylated protein, was secreted into the culture broth. The recombinant protein was purified to more than 90 % using Sephadex G-50 size-exclusion chromatography and Q Sepharose Fast Flow ion exchange. Finally, 120 mg of the protein was obtained at a relatively high purity from 3 l supernatant. Binding assay (ITC200 assay) shown the direct interaction of CD40-N and CD40 agonist antibody (G28-5). The bioactivity of recombinant CD40-N was confirmed by its ability to disrupt non-canonical NF-κB signaling activated by CD40 agonist antibody or CD40 ligand and to inhibit ant-CD40 agonist antibody-induced TNF-alpha expression in BJAB cells in vitro. In addition, our data indicate that the protein has curative potential in treating dextran sulfate sodium (DSS)-induced colitis in vivo.

CONCLUSIONS

The results show that the experimental procedure we have developed using P. pastoris can be used to produce large amounts of active CD40-N for research and industrial purposes. The protein fragment we have acquired has potential to be used in research or even treating inflammation diseases such as colitis.

Translational utility of experimental autoimmune encephalomyelitis: recent developments

Multiple sclerosis (MS) is a complex autoimmune condition with firmly established genetic and environmental components. Genome-wide association studies (GWAS) have revealed a large number of genetic polymorphisms in the vicinity of, and within, genes that associate to disease. However, the significance of these single-nucleotide polymorphisms in disease and possible mechanisms of action remain, with a few exceptions, to be established. While the animal model for MS, experimental autoimmune encephalomyelitis (EAE), has been instrumental in understanding immunity in general and mechanisms of MS disease in particular, much of the translational information gathered from the model in terms of treatment development (glatiramer acetate and natalizumab) has been extensively summarized. In this review, we would thus like to cover the work done in EAE from a GWAS perspective, highlighting the research that has addressed the role of different GWAS genes and their pathways in EAE pathogenesis. Understanding the contribution of these pathways to disease might allow for the stratification of disease subphenotypes in patients and in turn open the possibility for new and individualized treatment approaches in the future.

CDP7657, an anti-CD40L antibody lacking an Fc domain, inhibits CD40L-dependent immune responses without thrombotic complications: an in vivo study

INTRODUCTION

CD40 ligand (CD40L) blockade has demonstrated efficacy in experimental autoimmune models. However, clinical trials of hu5c8, an anti-human CD40L IgG1 antibody, in systemic lupus erythematosus (SLE) were halted due to an increased incidence of thrombotic events. This study evaluated CDP7657, a high affinity PEGylated monovalent Fab' anti-CD40L antibody fragment, to assess whether an Fc-deficient molecule retains efficacy while avoiding the increased risk of thrombotic events observed with hu5c8.

METHODS

The potency and cross-reactivity of CDP7657 was assessed in in vitro assays employing human and non-human primate leukocytes, and the capacity of different antibody formats to activate platelets in vitro was assessed using aggregometry and dense granule release assays. Given the important role CD40L plays in regulating humoral immunity, in vivo efficacy was assessed by investigating the capacity of Cynomolgus monkeys to generate immune responses to the tetanus toxoid antigen while the potential to induce thrombotic events in vivo was evaluated after repeat dosing of antibodies to Rhesus monkeys. A PEGylated anti-mouse CD40L was generated to assess efficacy in the New Zealand Black/White (NZB/W) mouse model of SLE.

RESULTS

CDP7657 dose-dependently inhibited antigen-specific immune responses to tetanus toxoid in Cynomolgus monkeys, and in contrast to hu5c8, there was no evidence of pulmonary thrombovasculopathy in Rhesus monkeys. Aglycosyl hu5c8, which lacks Fc receptor binding function, also failed to induce thrombotic events in Rhesus monkeys. In vitro experiments confirmed that antibody constructs lacking an Fc, including CDP7657, did not induce human or monkey platelet activation. A PEGylated monovalent Fab' anti-mouse CD40L antibody also inhibited disease activity in the NZB/W mouse model of SLE after administration using a therapeutic dosing regimen where mice received antibodies only after they had displayed severe proteinuria.

CONCLUSIONS

These findings demonstrate for the first time that anti-CD40L antibodies lacking a functional Fc region do not induce thrombotic events in Rhesus monkeys and fail to activate platelets in vitro but, nevertheless retain pharmacological activity and support the investigation of CDP7657 as a potential therapy for systemic lupus erythematosus and other autoimmune diseases.

From transcriptome analysis to therapeutic anti-CD40L treatment in the SOD1 model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive loss of motor neurons. Using unbiased transcript profiling in an ALS mouse model, we identified a role for the co-stimulatory pathway, a key regulator of immune responses. Furthermore, we observed that this pathway is upregulated in the blood of 56% of human patients with ALS. A therapy using a monoclonal antibody to CD40L was developed that slows weight loss, delays paralysis and extends survival in an ALS mouse model. This work demonstrates that unbiased transcript profiling can identify cellular pathways responsive to therapeutic intervention in a preclinical model of human disease.

CD40 and autoimmunity: the dark side of a great activator

CD40 is a tumor necrosis factor receptor superfamily member expressed by immune and non-immune cells. CD40:CD154 interactions mediate T-dependent B cell responses and efficient T cell priming. Thus, CD40 is a likely candidate to play roles in autoimmune diseases in which activated T and B cells cause pathology. Diseases in which CD40 plays a pathogenic role include autoimmune thyroiditis, type 1 diabetes, inflammatory bowel disease, psoriasis, multiple sclerosis, rheumatoid arthritis, and systemic lupus erythematosus. This review discusses the role of CD40:CD154 interaction in human and mouse autoimmunity, human polymorphisms associated with disease incidence, and disrupting CD40:CD154 interactions as an autoimmune therapy.

Therapeutic interventions targeting CD40L (CD154) and CD40: the opportunities and challenges

CD40 was originally identified as a receptor on B-cells that delivers contact-dependent T helper signals to B-cells through interaction with CD40 ligand (CD40L, CD154). The pivotal role played by CD40-CD40L interaction is illustrated by the defects in B-lineage cell development and the altered structures of secondary lymphoid tissues in patients and engineered mice deficient in CD40 or CD40L. CD40 signaling also provides critical functions in stimulating antigen presentation, priming of helper and cytotoxic T-cells and a variety of inflammatory reactions. As such, dysregulations in the CD40-CD40L costimulation pathway are prominently featured in human diseases ranging from inflammatory conditions to systemic autoimmunity and tissue-specific autoimmune diseases. Moreover, studies in CD40-expressing cancers have provided convincing evidence that the CD40-CD40L pathway regulates survival of neoplastic cells as well as presentation of tumor-associated antigens to the immune system. Extensive research has been devoted to explore CD40 and CD40L as drug targets. A number of anti-CD40L and anti-CD40 antibodies with diverse biological effects are in clinical development for treatment of cancer and autoimmune diseases. This chapter reviews the role of CD40-CD40L costimulation in disease pathogenesis, the characteristics of therapeutic agents targeting this pathway and status of their clinical development.

Fc-disabled anti-mouse CD40L antibodies retain efficacy in promoting transplantation tolerance

CD40L antibodies have proven to be powerful immunosuppressive agents in nonhuman primates but unfortunately perturb blood coagulation. Neither the therapeutic nor the prothrombotic mechanism of anti-CD40L is defined sufficiently to determine whether these effects can be uncoupled. Recent evidence suggests that the Fc region of anti-CD40L antibodies interacting with Fc receptors plays an important role in stabilizing platelet aggregates. An Fc-disabled, aglycosylated anti-CD40L heavy chain variant was therefore created to determine whether it might still be useful in promoting transplantation tolerance. In a number of mouse models an engineered aglycosyl anti-CD40L recapitulated the effects of the intact anti-CD40L antibody in tolerance protocols involving transplantation of allogeneic bone marrow and skin. In contrast, another anti-CD40L variant with a conventional rat gamma2b heavy chain was less effective in ensuring long-term skin graft survival, possibly associated with its faster clearance from the circulation. These results show that short pulses of anti-CD40L antibody therapy may still be useful in tolerance protocols even when the Fc region is disabled.

T cell tolerance induced by therapeutic antibodies

Ever since the discovery of Medawar, over 50 years ago, that immunological tolerance was an acquired phenomenon that could be manipulated in neonatal mice, the ability to induce therapeutic tolerance against autoantigens, allergens and organ grafts has been a major driving force in immunology. Within the last 20 years we have found that a brief treatment with monoclonal antibodies that block certain functional molecules on the surface of the T cell is able to reprogramme the established immune repertoire of the adult mouse, allowing indefinite acceptance of allografts or effective curing of autoimmune diseases. We are only now just beginning to define many of the regulatory mechanisms that induce and maintain the tolerant state with the aim of being able to safely and reliably apply these technologies to human clinical situations.

The FcRγ Chain Is Not Essential for Induction of Experimental Allergic Encephalomyelitis (EAE) or Anti-Myelin Antibody-Mediated Exacerbation of EAE

Macrophages are considered essential mediators in multiple sclerosis (MS) pathogenesis, presumably through myelin phagocytosis and release of inflammatory mediators. Macrophages and microglia express activating Fcgamma receptors (FcgammaRI and FcgammaRIII), which depend on the FcRgamma chain for surface expression and signaling. In MS lesions, crosslinking of FcgammaR by immunoglobulins (IgG) directed against myelin may enhance myelin phagocytosis and inflammation. We studied the role of FcgammaR and anti-myelin antibodies in MOG35-55-induced experimental allergic encephalomyelitis (EAE) in C57BL/6 mice, a model of MS-like disease. Incidence and severity of EAE were similar in FcRy chain-/- (FcRgamma-/-) and wild-type (wt) mice, albeit with delayed onset in FcRgamma-/- mice. This demonstrates that the FcRy chain is not essential for induction of EAE, but that FcRgamma signaling may contribute to the preclinical phase. The role of FcgammaR in antibody-mediated demyelination was addressed by injection of anti-myelin antibodies (Z12 mAb) at onset of MOG35-55-induced EAE. Injection of Z12 mAb rapidly reduced survival time in both wt and FcRgamma-/- mice, demonstrating that antibody-mediated exacerbation of EAE is independent of the FcRgamma chain. Interestingly, Z12-induced exacerbation of inflammation and demyelination persisted longer in wt than FcRgamma-/- mice, suggesting that IgG-FcgammaR interactions may contribute to a sustained pathologic effect of anti-myelin antibodies in the CNS.