Understanding autoimmune disease: new targets for drug discovery

Engineering antigen-presenting cells for immunotherapy of autoimmunity

Autoimmune diseases are burdensome conditions that affect a significant fraction of the global population. The hallmark of autoimmune disease is a host's immune system being licensed to attack its tissues based on specific antigens. There are no cures for autoimmune diseases. The current clinical standard for treating autoimmune diseases is the administration of immunosuppressants, which weaken the immune system and reduce auto-inflammatory responses. However, people living with autoimmune diseases are subject to toxicity, fail to mount a sufficient immune response to protect against pathogens, and are more likely to develop infections. Therefore, there is a concerted effort to develop more effective means of targeting immunomodulatory therapies to antigen-presenting cells, which are involved in modulating the immune responses to specific antigens. In this review, we highlight approaches that are currently in development to target antigen-presenting cells and improve therapeutic outcomes in autoimmune diseases.

New Label-Free Biosensing for the Evaluation of the AX-024 Inhibitor: Case Study for the Development of New Drugs in Autoimmune Diseases

We developed a new label-free assay to evaluate the inhibition capacity of AX-024 by means of a new Point-of-Care (PoC) device for application in the development of new drugs in autoimmune diseases. The technology of PoC is based on interferometric optical detection method (IODM). For this purpose, we have optimized and developed an assay protocol whereby a Glutathione S-Transferase modified protein (GST-SH3.1), which contains a functional domain of a protein involved in T-cell activation, together with the AX-024 inhibitor has been studied. The chips used are a sensing surface based on nitrocellulose. We used streptavidin and a biotinylated peptide as links for the immobilization process on the sensing surface. The biotinylated peptide and AX-024 inhibitor compete for the same functional group of the GST-SH3.1 modified protein. When the inhibitor binds its binding site on GST-SH3.1, the biotinylated peptide cannot bind to its pocket on the protein. This competition reduces the total molecular mass of protein fixed onto the biosensor. In order to quantify the inhibition capacity of AX-024, several Ax-024:GST-SH3.1 ratios have been studied. We have compared the read-out signal for GST-SH3.1 protein not interfered by the drug, which served as a positive blank, and the response of the GST-SH3.1 modified protein blocked by the inhibitor. The technology has been correlated with confocal fluorescence microscopy.

Discovery of Chromane-6-Sulfonamide Derivative as a Potent, Selective, and Orally Available Novel Retinoic Acid Receptor-Related Orphan Receptor γt Inverse Agonist

Interleukin-17 (IL-17) is a proinflammatory cytokine that plays a dominant role in inflammation, autoimmunity, and host defense. RORγt is a key transcription factor mediating T helper 17 (Th17) cell differentiation and IL-17 production, which is able to activate CD8⁺ T cells and elicit antitumor efficacy. A series of sulfonamide derivatives as novel RORγt inverse agonists were designed and synthesized. Using GSK2981278 (phase II) as a starting point, we engineered structural modifications that significantly improved the activity and pharmacokinetic profile. In animal studies, oral administration of compound d3 showed a robust and dose-dependent inhibition of the IL-17A cytokine expression in a mouse imiquimod-induced skin inflammation model. Docking analysis of the binding mode revealed that the compound d3 occupied the active pocket suitably. Thus, compound d3 was selected as a clinical compound for the treatment of Th17-driven autoimmune diseases.

Pharmacophore modeling of JAK1: A target infested with activity-cliffs

Janus kinase 1 (JAK1) is protein kinase involved in autoimmune diseases (AIDs). JAK1 inhibitors have shown promising results in treating AIDs. JAK1 inhibitors are known to exhibit regions of SAR discontinuity or activity cliffs (ACs). ACs represent fundamental challenge to successful QSAR/pharmacophore modeling because QSAR modeling rely on the basic premise that activity is a smooth continuous function of structure. We propose that ACs exist because active ACs members exhibit subtle, albeit critical, enthalpic features absent from their inactive twins. In this context we compared the performances of two computational modeling workflows in extracting valid pharmacophores from 151 diverse JAK1 inhibitors that include ACs: QSAR-guided pharmacophore selection versus docking-based comparative intermolecular contacts analysis (db-CICA). The two methods were judged based on the receiver operating characteristic (ROC) curves of their corresponding pharmacophore models and their abilities to distinguish active members among established JAK1 ACs. db-CICA modeling significantly outperformed ligand-based pharmacophore modeling. The resulting optimal db-CICA pharmacophore was used as virtual search query to scan the National Cancer Institute (NCI) database for novel JAK1 inhibitory leads. The most active hit showed IC₅₀ of 1.04 μM. This study proposes the use of db-CICA modeling as means to extract valid pharmacophores from SAR data infested with ACs.

Synthesis and Biological Evaluation of Subglutinol Analogs for Immunomodulatory Agents

Autoimmune diseases are chronic inflammatory diseases associated with high morbidity and mortality. Treatment options for autoimmune diseases have increased over the past several decades, but they are, in general, limited in their clinical efficacy due to high toxicity and lack of selectivity. Thus, efforts must be made to identify new immunomodulatory agents that are effective through a novel mechanism to circumvent existing side effects. To define the structural requirements of subglutinols for immunomodulatory activity and to provide guiding principles on future therapeutic development, we prepared and evaluated several subglutinol analogs for their immunomodulatory activities. Our efforts identified a subglutinol analog with reduced structural complexity as a potential lead compound for future autoimmune drug development. Our study will provide an important framework for the design of potent and nontoxic immunomodulating agents derived from subglutinols.

Selective Inhibitors of T Cell Receptor Recognition of Antigen-MHC Complexes for Rheumatoid Arthritis

Autoreactive T cells specific to human collagen type II have a crucial role in the development of rheumatoid arthritis (RA) in the context of MHC class II allele HLA-DRB1-*04. The protein-protein interactions between the T cell receptor (TCR) and the type II collagen bound to the allele MHC of class II may thus represent the target for the development of new drugs against RA. In this study, a structure-based pharmacophore model for potential small molecule inhibitors was developed from protein-protein interface structure. The 3D model obtained was used for a virtual screening workflow, which resulted in three hits for experimental follow up. Three compounds have been identified that interfere with the TCR/collagenII-MHCII (K _i values below 10 μM) and open up new possibilities in the treatment of RA.

AIPpred: Sequence-Based Prediction of Anti-inflammatory Peptides Using Random Forest

The use of therapeutic peptides in various inflammatory diseases and autoimmune disorders has received considerable attention; however, the identification of anti-inflammatory peptides (AIPs) through wet-lab experimentation is expensive and often time consuming. Therefore, the development of novel computational methods is needed to identify potential AIP candidates prior to in vitro experimentation. In this study, we proposed a random forest (RF)-based method for predicting AIPs, called AIPpred (AIP predictor in primary amino acid sequences), which was trained with 354 optimal features. First, we systematically studied the contribution of individual composition [amino acid-, dipeptide composition (DPC), amino acid index, chain-transition-distribution, and physicochemical properties] in AIP prediction. Since the performance of the DPC-based model is significantly better than that of other composition-based models, we applied a feature selection protocol on this model and identified the optimal features. AIPpred achieved an area under the curve (AUC) value of 0.801 in a 5-fold cross-validation test, which was ∼2% higher than that of the control RF predictor trained with all DPC composition features, indicating the efficiency of the feature selection protocol. Furthermore, we evaluated the performance of AIPpred on an independent dataset, with results showing that our method outperformed an existing method, as well as 3 different machine learning methods developed in this study, with an AUC value of 0.814. These results indicated that AIPpred will be a useful tool for predicting AIPs and might efficiently assist the development of AIP therapeutics and biomedical research. AIPpred is freely accessible at www.thegleelab.org/AIPpred.

Kinin B1 receptors as a therapeutic target for inflammation

INTRODUCTION

Kinins are peptide mediators exerting their pro-inflammatory actions by the selective stimulation of two distinct G-protein coupled receptors, termed BKB1R and BKB2R. While BKB2R is constitutively expressed in a multitude of tissues, BKB1R is hardly expressed at baseline but highly inducible by inflammatory mediators. In particular, BKB1R was shown to be involved in the pathogenesis of numerous inflammatory diseases. Areas covered: This review intends to evaluate the therapeutic potential of substances interacting with the BKB1R. To this purpose we summarize the published literature on animal studies with antagonists and knockout mice for this receptor. Expert Opinion: In most cases the pharmacological inhibition of BKB1R or its genetic deletion was beneficial for the outcome of the disease in animal models. Therefore, several companies have developed BKB1R antagonists and tested them in phase I and II clinical trials. However, none of the developed BKB1R antagonists was further developed for clinical use. We discuss possible reasons for this failure of translation of preclinical findings on BKB1R antagonists into the clinic.

Rheumatoid arthritis: Recent advances on its etiology, role of cytokines and pharmacotherapy

An autoimmune disease is defined as a clinical syndrome resulted from an instigation of both T cell and B cell or individually, in the absence of any present infection or any sort of distinguishable cause. Clonal deletion of auto reactive cells remains the central canon of immunology for decades, keeping the role of T cell and B cell aside, which are actually the guards to recognize the entry of foreign body. According to NIH, 23.5 million Americans are all together affected by these diseases. They are rare, but with the exception of RA. Rheumatoid arthritis is chronic and systemic autoimmune response to the multiple joints with unknown ethology, progressive disability, systemic complications, early death and high socioeconomic costs. Its ancient disease with an old history found in North American tribes since 1500 BCE, but its etiology is yet to be explored. Current conventional and biological therapies used for RA are not fulfilling the need of the patients but give only partial responses. There is a lack of consistent and liable biomarkers of prognosis therapeutic response, and toxicity. Rheumatoid arthritis is characterized by hyperplasic synovium, production of cytokines, chemokines, autoantibodies like rheumatoid factor (RF) and anticitrullinated protein antibody (ACPA), osteoclastogensis, angiogenesis and systemic consequences like cardiovascular, pulmonary, psychological, and skeletal disorders. Cytokines, a diverse group of polypeptides, play critical role in the pathogenesis of RA. Their involvement in autoimmune diseases is a rapidly growing area of biological and clinical research. Among the proinflammatory cytokines, IL-1α/β and TNF-α trigger the intracellular molecular signalling pathway responsible for the pathogenesis of RA that leads to the activation of mesenchymal cell, recruitment of innate and adaptive immune system cells, activation of synoviocytes which in term activates various mediators including tumour necrosis factor-alpha (TNF-α), interleukin-1 (IL-1), interleukin-6 (IL-6) and interleukin-8 (IL-8), resulting in inflamed synovium, increase angiogenesis and decrease lymphangiogensis. Their current pharmacotherapy should focus on their three phases of progression i.e. prearthritis phase, transition phase and clinical phase. In this way we will be able to find a way to keep the balance between the pro and anti-inflammatory cytokines that is believe to be the dogma of pathogenesis of RA. For this we need to explore new agents, whether from synthetic or natural source to find the answers for unresolved etiology of autoimmune diseases and to provide a quality of life to the patients suffering from these diseases specifically RA.

[Neutralizing Monoclonal and Chimeric Antibodies to Human IFN-γ]

Autoiminune disorders are chronic diseases characterized by abnormal immune response directed against self-antigens that leads to tissue damage and violation of its normal functioning. Such diseases often result in disability or even death of patients. Nowadays a number of monoclonal antibodies to pro-inflammatory cytokines and their receptors are successfully used for the targeted treatment of autoimmune diseases. One of the perspective targets in autoimmune disease therapy is interferon gamma, a key cytokine in Th1 cells differentiation, activation of macrophages, and inflammation. In the present work, 5 monoclonal antibodies to human IFN-γ were obtained. For the development of potential therapeutic agent, we have performed neutralizing activity and affinity analysis of the antibodies. Based on the data obtained, the monoclonal antibody F1 was selected. This antibody has a dissociation constant 1.7 x 10(-9) M and IC90 = 8.9 ± 2.0 nM measured upon antibody inhibition of the IFN-γ-induced HLA-DR expression on the surface of U937 cells. We have constructed a bicistronic vector for the production of recombinant chimeric Fab fragment F1 chim in E. coli cells. The recombinant chimeric Fab fragment Fl chim neutralizes IFN-γ activity in vitro and has a dissociation constant 1.8 x 10(-9) M.

Peptides and peptidomimetics as immunomodulators

Peptides and peptidomimetics can function as immunomodulating agents by either blocking the immune response or stimulating the immune response to generate tolerance. Knowledge of B- or T-cell epitopes along with conformational constraints is important in the design of peptide-based immunomodulating agents. Work on the conformational aspects of peptides, synthesis and modified amino acid side chains have contributed to the development of a new generation of therapeutic agents for autoimmune diseases and cancer. The design of peptides/peptidomimetics for immunomodulation in autoimmune diseases such as multiple sclerosis, rheumatoid arthritis, systemic lupus and HIV infection is reviewed. In cancer therapy, peptide epitopes are used in such a way that the body is trained to recognize and fight the cancer cells locally as well as systemically.

Biological evaluation of subglutinol a as a novel immunosuppressive agent for inflammation intervention

Subglutinol A (1) is an immunosuppressive natural product isolated from Fusarium subglutinans, an endophytic fungus from the vine Tripterygium wilfordii. We show that 1 exerts multimodal immune-suppressive effects on activated T cells in vitro: subglutinol A (1) effectively blocks T cell proliferation and survival while profoundly inhibiting pro-inflammatory IFNγ and IL-17 production by fully differentiated effector Th1 and Th17 cells. Our data further reveal that 1 may exert its anti-inflammatory effects by exacerbating mitochondrial damage in T cells. Additionally, we demonstrate that 1 significantly reduces lymphocytic infiltration into the footpad and ameliorates footpad swelling in the mouse model of Th1-driven delayed-type hypersensitivity. These results suggest the potential of 1 as a novel therapeutic for inflammatory diseases.

Protein kinase inhibitors in the treatment of inflammatory and autoimmune diseases

Protein kinases mediate protein phosphorylation, which is a fundamental component of cell signalling, with crucial roles in most signal transduction cascades: from controlling cell growth and proliferation to the initiation and regulation of immunological responses. Aberrant kinase activity is implicated in an increasing number of diseases, with more than 400 human diseases now linked either directly or indirectly to protein kinases. Protein kinases are therefore regarded as highly important drug targets, and are the subject of intensive research activity. The success of small molecule kinase inhibitors in the treatment of cancer, coupled with a greater understanding of inflammatory signalling cascades, has led to kinase inhibitors taking centre stage in the pursuit for new anti-inflammatory agents for the treatment of immune-mediated diseases. Herein we discuss the main classes of kinase inhibitors; namely Janus kinase (JAK), mitogen-activated protein kinase (MAPK) and spleen tyrosine kinase (Syk) inhibitors. We provide a mechanistic insight into how these inhibitors interfere with kinase signalling pathways and discuss the clinical successes and failures in the implementation of kinase-directed therapeutics in the context of inflammatory and autoimmune disorders.

A novel assay to measure B cell responses to keyhole limpet haemocyanin vaccination in healthy volunteers and subjects with systemic lupus erythematosus

The aim of the study was to characterize performance of a complementary set of assays to measure antigen-specific immune responses in subjects immunized with a neoantigen. Healthy volunteers (HV) (n = 8) and patients with systemic lupus erythematosus (SLE) (n = 6) were immunized with keyhole limpet haemocyanin (KLH) on days 1 and 29. Serum antibodies were detected using a flow cytometric bead array (CBA) that multiplexed the KLH response alongside pre-existing anti-tetanus antibodies. Peripheral blood mononuclear cells were studied by B cell ELISPOT. These assays were built upon precedent assay development in cynomolgus monkeys, which pointed towards their utility in humans. Primary anti-KLH IgG responses rose to a mean of 65-93-fold above baseline for HV and SLE patients, respectively, and secondary responses rose to a mean of 260-170-fold above baseline. High levels of anti-tetanus IgG were detected in pre-immunization samples and their levels did not change over the course of study. Anti-KLH IgG1-4 subclasses were characterized by a predominant IgG1 response, with no significant differences in subclass magnitude or distribution between HV and SLE subjects. Anti-KLH IgM levels were detectable, although the overall response was lower. IgM was not detected in two SLE subjects whodid generate an IgG response. All subjects responded to KLH by B cell ELISPOT, with no significant differences observed between HV and SLE subjects. The CBA and B cell ELISPOT assays reliably measured anti-KLH B cell responses, supporting use of this approach and these assays to assess the pharmacodynamic and potential safety impact of marketed/investigational immune-therapeutics.

Tight junction proteins expression and modulation in immune cells and multiple sclerosis

The tight junction proteins (TJPs) are major determinants of endothelial cells comprising physiological vascular barriers such as the blood-brain barrier, but little is known about their expression and role in immune cells. In this study we assessed TJP expression in human leukocyte subsets, their induction by immune activation and modulation associated with autoimmune disease states and therapies. A consistent expression of TJP complexes was detected in peripheral blood leukocytes (PBLs), predominantly in B and T lymphocytes and monocytes, whereas the in vitro application of various immune cell activators led to an increase of claudin 1 levels, yet not of claudin 5. Claudins 1 and 5 levels were elevated in PBLs of multiple sclerosis (MS) patients in relapse, relative to patients in remission, healthy controls and patients with other neurological disorders. Interestingly, claudin 1 protein levels were elevated also in PBLs of patients with type 1 diabetes (T1D). Following glucocorticoid treatment of MS patients in relapse, RNA levels of JAM3 and CLDN5 and claudin 5 protein levels in PBLs decreased. Furthermore, a correlation between CLDN5 pre-treatment levels and clinical response phenotype to interferon-β therapy was detected. Our findings indicate that higher levels of leukocyte claudins are associated with immune activation and specifically, increased levels of claudin 5 are associated with MS disease activity. This study highlights a potential role of leukocyte TJPs in physiological states, and autoimmunity and suggests they should be further evaluated as biomarkers for aberrant immune activity and response to therapy in immune-mediated diseases such as MS.

Autoimmune therapies targeting costimulation and emerging trends in multivalent therapeutics

Proteins participating in immunological signaling have emerged as important targets for controlling the immune response. A multitude of receptor-ligand pairs that regulate signaling pathways of the immune response have been identified. In the complex milieu of immune signaling, therapeutic agents targeting mediators of cellular signaling often either activate an inflammatory immune response or induce tolerance. This review is primarily focused on therapeutics that inhibit the inflammatory immune response by targeting membrane-bound proteins regulating costimulation or mediating immune-cell adhesion. Many of these signals participate in larger, organized structures such as the immunological synapse. Receptor clustering and arrangement into organized structures is also reviewed and emerging trends implicating a potential role for multivalent therapeutics is posited.

Differential pharmacological behaviour of p38 inhibitors in regulating the LPS-induced TNF-α production in human and rat whole blood in vitro

p38 inhibitors are potent TNF-α suppressors in LPS-stimulated human whole blood and promote efficacy in the rat adjuvant arthritis model. However, the anti-TNF-α activity of p38 inhibitors in rat whole blood has not been explored, preventing the establishment of a potential relation between in vitro and in vivo activity data in the same species. We have pharmacologically characterized a rat whole blood assay based on LPS stimulation. While p38 inhibitors showed good activity in the human assay, they failed to inhibit TNF-α in the rat whole blood assay. At high LPS concentration some compounds even potentiated TNF-α production in the rat assay, which could be reverted in the presence of the ERK pathway inhibitor U0126. Our results suggest that p38 contributes directly to TNF-α production in human whole blood while playing a negative regulatory role in rat blood which can be overridden by p38 inhibition in the presence of high stimulus concentration.

Endocrine autoimmune disease: genetics become complex

The endocrine system is a frequent target in pathogenic autoimmune responses. Type 1 diabetes and autoimmune thyroid disease are the prevailing examples. When several diseases cluster together in one individual, the phenomenon is called autoimmune polyglandular syndrome. Progress has been made in understanding the genetic factors involved in endocrine autoimmune diseases. Studies on monogenic autoimmune diseases such as autoimmune polyglandular syndrome type 1, immunodysregulation, polyendocrinopathy, enteropathy, X-linked and primary immune deficiencies helped uncover the role of key regulators in the preservation of immune tolerance. Alleles of the major histocompatibility complex have been known to contribute to the susceptibility to most forms of autoimmunity for more than 3 decades. Furthermore, sequencing studies revealed three non-major histocompatibility complex loci and some disease specific loci, which control T lymphocyte activation or signalling. Recent genome-wide association studies (GWAS) have enabled acceleration in the identification of novel (non-HLA) loci and hence other relevant immune response pathways. Interestingly, several loci are shared between autoimmune diseases, and surprisingly some work in opposite direction. This means that the same allele which predisposes to a certain autoimmune disease can be protective in another. Well powered GWAS in type 1 diabetes has led to the uncovering of a significant number of risk variants with modest effect. These studies showed that the innate immune system may also play a role in addition to the adaptive immune system. It is anticipated that next generation sequencing techniques will uncover other (rare) variants. For other autoimmune disease (such as autoimmune thyroid disease) GWAS are clearly needed.

Gene therapy in autoimmune diseases: challenges and opportunities

Clinical treatment of autoimmune disorders presents a special challenge. For decades, most clinical regimens in autoimmunity has been largely symptomatic and non-disease specific. Although data from vigorous research has lead to accumulating knowledge on the pathogenic and immunological mechanisms of many autoimmune diseases, their direct clinical applications have been sparse. Advances in biotechnology have laid the groundwork for potent and specific molecular targeting therapies by gene therapy, and have just begun to be investigated in the treatment of autoimmune disorders. Such work has been largely based on the availability of well-established animal models of common autoimmune disorders, and the efficacy of strategic approaches initially investigated and validated in these models. Although these preclinical animal model studies have provided the proof-of-concept for multiple potential applications, human clinical trials on gene therapy in autoimmunity are still at its infancy. The recent success of Phase I/II clinical trials of gene therapy in rheumatoid arthritis and multiple sclerosis, development of cutting edge technology in target identification, as well as gene delivery systems have now set the stage for a more thorough and vigorous pace in the near future to advance this exciting field.