Eric Assier

Interleukin-23: A key cytokine in inflammatory diseases

Abstract Interleukin-23 (IL-23) is a pro-inflammatory cytokine composed of two subunits, p19 and p40. The p40 subunit is shared with IL-12. IL-23 and IL-12 have different receptors and different effects. Whereas IL-12 induces development of Th1 cells, which produce interferon-γ, IL-23 is involved in differentiation of Th17 cells in a pro-inflammatory context and especially in the presence of TGF-β and IL-6. Activated Th17 cells produce IL-17A, IL-17F, IL-6, IL-22, TNF-α, and GM-CSF. Inflammatory macrophages express IL-23R and are activated by IL-23 to produce IL-1, TNF-α, and IL-23 itself. These effects identify IL-23 as a central cytokine in autoimmunity and a highly promising treatment target for inflammatory diseases. IL-23 is found in the skin of patients with psoriasis, in the bowel wall of patients with chronic inflammatory bowel disease, and in synovial membrane of patients with rheumatoid arthritis. IL-23 is involved in osteoclastogenesis, independently from IL-17, via induction of RANKL expression. Debate continues to surround the role for IL-23 in the pathophysiology of inflammatory joint diseases (rheumatoid arthritis and spondyloarthritis). Ustekinumab, which inhibits IL-12 and IL-23 by blocking p40, has been found effective in cutaneous psoriasis and psoriatic arthritis, as well as in Crohns disease. Treatments that specifically target IL-23 (antibodies to p19) are being developed.

Regulatory T cells (Treg) in rheumatoid arthritis

Modulation of the T-cell response depends chiefly on regulatory T cells (Treg), which express CD4 and CD25. Some Treg cells are present naturally, whereas others are induced in response to antigens. The immunomodulating effects of Treg cells are mediated by membrane molecules (e.g., CTLA4, GITR, and OX40) and cytokines. IL-35 seems to be a crucial mediator, although IL-10 and TGFbeta are also important. The role for Treg cells in rheumatoid arthritis (RA) has been established in both patients and animal models. Treg function is deficient in RA, whereas Treg counts vary. Treg counts increase in patients who are responding to TNFalpha antagonist therapy. Among current hypotheses, Treg expansion or transfer may hold promise for the treatment of RA.

Interleukin-6: From identification of the cytokine to development of targeted treatments

Interleukin-6 (IL-6) was identified based on extensive research conducted simultaneously on a variety of topics ranging from hepatocyte production of acute-phase proteins to plasmacytoma growth. IL-6 is a cytokine produced by a broad array of cell types and can exert its effects on virtually all cells. IL-6 can induce cell signaling not only via the classic pathway involving the transmembrane receptor IL-6Rα (restricted cellular expression) associated with gp130 (ubiquitous and responsible for signal transmission), but also via the soluble receptor IL-6Rα, which binds to IL-6 and induces a signal mediated by the ubiquitous gp130 molecule (transsignaling). IL-6 is deregulated in many inflammatory and autoimmune diseases, including rheumatoid arthritis (RA). By virtue of its multiple effects, IL-6 is involved in the various phases of RA development, including the acute phase, immuno-inflammatory phase, and destructive phase. IL-6 has an impact on the many pathogenic factors identified in RA and, consequently, holds promise for targeted treatments. However, anti-IL-6 monoclonal antibodies evaluated as IL-6 antagonists, instead, increased the half-life of the cytokine. In contrast, monoclonal antibody (tocilizumab) to transmembrane and soluble IL-6Rα has been found effective in patients with RA. Tocilizumab is now indicated for the treatment of adults with RA who have failed at least one synthetic disease-modifying antirheumatic drug or TNFα antagonist.

Active immunization against IL-23p19 improves experimental arthritis

INTRODUCTION IL-23 is a pro-inflammatory cytokine essential for the differentiation of Th17 lymphocytes, a subtype of T lymphocyte implied in auto-immunity. IL-23 shares a subunit with IL-12, IL-12/23p40, and comprises a specific subunit, IL-23p19. We previously demonstrated that active immunization against entire TNF-α and against peptides of IL-1β was protective in animal models of rheumatoid arthritis. The aim of this study was to evaluate the effect of peptide-based vaccines targeting the IL-23p19 subunit in collagen-induced arthritis (CIA). METHODS Using bioinformatics, the murine IL-23p19 subunit was modeled and two peptides were defined in the receptor interacting domain. Each peptide was coupled to keyhole limpet hemocyanin (KLH) to obtain two vaccines IL23-K1 and IL23-K2. Both vaccines were used for immunizations in incomplete Freund adjuvant (IFA) in groups of DBA/1 mice. Control groups received KLH or PBS at the same dates. CIA was induced by two subcutaneous injections of bovine type II collagen (CIIb), and the development of disease assessed during the next two months. Anti-CIIb and anti-IL-23 antibody levels were assessed by ELISA. Pro- and anti-inflammatory cytokines mRNA were quantified by qRT-PCR in the spleen and the synovium. T-cell populations in the spleen were evaluated by FACS analysis. RESULTS The clinical scores showed that mice treated with IL23-K1 developed less arthritis than negative controls (p<0.05). Mice immunized with IL23-K1 produced more anti-IL-23 antibodies than those immunized with IL23-K2 (p<0.001). mRNA quantification showed that the IL23-K1 immunization led to an increase of IL-10 in the spleen (p<0.05 vs. KLH), without any effect on IL-17 level. Histological examination showed that IL23-K1 strongly protected against joint destruction and inflammation (p<0.01 vs. KLH and p<0.001 vs. PBS). T-cell populations in the spleen were not modified by IL-23 modulation. CONCLUSION These data show that targeting IL-23p19 through a vaccination strategy is protective in CIA. This specific targeting of IL-23 might constitute a promising therapeutic approach to explore in rheumatoid arthritis.

Vaccination with cytokines in autoimmune diseases

Most autoimmune diseases have an unknown etiology, but all involve cytokines cascade in their development. At the present time, several cytokines have been identified as major targets in various autoimmune diseases, involving the development of monoclonal antibodies (MAbs) against those cytokines. Even if MAbs are indeed efficient, the passive immunotherapies also present some disadvantages and are expensive. To counter this, several strategies have been developed, including active immunotherapy, based on the vaccination principle. The aim of such a strategy is to induce a B cell response and to obtain autoantibodies able to neutralize the interaction of the self-cytokine with its receptor. To that purpose, cytokines (entire or peptide) are either coupled with a protein-carrier or virus-like particle, or modified with foreign Th cell epitopes. DNA vaccination can also be used with cytokine sequences. This review focuses on the different vaccination strategies with cytokines (including Tumor Necrosis Factor (TNF)α, Interleukin-1β (IL-1β), IL-17) in different autoimmune diseases in preclinical studies; the benefit/risk ratio of such a strategy and the present development of clinical trials in some autoimmune diseases are also discussed.

Blood vessels, a potential therapeutic target in rheumatoid arthritis?

New micro-vessels formation within synovium and macro-vessels endothelial damage with atheroma are two major features of rheumatoid arthritis, the former related to the articular involvement of the disease, the latter to its main systemic complication. The similarities between pannus development and solid tumors growth, and the efficacy of anti-angiogenic treatments in oncology, opened the perspective of directly targeting angiogenesis in arthritis. Nevertheless, despite the success of different anti-angiogenic therapeutic strategies in many arthritis experimental models, the application in human disease is still lacking. Recent data suggest that synovial neoangiogenesis and macro-vessels endothelial damage might be two linked phenomena. While synovial angiogenesis seems to be detrimental to endothelial damage repair, even anti-angiogenic treatments might paradoxically aggravate macro-vascular disease, especially in the context of uncontrolled inflammation. These elements induce to further explore the interconnections between inflammation and angiogenesis on one side and between micro- and macro-vascular diseases on the other, in order to establish the proper way to therapeutically target blood vessels in rheumatoid arthritis.

Active immunization to tumor necrosis factor-α is effective in treating chronic established inflammatory disease: a long-term study in a transgenic model of arthritis

IntroductionPassive blockade of tumor necrosis factor-alpha (TNF-α) has demonstrated high therapeutic efficiency in chronic inflammatory diseases, such as rheumatoid arthritis, although some concerns remain such as occurrence of resistance and high cost. These limitations prompted investigations of an alternative strategy to target TNF-α. This study sought to demonstrate a long-lasting therapeutic effect on established arthritis of an active immunotherapy to human (h) TNF-α and to evaluate the long-term consequences of an endogenous anti-TNF-α response.MethodshTNF-α transgenic mice, which spontaneously develop arthritides from 8 weeks of age, were immunized with a heterocomplex (TNF kinoid, or TNF-K) composed of hTNF-α and keyhole limpet hemocyanin after disease onset. We evaluated arthritides by clinical and histological assessment, and titers of neutralizing anti-hTNF-α antibody by enzyme-linked immunosorbent assay and L929 assay.ResultsArthritides were dramatically improved compared to control mice at week 27. TNF-K-treated mice exhibited high levels of neutralizing anti-hTNF-α antibodies. Between weeks 27 and 45, all immunized mice exhibited symptoms of clinical deterioration and a parallel decrease in anti-hTNF-α neutralizing antibodies. A maintenance dose of TNF-K reversed the clinical deterioration and increased the anti-hTNF-α antibody titer. At 45 weeks, TNF-K long-term efficacy was confirmed by low clinical and mild histological scores for the TNF-K-treated mice. Injections of unmodified hTNF-α did not induce a recall response to hTNF-α in TNF-K immunized mice.ConclusionsAnti-TNF-α immunotherapy with TNF-K has a sustained but reversible therapeutic efficacy in an established disease model, supporting the potential suitability of this approach in treating human disease.

TLR7/8 agonists impair monocyte-derived dendritic cell differentiation and maturation

Pathogen recognition by TLR activates the innate immune response and is typically followed by the development of an adaptive immune response initiated by antigen presentation. Dendritic cells (DC) are the most efficient APC and express diverse TLRs, including TLR7 and ‐8, which have been recently identified as targets for ssRNA recognition during viral infection. We have studied the effect of TLR7/8 agonists on DC differentiation and maturation from human monocytes. The synthetic agonist Resiquimod (R‐848) or the physiological agonist ssRNA impaired monocyte differentiation to DC phenotypically and functionally. Induced expression of the nonclassical MHC molecules of the CD1 family in DC was inhibited at the protein and mRNA levels, and antigen acquisition was inhibited. Proinflammatory cytokine (including IL‐6, IL‐8, TNF‐α, IL‐1β) and IL‐10 production were induced during DC differentiation. Cross‐talk between TLR4 and TLR7/8 was revealed as immature DC, which had been differentiated in the presence of R‐848 were insensitive to LPS‐mediated maturation and cytokine production but still induced allostimulation. These data lead us to suggest that ongoing viral activation of TLR7/8 could alter the adaptive immune response by modifying DC differentiation and by down‐regulating DC responsiveness to a subsequent bacterial TLR4‐mediated signal.

Anti-cytokine vaccination in autoimmune diseases.

The concept of therapeutic vaccination represents a novel strategy of active immunotherapy that can be applied to autoimmune disease. The principle is to design molecules which can trigger an immune response, targeting a cytokine that is pathogenic and over-expressed in a given disease. The mostly available vaccines are an application of vaccination using either the self-protein coupled to a carrier (type I A), or a modified form of the protein engineered to include neo-epitopes (type I B). These approaches have been developed in models of several autoimmune diseases, mainly in TNFα-dependent diseases such as rheumatoid arthritis and Crohns disease, but also in systemic lupus erythematosus, multiple sclerosis and myasthenia gravis. Clinical trials are in progress in rheumatoid arthritis, Crohns disease and diabetes. The benefit/risk ratio of anti-cytokine vaccination is currently under study to further develop the vaccination strategies.

Kinoid of human tumor necrosis factor-alpha for rheumatoid arthritis

Introduction: Anti-TNF-α drugs have dramatically changed treatment of rheumatoid arthritis (RA) in terms of both clinical control and articular damage prevention. Despite this, they hold some important drawbacks, such as frequent therapeutic failures and high costs. Anti-TNF-α active immunization, with a therapeutic vaccine against TNF-α, is a promising alternative anti-TNF-α targeting strategy, potentially devoid of treatment limitations of some of current anti-TNF blocking agents. Areas covered: This review covers the preclinical proof-of-concept of anti-TNF-α vaccination with the kinoid of human TNF-α (TNFK) and analyzes the body of evidence forming the rationale for the application of this strategy in RA and other TNF-α-dependent diseases. We describe the theoretical bases of anti-TNF-α active immunization and of experimental data supporting the applicability of TNFK to human disease in terms of both safety and efficacy. Expert opinion: Based on preclinical efficacy and safety data supporting its feasibility in a Phase I – II trial in Crohns disease, anti-TNF-α vaccination with TNFK has entered the phase of clinical development and promises to be a valuable anti-TNF-α targeting strategy in human disease. The focus is made in the first clinical trial in RA (Phase II) on the efficacy in active RA patients having developed antibodies against anti-TNF mAbs.