In Vivo Expansion of Activated Foxp3+ Regulatory T Cells and Establishment of a Type 2 Immune Response upon IL-33 Treatment Protect against Experimental Arthritis.

IL-33 is strongly involved in several inflammatory and autoimmune disorders with both pro- and anti-inflammatory properties. However, its contribution to chronic autoimmune inflammation, such as rheumatoid arthritis, is ill defined and probably requires tight regulation. In this study, we aimed at deciphering the complex role of IL-33 in a model of rheumatoid arthritis, namely, collagen-induced arthritis (CIA). We report that repeated injections of IL-33 during induction (early) and during development (late) of CIA strongly suppressed clinical and histological signs of arthritis. In contrast, a late IL-33 injection had no effect. The cellular mechanism involved in protection was related to an enhanced type 2 immune response, including the expansion of eosinophils, Th2 cells, and type 2 innate lymphoid cells, associated with an increase in type 2 cytokine levels in the serum of IL-33-treated mice. Moreover, our work strongly highlights the interplay between IL-33 and regulatory T cells (Tregs), demonstrated by the dramatic in vivo increase in Treg frequencies after IL-33 treatment of CIA. More importantly, Tregs from IL-33-treated mice displayed enhanced capacities to suppress IFN-γ production by effector T cells, suggesting that IL-33 not only favors Treg proliferation but also enhances their immunosuppressive properties. In concordance with these observations, we found that IL-33 induced the emergence of a CD39(high) Treg population in a ST2L-dependent manner. Our findings reveal a powerful anti-inflammatory mechanism by which IL-33 administration inhibits arthritis development.

Interplay between TNF and regulatory T cells in a TNF-driven murine model of arthritis.

CD4(+)CD25(+)Foxp3(+) regulatory T cells (Treg) are involved in several autoimmune diseases, including rheumatoid arthritis. TNF-α blockers induce therapeutic benefits in rheumatoid arthritis via a variety of mechanisms. We aimed to characterize the impact on Treg of TNF-α overexpression in vivo and of TNF-α inhibiting treatments. We used human TNF-α transgenic mice as a model of strictly TNF-α-dependent arthritis. Our study showed that initial Treg frequency was lower in TNF-α transgenic mice than in wild-type mice. However, the course of arthritis was marked by elevation of Treg frequency and a dramatic increase in expression of TNFR2. Antagonizing TNF-α with either the anti-human TNF-α Ab (infliximab) or active immunotherapy (TNF-kinoid) increased the Treg frequency and upregulated CTLA-4, leading to enhancement of suppressor activity. Moreover, both anti-TNF-α strategies promoted the differentiation of a CD62L(-) Treg population. In conclusion, in an in vivo model of TNF-α-driven arthritis, Treg frequency increased with inflammation but failed to control the inflammatory process. Both passive and active TNF-α-inhibiting strategies restored the suppressor activity of Treg and induced the differentiation of a CD62L(-) Treg population.

AIF-mediated caspase-independent necroptosis: a new chance for targeted therapeutics.

Cell death has been initially divided into apoptosis, in which the cell plays an active role, and necrosis, which is considered a passive cell death program. Intense research performed in the last decades has concluded that "programmed" cell death (PCD) is a more complex physiological process than initially thought. Indeed, although in most cases the PCD process is achieved via a family of Cys proteases known as caspases, an important number of regulated PCD pathways do not involve this family of proteases. As a consequence, active forms of PCD are initially referred to as caspase-dependent and caspase-independent. More recent data has revealed that there are also active caspase-independent necrotic pathways defined as necroptosis (programmed necrosis). The existence of necroptotic forms of death was corroborated by the discovery of key executioners such as the kinase RIP1 or the mitochondrial protein apoptosis-inducing factor (AIF). AIF is a Janus protein with a redox activity in the mitochondria and a pro-apoptotic function in the nucleus. We have recently described a particular form of AIF-mediated caspase-independent necroptosis that also implicates other molecules such as PARP-1, calpains, Bax, Bcl-2, histone H2AX, and cyclophilin A. From a therapeutic point of view, the unraveling of this new form of PCD poses a question: is it possible to modulate this necroptotic pathway independently of the classical apoptotic paths? Because the answer is yes, a wider understanding of AIF-mediated necroptosis could theoretically pave the way for the development of new drugs that modulate PCD. To this end, we present here an overview of the current knowledge of AIF and AIF-mediated necroptosis. We also summarize the state of the art in some of the most interesting therapeutic strategies that could target AIF or the AIF-mediated necroptotic pathway.

Mitochondrial AIF loss causes metabolic reprogramming, caspase-independent cell death blockade, embryonic lethality, and perinatal hydrocephalus.

OBJECTIVES: Apoptosis-Inducing Factor (AIF) is a protein involved in mitochondrial electron transport chain assembly/stability and programmed cell death. The relevant role of this protein is underlined because mutations altering mitochondrial AIF properties result in acute pediatric mitochondriopathies and tumor metastasis. By generating an original AIF-deficient mouse strain, this study attempted to analyze, in a single paradigm, the cellular and developmental metabolic consequences of AIF loss and the subsequent oxidative phosphorylation (OXPHOS) dysfunction. METHODS: We developed a novel AIF-deficient mouse strain and assessed, using molecular and cell biology approaches, the cellular, embryonic, and adult mice phenotypic alterations. Additionally, we conducted ex vivo assays with primary and immortalized AIF knockout mouse embryonic fibroblasts (MEFs) to establish the cell death characteristics and the metabolic adaptive responses provoked by the mitochondrial electron transport chain (ETC) breakdown. RESULTS: AIF deficiency destabilized mitochondrial ETC and provoked supercomplex disorganization, mitochondrial transmembrane potential loss, and high generation of mitochondrial reactive oxygen species (ROS). AIF-/Y MEFs counterbalanced these OXPHOS alterations by mitochondrial network reorganization and a metabolic reprogramming toward anaerobic glycolysis illustrated by the AMPK phosphorylation at Thr172, the overexpression of the glucose transporter GLUT-4, the subsequent enhancement of glucose uptake, and the anaerobic lactate generation. A late phenotype was characterized by the activation of P53/P21-mediated senescence. Notably, approximately 2% of AIF-/Y MEFs diminished both mitochondrial mass and ROS levels and spontaneously proliferated. These cycling AIF-/Y MEFs were resistant to caspase-independent cell death inducers. The AIF-deficient mouse strain was embryonic lethal between E11.5 and E13.5 with energy loss, proliferation arrest, and increased apoptotic levels. Contrary to AIF-/Y MEFs, the AIF KO embryos were unable to reprogram their metabolism toward anaerobic glycolysis. Heterozygous AIF+/- females displayed progressive bone marrow, thymus, and spleen cellular loss. In addition, approximately 10% of AIF+/- females developed perinatal hydrocephaly characterized by brain development impairment, meningeal fibrosis, and medullar hemorrhages; those mice died 5 weeks after birth. AIF+/- with hydrocephaly exhibited loss of ciliated epithelium in the ependymal layer. This phenotype was triggered by the ROS excess. Accordingly, it was possible to diminish the occurrence of hydrocephalus AIF+/- females by supplying dams and newborns with an antioxidant in drinking water. CONCLUSIONS: In a single knockout model and at 3 different levels (cell, embryo, and adult mice) we demonstrated that by controlling the mitochondrial OXPHOS/metabolism, AIF is a key factor regulating cell differentiation and fate. Additionally, by providing new insights into the pathological consequences of mitochondrial OXPHOS dysfunction, our new findings pave the way for novel pharmacological strategies.

AIF loss deregulates hematopoiesis and reveals different adaptive metabolic responses in bone marrow cells and thymocytes.

Mitochondrial metabolism is a tightly regulated process that plays a central role throughout the lifespan of hematopoietic cells. Herein, we analyze the consequences of the mitochondrial oxidative phosphorylation (OXPHOS)/metabolism disorder associated with the cell-specific hematopoietic ablation of apoptosis-inducing factor (AIF). AIF-null (AIF-/Y ) mice developed pancytopenia that was associated with hypocellular bone marrow (BM) and thymus atrophy. Although myeloid cells were relatively spared, the B-cell and erythroid lineages were altered with increased frequencies of precursor B cells, pro-erythroblasts I, and basophilic erythroblasts II. T-cell populations were dramatically reduced with a thymopoiesis blockade at a double negative (DN) immature state, with DN1 accumulation and delayed DN2/DN3 and DN3/DN4 transitions. In BM cells, the OXPHOS/metabolism dysfunction provoked by the loss of AIF was counterbalanced by the augmentation of the mitochondrial biogenesis and a shift towards anaerobic glycolysis. Nevertheless, in a caspase-independent process, the resulting excess of reactive oxygen species compromised the viability of the hematopoietic stem cells (HSC) and progenitors. This led to the progressive exhaustion of the HSC pool, a reduced capacity of the BM progenitors to differentiate into colonies in methylcellulose assays, and the absence of cell-autonomous HSC repopulating potential in vivo. In contrast to BM cells, AIF-/Y thymocytes compensated for the OXPHOS breakdown by enhancing fatty acid ß-oxidation. By over-expressing CPT1, ACADL and PDK4, three key enzymes facilitating fatty acid ß-oxidation (e.g., palmitic acid assimilation), the AIF-/Y thymocytes retrieved the ATP levels of the AIF +/Y cells. As a consequence, it was possible to significantly reestablish AIF-/Y thymopoiesis in vivo by feeding the animals with a high-fat diet complemented with an antioxidant. Overall, our data reveal that the mitochondrial signals regulated by AIF are critical to hematopoietic decision-making. Emerging as a link between mitochondrial metabolism and hematopoietic cell fate, AIF-mediated OXPHOS regulation represents a target for the development of new immunomodulatory therapeutics.

Modulation of anti-tumor necrosis factor alpha (TNF-α) antibody secretion in mice immunized with TNF-α kinoid.

Tumor necrosis factor alpha (TNF-α) blockade is an effective treatment for patients with TNF-α-dependent chronic inflammatory diseases, such as rheumatoid arthritis, Crohn's disease, and psoriasis. TNF-α kinoid, a heterocomplex of human TNF-α and keyhole limpet hemocyanin (KLH) (TNF-K), is an active immunotherapy targeting TNF-α. Since the TNF-K approach is an active immunization, and patients receiving this therapy also receive immunosuppressant treatment, we evaluated the effect of some immunosuppressive drugs on the generation of anti-TNF-α antibodies produced during TNF-K treatment. BALB/c mice were injected intramuscularly with TNF-K in ISA 51 adjuvant. Mice were also injected intraperitoneally with one of the following: phosphate-buffered saline, cyclophosphamide, methylprednisolone, or methotrexate. Anti-TNF-α and anti-KLH antibody levels were assessed by enzyme-linked immunosorbent assay and the anti-TNF-α neutralizing capacity of sera by L929 bioassay. Our results showed that current treatments used in rheumatoid arthritis, such as methylprednisolone and methotrexate, do not significantly alter anti-TNF-α antibody production after TNF-K immunization. In contrast, the administration of cyclophosphamide (200 mg/kg) after immunization significantly reduced anti-TNF-α antibody titers and their neutralizing capacity.

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 Crohn's 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.

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-1ß 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.

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 Crohn's disease, but also in systemic lupus erythematosus, multiple sclerosis and myasthenia gravis. Clinical trials are in progress in rheumatoid arthritis, Crohn's disease and diabetes. The benefit/risk ratio of anti-cytokine vaccination is currently under study to further develop the vaccination strategies.

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

INTRODUCTION: Passive blockade of tumor necrosis factor-alpha (TNF-alpha) 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-alpha. This study sought to demonstrate a long-lasting therapeutic effect on established arthritis of an active immunotherapy to human (h) TNF-alpha and to evaluate the long-term consequences of an endogenous anti-TNF-alpha response. METHODS: hTNF-alpha transgenic mice, which spontaneously develop arthritides from 8 weeks of age, were immunized with a heterocomplex (TNF kinoid, or TNF-K) composed of hTNF-alpha and keyhole limpet hemocyanin after disease onset. We evaluated arthritides by clinical and histological assessment, and titers of neutralizing anti-hTNF-alpha antibody by enzyme-linked immunosorbent assay and L929 assay. RESULTS: Arthritides were dramatically improved compared to control mice at week 27. TNF-K-treated mice exhibited high levels of neutralizing anti-hTNF-alpha antibodies. Between weeks 27 and 45, all immunized mice exhibited symptoms of clinical deterioration and a parallel decrease in anti-hTNF-alpha neutralizing antibodies. A maintenance dose of TNF-K reversed the clinical deterioration and increased the anti-hTNF-alpha 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-alpha did not induce a recall response to hTNF-alpha in TNF-K immunized mice. CONCLUSIONS: Anti-TNF-alpha 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.

Emerging applications of anticytokine vaccines.

Most chronic inflammatory diseases have an unknown etiology but all involve cytokine cascade in their development. Several cytokines have been identified as major targets in various autoimmune diseases, resulting in the development of monoclonal antibodies against those cytokines. Even if monoclonal antibodies are indeed efficient, passive immunotherapies present some disadvantages and are expensive. To counter this, several strategies have been developed, including active immunotherapy, based on vaccination principles. 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 to its receptor. Efficient vaccines have to induce a short-term response to avoid permanent inhibition of a given cytokine. This review focuses on the different therapeutic vaccination strategies with cytokines 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.

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)alpha, Interleukin-1beta (IL-1beta), 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.

TNFalpha kinoid vaccination-induced neutralizing antibodies to TNFalpha protect mice from autologous TNFalpha-driven chronic and acute inflammation.

The proinflammatory cytokine TNFalpha is a potent mediator of septic shock and a therapeutic target for chronic inflammatory pathologies including rheumatoid arthritis and Crohn's disease. As an alternative to anti-human TNFalpha (hTNFalpha) mAbs and other hTNFalpha blocker approved drugs, we developed an active anti-hTNFalpha immunotherapy, based on a vaccine comprised of a keyhole limpet hemocyanin-hTNFalpha heterocomplex immunogen (hTNFalpha kinoid) adjuvanted in incomplete Freund's adjuvant. In mice transgenic for hTNFalpha (TTg mice), hTNFalpha kinoid vaccination elicited high titers of Abs that neutralized hTNFalpha bioactivities but did not result in a cellular response to hTNFalpha. The vaccine was safe and effective in two experimental models. Kinoid-immunized but not control TTg mice resisted hTNFalpha-driven shock in one model and were prevented from spontaneous arthritis, inflammatory synovitis, and articular destruction in a second model. These data demonstrate an anti-cytokine induction of autoimmune protection against both acute and chronic hTNFalpha exposure. They show that active vaccination against a human cytokine can be achieved, and that the immune response can be effective and safe.