Christophe Richez

Murine Dendritic Cell Type I IFN Production Induced by Human IgG-RNA Immune Complexes Is IFN Regulatory Factor (IRF)5 and IRF7 Dependent and Is Required for IL-6 Production

Dendritic cell (DC) activation by nucleic acid-containing IgG complexes is implicated in systemic lupus erythematosus (SLE) pathogenesis. However, it has been difficult to definitively examine the receptors and signaling pathways by which this activation is mediated. Because mouse FcγRs recognize human IgG, we hypothesized that IgG from lupus patients might stimulate mouse DCs, thereby facilitating this analysis. In this study, we show that sera and purified IgG from lupus patients activate mouse DCs to produce IFN-α, IFN-β, and IL-6 and up-regulate costimulatory molecules in a FcγR-dependent manner. This activation is only seen in sera with reactivity against ribonucleoproteins and is completely dependent on TLR7 and the presence of RNA. As anticipated, IFN regulatory factor (IRF)7 is required for IFN-α and IFN-β production. Unexpectedly, however, IRF5 plays a critical role in IFN-α and IFN-β production induced not only by RNA-containing immune complexes but also by conventional TLR7 and TLR9 ligands. Moreover, DC production of IL-6 induced by these stimuli is dependent on a functional type I IFNR, indicating the need for a type I IFN-dependent feedback loop in the production of inflammatory cytokines. This system may also prove useful for the study of receptors and signaling pathways used by immune complexes in other human diseases.

Platelet CD154 Potentiates Interferon-α Secretion by Plasmacytoid Dendritic Cells in Systemic Lupus Erythematosus

In the autoimmune disease lupus, platelets activated by self-antigens contribute to pathology by triggering the secretion of interferon from immune cells. Taming the Big Bad Wolf Systemic lupus erythematosus (SLE)—a name some attribute to this disorder’s wolf-like ability to “devour” the affected organs—is an autoimmune inflammatory disease. It can affect virtually any part of the body, but often targets skin, kidney, and joints. A variety of immunological factors have been proposed to contribute to SLE, in particular the type I interferon (IFN) system, which is normally activated in response to viruses. Here, Duffau et al. point to platelets as the culprits in causing aberrant activation of IFN-α (a member of the type I IFN group) in lupus patients and suggest that a drug that blocks platelet activation could be a promising new treatment. A protein called CD154 (CD40 ligand) is found on T cells, where it helps to defend the body by activating cytotoxic immune cells during viral infections. It is also found on the surface of platelets that are activated for clotting and may contribute to the pathogenesis of inflammatory states such as atherosclerosis and autoimmune disorders, including SLE. Here, the authors collected platelets from patients experiencing SLE flare-ups of varying severity, as well as healthy controls, and demonstrated that CD154 abundance and shedding from platelets correlated with disease severity. Moreover, exposure of platelets from healthy donors to serum from patients with active SLE or to immune complexes similar to those in SLE patients triggered an increase in activation and CD154 production. These activated platelets, in turn, signaled to antigen-presenting cells to produce IFN-α, thus propagating an inflammatory cycle, both in vitro and in a murine model of lupus. To further test these ideas, Duffau et al. depleted the platelets in lupus-prone mice, which decreased inflammation in the animals’ kidneys, a commonly affected organ in lupus. They achieved a similar outcome by treating the mice with clopidogrel, an inhibitor of platelet activation already commonly used in patients with heart disease and stroke. In addition to experiencing less kidney damage, the clopidogrel-treated mice with lupus lived for an extra 3 months. The current mainstay of treatment for SLE is immunosuppressive therapy, achieved with steroids and chemotherapy-like medications. These drugs have numerous toxic effects, not the least of which is the immunosuppression itself, which predisposes patients to infections. Being able to treat lupus with an antiplatelet medication such as clopidogrel, which has few side effects, would markedly improve these patients’ safety and quality of life. A similar approach may prove useful in other autoimmune diseases such as rheumatoid arthritis, where it would also provide a badly needed alternative to immunosuppression. Systemic lupus erythematosus (SLE) is a systemic inflammatory autoimmune disease characterized by the involvement of multiple organs and an immune response against nuclear components. Although its pathogenesis remains poorly understood, type I interferon (IFN) and CD40 ligand (CD154) are known to contribute. Because platelets are involved in inflammatory processes and represent a major reservoir of CD154, we hypothesized that they participate in SLE pathogenesis. Here, we have shown that in SLE patients, platelets were activated by circulating immune complexes composed of autoantibodies bound to self-antigens through an Fc-γ receptor IIa (CD32)–dependent mechanism. Further, platelet activation correlated with severity of the disease and activated platelets formed aggregates with antigen-presenting cells, including monocytes and plasmacytoid dendritic cells. In vitro, activated platelets enhanced IFN-α secretion by immune complex–stimulated plasmacytoid dendritic cells through a CD154-CD40 interaction. Finally, in lupus-prone mice, depletion of platelets or administration of the P2Y(12) receptor antagonist (clopidogrel) improved all measures of disease and overall survival; transfusion of activated platelets worsened the disease course. Together, these data identify platelet activation as an important contributor to SLE pathogenesis and suggest that this process and its sequelae may provide a new therapeutic target.

Role for toll-like receptors in autoimmune disease: the example of systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is a multisystem disease characterized by an autoimmune response to nuclear antigens. Although the pathophysiology of SLE remains incompletely understood, many recent studies indicate a major role for innate immunity. The toll-like receptors (TLRs), which play a key role in innate responses to infections, are also involved in acute and chronic inflammatory processes induced by endogenous ligands. Numerous in vitro studies have established that TLR7 and TLR9 are involved in immune complex recognition. Activation of these receptors leads to activation of immune cells, most notably B cells and dendritic cells, and to the inappropriate production of many cytokines known to be directly involved in the pathogenesis of SLE. These data prompted studies in several murine models of SLE to assess the impact of inactivation or overexpression of genes encoding TLRs or molecules involved in TLR signaling pathways. The results confirmed the major role for TLR7 and suggested involvement of TLR4 in the induction of an aggressive autoimmune response. However, in vivo data suggest a protective effect of TLR9, thus contradicting the in vitro results. In humans, genetic studies have identified polymorphisms associated with increased susceptibility to SLE.

Requirement for DNA CpG Content in TLR9-Dependent Dendritic Cell Activation Induced by DNA-Containing Immune Complexes

Although TLR9 was originally thought to specifically recognize microbial DNA, it is now evident that mammalian DNA can be an effective TLR9 ligand. However, the DNA sequence required for TLR9 activation is controversial, as studies have shown conflicting results depending on the nature of the DNA backbone, the route of DNA uptake, and the cell type being studied. In systemic lupus erythematosus, a major route whereby DNA gains access to intracellular TLR9, and thereby activates dendritic cells (DCs), is through uptake as a DNA-containing immune complex. In this report, we used defined dsDNA fragments with a natural (phosphodiester) backbone and show that unmethylated CpG dinucleotides within dsDNA are required for murine DC TLR9 activation induced by a DNA-containing immune complex. The strongest activation is seen with dsDNA fragments containing optimal CpG motifs (purine-purine-CpG-pyrimidine-pyrimidine) that are common in microbial DNA but rare in mammalian DNA. Importantly, however, activation can also be induced by CpG-rich DNA fragments that lack these optimal CpG motifs and that we show are plentiful in CpG islands within mammalian DNA. No activation is induced by DNA fragments lacking CpG dinucleotides, although this CpG-free DNA can induce DC activation if internalized by liposomal transfection instead of as an immune complex. Overall, the data suggest that the release of CpG-rich DNA from mammalian DNA may contribute to the pathogenesis of autoimmune diseases such as systemic lupus erythematosus and psoriasis in which activation of TLR9 in DCs by self DNA has been implicated in disease pathogenesis.

The Peroxisome Proliferator-Activated Receptor γ Agonist Rosiglitazone Ameliorates Murine Lupus by Induction of Adiponectin

Systemic lupus erythematosus (SLE) is an inflammatory autoimmune disease for which current therapy is suboptimal. SLE is characterized by autoantibody production, with renal disease and premature atherosclerosis being common and severe manifestations causing appreciable morbidity and mortality. Peroxisome proliferator-activated receptor γ (PPARγ) agonists are widely used in the treatment of diabetes mellitus for their insulin-sensitizing properties, but also have immunomodulatory effects. In this report, we show that the PPARγ agonist rosiglitazone reduces autoantibody production, renal disease, and atherosclerosis in mouse models of SLE. The beneficial effect of rosiglitazone on SLE manifestations depends on the induction of adiponectin, because rosiglitazone has no effect on autoantibody production or renal disease in lupus mice that lack adiponectin. In addition, lupus mice that lack adiponectin develop more severe disease than adiponectin-sufficient lupus mice, indicating that endogenous adiponectin is involved in regulating disease activity. Furthermore, administration of exogenous adiponectin ameliorates disease. These experiments suggest that PPARγ agonists may be useful agents for the treatment of SLE. They also demonstrate that induction of adiponectin is a major mechanism underlying the immunomodulatory effects of PPARγ agonists.

IFN Regulatory Factor 5 Is Required for Disease Development in the FcγRIIB−/−Yaa and FcγRIIB−/− Mouse Models of Systemic Lupus Erythematosus

Polymorphisms in the transcription factor IFN regulatory factor 5 (IRF5) are strongly associated in human genetic studies with an increased risk of developing the autoimmune disease systemic lupus erythematosus. However, the biological role of IRF5 in lupus pathogenesis has not previously been tested in an animal model. In this study, we show that IRF5 is absolutely required for disease development in the FcγRIIB−/−Yaa and FcγRIIB−/− lupus models. In contrast to IRF5-sufficient FcγRIIB−/−Yaa mice, IRF5-deficient FcγRIIB−/−Yaa mice do not develop lupus manifestations and have a phenotype comparable to wild-type mice. Strikingly, full expression of IRF5 is required for the development of autoimmunity, as IRF5 heterozygotes had dramatically reduced disease. One effect of IRF5 is to induce the production of the type I IFN, IFN-α, a cytokine implicated in lupus pathogenesis. To address the mechanism by which IRF5 promotes disease, we evaluated FcγRIIB−/−Yaa mice lacking the type I IFN receptor subunit 1. Unlike the IRF5-deficient and IRF5-heterozygous FcγRIIB−/−Yaa mice, type I IFN receptor subunit 1-deficient FcγRIIB−/−Yaa mice maintained a substantial level of residual disease. Furthermore, in FcγRIIB−/− mice lacking Yaa, IRF5-deficiency also markedly reduced disease manifestations, indicating that the beneficial effects of IRF5 deficiency in FcγRIIB−/−Yaa mice are not due only to inhibition of the enhanced TLR7 signaling associated with the Yaa mutation. Overall, we demonstrate that IRF5 plays an essential role in lupus pathogenesis in murine models and that this is mediated through pathways beyond that of type I IFN production.

Pattern of demyelination occurring during anti-TNF-α therapy: a French national survey

OBJECTIVE To determine the pattern of demyelinating disorders (DDs) occurring during anti-TNF-α therapy. METHODS Between June 2005 and April 2008, 1800 French rheumatologists and internists were contacted to report cases of DDs occurring in patients treated with anti-TNF-α. RESULTS After a median of 10.2 (1.5-39.9) months of treatment, 33 patients developed DDs: 22 had CNS and 11 peripheral nervous system (PNS) involvement. Underlying diseases were RA (n = 16), AS (n = 11), PsA (n = 4), JIA (n = 1) and PM (n = 1). Anti-TNF-α was infliximab (n = 15), etanercept (n = 12) or adalimumab (n = 6). CNS involvement was encephalic lesions (n = 16), transverse myelitis (n = 8) or retrobulbar optic neuritis (n = 5). Cerebrospinal fluid (CSF) analysis in 16 patients and MRI in 20 patients were abnormal. All patients discontinued anti-TNF-α. Fifteen patients required steroids. Twenty patients initially improved. Five patients developed multiple sclerosis. PNS involvement was chronic (n = 9) or acute inflammatory demyelinating polyneuropathy (n = 2). CSF analysis revealed an increased protein level in nine patients. Nerve conduction studies confirmed DD in all these patients. Anti-TNF-α was discontinued in 10 patients and 8 received i.v. immunoglobulins. Two patients relapsed after introduction of another anti-TNF-α. Overall, a causal relationship between anti-TNF-α and DD was considered as probable in 31 patients and definite in 2 who had positive rechallenge. CONCLUSION Causal relationship between anti-TNF-α and induction of DD remains unclear, but in some cases the chronology of clinical events is suggestive. Nevertheless, DD might persist despite treatment discontinuation, suggesting that anti-TNF-α could trigger the demyelinating process, which further evolves independently.

TLR4 ligands induce IFN-alpha production by mouse conventional dendritic cells and human monocytes after IFN-beta priming.

Exacerbation of disease in systemic lupus erythematosus (SLE) is associated with bacterial infection. In conventional dendritic cells (cDCs), the TLR4 ligand bacterial LPS induces IFN-β gene expression but does not induce IFN-α. We hypothesized that when cDCs are primed by cytokines, as may frequently be the case in SLE, LPS would then induce the production of IFN-α, a cytokine believed to be important in lupus pathogenesis. In this study we show that mouse cDCs and human monocytes produce abundant IFN-α following TLR4 engagement whether the cells have been pretreated either with IFN-β or with a supernatant from DCs activated by RNA-containing immune complexes from lupus patients. This TLR4-induced IFN-α induction is mediated by both an initial TRIF-dependent pathway and a subsequent MyD88-dependent pathway, in contrast to TLR3-induced IFN-α production, which is entirely TRIF-dependent. There is also a distinct requirement for IFN regulatory factors (IRFs), with LPS-induced IFN-α induction being entirely IRF7- and partially IRF5-dependent, in contrast to LPS -induced IFN-β gene induction which is known to be IRF3-dependent but largely IRF7-independent. This data demonstrates a novel pathway for IFN-α production by cDCs and provides one possible explanation for how bacterial infection might precipitate disease flares in SLE.

Incidence of tuberculosis in patients with rheumatoid arthritis. A systematic literature review.

OBJECTIVES To determine the incidence and risk of tuberculosis in rheumatoid arthritis (RA) patients exposed or unexposed to TNFα antagonists, the impact of recommendations about managing latent tuberculosis, the time to diagnosis of active tuberculosis, and the proportion of extrapulmonary forms. METHODS Systematic review of articles retrieved using Medline. From each article, we abstracted the incidence and risk of tuberculosis in RA patients exposed or unexposed to TNFα antagonists, the duration of TNFα antagonist exposure at the diagnosis of tuberculosis, and the distribution of the tuberculosis foci. RESULTS We selected 14 articles. The risk of tuberculosis was increased 2- to 10-fold in RA patients unexposed to TNFα antagonists and 2- to 4-fold in those exposed to TNFα antagonists, compared to the general population. The incidence of tuberculosis in TNFα antagonist-treated patients varied across studies (9.3 to 449/100,000) according to the country, observation period, and TNFα antagonist used. The risk was greater with monoclonal antibodies than with the soluble receptor. Official recommendations have decreased the risk of tuberculosis in TNFα antagonist-treated patients. Over half the cases of active tuberculosis were diagnosed during the first treatment year. Among TNFα antagonist-treated patients with tuberculosis, 60% had extrapulmonary lesions. Disseminated tuberculosis was more common with monoclonal antibodies. CONCLUSIONS The risk of tuberculosis is increased during TNFα antagonist therapy, and the increase is larger with the monoclonal antibodies than with the soluble receptor. Tuberculosis during TNFα antagonist therapy is a rare event that occurs early after treatment initiation. Extrapulmonary involvement is common and potentially severe. Therefore, clinicians should direct careful attention to the risk of tuberculosis associated with TNFα antagonist therapy.

Non–TNF-Targeted Biologic vs a Second Anti-TNF Drug to Treat Rheumatoid Arthritis in Patients With Insufficient Response to a First Anti-TNF Drug: A Randomized Clinical Trial

Importance One-third of patients with rheumatoid arthritis show inadequate response to tumor necrosis factor α (TNF-α) inhibitors; little guidance on choosing the next treatment exists. Objective To compare the efficacy of a non-TNF-targeted biologic (non-TNF) vs a second anti-TNF drug for patients with insufficient response to a TNF inhibitor. Design, Setting, and Participants A total of 300 patients (conducted between 2009-2012) with rheumatoid arthritis, with persistent disease activity (disease activity score in 28 joints-erythrocyte sedimentation rate [DAS28-ESR]  ≥ 3.2 [range, 0-9.3]) and an insufficient response to anti-TNF therapy were included in a 52-week multicenter, pragmatic, open-label randomized clinical trial. The final follow-up date was in August 2013. Interventions Patients were randomly assigned (1:1) to receive a non-TNF-targeted biologic agent or an anti-TNF that differed from their previous treatment. The choice of the biologic prescribed within each randomized group was left to the treating clinician. Main Outcomes and Measures The primary outcome was the proportion of patients with good or moderate response according to the European League Against Rheumatism (EULAR) scale at week 24. Secondary outcomes included the EULAR response at weeks 12 and 52; at weeks 12, 24, and 52; DAS28ESR, low disease activity (DAS28 ≤3.2), remission (DAS28 ≤2.6); serious adverse events; and serious infections. Results Of the 300 randomized patients (243 [83.2%] women; mean [SD] age, 57.1 [12.2] years; baseline DAS28-ESR, 5.1 [1.1]), 269 (89.7%) completed the study. At week 24, 101 of 146 patients (69%) in the non-TNF group and 76 (52%) in the second anti-TNF group achieved a good or moderate EULAR response (OR, 2.06; 95% CI, 1.27-3.37; P = .004, with imputation of missing data; absolute difference, 17.2%; 95% CI, 6.2% to 28.2%). The DAS28-ESR was lower in the non-TNF group than in the second anti-TNF group (mean difference adjusted for baseline differences, -0.43; 95% CI, -0.72 to -0.14; P = .004). At weeks 24 and 52, more patients in the non-TNF group vs the second anti-TNF group showed low disease activity (45% vs 28% at week 24; OR, 2.09; 95% CI, 1.27 to 3.43; P = .004 and 41% vs 23% at week 52; OR, 2.26; 95% CI, 1.33 to 3.86; P = .003). Conclusions and Relevance Among patients with rheumatoid arthritis previously treated with anti-TNF drugs but with inadequate primary response, a non-TNF biologic agent was more effective in achieving a good or moderate disease activity response at 24 weeks than was the second anti-TNF medication. Trial Registration clinicaltrials.gov Identifier: NCT01000441.