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CORRESPONDENCE Virginia Pascual: Virginip{at}Baylorhealth.edu OR Jacques Banchereau: Jacquesb{at}Baylorhealth.edu
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10% of cases of arthritis that begin in childhood. The disease is unique in terms of clinical manifestations, severity of joint involvement, and lack of response to tumor necrosis factor blockade. Here, we show that serum from SoJIA patients induces the transcription of innate immunity genes, including interleukin (IL)-1 in healthy peripheral blood mononuclear cells (PBMCs). Upon activation, SoJIA PBMCs release large amounts of IL-1ß. We administered recombinant IL-1 receptor antagonist to nine SoJIA patients who were refractory to other therapies. Complete remission was obtained in seven out of nine patients and a partial response was obtained in the other two patients. We conclude that IL-1 is a major mediator of the inflammatory cascade that underlies SoJIA and that this cytokine represents a target for therapy in this disease.
V. Pascual and F. Allantaz contributed equally to this work.
Juvenile idiopathic arthritis (JIA), which affects an estimated 250,000 children in the United States alone, is an important cause of short- and long-term disability. The term JIA encompasses a heterogeneous group of diseases that is classified according to three major types of presentation: (a) oligoarthritis, (b) polyarthritis, and (c) systemic onset JIA (SoJIA). Each of these groups has a different prognosis and responds differently to available therapies (1, 2); this suggests that their pathogenesis also is unique.
Children who have SoJIA present with systemic symptoms, fever, and/or rash, which may precede the development of arthritis by months or even years. Fever, anemia, leukocytosis, and elevated erythrocyte sedimentation rate (ESR) are the main initial features of the disease. Because these symptoms are nonspecific, patients often undergo extensive diagnostic tests and hospitalizations. Although the disease outcome is highly variable, the overall prognosis seems to correlate with the persistence of systemic symptoms and the number of joints that is involved 6 mo into the disease course (36). Overall, up to 50% of SoJIA patients continue to have active arthritis 510 yr after diagnosis (2, 7, 8). Because long-term disability is correlated directly with duration of active disease, this group has the most severe outcome, and thus, represents the most serious challenge to pediatric rheumatologists. The pathogenesis of SoJIA remains an enigma, but increased levels of IL-6 seem to correlate with the systemic activity of the disease and with the development of arthritis (9).
Multi-drug treatment of SoJIA patients depends on the phase (systemic versus arthritic) of the disease and the extent of involvement. Although a minority of patients do well with nonsteroidal anti-inflammatory drugs, most patients require oral and/or systemic corticosteroids (10) and methotrexate (MTX) for prolonged periods to treat the systemic manifestations and arthritis, respectively. Steroid treatment results in significant morbidity, including vertebral compression fractures, cataracts, and severe growth retardation. Other medications that are used in recalcitrant cases include intravenous gamma globulin, cyclosporine, and thalidomide (11, 12). Anti-TNF therapy is effective against some types of JIA (13, 14), but most SoJIA patients do not respond to this treatment (15, 16). Here we show data which indicate that IL-1 is a major mediator of the inflammatory cascade that underlies SoJIA, and that IL-1Ra is an effective treatment for this disease.
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RESULTS
Top
Abstract
RESULTS
DISCUSSION
MATERIALS AND METHODS
References
Incubation of healthy PBMCs with SoJIA serum up-regulates transcription of innate immunity genes
We have previously shown that interferon-
, which is present in the serum of patients who have systemic lupus erythematosus (SLE), induces the differentiation of healthy monocytes into dendritic cells (17) and that all active SLE PBMCs display an interferon signature (18). After a similar strategy, we cultured healthy PBMCs with the serum of four active SoJIA patients and examined the induced gene transcription pattern using Affymetrix oligonucleotide microarrays (accession nos. are provided in Table S1, available at http://www.jem.org/cgi/content/full/jem.20050473/DC1). Each PBMC sample was processed: (a) fresh without culture; (2) after 6 h incubation with autologous serum; and (3) after 6 h incubation with SoJIA serum. Fig. 1 a shows 46 genes whose expression increased more than twofold in healthy PBMCs that were cultured with SoJIA serum. Up-regulated genes included several members of the IL-1 cytokine/cytokine receptor family. IL-1b transcription was induced by 4/4 SoJIA sera from 4- to 40-fold (median, 8.2-fold). IL-1a was up-regulated by 3/4 of the SoJIA sera (median 13-fold), as were their receptors, IL-1R1 and IL-1R2 (median four- and twofold, respectively). In contrast, IL-6 was up-regulated by only one of the SoJIA sera. RT-PCR analysis of IL-1b transcription confirmed the microarray data (unpublished data). SoJIA sera also induced the transcription of chemokines that are involved in the chemotaxis of stem cells (CXCL2), neutrophils (CXCL1, CXCL3, CXCL5, CXCL6), monocyte/macrophages (CCL2, CCL7), and lymphocyte/dendritic cells (CCL20; reference 19). CCR1, a receptor for numerous chemokines which is considered to be a target in autoimmunity (20), also was increased. Among receptors that are associated with pathogen recognition, fibronectin was the most significantly up-regulated (17-fold), followed by the diphtheria toxin receptor (9.6-fold); and the lectins, ANGPTL4 and MDL1/CLECSF5 (greater than fivefold). Pentraxin-3, the scavenger macrophage receptor with collagenous structure (MARCO), toll-like receptor 2, and the C1q receptor were up-regulated two- to fourfold by 3/4 SoJIA sera. Triggering receptor expressed on myeloid cells (TREM1) was up-regulated significantly only by the sera from the two untreated patients. Transcripts which encode molecules that are involved in cell adhesion and/or motility, as well as a variety of enzymes, including the proinflammatory cyclooxygenase-2, were up-regulated. Other up-regulated molecules are listed in Fig. 1 and Tables S1 and S2 (available at http://www.jem.org/cgi/content/full/jem.20050473/DC1).
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SoJIA sera induce healthy PBMCs to secrete IL-1b
The increased expression of IL-1b was analyzed further at the protein level. SoJIA sera induced healthy PBMCs to produce 63 ± 39 pg/ml of IL-1b (mean ± SD; range <10136 pg/ml; n = 10; P = 0.017), whereas healthy sera did not (<10 pg/ml; n = 3; Fig. 1 c). Sera from febrile SoJIA patients were more efficient at inducing IL-1b secretion than were sera from afebrile patients (P = 0.005), which, in turn, were more efficient than healthy sera (P = 0.003; Fig. 1 d). Taken together, these data indicate that SoJIA serum induces transcription and translation of IL-1b in healthy PBMCs.
Activated SoJIA PBMCs produce high levels of IL-1b
Recently, monocytes from patients who had autoinflammatory diseases were shown to produce higher levels of IL-1b than control monocytes (22). Thus, we tested the capacity of SoJIA patients' PBMCs to secrete IL-1b upon activation with PMA-ionomycin. After 24 h, PBMCs from five SoJIA patients secreted 333 ± 204 pg/ml (range, 154569 pg/ml), whereas PBMCs from five healthy controls secreted 21 ± 4 pg/ml IL-1b (mean ± SD; P = 0.007; Fig. 2 a). In the same cultures, IL-6 and TNF production was not significantly different between patients and controls (Fig. 2 b).
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| DISCUSSION |
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Although SoJIA serum induces IL-1b secretion by healthy PBMCs in vitro, IL-1b serum levels in our patients were as low as those of healthy individuals. Serum cytokine levels, however, may not reflect a cytokine's role in disease pathogenesis. For example, virtually all PBMCs from children who have SLE display an interferon-
signature, although this cytokine is detectable in the serum in less than 50% of patients (18). Furthermore, IL-1b is involved in the pathogenesis of familial autoinflammatory syndromes (22, 23), and blocking IL-1 with IL-1Ra resolves the clinical symptoms that are associated with mutations in the NALP3/cryopyrin gene (Muckle-Wells syndrome and neonatal onset multisystem inflammatory disease/chronic, infantile, neurologic, cutaneous and articular syndrome) (24). However, the serum IL-1 concentration and the cytokine mRNA in PBMCs from these patients are not raised either (25). Although SoJIA normally is a sporadic disease, de novo mutations and/or subtle polymorphisms of genes within the IL-1 pathway could contribute to its pathogenesis. The IL-1 family includes nine members (26), eight of which were not up-regulated using real-time PCR in patients' PBMCs (unpublished data).
The central role of IL-1 in SoJIA is illustrated by the remarkable clinical response of the patients to IL-1Ra. Nine out of nine patients who had long-standing disease that was resistant to other forms of treatment responded to this therapy. Seven of nine cleared symptoms and laboratory abnormalities within days to weeks of therapy initiation; one patient showed a clear trend toward improvement. One patient who had had active disease for 12 uninterrupted years had a quick response and remained afebrile for the 6-mo follow-up period. Her arthritis and laboratory abnormalities, however, improved only transiently. Microarray analysis showed that this patient had a modest (2.7-fold) up-regulation of the IL-1b gene (Table S2). Complete characterization of her IL-1b response to PBMC activation is underway.
IL-1b was shown to be a key mediator of synovial inflammation in experimental arthritis models. IL-1bdeficient mice fail to develop chronic, erosive arthritis in response to arthritogenic stimuli (27) and IL-1Radeficient mice develop autoimmunity and arthritis spontaneously (28). IL-1 blockade with recombinant IL-1Ra, however, did not offer significant advantages over anti-TNF blockade in rheumatoid arthritis patients, and did not show efficacy in patients who were failing anti-TNF treatment (29, 30). Increased serum level of soluble TNF receptors have been described in SoJIA (31), and it has been suggested that TNF probably is more important than IL-1 in the systemic inflammation that characterizes this disease (32). However, although anti-TNF agents are efficacious in children within other JIA subgroups (14), most SoJIA patients do not respond to this therapy. Furthermore, a subgroup of these patients progresses to an unremitting course that is unresponsive to any combination of therapies. These patients also experience significant morbidity from treatment.
Based on our observation that IL-1 production is dysregulated in SoJIA, we treated nine SoJIA patients who were failing other therapies with IL-1 blockade and obtained complete disease remission in seven of them. Lack of full response in two patients may suggest a level of disease heterogeneity that needs to be addressed further. Two other SoJIA patients who had prolonged, therapy-resistant disease recently were reported to respond to IL-1 blockade (33). The unique pattern of cytokine abnormalities and response to biologic therapy that we describe suggests that SoJIA may be classified better as an autoinflammatory syndrome, rather than as an autoimmune disease under the broad spectrum of JIA.
The availability of IL-1Ra may represent a major step toward preventing the development of severe, deforming arthritis and avoiding the use of prolonged corticosteroids and their devastating side effects in this group of patients. Controlled clinical trials are necessary to delineate clinical response, remission duration, and the use of IL-1Ra to substitute eventually for corticosteroids as the first-line treatment for this disease. The current findings should encourage the development of other IL-1 antagonists with improved potency and pharmacokinetics.
| MATERIALS AND METHODS |
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PBMC cultures and RNA extraction
PBMCs were obtained by Ficoll-Histopaque gradient centrifugation of 20 ml of blood. PBMCs were cultured (106/ml) in RPMI 1640 supplemented with 20% autologous or SoJIA patient serum for 6 h. RNA was extracted using RNAeasy kit (QIAGEN) and assessed using an Agilent 2100 Bioanalyzer (Agilent Technologies). Supernatants were frozen at 80°C. PBMCs were cultured with RPMI 1640 and 10% FCS with PMA (50 ng/ml)Ionomycin (1 µg/ml) for 24 h. Cells were harvested and the RNA was extracted as above. Supernatants were frozen at 80°C.
Microarrays and real-time PCR
Samples for microarray analysis were processed as described previously (18) and hybridized to the HG U133A Affymetrix GeneChip array containing 22,283 probe sets (Affymetrix, Inc.) at 45°C for 16 h. GeneChip arrays were washed, stained, and scanned according to protocols that are described in the GeneChip Expression Analysis Technical Manual (Affymetrix Inc.). Scanned GeneChips were inspected visually for abnormalities or irregularities.
Data analysis
Intensity values were scaled to 500 using global scaling in MAS 5.0 and data were exported in MS Excel for import into GeneSpring software (Silicon Genetics) for gene expression analyses. No "per chip" normalization was performed because global scaling had been applied in MAS 5.0. Global scaling adjusts for chip-to-chip variations in hybridization intensities. Subsequent samples were normalized to pediatric healthy controls and/or to the median of all samples. Statistical comparisons were performed in GeneSpring using parametric (Welch's approximate t test) and nonparametric (Mann-Whitney U-test) methods. Unsupervised hierarchical clustering was performed to visualize transcripts that had a control signal of 50 or greater (above the background intensity) and that were identified as "present" according to MAS 5.0 in 75% of all samples. Statistical comparisons were performed in GeneSpring using parametric (Welch's approximate t test) and nonparametric (Mann-Whitney U-test) methods. Unsupervised hierarchical clustering was performed to visualize transcript/sample relationships using standard correlation, Pearson correlation, or Euclidian distance where indicated.
The GenBank/EMBL/DDBJ accession numbers of the genes presented in Fig. 1 are (in order of appearance on the figure): M15329; NM_000576; NM_000877; NM_004633; NM_000600; S69738; NM_002090; NM_006273; NM_001511; M57731; AK026546; NM_004591; NM_002993; AI421071; BC005858; NM_001945; NM_013252; NM_016109; NM_002852; NM_006770; NM_003264; NM_012072; NM_018643; NM_022842; AI380298; AA576961; AA156721; H97931; NM_002575; U38321; NM_000963; NM_001912; X91817; NM_005084; NM_024524; NM_025195; NM_002826; NM_001995; NM_000361; BF511231; NM_004430; NM_005461; NM_005306; M74921; BF062629; U73191.
Two-step RT-PCR was performed using Applied Biosystems TaqMan Assays on Demand probe and primer sets according to the manufacturer's instructions and the ABI Prism 7700 Sequence detection System (Applied Biosystems). The endogenous GAPDH gene and/or 18S RNA were used for correcting the results with the comparative threshold cycle method for relative quantification as described by the manufacturer.
Multiplex analysis
Culture supernatants were analyzed for six cytokines and chemokines using the FluorikineMAP cytokine assay kit (R&D Systems) as per the manufacturer's protocol.
Online supplemental material
Table S1 provides a description of the genes that were up-regulated by SoJIA serum (from Fig. 1, a and b). Table S2 displays the microarray data corresponding to the 46 probes from Fig. 1 (a and b). For each gene probe, raw (top) and normalized (bottom) values are provided. Normalization was done to the value of the corresponding autologous serum cultures (for the in vitro experiments), and to the median of 12 healthy pediatric controls (for the patient's data). Tables S3S6 show the demographics, clinical symptoms, and treatment of the patients whose sera was used in the experiments that are depicted in Figs. 1, ad and Fig. 2, ac, respectively. Tables S7S15 summarize the core set criteria for visits 0 (time of initiation of Anakinra treatment and 1 (2-mo follow-up), and the last clinic visit (212-mo follow-up). Online supplemental material is available at http://www.jem.org/cgi/content/full/jem.20050473/DC1.
| Acknowledgments |
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This work was supported by Baylor Health Care System Foundation and the National Institutes of Health grant nos. R01 AR050770-01 (to V. Pascual) and CA78846 and U19A1057234-02 (to J. Banchereau). J. Banchereau holds the Caruth Chair for Transplantation Immunology.
The authors have no conflicting financial interests.
Submitted: 4 March 2005
Accepted: 28 March 2005
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