Established Collagen-induced Arthritis Research Articles

IVIG ameliorate inflammation in collagen-induced arthritis: projection for IVIG therapy in rheumatoid arthritis.

Rheumatoid arthritis (RA) is a systemic inflammatory autoimmune disease that leads to joint destruction and disability. Despite a significant progress in administration of biological agents for RA patients, there is still a need for improved therapy. Intravenous immunoglobulins (IVIG), a pooled polyspecific immunoglobulin (Ig)G extracted from 5000 to 20 000 healthy subjects, showed beneficial therapeutic effect in patients with immune deficiency, sepsis and autoimmune diseases. The current study aimed to investigate the beneficial effect of treatment with IVIG in established collagen-induced arthritis in DBA/1j mice. Murine arthritis was induced in DBA/1j mice. Treatment with IVIG began when the disease was established. The clinical score was followed twice a week until day 48. The mice were bled for plasma and the paws were hematoxylin and eosin (H&E)-stained. Cytokine profile in the plasma was analyzed by Luminex technology and titers of circulating anti-collagen antibodies in the plasma was tested by enzyme-linked immunosorbent assay. Our results show that treatment with IVIG in murine significantly reduced the clinical arthritis score (P<0·001). Moreover, mode of action showed that IVIG significantly reduced circulating levels of inflammatory cytokines [interferon (IFN)-γ, interleukin (IL)-1β, IL-17, IL-6, tumor necrosis factor (TNF)-α, P<0·001], inhibiting anti-collagen antibodies (P<0·001) in the plasma of collagen-induced arthritis mice. Importantly, histopathological examination revealed that IVIG treatment prevented the migration of inflammatory immune cells into the cartilage and synovium, reduced the extent of joint damage and preserved joint architecture. Our results proved for the first time the valuable anti-inflammatory treatment of IVIG in experimental RA. We propose IVIG therapy for a subgroup of patients with rheumatologically related diseases.

Helminths-based bi-functional molecule, tuftsin-phosphorylcholine (TPC), ameliorates an established murine arthritis.

A novel small molecule named tuftsin-phosphorylcholine (TPC), which is linked to the biological activity of helminths, was constructed. The current study address the effect of TPC treatment in established collagen-induced arthritis (CIA) mice and propose TPC bi-functional activity. TPC treatment was initiated when clinical score was 2 to 4. Arthritis scores in TPC treated mice were lower compared to mice treated with vehicle (P < 0.001). Joint staining showed normal joint structure in TPC-treated mice compared to control groups treated with phosphate buffered saline (PBS), phosphorylcholine, or tuftsin, which exhibited severely inflamed joints. TPC enhanced anti-inflammatory response due to increased IL-10 secretion, and reduced pro-inflammatory cytokine secretion (IL-1-β, IL-6, TNF-αP < 0.001). Furthermore, TPC therapy increased expansion of CD4+CD25+FOXP3+T regulatory cells and IL-10+CD5+CD1d+B regulatory cells. We propose that the immunomodulatory activity of TPC can be a result of a bi-specific activity of TPC: (a) The tuftsin part of the TPC shifts RAW macrophage cells from pro-inflammatory macrophages M1 to anti-inflammatory M2-secreting IL-10 (P < 0.001) through neuropilin-1 and (b) TPC significantly reduce mouse TLR4 expression via NFkB pathway by HEKTM cells (P < 0.02) via the phosphorylcholine site of the molecule. Our results indicate that TPC, significantly ameliorated established CIA by its immunomodulatory activity. These data could lead to a novel self bi-functional small molecule for treating patients with progressive RA.

ICOS-mediated phosphoinositide 3-kinase signaling controls induction and maintenance of collagen-induced arthritis

Abstract The inducible T-cell costimulator (ICOS) is a key costimulatory receptor facilitating differentiation and function of follicular helper T cells and inflammatory T cells. Rheumatoid arthritis patients were shown to have elevated levels of ICOS+ T cells in the synovial fluid suggesting a potential role of ICOS-mediated T cell costimulation in autoimmune joint inflammation. In this study, using ICOS knockout and knockin mouse models, we found that ICOS-mediated phosphoinositide 3-kinase (PI3K) signaling is required for the induction and maintenance of collagen-induced arthritis (CIA), a murine model of rheumatoid arthritis. For the initiation of CIA, ICOS-mediated PI3K signaling was critical for antibody production and expansion of inflammatory T cells. Further, we found that ICOS-PI3K signaling is important for maintenance of CIA in an antibody independent manner. Importantly, we found that a small molecule inhibitor of glycolysis, 3-bromopyruvate, ameliorates established CIA suggesting a potential link between ICOS-PI3K signaling and glucose metabolism. Thus, we identified ICOS-PI3K axis as a key signaling pathway that controls induction and maintenance of CIA and provide evidence that T cell glycolytic pathways can be potential therapeutic targets for rheumatoid arthritis.

ICOS Signaling Controls Induction and Maintenance of Collagen-Induced Arthritis.

ICOS is a key costimulatory receptor facilitating differentiation and function of follicular helper T cells and inflammatory T cells. Rheumatoid arthritis patients were shown to have elevated levels of ICOS+ T cells in the synovial fluid, suggesting a potential role of ICOS-mediated T cell costimulation in autoimmune joint inflammation. In this study, using ICOS knockout and knockin mouse models, we found that ICOS signaling is required for the induction and maintenance of collagen-induced arthritis (CIA), a murine model of rheumatoid arthritis. For the initiation of CIA, the Tyr181-based SH2-binding motif of ICOS that is known to activate PI3K was critical for Ab production and expansion of inflammatory T cells. Furthermore, we found that Tyr181-dependent ICOS signaling is important for maintenance of CIA in an Ab-independent manner. Importantly, we found that a small molecule inhibitor of glycolysis, 3-bromopyruvate, ameliorates established CIA, suggesting an overlap between ICOS signaling, PI3K signaling, and glucose metabolism. Thus, we identified ICOS as a key costimulatory pathway that controls induction and maintenance of CIA and provide evidence that T cell glycolytic pathways can be potential therapeutic targets for rheumatoid arthritis.

Stimulation of TNF receptor type 2 expands regulatory T cells and ameliorates established collagen-induced arthritis in mice.

Tumor necrosis factor (TNF) and its receptors TNF receptor type 1 (TNFR1) and type 2 (TNFR2) have a central role in chronic inflammatory diseases. While TNFR1 mainly confers inflammation, activation of TNFR2 elicits not only pro-inflammatory but also anti-inflammatory effects. In this study, we wanted to investigate the anti-inflammatory therapeutic potential of selective activation of TNFR2 in mice with established collagen-induced arthritis. Mice with established arthritis induced by immunization with bovine collagen type II were treated with six injections of the TNFR2-specific agonist TNCscTNF80, given every second day. Two days after treatment cessation, the cell compositions of bone marrow, spleen and lymph nodes were analyzed. Mice were visually scored until day 30 after the start of therapy and the degree of joint inflammation was determined by histology. Treatment with TNCscTNF80 increased arthritis-induced myelopoiesis. Little effect was seen on the infiltration rate of inflammatory immature myeloid cells and on the reduction of lymphoid cells in secondary lymphoid organs. Upon treatment, frequency of regulatory T (Treg) cells in the CD4+ T-cell population was increased in both spleen and inguinal lymph nodes. In addition, the expression of TNFR2 on Treg cells was enhanced. The clinical score started to improve 1 week after cessation treatment and remained lower 30 days after initiation of therapy. The histological score also revealed amelioration of joint inflammation in TNCscTNF80-treated versus control mice. Activation of TNFR2 might provide a suitable therapeutic strategy in autoimmune arthritis by increasing the numbers of regulatory cell types, in particular Treg cells, and by attenuation of arthritis.

Repository corticotropin injection (H.P. Acthar® Gel) attenuates established collagen-induced arthritis when used alone or as adjuvant therapy with etanercept (Enbrel®) (THER5P.902)

Abstract Melanocortins have anti-inflammatory and immunomodulatory properties mediated by receptors expressed on cells relevant to the pathophysiology of immune-mediated arthritis. Repository corticotropin, a melanocortin preparation, is approved as adjunctive therapy for rheumatoid arthritis (RA), but its mechanism of action in RA has not been determined. We therefore explored the efficacy of corticotropin when used alone or as adjunct therapy with etanercept in a rat collagen-induced arthritis (CIA) model. Corticotropin (160 or 400 U/kg) administered after disease onset significantly attenuated CIA-related changes in ankle diameter and paw weight compared to vehicle treatment (p ≤ 0.05). Corticotropin (400 U/kg) also significantly reduced clinical (4.15 ± 0.38 vs 5.65 ± 0.21, p ≤ 0.01) and summed ankle histopathology (9.90 ± 0.88 vs 15.20 ± 0.85, p ≤ 0.0001) scores below those in vehicle treated rats. Overall efficacy of corticotropin and etanercept used alone in established CIA were comparable, however corticotropin in combination with etanercept synergistically attenuated anti-collagen antibodies and both clinical and histopathologic measures of CIA vs etanercept alone (p ≤ 0.05). In addition, corticotropin administered with etanercept significantly attenuated CIA-induced decreased average bone density, whereas neither drug alone was efficacious (p ≤ 0.05). These data support the potential clinical efficacy of repository corticotropin as an adjunctive therapy for patients with RA.

TGF-β-induced CD4+ regulatory T cells but not nTregs ameliorate autoimmune arthritis by shifting the balance between Tregs and Th17 cells In vivo (179.14)

Abstract Transferred CD4+CD25+Foxp3+ regulatory cells (Tregs) can prevent autoimmune disease, but generally fail to ameliorate established disease. Here we demonstrate that antigen-specific Tregs induced with IL-2 and TGF-β ex-vivo (iTregs), but not equivalent expanded thymus-derived nTregs can prevent progression of established collagen-induced arthritis. This was because following transfer, nTregs exhibited decreased Foxp3 and Bcl-2 expression, decreased suppressive activity, and many converted to Th17 cells. By contrast, transferred iTregs were more numerous, retained their suppressive activity in the presence of IL-6 and were resistant to conversion. Remarkably, ten days after transfer iTregs shifted the predominance from Th17 to Treg cells in draining LNs. These findings provide evidence that transferred TGF-β-induced iTregs are more stable and functional than nTregs in mice with established autoimmunity. Moreover, iTregs can have tolerogenic effects even in the presence of ongoing inflammation. The therapeutic potential of iTregs in subjects with chronic, immune-mediated inflammatory diseases deserves to be investigated.

Inhibition of Epidermal Growth Factor Receptor Tyrosine Kinase Ameliorates Collagen-Induced Arthritis

Rheumatoid arthritis (RA) is an autoimmune synovitis characterized by the formation of pannus and the destruction of cartilage and bone in the synovial joints. Although immune cells, which infiltrate the pannus and promote inflammation, play a prominent role in the pathogenesis of RA, other cell types also contribute. Proliferation of synovial fibroblasts, for example, underlies the formation of the pannus, while proliferation of endothelial cells results in neovascularization, which supports the growth of the pannus by supplying it with nutrients and oxygen. The synovial fibroblasts also promote inflammation in the synovium by producing cytokines and chemokines. Finally, osteoclasts cause the destruction of bone. In this study, we show that erlotinib, an inhibitor of the tyrosine kinase epidermal growth factor receptor (EGFR), reduces the severity of established collagen-induced arthritis, a mouse model of RA, and that it does so by targeting synovial fibroblasts, endothelial cells, and osteoclasts. Erlotinib-induced attenuation of autoimmune arthritis was associated with a reduction in number of osteoclasts and blood vessels, and erlotinib inhibited the formation of murine osteoclasts and the proliferation of human endothelial cells in vitro. Erlotinib also inhibited the proliferation and cytokine production of human synovial fibroblasts in vitro. Moreover, EGFR was highly expressed and activated in the synovium of mice with collagen-induced arthritis and patients with RA. Taken together, these findings suggest that EGFR plays a central role in the pathogenesis of RA and that EGFR inhibition may provide benefits in the treatment of RA.

A non-peptide AT2 receptor agonist attenuates clinical and histological signs in murine collagen-induced arthritis

Background and objectivesThe renin-angiotensin system is known to play a critical role in inflammation, fibrosis, and end-organ damage. Nevertheless, anti-inflammatory, antifibrotic and antiapoptotic features regulated by angiotensin II type 2...

Immune-Regulatory Mechanisms in Systemic Autoimmune and Rheumatic Diseases

Immune-Regulatory Mechanisms in Systemic Autoimmune and Rheumatic Diseases

Polymerized-Type I Collagen Induces Upregulation of Foxp3-Expressing CD4 Regulatory T Cells and Downregulation of IL-17-Producing CD4+T Cells (Th17) Cells in Collagen-Induced Arthritis

Previous studies showed that polymerized-type I collagen (polymerized collagen) exhibits potent immunoregulatory properties. This work evaluated the effect of intramuscular administration of polymerized collagen in early and established collagen-induced arthritis (CIA) in mice and analyzed changes in Th subsets following therapy. Incidence of CIA was of 100% in mice challenged with type II collagen. Clinimorphometric analysis showed a downregulation of inflammation after administration of all treatments (P < 0.05). Histological analysis showed that the CIA-mice group had extensive bone erosion, pannus and severe focal inflammatory infiltrates. In contrast, there was a remarkable reduction in the severity of arthritis in mice under polymerized collagen, methotrexate or methotrexate/polymerized collagen treatment. Polymerized Collagen but not methotrexate induced tissue joint regeneration. Polymerized Collagen and methotrexate/polymerized collagen but not methotrexate alone induces downregulation of CD4+/IL17A+ T cells and upregulation of Tregs and CD4+/IFN-γ + T cells. Thus, Polymerized Collagen could be an effective therapeutic agent in early and established rheumatoid arthritis by exerting downregulation of autoimmune inflammation.

The sympathetic nervous system stimulates anti-inflammatory B cells in collagen-type II-induced arthritis

BackgroundAs previously shown, the sympathetic nervous system (SNS) shows proinflammatory activity during initiation of arthritis but is anti-inflammatory in established collagen-induced arthritis (CIA). Interleukin 10 (IL-10)-producing B cells suppress arthritis...

Therapeutic effect of tolerogenic dendritic cells in established collagen-induced arthritis is associated with a reduction in Th17 responses.

Tolerogenic dendritic cells (DCs) are antigen-presenting cells with an immunosuppressive function. They are a promising immunotherapeutic tool for the attenuation of pathogenic T cell responses in autoimmune arthritis. The aims of this study were to determine the therapeutic action of tolerogenic DCs in a type II collagen-induced arthritis model and to investigate their effects on Th17 cells and other T cell subsets in mice with established arthritis. Tolerogenic DCs were generated by treating bone marrow-derived DCs with dexamethasone and vitamin D(3) during lipopolysaccharide-induced maturation. Mice with established arthritis received 3 intravenous injections of tolerogenic DCs, mature DCs, or saline. Arthritis severity was monitored for up to 4 weeks after treatment. Fluorescence-labeled tolerogenic DCs were used for in vivo trafficking studies. The in vivo effect of tolerogenic DCs on splenic T cell populations was determined by intracellular cytokine staining and flow cytometry. Tolerogenic DCs displayed a semi-mature phenotype, produced low levels of inflammatory cytokines, and exhibited low T cell stimulatory capacity. Upon intravenous injection into arthritic mice, tolerogenic DCs migrated to the spleen, liver, lung, feet, and draining lymph nodes. Treatment of arthritic mice with type II collagen-pulsed tolerogenic DCs, but not unpulsed tolerogenic DCs or mature DCs, significantly inhibited disease severity and progression. This improvement coincided with a significant decrease in the number of Th17 cells and an increase in the number of interleukin-10-producing CD4+ T cells, whereas tolerogenic DC treatment had no detectable effect on Th1 cells or interleukin-17-producing γ/δ T cells. Treatment with type II collagen-pulsed tolerogenic DCs decreases the proportion of Th17 cells in arthritic mice and simultaneously reduces the severity and progression of arthritis.

Grape seed proanthocyanidin extract (GSPE) differentially regulates Foxp3 + regulatory and IL-17 + pathogenic T cell in autoimmune arthritis

Grape seed proanthocyanidin extract (GSPE), which is the antioxidant derived from grape seeds, has been reported to possess a variety of potent properties. We have previously shown that GSPE attenuates collagen-induced arthritis. However the mechanism by which GSPE regulates the immune response remains unclear, although it may involve effects on the regulation of pathogenic T cells in autoimmune arthritis. To clarify this issue, we have assessed the effects of GSPE on differential regulation of Th17 and regulatory T (Treg) cells subsets in vitro in mouse and human CD4 + T cells. We observed that GSPE decreased the frequency of IL-17 +CD4 +Th17 cells and increased induction of CD4 +CD25 +forkhead box protein 3 (Foxp3) + Treg cells. In vivo, GSPE effectively attenuated clinical symptoms of established collagen-induced arthritis in mice with concomitant suppression of IL-17 production and enhancement of Foxp3 expression (type II collagen-reactive Treg cells) in CD4 + T cells of joints and splenocytes. The presence of GSPE decreased the levels of IL-21, IL-22, IL-26 and IL-17 production by human CD4 + T cells in a STAT3-dependent manner. In contrast, GSPE induces Foxp3 + Treg cells in humans. Our results suggest that GSPE possesses a reciprocal control over IL-17 and Foxp3. By potently regulating inflammatory T cell differentiation, GSPE may serve as a possible novel therapeutic agent for inflammatory and autoimmune diseases, including rheumatoid arthritis.

Cutting Edge: All-Trans Retinoic Acid Sustains the Stability and Function of Natural Regulatory T Cells in an Inflammatory Milieu

Recent studies have demonstrated that plasticity of naturally occurring CD4(+)Foxp3(+) regulatory T cells (nTregs) may account for their inability to control chronic inflammation in established autoimmune diseases. All-trans retinoic acid (atRA), the active derivative of vitamin A, has been demonstrated to promote Foxp3(+) Treg differentiation and suppress Th17 development. In this study, we report a vital role of atRA in sustaining the stability and functionality of nTregs in the presence of IL-6. We found that nTregs treated with atRA were resistant to Th17 and other Th cell conversion and maintained Foxp3 expression and suppressive activity in the presence of IL-6 in vitro. atRA decreased IL-6R expression and signaling by nTregs. Of interest, adoptive transfer of nTregs even from arthritic mice treated with atRA suppressed progression of established collagen-induced arthritis. We suggest that nTregs treated with atRA may represent a novel treatment strategy to control established chronic immune-mediated inflammatory diseases.

Individual Isomers of Conjugated Linoleic Acid Reduce Inflammation Associated with Established Collagen-Induced Arthritis in DBA/1 Mice ,

Previously, dietary conjugated linoleic acid [(CLA), an equal mixture of cis-9, trans-11 (c9t11) and trans-10, cis-12 (t10c12) CLA isomers], was found to reduce inflammation in the murine collagen antibody-induced arthritis model, but less so in the murine collagen-induced arthritis (CIA) model, an arthritic model dependent upon acquired immunity. Because CLA is known to alter the acquired immune response, it was hypothesized that feeding CLA after the establishment of arthritis would reduce paw swelling in the CIA model. In this study, upon the establishment of arthritic symptoms, mice were randomized to the following dietary treatments: corn oil (CO) control (n = 6), 0.5% c9t11-CLA (n = 8), 0.5% t10c12-CLA (n = 6), or 1% combined CLA (1:1 c9t11:t10c12-CLA, n = 6). Paws were scored for severity of arthritis and measured for changes in thickness during an 84-d study period. Dietary c9t11- and combined-CLA similarly decreased the arthritic score (29%, P = 0.036, P = 0.049, respectively, when normalized to initial score) and paw thickness (0.11 mm, P = 0.027, P = 0.035, respectively) compared with CO. Dietary t10c12-CLA reduced the arthritic score (41%, P = 0.007 when normalized) and paw thickness (0.12 mm, P = 0.013) relative to CO. Reduced interleukin-1β on d 7 and 21 for all CLA treatments (n = 3) relative to CO suggested that antiinflammatory effects of CLA isomers might work by common mechanisms of known pathways involved in chronic inflammation. In conclusion, dietary CLA reduced inflammation associated with CIA, and both c9t11-CLA and t10c12-CLA exhibited antiinflammatory effects.

Exosomes derived from interleukin-10-treated dendritic cells can inhibit trinitrobenzene sulfonic acid-induced rat colitis

Objective. Inflammatory bowel disease (IBD), which mainly refers to Crohn's disease and ulcerative colitis, is characterized by chronic inflammation of the gastrointestinal tract. Recent reports have demonstrated that exosomes derived from interleukin-10 (IL-10)-treated bone marrow-derived dendritic cells (DCs) can reduce the incidence and severity of established collagen-induced arthritis (CIA) in mice. Based on the essential role of IL-10 in the development of normal mucosal immunity, we investigated whether exosomes derived from DCs treated with IL-10 (known as IL-10-exosomes) can suppress the trinitrobenzene sulfonic acid (TNBS)-induced colitis. Material and Methods. We used the rat TNBS-induced colitis model to address the therapeutic potential of IL-10-exosomes in vivo. More specifically, a rectal enema of TNBS was administered to Wistar rats, and IL-10-exosomes were injected intraperitoneally on Day 3. Results. In the context of a high level of major histocompatibility complex class II (MHC II) and a low level of co-stimulatory molecule and membrane-bound IL-10 expression, IL-10-exosomes treatment substantially reduced all analyzed clinical, macroscopic, and histopathologic parameters of TNBS-induced colitis. The therapeutic effects of IL-10-exosomes were associated with a down-regulation mRNA expression of IL-2, IFN-γ and TNF-α in colon tissues. Importantly, treatment with IL-10-exosomes resulted in a pronounced up-regulation of IL-10mRNA expression in colon tissues and regulatory T cells (Tregs) in Colonic lamina propria. Conclusions. The results suggest that IL-10-exosomes treatment can suppress acute TNBS-induced colitis and may offer a promising new therapeutic strategy for IBD.

Therapeutic efficacy of experimental rheumatoid arthritis with low-dose methotrexate by increasing partially CD4 +CD25 +Treg cells and inducing Th1 to Th2 shift in both cells and cytokines

Low-dose methotrexate (MTX), a traditional folate antagonist and disease-modifying antirheumatic drug administered weekly either alone or as combination therapy, is widely accepted as the gold standard in rheumatoid arthritis (RA) treatment. Although its mechanism of action in RA is still poorly understood, MTX potentially acts via antiproliferative, anti-inflammatory, and/or immunosuppressive means. The therapeutic mechanisms and efficacy of low-dose MTX and the oral tolerance protein natural chicken type II collagen (nCCII) were compared in vitro and in vivo using an established collagen-induced arthritis (CIA) rat model. We used clinical visual scoring, radiographic X-ray analysis, histopathological examination, and sera anti-CII IgG measurements to determine the severity of disease with and without treatment. Low-dose MTX had significant clinical therapeutic efficacy against established CIA. Similar to nCCII, MTX mediated CIA by specific immunotolerant effects and not by nonspecific immunosuppression. The mechanism underlying the therapeutic efficacy could be at least partially attributed to the increased production of CD4 +CD25 + Treg cells. These cells specifically downmodulated the T lymphocyte proliferative response to CCII but not PHA, induced a Th1-to-Th2 shift, downregulated Th1 cytokines, and upregulated both Th2 and Th3 cytokines. To the best of our knowledge, this is the first demonstration that low-dose MTX probably serves as a potent inducer of specific immunotolerance but not of nonspecific immunosuppression in the treatment of RA.

TGF-β-induced CD4+Foxp3+ Cells but not Natural CD4+CD25+ Cells Suppress Established Collagen-induced Arthritis

TGF-β-induced CD4+Foxp3+ Cells but not Natural CD4+CD25+ Cells Suppress Established Collagen-induced Arthritis

The treatment of established murine collagen-induced arthritis with a TNFR1-selective antagonistic mutant TNF

Blocking the binding of TNF-α to TNF receptor subtype-1 (TNFR1) is an important strategy for the treatment of rheumatoid arthritis (RA). We recently succeeded in developing a TNFR1-selective antagonistic TNF mutant, R1antTNF. Here, we report the anti-inflammatory effects of R1antTNF in a murine collagen-induced arthritis model. To improve the in vivo stability of R1antTNF, we first engineered PEG (polyethylene glycol)-modified R1antTNF (PEG–R1antTNF). In prophylactic protocols, PEG–R1antTNF clearly improved the incidence, and the clinical score of arthritis due to its long plasma half-life. Although, the effect of PEG–R1antTNF on the incidence and production of IL1-β was less than that of the existing TNF-blocking drug Etanercept, its effect on severity was almost as marked as Etanercept. Interestingly, in therapeutic protocols, PEG–R1antTNF showed greater therapeutic effect than Etanercept. These data suggest that the anti-inflammatory effects of PEG–R1antTNF depend on the stage of arthritis. Recently, there has been much concern over the reactivation of viral infection caused by TNF blockade. Unlike Etanercept, PEG–R1antTNF did not reactivate viral infection. Together, these results indicate that selective inhibition of TNF/TNFR1 could be effective in treating RA and that PEG–R1antTNF could serve as a promising anti-inflammatory drug for this purpose.