Association of the response to tumor necrosis factor antagonists with plasma type I interferon activity and interferon-beta/alpha ratios in rheumatoid arthritis patients: a post hoc analysis of a predominantly Hispanic cohort

The interferon signature in autoimmune diseases

PURPOSE OF REVIEW

An increased expression of type I interferon (IFN) regulated genes (an IFN signature) has been reported in blood and tissue cells from patients with SLE and other autoimmune diseases. We review the possible mechanisms behind the IFN signature as well as clinical and therapeutic consequences of this observation.

RECENT FINDINGS

Autoantigens from dying cells trigger plasmacytoid dendritic cells to a continuous synthesis of type I IFN, which is promoted by natural killer (NK) cells and B cells. A growing number of genes connected to type I IFN production and response associates with an increased susceptibility to autoimmunity. Besides type I IFN, type III IFN (IFN-λ) may contribute to the IFN signature. In SLE and primary Sjögren's syndrome, a prominent IFN signature is connected to an active disease, whereas in rheumatoid arthritis the IFN signature defines a disease subset with poor clinical outcome and treatment failure to B-cell depleting therapy. Several therapies aiming to inhibit the IFN signature are in clinical trials and early data suggest clinical benefits without major safety problems.

SUMMARY

The observed IFN signature in several autoimmune diseases is a biomarker of active disease and is investigated as a tool when selecting treatment for individual patients.

The physiologic increase in expression of some type I IFN-inducible genes during pregnancy is not associated with improved disease activity in pregnant patients with rheumatoid arthritis

During pregnancy, most patients with rheumatoid arthritis (RA) experience a spontaneous improvement in their condition. Since type I interferons (IFN) have immunomodulatory properties, we investigated whether type I IFN-inducible genes are upregulated in pregnant patients with RA. Peripheral blood mononuclear cells were evaluated using quantitative real-time polymerase chain reaction for type I IFN-inducible genes (IFI 35, IFI44, IFI44L, IFIT3, OAS1, and Siglec1) in patients with RA and healthy women during and after pregnancy as well as in nonpregnant controls. IFN-alpha and IFN-beta levels in sera of patients and healthy donors were analyzed by enzyme linked immunosorbent assay. It was found that healthy women did not show a change of gene expression levels from the second trimester until postpartum, yet some type I IFN-inducible genes were significantly upregulated in pregnant and postpartum women compared with nonpregnant individuals. In patients with RA, a pronounced upregulation of IFI35 and IFI44 at the second trimester and a peak expression of Siglec1 at the third trimester were observed. Pregnancy levels of IFI35 and IFI44 in patients with RA were higher than those of nonpregnant patients with RA. No significant association of gene expression levels with disease activity was found. In the sera of patients and healthy women, IFN-beta was undetectable and IFN-alpha levels remained stable throughout pregnancy and postpartum. Thus, pregnancy can give rise to an increased expression of type I IFN-inducible genes, reflecting an upregulation of the innate immune system. However, an association of type I IFN-inducible genes with pregnancy induced disease amelioration seems unlikely.

Serum interleukin 6 before and after therapy with tocilizumab is a principal biomarker in patients with rheumatoid arthritis

OBJECTIVE

Biologic treatments including the humanized anti-interleukin 6 (anti-IL-6) receptor antibody tocilizumab (TCZ) provide therapeutic options for patients with rheumatoid arthritis (RA). We investigated useful biomarkers to predict the responsiveness to TCZ by measurement of serum proinflammatory cytokine concentrations.

METHODS

Serum samples were collected from 61 patients with RA before biologic treatment and at 4 weeks after initial administration of either TCZ (n = 32) or infliximab (IFX; n = 29) and from 13 healthy serum donor controls. Disease Activity Score of 28 joints (DAS28) was determined at baseline and after treatment.

RESULTS

Although IL-1β, IL-2, IL-6, IL-17A, IL-17F, interferon-α, and tumor necrosis factor-α (TNF-α) were all increased in sera from patients with RA compared with controls, only the IL-6 level was significantly correlated with DAS28 before treatment. The IL-6 level before treatment was positively correlated with DAS28 after TCZ treatment, and was significantly lower in TCZ-responsive patients (as judged by a post-treatment DAS28 < 3.2) than in TCZ-resistant patients (post-treatment DAS28 ≥ 3.2). DAS28 after TCZ was significantly lower than after administration of IFX in patients with low pretreatment IL-6 (< 51.5 pg/ml, the mean baseline value of IL-6 in all RA patients), but not in those with high pretreatment IL-6. These results indicate that low serum IL-6 is associated with a favorable response to TCZ.

CONCLUSION

Although both TNF-α and IL-6 are major targets of therapeutic intervention in RA, baseline serum IL-6 but not baseline TNF-α level is a potential biomarker reflecting disease activity. Measurement of serum IL-6 in RA before treatment may be useful to estimate residual disease activity after TCZ treatment and to predict responsiveness to TCZ treatment.

The interferon signature and STAT1 expression in rheumatoid arthritis synovial fluid macrophages are induced by tumor necrosis factor α and counter-regulated by the synovial fluid microenvironment

OBJECTIVE

Type I interferons (IFNs) have emerged as potential activators of the IFN signature and elevated STAT-1 expression in rheumatoid arthritis (RA) synovium, but mechanisms that induce synovial IFN expression are unknown. Recently, tumor necrosis factor α (TNFα) was shown to induce a delayed IFN response in macrophages. We undertook this study to test whether TNFα, classically thought to activate inflammatory NF-κB target genes in RA, also contributes to the "IFN signature" in RA synovial macrophages.

METHODS

Synovial fluid (SF) macrophages purified from 24 patients with RA and 18 patients with spondylarthritides (SpA) were lysed immediately after isolation or were cultured ex vivo in the absence or presence of blockade of endogenous type I IFN or TNFα. Expression of IFN-inducible target genes was measured by quantitative reverse transcription-polymerase chain reaction, and expression of their corresponding proteins was measured by enzyme-linked immunosorbent assay.

RESULTS

Expression of an IFN signature and STAT1 in RA synovial macrophages was suppressed when type I IFNs or TNFα were blocked, whereas TNFα blockade did not affect expression of IFN response genes or STAT1 in SpA synovial macrophages. RA SF suppressed the IFN signature in RA synovial macrophages and in TNFα-, IFNα-, and IFNβ-stimulated control macrophages. Type I IFNs suppressed expression of IL8 and MMP9 in RA synovial macrophages and in TNFα-stimulated control macrophages.

CONCLUSION

Our findings identify a new function of TNFα in RA synovitis by implicating TNFα as a major inducer of the RA synovial IFN response. The results suggest that the expression of IFN response genes in RA synovium is regulated by interplay between TNFα and opposing homeostatic factors expressed in the synovial microenvironment.

Interferon signals and monocytic sensitization of the interferon-γ signaling pathway in the peripheral blood of patients with rheumatoid arthritis

OBJECTIVE

Both type I interferons (IFNα and IFNβ) and type II IFN (IFNγ) signal via pSTAT-1. Immunohistochemistry and the gene expression signatures of rheumatoid arthritis (RA) synovial tissue suggest an activated IFN/STAT-1 signaling pathway. The aim of this study was to determine the systemic activity of the IFN/STAT-1 signaling pathway in the peripheral blood cells of patients with RA.

METHODS

Fluorocytometry or quantitative polymerase chain reaction was used to measure the expression of STAT-1, pSTAT-1, and IFN-inducible genes (monokine induced by interferon-γ [MIG], interferon-γ-inducible protein 10 [IP-10], and 2',5'-oligoadenylate synthetase [OAS]) in the peripheral blood mononuclear cells (PBMCs) and purified CD14+ peripheral blood monocytes of patients with RA and healthy control subjects. PBMCs were also incubated for 48 hours with IFNs and several other cytokines to investigate influences on STAT-1 levels. To examine the significance of STAT-1 activation in RA monocytes after stimulation with IFNγ, the expression of pSTAT-1 and of the IFNγ-inducible chemokine MIG was measured using fluorocytometry.

RESULTS

Levels of STAT-1 were significantly increased in peripheral lymphocytes and monocytes from patients with RA compared with those from healthy control subjects. STAT-1 levels correlated well with RA disease activity, as measured by the Disease Activity Score in 28 joints and the Clinical Disease Activity Index. Furthermore, STAT-1 messenger RNA expression in RA CD14+ monocytes correlated with the expression of other IFN-target genes, such as IP-10, OAS, or MIG. In RA PBMCs, STAT-1 expression was increased not only by IFNs but also by tumor necrosis factor. RA monocytes demonstrated a considerably higher increase in pSTAT-1 and MIG levels upon IFNγ stimulation when compared with monocytes from control subjects, indicating that RA monocytes are more sensitive to IFNγ stimulation.

CONCLUSION

In addition to supporting the role of IFNs in systemic proinflammatory activity, the results of this study further suggest preactivation of the IFNγ/STAT-1 signaling pathway, especially in RA monocytes.

Endothelial cells and fibroblasts amplify the arthritogenic type I IFN response in murine Lyme disease and are major sources of chemokines in Borrelia burgdorferi-infected joint tissue

Localized elevation in type I IFN has been uniquely linked to the severe Lyme arthritis that develops in C3H mice infected with the spirochete Borrelia burgdorferi. In this study, the dynamic interactions that result in generation of these responses were further examined in C3H mice carrying the type I IFN receptor gene ablation, which effectively blocks all autocrine/paracrine signaling crucial to induction of downstream effectors. Reciprocal radiation chimeras between C3H and IFNAR1⁻/⁻ mice implicated both radiation-sensitive and radiation-resistant cells of the joint tissue in the proarthritic induction of type I IFN. Ex vivo analysis of cells from the naive joint revealed CD45⁺ cells residing in the tissue to be uniquely capable of initiating the type I IFN response to B. burgdorferi. Type I IFN responses were analyzed in real time by lineage sorting of cells from infected joint tissue. This demonstrated that myeloid cells, endothelial cells, and fibroblasts were responsible for propagating the robust IFN response, which peaked at day 7 postinfection and rapidly resolved. Endothelial cells and fibroblasts were the dominant sources of IFN signature transcripts in the joint tissue. Fibroblasts were also the major early source of chemokines associated with polymorphonuclear leukocyte and monocyte/macrophage infiltration, thus providing a focal point for arthritis development. These findings suggest joint-localized interactions among related and unrelated stromal, endothelial, and myeloid cell lineages that may be broadly applicable to understanding the pathogeneses of diseases associated with type I IFN signature, including systemic lupus erythematosus and some rheumatoid arthritides.

The interferon type I signature towards prediction of non-response to rituximab in rheumatoid arthritis patients

Introduction

B cell depletion therapy is efficacious in rheumatoid arthritis (RA) patients failing on tumor necrosis factor (TNF) blocking agents. However, approximately 40% to 50% of rituximab (RTX) treated RA patients have a poor response. We investigated whether baseline gene expression levels can discriminate between clinical non-responders and responders to RTX.

Methods

In 14 consecutive RA patients starting on RTX (test cohort), gene expression profiling on whole peripheral blood RNA was performed by Illumina^® HumanHT beadchip microarrays. Supervised cluster analysis was used to identify genes expressed differentially at baseline between responders and non-responders based on both a difference in 28 joints disease activity score (ΔDAS28 < 1.2) and European League against Rheumatism (EULAR) response criteria after six months RTX. Genes of interest were measured by quantitative real-time PCR and tested for their predictive value using receiver operating characteristics (ROC) curves in an independent validation cohort (n = 26).

Results

Genome-wide microarray analysis revealed a marked variation in the peripheral blood cells between RA patients before the start of RTX treatment. Here, we demonstrated that only a cluster consisting of interferon (IFN) type I network genes, represented by a set of IFN type I response genes (IRGs), that is, LY6E, HERC5, IFI44L, ISG15, MxA, MxB, EPSTI1 and RSAD2, was associated with ΔDAS28 and EULAR response outcome (P = 0.0074 and P = 0.0599, respectively). Based on the eight IRGs an IFN-score was calculated that reached an area under the curve (AUC) of 0.82 to separate non-responders from responders in an independent validation cohort of 26 patients using Receiver Operator Characteristics (ROC) curves analysis according to ΔDAS28 < 1.2 criteria. Advanced classifier analysis yielded a three IRG-set that reached an AUC of 87%. Comparable findings applied to EULAR non-response criteria.

Conclusions

This study demonstrates clinical utility for the use of baseline IRG expression levels as a predictive biomarker for non-response to RTX in RA.

Relationship between the type I interferon signature and the response to rituximab in rheumatoid arthritis patients

OBJECTIVE

To analyze the relationship between the type I interferon (IFN) signature and clinical response to rituximab in rheumatoid arthritis (RA) patients.

METHODS

Twenty RA patients were treated with rituximab (cohort 1). Clinical response was defined as a decrease in the Disease Activity Score evaluated in 28 joints (DAS28) and as a response according to the European League Against Rheumatism (EULAR) criteria at week 12 and week 24. The presence of an IFN signature was analyzed in peripheral blood mononuclear cells by measuring the expression levels of 3 IFN response genes by quantitative polymerase chain reaction analysis. After comparison with the findings in healthy controls, patients were classified as having an IFN high or an IFN low signature. The data were confirmed in a second independent cohort (n = 31). Serum IFNα bioactivity was analyzed using a reporter assay.

RESULTS

In cohort 1, there was a better clinical response to rituximab in the IFN low signature group. Consistent with these findings, patients with an IFN low signature had a significantly greater reduction in the DAS28 and more often achieved a EULAR response at weeks 12 and 24 as compared with the patients with an IFN high signature in cohort 2 versus cohort 1. The pooled data showed a significantly stronger decrease in the DAS28 in IFN low signature patients at weeks 12 and 24 as compared with the IFN high signature group and a more frequent EULAR response at week 12. Accordingly, serum IFNα bioactivity at baseline was inversely associated with the clinical response, although this result did not reach statistical significance.

CONCLUSION

The type I IFN signature negatively predicts the clinical response to rituximab treatment in patients with RA. This finding supports the notion that IFN signaling plays a role in the immunopathology of RA.

Type I interferon in organ-targeted autoimmune and inflammatory diseases

A significant role for IFNα in the pathogenesis of systemic lupus erythematosus is well supported, and clinical trials of anti-IFNα monoclonal antibodies are in progress in this disease. In other autoimmune diseases characterized by substantial inflammation and tissue destruction, the role of type I interferons is less clear. Gene expression analysis of peripheral blood cells from patients with rheumatoid arthritis and multiple sclerosis demonstrate an interferon signature similar to but less intense than that seen in patients with lupus. In both of those diseases, presence of the interferon signature has been associated with more significant clinical manifestations. At the same time, evidence supports an anti-inflammatory and beneficial role of IFNβ locally in the joints of patients with rheumatoid arthritis and in murine arthritis models, and many patients with multiple sclerosis show a clinical response to recombinant IFNβ. As can also be proposed for type I diabetes mellitus, type I interferon appears to contribute to the development of autoimmunity and disease progression in multiple autoimmune diseases, while maintaining some capacity to control established disease - particularly at local sites of inflammation. Recent studies in both rheumatoid arthritis and multiple sclerosis suggest that quantification of type I interferon activity or target gene expression might be informative in predicting responses to distinct classes of therapeutic agents.