Reactive arthritis: developments and challenges in diagnosis and treatment

Reactive arthritis (ReA) has traditionally been described as a nonseptic arthritis occurring in the joint following an extra-articular bacterial infection. This concept became clinically associated with antecedent infections of either the gastrointestinal or genitourinary tract. Yet this operational definition of ReA has led to diagnostic uncertainty in different clinical settings. There are several scenarios in which the ReA has been complex. One is in the SAPHO syndrome, which shares many features with ReA. Another is the development of arthritis after infection with atypical organisms such as Clostridium difficile and Giardia lamblia. Treatment of ReA remains an area of ongoing investigation. There has been a randomized controlled trial of combination antibiotics in Chlamydia-induced ReA, which reported a positive result. There are several uncontrolled reports of anti-TNF agents being used successfully in refractory ReA. These studies in treatment modalities require validation on larger samples but do provide some encouraging preliminary findings from which to develop new therapeutic approaches.

Chlamydia and chronic arthritis

Certain bacterial infections have been demonstrated to be causative of reactive arthritis. The most common bacterial trigger of reactive arthritis is Chlamydia trachomatis. Chlamydia pneumoniae is another known cause, albeit far less frequently. Although Chlamydia-induced reactive arthritis will often spontaneously remit, approximately 30% of patients will develop a chronic course. Modern medicine has provided rather remarkable advances in our understanding of the chlamydiae, as these organisms relate to chronic arthritis and the delicate balance between host and pathogen. C. trachomatis and C. pneumoniae both have a remarkable ability to disseminate from the initial site of infection and establish persistently viable organisms in distant organ sites, namely the synovial tissue. How these persistent chlamydiae contribute to disease maintenance remains to be fully established, but recent data demonstrating that long-term combination antimicrobial treatment can not only ameliorate the symptoms but eradicate the persistent infection suggest that these chronically infecting chlamydiae are indeed a driving force behind the chronic inflammation. We are beginning to learn that this all appears possible even after an asymptomatic initial chlamydial infection. Both C. trachomatis and C. pneumoniae are a clear cause of chronic arthritis in the setting of reactive arthritis; the possibility remains that these same organisms are culpable in other forms of chronic arthritis as well.

Chlamydia trachomatis vacuole maturation in infected macrophages

Chlamydia trachomatis is an obligate intracellular bacterium responsible for one of the most common sexually transmitted diseases. In epithelial cells, C. trachomatis resides in a modified membrane-bound vacuole known as an inclusion, which is isolated from the endocytic pathway. However, the maturation process of C. trachomatis within immune cells, such as macrophages, has not been studied extensively. Here, we demonstrated that RAW macrophages effectively suppressed C. trachomatis growth and prevented Golgi stack disruption, a hallmark defect in epithelial cells after C. trachomatis infection. Next, we systematically examined association between C. trachomatis and various endocytic pathway markers. Spinning disk confocal time-lapse studies revealed significant and rapid association between C. trachomatis with Rab7 and LAMP1, markers of late endosomes and lysosomes. Moreover, pretreatment with an inhibitor of lysosome acidification led to significant increases in C. trachomatis growth in macrophages. At later stages of infection, C. trachomatis associated with the autophagy marker LC3. TEM analysis confirmed that a significant portion of C. trachomatis resided within double-membrane-bound compartments, characteristic of autophagosomes. Together, these results suggest that macrophages can suppress C. trachomatis growth by targeting it rapidly to lysosomes; moreover, autophagy is activated at later stages of infection and targets significant numbers of the invading bacteria, which may enhance subsequent chlamydial antigen presentation.

Nafamostat mesylate, a serine protease inhibitor, demonstrates novel antimicrobial properties and effectiveness in Chlamydia-induced arthritis

Introduction

Effective treatment of reactive arthritis would ideally achieve both control of inflammation and eradication of persisting arthritogenic pathogens. We use a model of experimental Chlamydia trachomatis-induced arthritis (CtIA) to evaluate the effectiveness of nafamostat mesilate (NM), a serine protease inhibitor with complement-modifying effects and anticoagulant properties. To date clinical use of NM has largely been in Asia and has been primarily confined to inflammatory states such as pancreatitis.

Methods

In vitro studies examined inhibition of Chlamydia proliferation using fibroblast cell lines as targets and phase contrast microscopy. In vivo studies used an established protocol, experimental CtIA, induced in Lewis rats by injection of synoviocyte-packaged C. trachomatis. NM was dissolved in water and administered by daily intraperitoneal injection at a dose of 10 mg/kg beginning the day prior to the administration of Chlamydia. Readouts in vivo included (i) joint swelling, (ii) histopathology scoring of severity of arthritis, (iii) host clearance of the pathogen (by ELISA, the IDEIA PCE Chlamydia).

Results

NM exerted a dose-dependent inhibition of chlamydial proliferation in vitro. Without NM, the mean number of inclusion bodies (IB) per well was 17,886 (± 1415). At 5 μg/mL NM, there were 8,490 (± 756) IB, at 25 μg/mL NM there were 35 IB and at 50 μg/mL NM no IB was observed. Chlamydial antigens in each well along the concentration gradient were assayed by ELISA, demonstrating that at 25 μg/mL NM inhibition of Chlamydia was almost complete. In the experimental arthritis model, joint swelling was significantly reduced with NM treatment: average joint width for the NM-treated animals was 8.55 mm (s.d. ± 0.6578, n = 10) versus 11.18 mm (s.d. ± 0.5672, n = 10) in controls (P < 0.001). Histopathology scoring indicated that NM resulted in a marked attenuation of the inflammatory infiltration and joint damage: mean pathology score in NM-treated animals was 10.9 (± 2.45, n = 11) versus 15.9 (± 1.45, n = 10) in controls (P < 0.0001). With respect to persistence of Chlamydia within the synovial tissues, NM treatment was accompanied by a reduction in the microbial load in the joint: mean optical density (O.D.) for ELISA with NM treatment was 0.05 (± 0.02, n = 4) versus 0.18 (± 0.05, n = 4) in controls (P < 0.001).

Conclusions

NM is a protease inhibitor not previously recognized to possess antimicrobial properties. The present study demonstrates for the first time that NM exerts significant impact on C. trachomatis-induced arthritis and suggests that such approaches may prove clinically useful in chronic reactive arthritis.

Postural control is altered in patients with ankylosing spondylitis

BACKGROUND

Ankylosing spondylitis is a chronic inflammatory disorder that can lead to increased axial and peripheral joint stiffness, impairing joint mobility. Impaired axial mobility due to vertebral ankylosis may result in changes in standing postural control. Little research has addressed changes in standing postural control in the ankylosing spondylitis population, nor how these issues might affect clinical understanding and treatment.

METHODS

Sixteen ankylosing spondylitis patients, and 17 healthy controls participated. Each individual completed two 120-second quiet standing trials with eyes open and eyes closed, while standing upon two force platforms. Net center of pressure displacement and mean power frequency in the frontal and sagittal planes were calculated. A Spearman's rank correlation analysis was performed between net center of pressure measures and several clinical measures of disease activity.

FINDINGS

Frontal plane net center of pressure displacement and frequency content, and sagittal plane net center of pressure displacement were significantly greater within the ankylosing spondylitis patient group. Ankylosing spondylitis patients demonstrated a significant increase in frontal plane net center of pressure displacement in the eyes-closed condition. Net center of pressure displacement and frequency were significantly correlated to the Bath Ankylosing Spondylitis Functional Index, and individual components of the Bath Ankylosing Spondylitis Metrology Index.

INTERPRETATION

Quiet standing postural control was altered particularly so in the frontal plane in patients with ankylosing spondylitis, which may be associated with increased fall risk. Posturographic measures of postural control may serve as valuable clinical tools for the monitoring of disease progression and disease status in ankylosing spondylitis.

Endoplasmic reticulum aminopeptidase 1 (ERAP1) exhibits functionally significant interaction with HLA-B27 and relates to subtype specificity in ankylosing spondylitis

OBJECTIVES

The functional interaction of endoplasmic reticulum aminopeptidase 1 (ERAP1) with human leucocyte antigen (HLA)-B*27 could be important in the pathogenesis of ankylosing spondylitis (AS). AS is associated with B*27:04 and B*27:05, but not with B*27:06 and B*27:09. The authors studied the surface expression of peptide-HLA(pHLA)-B27 complexes and HLA class-I free heavy chains (FHCs) on peripheral blood mononuclear cells of patients with AS with different ERAP1 single nucleotide polymorphisms. The effects of ERAP1 suppression on HLA-B*27 subtypes were tested.

METHODS

Peripheral blood mononuclear cells were collected from Caucasian patients with AS for flow cytometry and were stained for pHLA and FHCs. Genotyping was performed for two ERAP1 single nucleotide polymorphisms (rs27044(C/G) and rs30187(C/T)). C1R cells transfected with different HLA-B27 subtypes (B*27:04, B*27:05, B*27:06 and B*27:09) were subjected to ERAP1 suppression by small interfering RNA and stained using the monoclonal antibody (mAb) MARB4 as well as antibodies for pHLA, FHC, intracellular FHC (IC-FHC). MARB4 has been reported to bind to HLA-B27 with extended peptides.

RESULTS

The authors found variations in FHC expression on the monocytes of patients with AS, depending on different ERAP1 variants. Subsequently, using Hmy2.C1R cells in vitro, the authors show that ERAP1 suppression leads to increased IC-FHC and surface pHLA that react with the monoclonal antibody MARB4. The functional interaction between ERAP1 and HLA-B27 molecules appears to be subtype-specific, since ERAP1 suppression leads to changes only in cells expressing B*27:04 or B*27:05, but not B*27:06 or B*27:09.

CONCLUSIONS

Direct or indirect alterations in the ERAP1-HLA-B27 interaction could be crucial by causing changes in peptide presentation or FHC formation by HLA-B27 molecules, as well as by contributing to differential subtype association in spondyloarthropathies.

Aberrant chondrocyte hypertrophy and activation of β-catenin signaling precede joint ankylosis in ank/ank mice

OBJECTIVE

We assessed the role of Ank in the maintenance of postnatal articular cartilage using the ank/ank mouse (mice homozygous for progressive ankylosis).

METHODS

We analyzed ank/ank mice and wild-type littermates (8, 12, and 18 weeks old). Sections from decalcified, paraffin-embedded joints were stained with hematoxylin and eosin. Articular chondrocyte size and cartilage thickness were determined using morphometric methods. Immuno-histochemical staining was performed with anticollagen X, antitissue nonspecific alkaline phosphatase (TNAP), and anti-ß-catenin antibodies on fixed joint sections. Axin2 expression in paw joint lysates in wild-type versus ank/ank mice were compared using Western blot analysis.

RESULTS

In all age groups of normal mice studied, calcified cartilage (CC) chondrocyte areas were significantly larger than those of uncalcified cartilage (UC) chondrocytes. However, similar chondrocyte areas (UC vs CC) were found in 12-week and 18-week-old ank/ank mice, indicating that hypertrophic chondrocytes were present in the UC of these mutant mice. The ank/ank mice showed an increase in CC thickness. The ank/ank UC hypertrophic chondrocytes showed diffuse immuno-reactivity for collagen X and TNAP. Increased ß-catenin activation was demonstrated by nuclear localization of ß-catenin staining in ank/ank chondrocytes. Axin2 expression from paw lysates was downregulated in ank/ank mice.

CONCLUSION

We identified a previously unrecognized phenotype in the articular cartilage of ank/ank mice: collagen X-positive hypertrophic chondrocytes in the UC. It is possible that consequent to downregulation of axin2 expression, ß-catenin signaling was activated, leading to accelerated chondrocyte maturation and eventual ankylosis in ank/ank joints. Our studies shed new light on the contribution of a key signaling pathway in this model of joint ankylosis.

Gene silencing of IL-12 in dendritic cells inhibits autoimmune arthritis

Background

We have previously demonstrated that immune modulation can be accomplished by administration of gene silenced dendritic cells (DC) using siRNA. In this study, we demonstrate the therapeutic utilization of shRNA-modified DC as an antigen-specific tolerogenic vaccine strategy for autoimmune arthritis.

Methods

A shRNA that specifically targets IL-12 p35 was designed and cloned into a plasmid vectors (IL-12 shRNA). Bone marrow-derived DC from DBA/1 mice were transfected with the IL-12 shRNA construct in vitro. Mice with collagen II (CII)-induced arthritis (CIA) were treated with the modified DCs expressing the shRNA. Recall response and disease progression were assessed.

Results

After gene silencing of IL-12 in DC, DC were shown to selectively inhibit T cell proliferation on recall responses and in an MLR. In murine CIA, we demonstrated that administration of IL-12 shRNA-expressing DC that were pulsed with CII inhibited progression of arthritis. The therapeutic effects were evidenced by decreased clinical scores, inhibition of inflammatory cell infiltration in the joint, and suppression of T cell and B cell responses to CII.

Conclusion

We demonstrate a novel tolerance-inducing protocol for the treatment of autoimmune inflammatory joint disease in which the target antigen is known, utilizing DNA-directed RNA interference.

Golimumab reduces spinal inflammation in ankylosing spondylitis: MRI results of the randomised, placebo- controlled GO-RAISE study

Objective

To evaluate golimumab's effect on MRI-detected spinal inflammation in ankylosing spondylitis (AS).

Methods

Patients were randomly assigned to subcutaneous injections of placebo (n=78), golimumab 50 mg (n=138), or golimumab 100 mg (n=140) every 4 weeks. An MRI substudy comprising 98 patients (placebo n=23, 50 mg n=37, 100 mg n=38) at eligible MRI substudy sites had serial spine MRI scans (sagittal plane, 1.5T scanners, T1 and short tau inversion recovery sequences) at baseline and weeks 14 and 104. Two blinded (treatment, image order) readers independently evaluated MRI spinal inflammation using AS spine MRI-activity (ASspiMRI-a) scores; reader scores were averaged. Changes from baseline to weeks 14 and 104 were compared among treatment groups using analysis of variance on van der Waerden normal scores both with (post-hoc) and without (prespecified) adjustment for baseline ASspiMRI-a scores.

Results

Median baseline ASspiMRI-a scores were lower in the 100 mg (3.5) than placebo (6.8) and 50 mg (7.8) groups. Median decreases in activity scores from baseline to week 14 were −0.5 for placebo, −3.5 for 50 mg (p=0.047 vs placebo), and −1.5 for 100 mg (p=0.14 vs placebo). After adjusting for baseline ASspiMRI-a score imbalance, significant improvements were observed with both 50 mg (p=0.011) and 100 mg (p=0.002) versus placebo. ASspiMRI-a scores improvement achieved with golimumab was maintained at week 104. Improvement in ASspiMRI-a scores correlated with improvement in the recently developed AS disease activity score (ASDAS) and C-reactive protein (CRP) levels but not with other key AS clinical outcomes.

Conclusion

Golimumab significantly reduced MRI-detected spinal inflammation of AS; improvements were sustained to week 104 and correlated with improvement in ASDAS and CRP.

Serum markers associated with clinical improvement in patients with ankylosing spondylitis treated with golimumab

Objective

Identify serum biomarkers modulated by golimumab treatment and associated with clinical response in patients with ankylosing spondylitis (AS).

Methods

Sera were collected at weeks 0, 4 and 14 from 100 patients with active AS in the GO–RAISE study. Patients were randomly assigned subcutaneous injections of placebo, golimumab 50 mg, or golimumab 100 mg every 4 weeks. Samples were tested for select inflammatory, bone and cartilage markers, and protein profiling was also performed.

Results

Golimumab treatment resulted in significant decreases in several serum proteins at weeks 4 and 14 compared with placebo. Patients who achieved clinical response at week 14, as assessed by a ≥20% improvement in the Assessment in SpondyloArthitis international Society response criteria (ASAS 20), demonstrated a distinct biomarker profile with lower levels of acute phase reactants and inflammatory biomarkers compared with patients who did not. Notably, combinations of two or three biomarkers assessed at baseline were predictive of various clinical outcomes (ASAS 20, Bath ankylosing spondylitis disease activity index 50 or Bath ankylosing spondylitis functional index) using a logistic regression analysis, and the overall predictive values for these combined biomarkers were greater than observed for C-reactive protein (CRP) alone.

Conclusion

Golimumab modulated acute phase reactants and inflammatory markers in patients with active AS. Specific combinations of biomarkers at baseline demonstrated a stronger prediction for clinical efficacy than CRP alone. These data provide insights into the mechanism of golimumab on inflammatory processes driving AS pathology, and may have utility in managing the treatment of patients with AS.

Radiographic severity of ankylosing spondylitis is associated with polymorphism of the large multifunctional peptidase 2 gene in the Spondyloarthritis Research Consortium of Canada cohort

OBJECTIVE

There are limited data on genetic predictors of radiographic progression. The aim of this study was to examine polymorphisms in genes involved in antigen presentation and their effect on radiographic severity and progression.

METHODS

Caucasian patients with ankylosing spondylitis (AS) (diagnosed according to the modified New York criteria) from 2 Canadian centers were enrolled. Patients in the progression part of the study had at least 2 sets of radiographs obtained at a minimum gap of 1.5 years, with a modified Stoke Ankylosing Spondylitis Spine Score (mSASSS). Peripheral blood DNA was used for genotyping a panel of 13 coding-region single-nucleotide polymorphisms (SNPs) in ERAP1, LMP2, LMP7, TAP1, and TAP2. Linear regression analysis was performed to identify the predictors of the baseline mSASSS and logistic regression for predictors of progression. Progression was defined as an increase of 1 mSASSS unit per year.

RESULTS

A total of 241 AS patients (81% males; 82% HLA-B27-positive) were enrolled from the 2 centers for analysis of the predictors of baseline radiographic severity. In univariate analyses, the baseline mSASSS was associated with sex, disease duration, and SNPs rs30187 (ERAP1) and rs17587 (LMP2). In multivariate analyses, duration of disease (B = 0.74; P = 1 × 10(-11) ), sex (B = 12.1; P = 5 × 10(-5) ), and the LMP2 SNP rs17587 (B = 6.2; P = 0.01) were significantly associated with the baseline mSASSS. In multivariate analyses of progression, only the baseline mSASSS was a significant predictor (B = 0.03; P = 0.003).

CONCLUSION

This is the first study to demonstrate that LMP2 variants can affect radiographic severity in AS. The baseline mSASSS remains the strongest predictor of radiographic progression but explains only a fraction of the variability seen.

Golimumab administered subcutaneously every 4 weeks in ankylosing spondylitis: 104-week results of the GO-RAISE study

OBJECTIVE

To assess the efficacy and safety of golimumab over 104 weeks in patients with active ankylosing spondylitis.

METHODS

At baseline, patients with active ankylosing spondylitis (n=356) were randomly assigned (1:1.8:1.8) to subcutaneous injections of placebo (group 1), golimumab 50 mg (group 2) or golimumab 100 mg (group 3) every 4 weeks. At week 16, patients in groups 1 and 2 with <20% improvement in total back pain and morning stiffness entered early escape to 50 or 100 mg, respectively. At week 24, patients still receiving placebo crossed over to golimumab 50 mg. Findings through week 24 were previously reported; those through week 104 are presented herein.

RESULTS

At week 104, 38.5%, 60.1% and 71.4% of patients in groups 1, 2 and 3, respectively, had at least 20% improvement in the Assessment in SpondyloArthritis international Society response criteria (ASAS20); 38.5%, 55.8% and 54.3% had an ASAS40 response and 21.8%, 31.9% and 30.7% were in ASAS partial remission. Mean Bath Ankylosing Spondylitis Disease Activity Index and Bath Ankylosing Spondylitis Functional Index scores were <3 at week 104 for all the treatment regimens. Golimumab safety through week 104 was similar to that through week 24.

CONCLUSION

Clinical response that was achieved by patients receiving golimumab through 24 weeks was sustained through 52 and 104 weeks. The golimumab safety profile appeared to be consistent with the known safety profile of tumour necrosis factor inhibitors.

Aberrant axial mineralization precedes spinal ankylosis: a molecular imaging study in ank/ank mice

INTRODUCTION

The diagnosis of ankylosing spondylitis is made from a combination of clinical features and the presence of radiographic evidence that may be detected only after many years of inflammatory back pain. It is not uncommon to have a diagnosis confirmed 5 to 10 years after the initial onset of symptoms. Development of a more-sensitive molecular imaging technology to detect structural changes in the joints would lead to earlier diagnosis and quantitative tracking of ankylosis progression. Progressive ankylosis (ank/ank) mice have a loss of function in the Ank gene, which codes for a regulator of PPi transport. In this study, we used these ank/ank mutant mice to assess a noninvasive, quantitative measure of joint ankylosis with near-infrared (NIR) molecular imaging in vivo.

METHODS

Three age groups (8, 12, and 18 weeks) of ank/ank (15 mice) and wild-type littermates (12 +/+ mice) were assessed histologically and radiographically. Before imaging, OsteoSense 750 (bisphosphonate pamidronate) was injected i.v. Whole-body images were analyzed by using the multispectral Maestro imaging system.

RESULTS

OsteoSense 750 signals in the paw joints were higher in ank/ank mice in all three age groups compared with controls. In the spine, significantly higher OsteoSense 750 signals were detected early, in 8-week-old ank/ank mice compared with controls, although minimal radiographic differences were noted at this time point. The molecular imaging changes in the ank/ank spine (8 weeks) were supported by histologic changes, including calcium apatite crystals at the edge of the vertebral bodies and new syndesmophyte formation.

CONCLUSIONS

Changes in joint pathology of ank/ank mice, as evaluated by histologic and radiographic means, are qualitative, but only semiquantitative. In contrast, molecular imaging provides a quantitative assessment. Ankylosis in ank/ank mice developed simultaneously in distal and axial joints, contrary to the previous notion that it is a centripetal process. NIR imaging might be feasible for early disease diagnosis and for monitoring disease progression in ankylosing spondylitis.

Measuring participation in people with spondyloarthritis using the social role participation questionnaire

OBJECTIVES

People with spondyloarthritis (SpA), ankylosing spondylitis (AS) and psoriatic arthritis (PsA) have identified the importance of understanding how their disease and its treatment impacts on their social roles. This requires a reliable and valid standardised measure, and this study evaluates these measurement properties of the Social Role Participation Questionnaire (SRPQ).

METHODS

109 participants (44 with AS, 65 with PsA) completed questionnaires on demographics, participation measures (SRPQ, Keele Assessment of Participation (KAP), Late Life Disability Instrument (LLDI)), disease severity (physician global) and activity (pain, fatigue, Bath Ankylosing Spondylitis Disease Activity Index), psychological measures (depressive symptoms (Hospital Anxiety and Depression Scale), Illness Intrusiveness)) and function (Health Assessment Questionnaire, Bath Ankylosing Spondylitis Functional Index). After testing scaling properties, test-retest reliability of the SRPQ was evaluated using intraclass correlation coefficients (ICC) and hypotheses of construct validity were evaluated using correlation coefficients.

RESULTS

Patients with AS had a mean age of 40 years and 65% were male, whereas patients with PsA had a mean age of 53 years and 63% were male. Although there were some differences between AS and PsA participants in their social role participation, scaling properties were good for both groups. ICCs were >0.90 for the satisfaction subscales of the SRPQ. For construct validity, SRPQ satisfaction subscales were moderately correlated with the KAP and LLDI (0.64-0.78), and less satisfaction was associated with higher disease severity and activity, more depressive symptoms, more illness intrusiveness and more disability (coefficients -0.67 to -0.88).

CONCLUSION

Social role participation is an important concept for people with SpA, and the SRPQ is a reliable and valid measure for use with people with AS and PsA.

2010 update of the ASAS/EULAR recommendations for the management of ankylosing spondylitis

This first update of the ASAS/EULAR recommendations on the management of ankylosing spondylitis (AS) is based on the original paper, a systematic review of existing recommendations and the literature since 2005 and the discussion and agreement among 21 international experts, 2 patients and 2 physiotherapists in a meeting in February 2010. Each original bullet point was discussed in detail and reworded if necessary. Decisions on new recommendations were made — if necessary after voting. The strength of the recommendations (SOR) was scored on an 11-point numerical rating scale after the meeting by email. These recommendations apply to patients of all ages that fulfill the modified NY criteria for AS, independent of extra-articular manifestations, and they take into account all drug and non-drug interventions related to AS. Four overarching principles were introduced, implying that one bullet has been moved to this section. There are now 11 bullet points including 2 new ones, one related to extra-articular manifestations and one to changes in the disease course. With a mean score of 9.1 (range 8-10) the SOR was generally very good.

Interaction between ERAP1 and HLA-B27 in ankylosing spondylitis implicates peptide handling in the mechanism for HLA-B27 in disease susceptibility

Ankylosing spondylitis is a common form of inflammatory arthritis predominantly affecting the spine and pelvis that occurs in approximately 5 out of 1,000 adults of European descent. Here we report the identification of three variants in the RUNX3, LTBR-TNFRSF1A and IL12B regions convincingly associated with ankylosing spondylitis (P < 5 × 10(-8) in the combined discovery and replication datasets) and a further four loci at PTGER4, TBKBP1, ANTXR2 and CARD9 that show strong association across all our datasets (P < 5 × 10(-6) overall, with support in each of the three datasets studied). We also show that polymorphisms of ERAP1, which encodes an endoplasmic reticulum aminopeptidase involved in peptide trimming before HLA class I presentation, only affect ankylosing spondylitis risk in HLA-B27-positive individuals. These findings provide strong evidence that HLA-B27 operates in ankylosing spondylitis through a mechanism involving aberrant processing of antigenic peptides.

Atlanto-axial subluxation as the initial manifestation of spondyloarthritis

Patients with spondyloarthritis (SpA) typically present with inflammatory back pain, peripheral arthritis and enthesitis, often with distinctive clinical features such as psoriasis and inflammatory bowel diseases. Atlanto-axial subluxation (AAS) is a complication occurring rarely in these patients, and usually is seen in patients with longstanding, severe disease. We present three cases of AAS whose initial presentation of AAS was followed by subsequent development of signs and symptoms meeting the European Spondyloarthropathy Study Group (ESSG) classification criteria for SpA. All three patients were less than 30 years of age and had no other explanation for the AAS. Significantly, all three patients required C1/C2 surgical fusion within 1 year of symptom onset due to severe pain, though none of them developed neurologic complications related to AAS such as myelopathy. Peripheral arthritis/tendonitis, the presence of HLA-B27 gene and family history of SpA appeared to be associated with higher risk of evolution to SpA in these patients. No medical therapy has been systematically examined in this condition.

Pathophysiology and pathogenesis of immune-mediated inflammatory diseases: commonalities and differences

Immune-mediated inflammatory diseases (IMID) represent a diverse group of chronic conditions that share common pathways. Although the etiology of IMID has yet to be identified, it is well known that both genetic and environmental factors play an important role in the development of these disorders. Genome-wide association (GWA) studies and GW nonsynonymous single-nucleotide polymorphism (nsSNP) scans have recently led to identification of genes commonly found in several different IMID as well as those that are disease-specific. Current epidemiological, clinical, and experimental evidence has also confirmed an association between IMID and a large number of seemingly unrelated environmental factors, which include smoking, diet, drugs, geographical and social status, stress, and microbial agents. Data supporting the involvement of each of these factors in predisposing to, triggering, or modulating the course or outcome of IMID vary from strong to tenuous. The notion of shared genetic pathways creates new and powerful approaches for discovering the full spectrum and potential of susceptible genes in these potentially disabling chronic conditions. Insights relating to a specific immune pathway could provide targets for therapeutic interventions.

Predicting the outcome of ankylosing spondylitis therapy

Objectives

To create a model that provides a potential basis for candidate selection for anti-tumour necrosis factor (TNF) treatment by predicting future outcomes relative to the current disease profile of individual patients with ankylosing spondylitis (AS).

Methods

ASSERT and GO–RAISE trial data (n=635) were analysed to identify baseline predictors for various disease-state and disease-activity outcome instruments in AS. Univariate, multivariate, receiver operator characteristic and correlation analyses were performed to select final predictors. Their associations with outcomes were explored. Matrix and algorithm-based prediction models were created using logistic and linear regression, and their accuracies were compared. Numbers needed to treat were calculated to compare the effect size of anti-TNF therapy between the AS matrix subpopulations. Data from registry populations were applied to study how a daily practice AS population is distributed over the prediction model.

Results

Age, Bath ankylosing spondylitis functional index (BASFI) score, enthesitis, therapy, C-reactive protein (CRP) and HLA-B27 genotype were identified as predictors. Their associations with each outcome instrument varied. However, the combination of these factors enabled adequate prediction of each outcome studied. The matrix model predicted outcomes as well as algorithm-based models and enabled direct comparison of the effect size of anti-TNF treatment outcome in various subpopulations. The trial populations reflected the daily practice AS population.

Conclusion

Age, BASFI, enthesitis, therapy, CRP and HLA-B27 were associated with outcomes in AS. Their combined use enables adequate prediction of outcome resulting from anti-TNF and conventional therapy in various AS subpopulations. This may help guide clinicians in making treatment decisions in daily practice.