Daniel J. Kingsbury

Novel Propeptide Function in 20 S Proteasome Assembly Influences β Subunit Composition

The assembly of eukaryotic 20 S proteasomes involves the formation of half-proteasomes where precursor β-type subunits gather in position on an α-subunit ring, followed by the association of two half-proteasomes and β-subunit processing. In vertebrates three additional β-subunits (β1i/LMP2, β2i/MECL1, and β5i/LMP7) can be synthesized and substituted for constitutive homologues (β1/delta, β2/Z, and β5/X) to yield immunoproteasomes, which are important for generating certain antigenic peptides. We have shown previously that when all six β-subunits are present, cooperative assembly mechanisms limit the diversity of proteasome populations. Specifically, LMP7 is incorporated preferentially over X into preproteasomes containing LMP2 and MECL1. We show here that the LMP7 propeptide is responsible for this preferential incorporation, and it also enables LMP7 to incorporate into proteasomes containing delta and Z. In contrast, the X propeptide restricts incorporation to proteasomes with delta and Z. Furthermore, we demonstrate that the LMP7 propeptide can function in trans when expressed on LMP2, and that its NH2-terminal and mid-regions are particularly critical for function. In addition to identifying a novel propeptide function, our results raise the possibility that one consequence of LMP7 incorporation into both immunoproteasomes and delta/Z proteasomes may be to increase the diversity of antigenic peptides that can be generated.

Osteopoikilosis, short stature and mental retardation as key features of a new microdeletion syndrome on 12q14

This report presents the detection of a heterozygous deletion at chromosome 12q14 in three unrelated patients with a similar phenotype consisting of mild mental retardation, failure to thrive in infancy, proportionate short stature and osteopoikilosis as the most characteristic features. In each case, this interstitial deletion was found using molecular karyotyping. The deletion occurred as a de novo event and varied between 3.44 and 6 megabases (Mb) in size with a 3.44 Mb common deleted region. The deleted interval was not flanked by low-copy repeats or segmental duplications. It contains 13 RefSeq genes, including LEMD3, which was previously shown to be the causal gene for osteopoikilosis. The observation of osteopoikilosis lesions should facilitate recognition of this new microdeletion syndrome among children with failure to thrive, short stature and learning disabilities.

Development of spontaneous arthritis in β2-microglobulin-deficient mice without expression of HLA-B27: Association with deficiency of endogenous major histocompatibility complex class I expression

OBJECTIVE Mice deficient in beta2-microglobulin (beta2m), but expressing the human major histocompatibility complex (MHC) class I molecule HLA-B27, have been reported to develop spontaneous inflammatory arthritis (SA). We sought to determine whether, under certain conditions, beta2m deficiency alone was sufficient to cause SA, and if this might be a result of class I deficiency. METHODS The following types of mice were produced: mice of the MHC b haplotype genetically deficient in beta2m (beta2m(0)) on several genetic backgrounds (C57BL/6J [B6], BALB/cJ, SJL/J, MRL/MpJ, and B6,129), mice deficient in the transporter associated with antigen processing (TAP1(0)) on a B6,129 background, and HLA-B27-transgenic beta2m(0) mice on a B6 background. Cohorts were transferred from specific pathogen-free (SPF) to conventional (non-SPF) animal rooms, and evaluated clinically and histologically for the development of SA. RESULTS SA occurred in TAP1(0) and beta2m(0)/class I-deficient mice with a mixed B6,129 genome at a frequency of 30-50%, while 10-15% of B6, SJL/J, and BALB/cJ beta2m(0) mice developed this arthropathy. MRL/ MpJ beta2m(0) mice were unaffected. Expression of B27 did not increase the frequency of SA in B27-transgenic B2m(0) B6 mice compared with that in beta2m(0) B6 controls. CONCLUSION Class I deficiency is sufficient to cause SA in mice. The frequency of disease, as well as B27-specific SA, is markedly dependent on a non-MHC genetic background. These results suggest that class I deficiency in a genetically susceptible mouse can mimic B27-associated arthropathy.

The 12q14 microdeletion syndrome: Additional patients and further evidence that HMGA2 is an important genetic determinant for human height

Characteristic features of the 12q14 microdeletion syndrome include low birth weight, failure to thrive, short stature, learning disabilities and Buschke-Ollendorff lesions in bone and skin. This report on two additional patients with this microdeletion syndrome emphasizes the rather constant and uniform phenotype encountered in this disorder and refines the critical region to a 2.61 Mb interval on 12q14.3, encompassing 10 RefSeq genes. We have previously shown that LEMD3 haploinsufficiency is responsible for the Buschke-Ollendorff lesions and now provide strong evidence that a heterozygous deletion of HMGA2 is causing the growth failure observed in this disorder. The identification of an intragenic HMGA2 deletion in a boy with proportionate short stature and the cosegregation of this deletion with reduced adult height in the extended family of the boy further underscore the role of HMGA2 in regulating human linear growth.

Increased sensitivity of the European medicines agency algorithm for classification of childhood granulomatosis with polyangiitis.

Objective. Granulomatosis with polyangiitis (Wegener’s; GPA) and other antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAV) are rare in childhood and are sometimes difficult to discriminate. We compared use of adult-derived classification schemes for GPA against validated pediatric criteria in the ARChiVe (A Registry for Childhood Vasculitis e-entry) cohort, a Childhood Arthritis and Rheumatology Research Alliance initiative. Methods. Time-of-diagnosis data for children with physician (MD) diagnosis of AAV and unclassified vasculitis (UCV) from 33 US/Canadian centers were analyzed. The European Medicines Agency (EMA) classification algorithm and European League Against Rheumatism/Paediatric Rheumatology International Trials Organisation/Paediatric Rheumatology European Society (EULAR/PRINTO/PRES) and American College of Rheumatology (ACR) criteria for GPA were applied to all patients. Sensitivity and specificity were calculated (MD-diagnosis as reference). Results. MD-diagnoses for 155 children were 100 GPA, 25 microscopic polyangiitis (MPA), 6 ANCA-positive pauciimmune glomerulonephritis, 3 Churg-Strauss syndrome, and 21 UCV. Of these, 114 had GPA as defined by EMA, 98 by EULAR/PRINTO/PRES, and 87 by ACR. Fourteen patients were identified as GPA by EULAR/PRINTO/PRES but not by ACR; 3 were identified as GPA by ACR but not EULAR/PRINTO/PRES. Using the EMA algorithm, 135 (87%) children were classifiable. The sensitivity of the EMA algorithm, the EULAR/PRINTO/PRES, and ACR criteria for classifying GPA was 90%, 77%, and 69%, respectively, with specificities of 56%, 62%, and 67%. The relatively poor sensitivity of the 2 criteria related to their inability to discriminate patients with MPA. Conclusion. EULAR/PRINTO/PRES was more sensitive than ACR criteria in classifying pediatric GPA. Neither classification system has criteria for MPA; therefore usefulness in discriminating patients in ARChiVe was limited. Even when using the most sensitive EMA algorithm, many children remained unclassified.

Assessing the performance of the Birmingham vasculitis activity score at diagnosis for Children with antineutrophil cytoplasmic antibody-associated vasculitis in a registry for childhood vasculitis (ARChiVe)

Objective. There are no validated tools for measuring disease activity in pediatric vasculitis. The Birmingham Vasculitis Activity Score (BVAS) is a valid disease activity tool in adult vasculitis. Version 3 (BVAS v.3) correlates well with physician’s global assessment (PGA), treatment decision, and C-reactive protein in adults. The utility of BVAS v.3 in pediatric vasculitis is not known. We assessed the association of BVAS v.3 scores with PGA, treatment decision, and erythrocyte sedimentation rate (ESR) at diagnosis in pediatric antineutrophil cytoplasmic antibody-associated vasculitis (AAV). Methods. Children with AAV diagnosed between 2004 and 2010 at all ARChiVe centers were eligible. BVAS v.3 scores were calculated with a standardized online tool (www.vasculitis.org). Spearman’s rank correlation coefficient (rs) was used to test the strength of association between BVAS v.3 and PGA, treatment decision, and ESR. Results. A total of 152 patients were included. The physician diagnosis of these patients was predominantly granulomatosis with polyangiitis (n = 99). The median BVAS v.3 score was 18.0 (range 0–40). The BVAS v.3 correlations were rs = 0.379 (95% CI 0.233 to 0.509) with PGA, rs = 0.521 (95% CI 0.393 to 0.629) with treatment decision, and rs = 0.403 (95% CI 0.253 to 0.533) with ESR. Conclusion. Applied to children with AAV, BVAS v.3 had a weak correlation with PGA and moderate correlation with both ESR and treatment decision. Prospective evaluation of BVAS v.3 and/or pediatric-specific modifications to BVAS v.3 may be required before it can be formalized as a disease activity assessment tool in pediatric AAV.

Subcutaneous golimumab for children with active polyarticular-course juvenile idiopathic arthritis: results of a multicentre, double-blind, randomised-withdrawal trial

Objective This report aims to determine the safety, pharmacokinetics (PK) and efficacy of subcutaneous golimumab in active polyarticular-course juvenile idiopathic arthritis (polyJIA). Methods In this three-part randomised double-blinded placebo-controlled withdrawal trial, all patients received open-label golimumab (30 mg/m2 of body surface area; maximum: 50 mg/dose) every 4 weeks together with weekly methotrexate during Part 1 (weeks 0–16). Patients with at least 30% improvement per American College of Rheumatology Criteria for JIA (JIA ACR30) in Part 1 entered the double-blinded Part 2 (weeks 16–48) after 1:1 randomisation to continue golimumab or start placebo. In Part 3, golimumab was continued or could be restarted as in Part 1. The primary outcome was JIA flares in Part 2; secondary outcomes included JIA ACR50/70/90 responses, clinical remission, PK and safety. Results Among 173 patients with polyJIA enrolled, 89.0% (154/173) had a JIA ACR30 response and 79.2%/65.9%/36.4% demonstrated JIA ACR50/70/90 responses in Part 1. At week 48, the primary endpoint was not met as treatment groups had comparable JIA flare rates (golimumab vs placebo: 32/78=41% vs 36/76=47%; p=0.41), and rates of clinical remission were comparable (golimumab vs placebo: 10/78=12.8% vs 9/76=11.8%). Adverse event and serious adverse event rates were similar in the treatment groups during Part 2. Injection site reactions occurred with <1% of all injections. PK analysis confirmed adequate golimumab dosing for polyJIA. Conclusion Although the primary endpoint was not met, golimumab resulted in rapid, clinically meaningful, improvement in children with active polyJIA. Golimumab was well tolerated, and no unexpected safety events occurred. Clinical Trial Registration NCT01230827; Results.

Do adult disease severity subclassifications predict use of cyclophosphamide in children with ANCA-associated vasculitis? An analysis of ARChiVe study treatment decisions.

Objective. To determine whether adult disease severity subclassification systems for antineutrophil cytoplasmic antibody-associated vasculitis (AAV) are concordant with the decision to treat pediatric patients with cyclophosphamide (CYC). Methods. We applied the European Vasculitis Study (EUVAS) and Wegener’s Granulomatosis Etanercept Trial (WGET) disease severity subclassification systems to pediatric patients with AAV in A Registry for Childhood Vasculitis (ARChiVe). Modifications were made to the EUVAS and WGET systems to enable their application to this cohort of children. Treatment was categorized into 2 groups, “cyclophosphamide” and “no cyclophosphamide.” Pearson’s chi-square and Kendall’s rank correlation coefficient statistical analyses were used to determine the relationship between disease severity subgroup and treatment at the time of diagnosis. Results. In total, 125 children with AAV were studied. Severity subgroup was associated with treatment group in both the EUVAS (chi-square 45.14, p < 0.001, Kendall’s tau-b 0.601, p < 0.001) and WGET (chi-square 59.33, p < 0.001, Kendall’s tau-b 0.689, p < 0.001) systems; however, 7 children classified by both systems as having less severe disease received CYC, and 6 children classified as having severe disease by both systems did not receive CYC. Conclusion. In this pediatric AAV cohort, the EUVAS and WGET adult severity subclassification systems had strong correlation with physician choice of treatment. However, a proportion of patients received treatment that was not concordant with their assigned severity subclass.

Early changes in gene expression and inflammatory proteins in systemic juvenile idiopathic arthritis patients on canakinumab therapy

BackgroundCanakinumab is a human anti-interleukin-1β (IL-1β) monoclonal antibody neutralizing IL-1β-mediated pathways. We sought to characterize the molecular response to canakinumab and evaluate potential markers of response using samples from two pivotal trials in systemic juvenile idiopathic arthritis (SJIA).MethodsGene expression was measured in patients with febrile SJIA and in matched healthy controls by Affymetrix DNA microarrays. Transcriptional response was assessed by gene expression changes from baseline to day 3 using adapted JIA American College of Rheumatology (aACR) response criteria (50 aACR JIA). Changes in pro-inflammatory cytokines IL-6 and IL-18 were assessed up to day 197.ResultsMicroarray analysis identified 984 probe sets differentially expressed (≥2-fold difference; P < 0.05) in patients versus controls. Over 50% of patients with ≥50 aACR JIA were recognizable by baseline expression values. Analysis of gene expression profiles from patients achieving ≥50 aACR JIA response at day 15 identified 102 probe sets differentially expressed upon treatment (≥2-fold difference; P < 0.05) on day 3 versus baseline, including IL-1β, IL-1 receptors (IL1-R1 and IL1-R2), IL-1 receptor accessory protein (IL1-RAP), and IL-6. The strongest clinical response was observed in patients with higher baseline expression of dysregulated genes and a strong transcriptional response on day 3. IL-6 declined by day 3 (≥8-fold decline; P < 0.0001) and remained suppressed. IL-18 declined on day 57 (≥1.5-fold decline, P ≤ 0.002).ConclusionsTreatment with canakinumab in SJIA patients resulted in downregulation of innate immune response genes and reductions in IL-6 and clinical symptoms. Additional research is needed to investigate potential differences in the disease mechanisms in patients with heterogeneous gene transcription profiles.Trial registrationClinicaltrials.gov: NCT00886769 (trial 1). Registered on 22 April 2009; NCT00889863 (trial 2). Registered on 21 April 2009.

Race, Income, and Disease Outcomes in Juvenile Dermatomyositis

Objective To determine the relationships among race, income, and disease outcomes in children with juvenile dermatomyositis (JDM). Study design Data from 438 subjects with JDM enrolled in the Childhood Arthritis and Rheumatology Research Alliance (CARRA) Legacy Registry were analyzed. Demographic data included age, sex, race, annual family income, and insurance status. Clinical outcomes included muscle strength, presence of rash, calcinosis, weakness, physical function, and quality of life measures. Disease outcomes were compared based on race and income. Results Minority subjects were significantly more likely to have low annual family income and significantly worse scores on measures of physical function, disease activity, and quality of life measures. Subjects with lower annual family income had worse scores on measures of physical function, disease activity, and quality of life scores, as well as weakness. Black subjects were more likely to have calcinosis. Despite these differences in outcome measures, there were no significant differences among the racial groups in time to diagnosis or duration of disease. Using calcinosis as a marker of disease morbidity, black race, annual family income <