Clair, E. William St.

ObjectiveTo examine the association between macrophage migration inhibitory factor (MIF) promoter polymorphisms and granulomatosis with polyangiitis (GPA) in human subjects, and to assess the role of MIF in a murine model of granulomatous vasculitis.MethodsThe human study involved 1,077 patients with GPA and healthy controls whose serum was genotyped by capillary electrophoresis for the MIF −794 CATT5−8 promoter microsatellite (rs5844572). MIF promoter, CATT‐length–dependent gene expression in response to β‐glucan was assessed by gene reporter assays. In mouse studies, granulomatous disease was induced by injection of Candida albicans β‐glucan into wild‐type (WT) or Mif‐knockout (Mif‐KO) C57BL/6 mice and C57BL/6 mice transgenically overexpressing Mif in lung epithelium (Mif lung–Tg2.1). Mice were treated with a neutralizing anti‐MIF antibody and analyzed for the density of pulmonary granulomas, expression of inflammatory chemokines, and frequency of mortality.ResultsThe percentage of human subjects carrying >5 CATT repeats in each MIF allele (high genotypic MIF expressers) was 60.2% among patients with GPA and 53.9% among healthy controls (adjusted P = 0.049). In response to granulomatous stimulation, human MIF gene expression increased proportionally with CATT length. Mif lung–Tg2.1 mice exhibited more pulmonary granulomas than WT mice, which in turn showed more granulomas than Mif‐KO mice. A significantly higher percentage of Mif lung–Tg2.1 mice, compared to Mif‐KO or WT mice, died when injected with Candida albicans β‐glucan, and treatment of these mice with an anti‐MIF monoclonal antibody protected against a lethal outcome. Levels of MIF‐dependent neutrophil/macrophage chemokines were elevated in the bronchoalveolar lavage fluid or plasma of Mif lung–Tg2.1 mice.ConclusionPatients with GPA have an increased frequency of high MIF expression CATT alleles. Higher Mif expression increases the incidence of mortality and pulmonary granulomas in Mif lung–Tg2.1 mice, while anti‐MIF treatment protects these mice against death. Blockade of MIF in high genotypic MIF expressers may therefore offer a selective pharmacologic therapy for GPA.

ObjectiveTo evaluate circulating cytokine profiles in patients with antineutrophil cytoplasmic antibody–associated vasculitis (AAV), classified by antineutrophil cytoplasmic antibody (ANCA) specificity (proteinase 3 ANCA [PR3‐ANCA] versus myeloperoxidase ANCA [MPO‐ANCA]) or by clinical diagnosis (granulomatosis with polyangiitis [GPA] versus microscopic polyangiitis [MPA]).MethodsA panel of 29 cytokines was tested in 186 patients with active AAV at inclusion into the Rituximab in AAV trial. Cytokine concentrations were compared between groups within each classification system. Multivariable analyses adjusted for age, sex, and renal insufficiency were performed, with each biomarker as a dependent variable and ANCA specificity and clinical diagnosis as explanatory variables of interest.ResultsLevels of 9 circulating cytokines (interleukin‐6 [IL‐6], granulocyte–macrophage colony‐stimulating factor [GM‐CSF], IL‐15, IL‐18, CXCL8/IL‐8, CCL‐17/thymus and activation–regulated chemokine [TARC], IL‐18 binding protein [IL‐18 BP], soluble IL‐2 receptor α [sIL‐2Rα], and nerve growth factor β [NGFβ]) were significantly higher in PR3‐AAV than MPO‐AAV, 4 cytokines (sIL6R, soluble tumor necrosis factor receptor type II [sTNFRII], neutrophil gelatinase–associated lipocalin [NGAL], and soluble intercellular adhesion molecule 1 [sICAM‐1]) were higher in MPO‐AAV than in PR3‐AAV, 6 cytokines (IL‐6, GM‐CSF, IL‐15, IL‐18, sIL‐2Rα, and NGFβ) were higher in GPA than in MPA, and 3 cytokines (osteopontin, sTNFRII, and NGAL) were higher in MPA than in GPA (all P < 0.05). For nearly all cytokines, the difference between PR3‐AAV and MPO‐AAV was larger than that between GPA and MPA. The multivariate analysis showed that 8 cytokines (IL‐15, IL‐8, IL‐18 BP, NGF‐β, sICAM‐1, TARC, osteopontin, and kidney injury molecule 1 (P < 0.05) distinguished patients with AAV better (lower P values and larger effect sizes) when grouped by ANCA specificity than by clinical diagnosis.ConclusionDistinct cytokine profiles were identified for PR3‐AAV versus MPO‐AAV and for GPA versus MPA. Differences in these circulating immune mediators are more strongly associated with ANCA specificity than with clinical diagnosis, suggesting that heterogeneity in the AAV subtypes extends beyond clinical phenotypes.

Summary Anti-neutrophil cytoplasmic antibodies (ANCA) appear to play an important role in the pathogenesis of ANCA-associated vasculitis (AAV). However, ANCA alone are not sufficient to generate disease, and some evidence suggests that infectious triggers may serve as inciting events for AAV disease activity. Antibodies of the immunoglobulin (Ig)M isotype often serve as markers of recent infection, and IgM ANCA have been identified previously in patients with AAV, although the frequency and clinical relevance of IgM ANCA is not well established. We sought to characterize IgM ANCA more clearly by creating a novel enzyme-linked immunosorbent assay (ELISA) for IgM antibodies to proteinase 3 [IgM proteinase 3 (PR3)–ANCA], which we applied to two large, clinically well-characterized trial cohorts of patients with granulomatosis with polyangiitis and microscopic polyangiitis. In the first cohort, IgM PR3–ANCA occurred with a frequency of 15·0%, and were associated with a higher degree of disease severity and a trend towards a higher rate of alveolar haemorrhage (29·6 versus 15·7%, P = 0·10). Analysis of follow-up samples in this cohort showed that the presence of IgM PR3–ANCA was transient, but could recur. In the second cohort, IgM PR3–ANCA occurred with a frequency of 41·1%, and were also associated with a higher degree of disease severity. A higher rate of alveolar haemorrhage was observed among those with IgM PR3–ANCA (45·3 versus 15·8%; P &lt; 0·001). The association of transient IgM PR3–ANCA with an acute respiratory manifestation of AAV suggests a possible link between an infectious trigger and AAV disease activity.

Objective To identify risk alleles relevant to the causal and biologic mechanisms of antineutrophil cytoplasmic antibody (ANCA)–associated vasculitis (AAV). Methods A genome‐wide association study and subsequent replication study were conducted in a total cohort of 1,986 cases of AAV (patients with granulomatosis with polyangiitis [Wegener's] [GPA] or microscopic polyangiitis [MPA]) and 4,723 healthy controls. Meta‐analysis of these data sets and functional annotation of identified risk loci were performed, and candidate disease variants with unknown functional effects were investigated for their impact on gene expression and/or protein function. Results Among the genome‐wide significant associations identified, the largest effect on risk of AAV came from the single‐nucleotide polymorphism variants rs141530233 and rs1042169 at the HLA–DPB1 locus (odds ratio [OR] 2.99 and OR 2.82, respectively) which, together with a third variant, rs386699872, constitute a triallelic risk haplotype associated with reduced expression of the HLA–DPB1 gene and HLA–DP protein in B cells and monocytes and with increased frequency of complementary proteinase 3 (PR3)–reactive T cells relative to that in carriers of the protective haplotype. Significant associations were also observed at the SERPINA1 and PTPN22 loci, the peak signals arising from functionally relevant missense variants, and at PRTN3 , in which the top‐scoring variant correlated with increased PRTN3 expression in neutrophils. Effects of individual loci on AAV risk differed between patients with GPA and those with MPA or between patients with PR3‐ANCAs and those with myeloperoxidase‐ANCAs, but the collective population attributable fraction for these variants was substantive, at 77%. Conclusion This study reveals the association of susceptibility to GPA and MPA with functional gene variants that explain much of the genetic etiology of AAV, could influence and possibly be predictors of the clinical presentation, and appear to alter immune cell proteins and responses likely to be key factors in the pathogenesis of AAV.

ObjectiveWe investigated the relationships between glucocorticoid use, disease activity, and changes in body mass index (BMI) in patients with antineutrophil cytoplasmic antibody–associated vasculitis (AAV).MethodsWe analyzed AAV patients enrolled in the Rituximab in AAV trial. Glucocorticoid use, BMI, and disease activity were measured regularly during the trial period. We performed mixed‐effects regressions to examine the associations of time‐dependent cumulative average glucocorticoid use and disease activity with changes in BMI over time, while adjusting for potential confounders.ResultsThe mean ± SD baseline BMI of the 197 patients enrolled was 28.8 ± 6.3 kg/m2. Patients with newly diagnosed AAV tended to have a lower mean ± SD BMI than those with relapsing disease (28.0 ± 5.7 kg/m2 versus 29.6 ± 6.8 kg/m2) and higher disease activity (mean ± SD Birmingham Vasculitis Activity Score for Wegener's Granulomatosis 8.7 ± 3.3 versus 7.4 ± 2.7). The most significant change in BMI occurred during the first 6 months of the trial (mean ± SD increase of 1.1 ± 2.2 kg/m2; P < 0.0001). Disease activity improvement, glucocorticoid exposure, and randomization to rituximab were each independently associated with an increase in BMI (P < 0.001 for all analyses).ConclusionOur findings suggest that changes in BMI, as well as glucocorticoid exposure, are independently associated with improvements in disease activity in AAV. Rituximab may also have effects on BMI independent of its impact on disease activity.

ObjectiveThe Rituximab in ANCA‐Associated Vasculitis (RAVE) trial compared rituximab to cyclophosphamide as induction therapy for the treatment of antineutrophil cytoplasmic antibody (ANCA)–associated vasculitis. We undertook the current study to determine whether known single‐nucleotide polymorphisms (SNPs) for Fcγ receptors (FcγR) or cytochrome P450 (CYP) enzymes were associated with the response to treatment with rituximab and cyclophosphamide, respectively.MethodsFunctional SNPs for FcγR (FcγRIIa 519G>A, FcγRIIb 695T>C, FcγRIIIa 559T>G) and CYP enzymes (CYP2B6 1459C>T, CYP2C19 681G>A) were analyzed by direct sequencing of polymerase chain reaction–amplified genomic DNA. Each SNP was tested as a predictor of complete remission at 6 months or remission with continued prednisone administration using logistic regression and including the covariates of baseline Birmingham Vasculitis Activity Score for Wegener's Granulomatosis, ANCA type, and new versus relapsing disease. The associations of these SNPs with the secondary outcomes of time to complete remission, time to relapse, or time to B cell reconstitution were analyzed by Cox proportional hazard tests.ResultsNo significant associations were identified between complete remission and any FcγR genotype in the rituximab group or any CYP genotype in the cyclophosphamide group. However, when the treatment groups were combined, an association was found between the 519AA genotype of FcγRIIa and complete remission (P = 0.01). The 519AA genotype predicted complete remission (P = 0.006) and a shorter time to complete remission (P < 0.001).ConclusionThe finding that the homozygous FcγRIIa 519AA variant was associated with complete response and a shorter time to complete response in the RAVE trial, independent of treatment type, implies that FcγRIIa may be broadly involved in disease pathogenesis and response to therapy.

Objective S100A8/A9 (calprotectin) has shown promise as a biomarker for predicting relapse in antineutrophil cytoplasmic antibody (ANCA)–associated vasculitis (AAV). This study was undertaken to investigate serum S100A8/A9 level as a biomarker for predicting future relapse in a large cohort of patients with severe AAV. Methods Serum levels of S100A8/A9 were measured at baseline and months 1, 2, and 6 following treatment initiation in 144 patients in the Rituximab in ANCA‐Associated Vasculitis trial (cyclophosphamide/azathioprine versus rituximab [RTX] for induction of remission) in whom complete remission was attained. Results Patients were divided into 4 groups: proteinase 3 (PR3)–ANCA with relapse (n = 37), PR3‐ANCA without relapse (n = 56), myeloperoxidase (MPO)–ANCA with relapse (n = 6), and MPO‐ANCA without relapse (n = 45). Serum S100A8/A9 level decreased in all groups during the first 6 months of treatment. The percentage reduction from baseline to month 2 was significantly different between patients who experienced a relapse and those who did not in the PR3‐ANCA group ( P = 0.046). A significantly higher risk of relapse was associated with an increase in S100A8/A9 level between baseline and month 2 ( P = 0.0043) and baseline and month 6 ( P = 0.0029). Subgroup analysis demonstrated that patients treated with RTX who had increased levels of S100A8/A9 were at greatest risk of future relapse ( P = 0.028). Conclusion An increase in serum S100A8/A9 level by month 2 or 6 compared to baseline identifies a subgroup of PR3‐ANCA patients treated with RTX who are at higher risk of relapse by 18 months. Since RTX is increasingly used for remission induction in PR3‐ANCA–positive patients experiencing a relapse, S100A8/A9 level may assist in identifying those patients requiring more intensive or prolonged treatment.