C. O. S. Savage

Genetically Distinct Subsets within ANCA-Associated Vasculitis

BACKGROUND Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis is a severe condition encompassing two major syndromes: granulomatosis with polyangiitis (formerly known as Wegeners granulomatosis) and microscopic polyangiitis. Its cause is unknown, and there is debate about whether it is a single disease entity and what role ANCA plays in its pathogenesis. We investigated its genetic basis. METHODS A genomewide association study was performed in a discovery cohort of 1233 U.K. patients with ANCA-associated vasculitis and 5884 controls and was replicated in 1454 Northern European case patients and 1666 controls. Quality control, population stratification, and statistical analyses were performed according to standard criteria. RESULTS We found both major-histocompatibility-complex (MHC) and non-MHC associations with ANCA-associated vasculitis and also that granulomatosis with polyangiitis and microscopic polyangiitis were genetically distinct. The strongest genetic associations were with the antigenic specificity of ANCA, not with the clinical syndrome. Anti-proteinase 3 ANCA was associated with HLA-DP and the genes encoding α(1)-antitrypsin (SERPINA1) and proteinase 3 (PRTN3) (P=6.2×10(-89), P=5.6×10(-12,) and P=2.6×10(-7), respectively). Anti-myeloperoxidase ANCA was associated with HLA-DQ (P=2.1×10(-8)). CONCLUSIONS This study confirms that the pathogenesis of ANCA-associated vasculitis has a genetic component, shows genetic distinctions between granulomatosis with polyangiitis and microscopic polyangiitis that are associated with ANCA specificity, and suggests that the response against the autoantigen proteinase 3 is a central pathogenic feature of proteinase 3 ANCA-associated vasculitis. These data provide preliminary support for the concept that proteinase 3 ANCA-associated vasculitis and myeloperoxidase ANCA-associated vasculitis are distinct autoimmune syndromes. (Funded by the British Heart Foundation and others.).

Early mortality in systemic vasculitis: relative contribution of adverse events and active vasculitis

Objective To contrast the effect of the burden of vasculitis activity with the burden of adverse events on 1-year mortality of patients with antineutrophil cytoplasmic antibody-associated vasculitis (AAV). Methods This study assessed the outcome and adverse events in patients prospectively recruited to four European AAV clinical trials. Data on 524 patients with newly diagnosed AAV were included. The burden of adverse events was quantified using a severity score for leucopenia, infection and other adverse events, with an additional weighting for follow-up duration. A ‘combined burden of events’ (CBOE) score was generated for each patient by summing the individual scores. Vasculitis severity was quantified using the Birmingham vasculitis activity score and glomerular filtration rate (GFR). Results 1-year mortality probability was 11.1%; 59% and 14% of deaths were caused by therapy-associated adverse events and active vasculitis, respectively. Using Cox regression analysis, infection score (p<0.001), adverse event score (p<0.001), leucopenia score (p<0.001) and GFR (p=0.002) were independently associated with mortality. The risk of 1-year mortality remained low (5%) with CBOE scores less than 7, but increased dramatically with scores above this. Hazard ratio for death with a CBOE greater than 7 was 14.4 (95% CI 8.4 to 24.8). Age and GFR were independent predictors of CBOE score. Conclusions The greatest threat to patients with AAV in the first year of therapy is from adverse events rather than active vasculitis. The accumulation of adverse events, monitored using this scoring method, should prompt increased awareness that the patient is at high risk of death.

Primary systemic vasculitis

Systemic vasculitides are multisystem diseases characterised pathologically by necrotising inflammation of blood vessels. The clinical presentation of vasculitis depends on the vessels involved. Classification of such diseases is now by the size of the affected vessel. This review focuses predominantly on the small vessel vasculitides shown to be associated with the presence of anti-neutrophil cytoplasmic antibodies (ANCA), that is Wegeners granulomatosis, microscopic polyangiitis and Churg-Strauss syndrome. It will examine the clinical characteristics of these diseases, the use of ANCA in diagnosis and monitoring of disease along with current and novel treatment strategies. The immunopathology of the ANCA-associated vasculitides will also be explored reviewing the roles of ANCA, neutrophils, T cells and apoptosis in the production of disease.

Vascular damage in Wegener's granulomatosis and microscopic polyarteritis: presence of anti-endothelial cell antibodies and their relation to anti-neutrophil cytoplasm antibodies.

To define mechanisms of vascular injury in Wegeners granulomatosis and microscopic potyarteritis, anti‐endothelial cell antibodies (AECA) were sought in serum from 168 patients, all of whom had anti‐neutrophil cytoplasm antibodies (ANCA) detectable by indirect immunofluorescence. Using an ELISA with human umbilical vein endothelial cells (HUVEC), IgG AECA were demonstrated in 59% and IgM AECA in 68% of patients. Pretreatment of HUVEC with tumour necrosis factor (TNF). IL‐1 or interferon‐gamma (IFN‐γ) led to increased binding. Adsorption of AECA/ANCA‐containing serum with HUVEC or neutrophils demonstrated that AECA and ANCA recognized different targets, von Willebrand factor (vWf) antigen levels in the patient samples were markedly elevated, with a mean of 3‐10+ 1‐89 U/ml (control population mean 1‐04 + 0‐36 U/ml). suggesting widespread endothelial cell damage. Studies using an’ In‐labelled HUVEC release assay with 29 AECA‐containing sera did not demonstrate complement‐mediated cytotoxicity. even following activation of HUVEC with TNF. Four out of 16 AECA‐containing sera tested showed antibody‐dependent cellular cytotoxicity with unfractionated peripheral blood mononuclear cells. These data suggest that patients with Wegeners granulomatosis or microscopic polyarteritis can develop AECA to constitutively expressed but cytokine modulated determinants on HUVEC. These antibodies do not appear to support complement‐mediated cytotoxicity. but a proportion can support antibody‐dependent cellular cytotoxicity, suggesting that they may contribute to vascular injury.

EULAR points to consider in the development of classification and diagnostic criteria in systemic vasculitis

Objectives The systemic vasculitides are multiorgan diseases where early diagnosis and treatment can significantly improve outcomes. Robust nomenclature reduces diagnostic delay. However, key aspects of current nomenclature are widely perceived to be out of date, these include disease definitions, classification and diagnostic criteria. Therefore, the aim of the present work was to identify deficiencies and provide contemporary points to consider for the development of future definitions and criteria in systemic vasculitis. Methods The expert panel identified areas of concern within existing definitions/criteria. Consequently, a systematic literature review was undertaken looking to address these deficiencies and produce ‘points to consider’ in accordance with standardised European League Against Rheumatism (EULAR) operating procedures. In the absence of evidence, expert consensus was used. Results There was unanimous consensus for re-evaluating existing definitions and developing new criteria. A total of 17 points to consider were proposed, covering 6 main areas: biopsy, laboratory testing, diagnostic radiology, nosology, definitions and research agenda. Suggestions to improve and expand current definitions were described including the incorporation of anti-neutrophil cytoplasm antibody and aetiological factors, where known. The importance of biopsy in diagnosis and exclusion of mimics was highlighted, while equally emphasising its problems. Thus, the role of alternative diagnostic tools such as MRI, ultrasound and surrogate markers were also discussed. Finally, structures to develop future criteria were considered. Conclusions Limitations in current classification criteria and definitions for vasculitis have been identified and suggestions provided for improvement. Additionally it is proposed that, in combination with the updated evidence, these should form the basis of future attempts to develop and validate revised criteria and definitions of vasculitis.

Anti-proteinase 3 anti-neutrophil cytoplasm autoantibodies recapitulate systemic vasculitis in mice with a humanized immune system.

Evidence is lacking for direct pathogenicity of human anti-proteinase-3 (PR3) antibodies in development of systemic vasculitis and granulomatosis with polyangiitis (GPA, Wegeners granulomatosis). Progress in study of these antibodies in rodents has been hampered by lack of PR3 expression on murine neutrophils, and by different Fc-receptor affinities for IgG across species. Therefore, we tested whether human anti-PR3 antibodies can induce acute vasculitis in mice with a human immune system. Chimeric mice were generated by injecting human haematopoietic stem cells into irradiated NOD-scid-IL2Rγ−/− mice. Matched chimera mice were treated with human IgG from patients with: anti-PR3 positive renal and lung vasculitis; patients with non-vasculitic renal disease; or healthy controls. Six-days later, 39% of anti-PR3 treated mice had haematuria, compared with none of controls. There was punctate bleeding on the surface of lungs of anti-PR3 treated animals, with histological evidence of vasculitis and haemorrhage. Anti-PR3 treated mice had mild pauci-immune proliferative glomerulonephritis, with infiltration of human and mouse leukocytes. In 3 mice (17%) more severe glomerular injury was present. There were no glomerular changes in controls. Human IgG from patients with anti-PR3 autoantibodies is therefore pathogenic. This model of anti-PR3 antibody-mediated vasculitis may be useful in dissecting mechanisms of microvascular injury.

ANCA-associated vasculitis is linked to carriage of the Z allele of α1 antitrypsin and its polymers

Background Small studies have linked α1 antitrypsin (α1AT) deficiency to patients with antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV). Objective To test the validity and the mechanism of this association between α1AT and AAV. Methods The distribution of α1AT deficiency alleles Z and S was compared between 856 White Europeans with AAV and 1505 geographic and ethnically matched healthy controls. Genotyping was performed by allelic discrimination assay. Results were compared between cases and controls using χ2 tests. The serum and renal biopsies for α1AT polymers were compared using the polymer-specific 2C1 antibody. The role of α1AT polymers in promoting inflammation was investigated by examining their ability to prime neutrophils for ANCA activation as assessed by CD62L shedding, superoxide production and myeloperoxidase degranulation. Results The Z but not the S allele was over-represented in the patients compared with controls (HR=2.25, 95% CI 1.60 to 3.19). Higher concentrations of polymers of α1AT were detected in serum from patients carrying the Z allele than in those not carrying the Z allele (median (IQR) 1.40 (0.91–3.32) mg/dl vs 0.17 (0.06–0.28) mg/dl, p<0.001); polymers of α1AT were also seen in the renal biopsy of a patient with vasculitic glomerulonephritis. Polymers of α1AT primed neutrophils with CD62L shedding and increased superoxide production following ANCA activation. Carriage of the Z allele was not associated with disease severity, survival or relapse. Conclusions The Z but not the S deficiency allele is associated with AAV. Polymers of α1AT are present in the serum and glomeruli of at least some patients with the Z allele, which may promote inflammation through priming of neutrophils.

ANCA-stimulated neutrophils release BLyS and promote B cell survival: a clinically relevant cellular process

Objectives To determine a role for antineutrophil cytoplasmic antibody (ANCA)-activated neutrophils in promoting B cell survival through the release of B lymphocyte stimulator (BLyS). Methods Neutrophil BLyS expression was measured by flow cytometry. Concentrations of BLyS in cell supernatants and donor serum samples were measured by ELISA. Cell survival assays were carried out using an L3055 cell line and viability measured by flow cytometry. Results Tumour necrosis factor α and formyl-Met-Leu-Phe (fMLP) treatment of non-primed neutrophils and treatment of primed neutrophils with anti-PR3 ANCA IgG resulted in a significant increase in surface expression of BLyS within 30 min which returned to basal levels by 2 h. Supernatants from ANCA-stimulated neutrophils were shown to contain increased levels of BLyS and to promote the survival of the centroblast cell line L3055. Serum BLyS concentrations are increased in patients with active ANCA-associated systemic vasculitis and these levels are increased further following 1–3 months of treatment with rituximab. Conclusions ANCA specifically causes the release of BLyS from activated neutrophils which can support B cell survival in vitro. The presence of serum BLyS in active disease and its increase following B cell depletion suggest it is an important factor in disease pathogenesis and may facilitate disease relapse.

What you should know about PR3-ANCA: Evidence for the role of T cells in the pathogenesis of systemic vasculitis

The pathogenesis of systemic vasculitis is complex and is likely to involve many mechanisms. There is a growing body of evidence that T cells may contribute to the pathogenesis of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides. Predominantly, T cells and monocytes are found in inflammatory infiltrates in patients with Wegeners granulomatosis (WG). The production of ANCA appears to be T-cell-dependent. T lymphocytes from the peripheral blood of patients with ANCA-associated vasculitis have been shown to proliferate in response to proteinase 3 (PR3). These and other findings outlined in this review indicate T-cell involvement, although further studies are still needed to elucidate the exact contribution of T cells to the pathogenesis of systemic vasculitis.

Review article: Leukocyte‐endothelial dysregulation in systemic small vessel vasculitis

Aberrant interaction between the leukocyte and the endothelial cell (EC) results in the uncontrolled inflammation seen in systemic small vessel vasculitis. This review discusses our current understanding of this process and includes consideration of the role of adhesion molecules, proteases and the neutrophil respiratory burst. The effects of anti‐neutrophil cytoplasm antibodies and anti‐endothelial cell antibodies and their pathogenic roles are examined, and we look at experimental disease models. Specificity of disease‐targetted endothelial beds and the role of circulating EC are discussed.