Genetics of toll like receptor 9 in ANCA associated vasculitides

OBJECTIVES

To investigate the contribution of genetic polymorphisms of toll like receptor (TLR) 9 and related genes on the susceptibility and clinical manifestation of anti-neutrophil cytoplasmic antibody (ANCA) associated vasculitides (AAV).

METHODS

Four single nucleotide polymorphisms (SNPs) in TLR9 were genotyped in 863 German AAV cases and 1344 healthy controls. Significant results were replicated in a cohort of 426 Dutch and British AAV cases. 11 polymorphisms in TLR9 related genes were studied concomitantly.

RESULTS

A strong association of TLR9 genotypes and haplotypes with granulomatosis with polyangiitis was observed as well as a contrariwise association with microscopic polyangiitis. The association was confirmed when cases were compared according to ANCA status rather than to clinical entity. This was partly replicated in the second cohort leading to a striking overall difference in TLR9 allele/haplotype frequencies between proteinase 3 (PR3) ANCA+ and myeloperoxidase (MPO) ANCA+ cases (p=0.00000398, pc=0.000016, OR 1.68 (95% CI 1.35 to 2.1) for rs352140; p=0.000011, pc=0.000044, OR 1.64 (95% CI 1.31 to 2.04) for a 3-SNP haplotype). No significant association or epistatic effect was detected for TLR9 related genes: interleukin 6, interleukin 23 receptor, myeloid differentiation primary response 88, TNF receptor-associated factor 6, interleukin-1 receptor-associated kinase 4, discs large homolog 5 and nucleotide-binding oligomerisation domain containing 2.

CONCLUSIONS

We provide further evidence that PR3-ANCA+ AAV differs genetically from MPO-ANCA+ AAV. TLR9 signalling may be involved in disease pathology, favouring models of infectious agents triggering AAV development.

Toll-like receptor TLR2 and TLR9 ligation triggers neutrophil activation in granulomatosis with polyangiitis

OBJECTIVE

The aim of the study was to characterize the expression of TLR2, TLR4 and TLR9 in PMNs of patients with granulomatosis with polyangiitis (GPA) and to elucidate the role of these receptors in GPA with respect to neutrophil activation.

METHODS

The expression of TLR2, TLR4 and TLR9 was determined on ex vivo PMNs in whole blood samples of GPA patients (n = 35) and healthy controls (HCs) (n = 24). Isolated PMNs were stimulated in vitro with TLR agonists and assessed for degranulation, membrane proteinase 3 (mPR3) expression, soluble l-selectin shedding and cytokine production (IL-8) in five GPA patients and five HCs. The priming effects of TLR2 and TLR9 ligation were assessed by measurement of serine protease activity after stimulation with PR3-ANCA.

RESULTS

There were no significant differences in the ex vivo expression of TLRs on PMNs in HCs and GPA patients. Stimulation of TLR4 and TLR9 induced MPO release, stimulation with TLR2, TLR4 and TLR9 ligands elicited IL-8 production and stimulation of TLR2 and TLR9 led to an upregulation in mPR3 expression on PMNs with no significant differences between GPA and HC after 1 or 24 h stimulation. Priming of PMNs with TLR2 and TLR9 ligands induced degranulation after subsequent stimulation with PR3-ANCA, which was comparable to priming with TNF-α.

CONCLUSION

Expression of TLR2, TLR4 and TLR9 in PMNs and the TLR-induced activation of PMNs was comparable in GPA and HC. mPR3 upregulation by TLR2 and TLR9 stimulation and the priming effect of TLR ligands on PMNs may have a potential implication for triggering disease activity during infection in GPA.

[Update on granulomatosis with polyangitis (GPA, Wegener's granulomatosis)]

Granulomatosis with polyangitis (GPA, Wegener's granulomatosis) is characterized by a granulomatous inflammation of the respiratory tract and a necrotizing ANCA-associated small to medium-size vessel vasculitis with a predilection for the lungs (pulmonary capillaritis) and kidneys (necrotizing glomerulonephritis). The disease evolves stage-wise and typically starts as inflammation of the respiratory tract followed by development of systemic vasculitis manifestations. Today, treatment is evidence-based and adapted according to activity and disease stage which has resulted in a significant improvement in long-term outcome. Early mortality during the first year of treatment poses one of the main problems and is a result of infections under immunosuppressive treatment. Furthermore, treatment of refractory disease activity which is often represented by granulomatous manifestations is still a challenge and may result in significant organ damage if not treated successfully.

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 Wegener's 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.).

Comparative analysis of different commercial ELISA systems for the detection of anti-neutrophil cytoplasm antibodies in ANCA-associated vasculitides

OBJECTIVES

To assess the diagnostic performance of 11 commercial PR3- and MPO-ANCA ELISA systems (direct, capture and high sensitive [hs] ELISA).

METHODS

Sera from 90 patients with AAV (GPA, MPA and CSS) and 20 disease controls (SLE; RA) and healthy individuals were tested for the presence of ANCA by IFT and by different ELISAs for the presence of PR3-and MPO-ANCA, respectively. Furthermore, the binding capacity of the IUIS-CDC reference sera for PR3-/MPO-ANCA in different commercial assays was analysed.

RESULTS

Commercial ELISA kits for PR3-ANCA differed moderately in their sensitivity (from 45% to 62.5%). The highest sensitivity for PR3-ANCA was obtained with hs ELISA (kit A) and capture ELISA (kit N). Testing for MPO-ANCA the highest sensitivity (85%) was obtained with direct ELISA (kit D and I). Specificity was high in all kits. Only three PR3-ANCA commercial kits and three MPO-ANCA kits produced binding at the expected value for the IUIS-CDC reference sera (100 U/ml). In all of the kits, serial dilutions of the reference sera did not yield linearity.

CONCLUSIONS

Second (capture) and third (high sensitivity) generation PR3-ANCA ELISA kits are superior to conventional ELISAs. Direct and capture MPO-ANCA ELISAs showed a good overall performance in all kits. Most of the kits have not been standardised to allow their results to be compared.

Rituximab for refractory granulomatosis with polyangiitis (Wegener's granulomatosis): comparison of efficacy in granulomatous versus vasculitic manifestations

OBJECTIVE

First, to investigate the overall efficacy and safety of rituximab (RTX) in refractory granulomatosis with polyangiitis (GPA) in a tertiary referral centre. Second, to compare the efficacy of RTX in granulomatous and vasculitic manifestations in GPA.

PATIENTS AND METHODS

This study comprised a retrospective, standardised data collection from all patients who received RTX for refractory Wegener's granulomatosis from 2002 to 2010. Patients were assessed by a standardised interdisciplinary diagnostic procedure (including ear, nose and throat and ophthalmology assessment, MRI, immunodiagnostics, B-cell levels and Birmingham Vasculitis Activity Score) and were treated by standardised therapeutic regimens according to available evidence.

RESULTS

59 patients received 75 cycles of RTX. 9.3% achieved complete remission. A response was documented in 61.3% (improvement in 52%, unchanged disease activity in 9.3%), 26.7% had refractory disease. Birmingham Vasculitis Activity Score, disease extent index, erythrocyte sedimentation rate, C-reactive protein and prednisolone demand decreased significantly. All patients achieved B-cell depletion. Granulomatous manifestations such as orbital granuloma and pachymeningitis were more frequently refractory to RTX than vasculitis or other granulomatous manifestations. Thus, for example, complete remission/improvement was found in 89.2% of patients with renal disease and in only 44.4% of those with orbital masses (p=0.003). The relapse rate was 44.4% after a median period of 13.5 months. Adverse events occurred in 29%, pneumonia in 15% and death in 3%.

CONCLUSION

The overall response rate of refractory GPA to RTX was high (61.3% complete remission or improvement). Response rates of vasculitic manifestations were excellent; failure of response/progress was mostly due to granulomatous manifestations, especially orbital masses. Relapse rates were high (40%) despite maintenance treatment.

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 χ(2) 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.

Conditions in subjects with rheumatic diseases: pulmonary manifestations of vasculitides

Pulmonary involvement is a common complication of vasculitides, especially small vessel vasculitides. This review provides an overview of vasculitic manifestations of the lung as well as of other organs involved in vasculitides. Furthermore, it provides the diagnostic procedures required to asses a patient with vasculitic lung involvement and gives an overview of current treatment strategies.

[The genetics of vasculitides]

Genetic association studies have been of great value in the past by contributing to the understanding of pathophysiological mechanisms of chronic inflammatory and autoimmune diseases. Many genetic risk factors have been identified which confer susceptibility for one or several (autoimmune) disease(s). Using a candidate-gene approach, the first genetic risk factors and polymorphisms of vasculitides have been identified. Due to the rarity of autoimmune vasculitides often only small sample numbers have been generated and analysed, leading to inconsistent results. Furthermore, differences in ethnic background may complicate analysis. Only few of the detected risk factors have been reliably replicated in larger cohorts, such as the association of the PTPN22*620W allele with WG and MPA, the deficiency allele Pi*Z of the alpha1 antitrypsin gene and the HLA-DPB*04041 allele with WG and the HLA-DRB3/DRB4 with CSS. Genome-wide association studies (GWAS) offer the advantage of screening the whole genome for risk factors rather than relying on disease models postulated by the investigator; however, they require even larger sample sizes. Initial results from GWA studies are available for Behçet's disease and Kawasaki syndrome, which identified new genetic associations but require replication, especially since some of the identified risk factors could not be linked to pathophysiological pathways to date.

[Classification and therapy of vasculitis according to recommendations of the European League Against Rheumatism (EULAR)]

Vasculitis is still being classified according the criteria of the American College of Rheumatology and the Chapel Hill Consensus Conference Definitions. Diagnostic criteria are currently being established. The classification criteria are based on the size of the inflamed blood vessel (e.g. large vessel vasculitis with inflammation of the aorta and its branches), clinical symptoms and findings (such as cephalalgia in giant cell arteritis) and histological findings. In recent years a definition of disease stages and activity has been established and a number of controlled trials have been carried out in order to provide evidence-based stage and activity adapted therapy regimens. Recommendations for the management of vasculitis have been published in 2009 by EULAR (European League Against Rheumatism). This article gives a review of the classification of vasculitis and summarizes the current European guidelines on management.

Diagnostic and therapeutic management of Churg-Strauss syndrome

Churg-Strauss syndrome is a rare small-vessel vasculitis that is associated with asthma, granulomatous inflammation, peripheral/tissue eosinophilia and a positive antineutrophil cytoplasmic antibody status (in approximately 40% of patients). The disease can be organ- and life-threatening, either due to tissue eosinophil infiltration such as myocarditis or due to vasculitis manifestations, for example glomerulonephritis. Furthermore, life-threatening disease can also occur due to the side effects of immunosuppression, for example, infection. A thorough diagnostic work-up should be performed in order to identify all organs involved and to rule out other disorders with similar features, such as hypereosinophilic syndrome. Therapeutic management is conducted according to disease stage and activity. Glucocorticoids remain the mainstay of therapy; however, further immunosuppressants (e.g., cyclophosphamide for life-threatening disease) are usually required. Future promising therapy options target cytokines involved in the disease process, such as IL-5.

Prospective long-term follow-up of patients with localised Wegener's granulomatosis: does it occur as persistent disease stage?

Objective

To identify patients with localised Wegener's granulomatosis (locWG) to assess whether it occurs as a long-term disease stage or phenotype and to characterise its outcome.

Methods

Patients in a ‘localised stage’ with histological criteria compatible with WG and a follow-up period of ≥1 year were included. They were prospectively followed at the Vasculitis Center Schleswig-Holstein from 1989 to 2009 and the clinical manifestations, antineutrophil cytoplasmic autoantibodies (ANCA) status and damage were evaluated. Immunosuppression was adapted to disease activity and severity in a step-up regimen.

Results

Of 1024 patients with suspected WG, 99 were clinically diagnosed with locWG and 50 fulfilled the inclusion criteria (72% women, median age 43 years, 46% ANCA-positive). The median follow-up was 48 months. All achieved a response to treatment, 34% achieved complete remission, 1–4 relapses occurred in 46%, 5 (10%) had generalised disease (median 6 years after onset). ANCA status was not associated with relapse (p=0.98), transition to generalised disease (p=0.51) or refractory manifestations (p=0.60). 47% required cyclophosphamide for localised manifestations, 36% of them for pulmonary masses and 24% for orbital masses. 66% developed organ damage, mostly due to bony destruction or space obturation (28% saddle nose, 24% septal perforation, 10% orbital wall destruction). There were two deaths that were not related to WG.

Conclusion

There is evidence that locWG is a long-term disease stage or phenotype (5% of all patients with WG), 46% of whom are ANCA-positive. LocWG is characterised by destructive and/or space-consuming lesions associated with high relapse rates (46%) and local damage.

A functionally relevant IRF5 haplotype is associated with reduced risk to Wegener's granulomatosis

Wegener's granulomatosis (WG), characterized by systemic vasculitis and granulomatous inflammation, is a rare chronic rheumatic condition potentially sharing some etiopathological principles with other autoimmune disorders, e.g., rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Several large association studies have identified genetic risk factors for RA and SLE. Thereof, we have evaluated the relevance of the most promising ones in WG. 22 single nucleotide polymorphisms (SNPs) within or in the vicinity of CCL21, CD40, CDK6, IL21, IL2RB, IRF5, KIF5A, KLF12, MMEL1, PRKCQ, STAT4, TNFAIP3, and TRAF1/C5 have been genotyped in >600 German WG cases and >800 matched controls. While most polymorphisms did not show suspicious effects on WG susceptibility, SNPs representing TNFAIP3 (rs6922466, p = 0.032, odds ratio (OR) 0.83, 95% confidence interval (CI) 0.7--0.98) and CDK6 (rs42041, p = 0.0201, OR 1.21, 95% CI 1.03-1.43) revealed nominally significant differences in allele distribution. The strongest association was detected for a functionally relevant four SNP haplotype of IRF5, which comprised a protective effect (p = 0.0000897, p (corrected) = 0.0012, OR 0.73, 95% CI 0.62-0.85) similar to those previously seen in RA and SLE. Thus, we suggest that WG, SLE, and RA share some, but not many, genetic risk factors, which supports models of partly overlapping etiopathological mechanisms in these disorders.