Nader Khalidi

Distribution of arterial lesions in Takayasu's arteritis and giant cell arteritis

Objectives To compare patterns of arteriographic lesions of the aorta and primary branches in patients with Takayasus arteritis (TAK) and giant cell arteritis (GCA). Methods Patients were selected from two North American cohorts of TAK and GCA. The frequency of arteriographic lesions was calculated for 15 large arteries. Cluster analysis was used to derive patterns of arterial disease in TAK versus GCA and in patients categorised by age at disease onset. Using latent class analysis, computer derived classification models based upon patterns of arterial disease were compared with traditional classification. Results Arteriographic lesions were identified in 145 patients with TAK and 62 patients with GCA. Cluster analysis demonstrated that arterial involvement was contiguous in the aorta and usually symmetric in paired branch vessels for TAK and GCA. There was significantly more left carotid (p=0.03) and mesenteric (p=0.02) artery disease in TAK and more left and right axillary (p<0.01) artery disease in GCA. Subclavian disease clustered asymmetrically in TAK and in patients ≤55 years at disease onset and clustered symmetrically in GCA and patients >55 years at disease onset. Computer derived classification models distinguished TAK from GCA in two subgroups, defining 26% and 18% of the study sample; however, 56% of patients were classified into a subgroup that did not strongly differentiate between TAK and GCA. Conclusions Strong similarities and subtle differences in the distribution of arterial disease were observed between TAK and GCA. These findings suggest that TAK and GCA may exist on a spectrum within the same disease.

Immunochip Analysis Identifies Multiple Susceptibility Loci for Systemic Sclerosis

In this study, 1,833 systemic sclerosis (SSc) cases and 3,466 controls were genotyped with the Immunochip array. Classical alleles, amino acid residues, and SNPs across the human leukocyte antigen (HLA) region were imputed and tested. These analyses resulted in a model composed of six polymorphic amino acid positions and seven SNPs that explained the observed significant associations in the region. In addition, a replication step comprising 4,017 SSc cases and 5,935 controls was carried out for several selected non-HLA variants, reaching a total of 5,850 cases and 9,401 controls of European ancestry. Following this strategy, we identified and validated three SSc risk loci, including DNASE1L3 at 3p14, the SCHIP1-IL12A locus at 3q25, and ATG5 at 6q21, as well as a suggested association of the TREH-DDX6 locus at 11q23. The associations of several previously reported SSc risk loci were validated and further refined, and the observed peak of association in PXK was related to DNASE1L3. Our study has increased the number of known genetic associations with SSc, provided further insight into the pleiotropic effects of shared autoimmune risk factors, and highlighted the power of dense mapping for detecting previously overlooked susceptibility loci.

Identification of multiple genetic susceptibility loci in Takayasu arteritis

Takayasu arteritis is a rare inflammatory disease of large arteries. The etiology of Takayasu arteritis remains poorly understood, but genetic contribution to the disease pathogenesis is supported by the genetic association with HLA-B*52. We genotyped ~200,000 genetic variants in two ethnically divergent Takayasu arteritis cohorts from Turkey and North America by using a custom-designed genotyping platform (Immunochip). Additional genetic variants and the classical HLA alleles were imputed and analyzed. We identified and confirmed two independent susceptibility loci within the HLA region (r(2) < 0.2): HLA-B/MICA (rs12524487, OR = 3.29, p = 5.57 × 10(-16)) and HLA-DQB1/HLA-DRB1 (rs113452171, OR = 2.34, p = 3.74 × 10(-9); and rs189754752, OR = 2.47, p = 4.22 × 10(-9)). In addition, we identified and confirmed a genetic association between Takayasu arteritis and the FCGR2A/FCGR3A locus on chromosome 1 (rs10919543, OR = 1.81, p = 5.89 × 10(-12)). The risk allele in this locus results in increased mRNA expression of FCGR2A. We also established the genetic association between IL12B and Takayasu arteritis (rs56167332, OR = 1.54, p = 2.18 × 10(-8)).

A Randomized, Double-Blind Trial of Abatacept (CTLA-4Ig) for the Treatment of Takayasu Arteritis

To compare the efficacy of abatacept to that of placebo for the treatment of giant cell arteritis (GCA).

Association of granulomatosis with polyangiitis (Wegener's) with HLA-DPB1*04 and SEMA6A gene variants: Evidence grom genome-wide analysis

OBJECTIVE To identify genetic determinants of granulomatosis with polyangiitis (Wegeners) (GPA). METHODS We carried out a genome-wide association study (GWAS) of 492 GPA cases and 1,506 healthy controls (white subjects of European descent), followed by replication analysis of the most strongly associated signals in an independent cohort of 528 GPA cases and 1,228 controls. RESULTS Genome-wide significant associations were identified in 32 single-nucleotide polymorphic (SNP) markers across the HLA region, the majority of which were located in the HLA-DPB1 and HLA-DPA1 genes encoding the class II major histocompatibility complex (MHC) DPβ chain 1 and DPα chain 1 proteins, respectively. Peak association signals in these 2 genes, emanating from SNPs rs9277554 (for DPβ chain 1) and rs9277341 (DPα chain 1) were strongly replicated in an independent cohort (in the combined analysis of the initial cohort and the replication cohort, P = 1.92 × 10(-50) and 2.18 × 10(-39) , respectively). Imputation of classic HLA alleles and conditional analyses revealed that the SNP association signal was fully accounted for by the classic HLA-DPB1*04 allele. An independent single SNP, rs26595, near SEMA6A (the gene for semaphorin 6A) on chromosome 5, was also associated with GPA, reaching genome-wide significance in a combined analysis of the GWAS and replication cohorts (P = 2.09 × 10(-8) ). CONCLUSION We identified the SEMA6A and HLA-DP loci as significant contributors to risk for GPA, with the HLA-DPB1*04 allele almost completely accounting for the MHC association. These two associations confirm the critical role of immunogenetic factors in the development of GPA.

Granulomatosis with polyangiitis (Wegener's) is associated with HLA-DPB1*04 and SEMA6A gene variants: Evidence from genome-wide analysis.

OBJECTIVE To identify genetic determinants of granulomatosis with polyangiitis (Wegeners) (GPA). METHODS We carried out a genome-wide association study (GWAS) of 492 GPA cases and 1,506 healthy controls (white subjects of European descent), followed by replication analysis of the most strongly associated signals in an independent cohort of 528 GPA cases and 1,228 controls. RESULTS Genome-wide significant associations were identified in 32 single-nucleotide polymorphic (SNP) markers across the HLA region, the majority of which were located in the HLA-DPB1 and HLA-DPA1 genes encoding the class II major histocompatibility complex (MHC) DPβ chain 1 and DPα chain 1 proteins, respectively. Peak association signals in these 2 genes, emanating from SNPs rs9277554 (for DPβ chain 1) and rs9277341 (DPα chain 1) were strongly replicated in an independent cohort (in the combined analysis of the initial cohort and the replication cohort, P = 1.92 × 10(-50) and 2.18 × 10(-39) , respectively). Imputation of classic HLA alleles and conditional analyses revealed that the SNP association signal was fully accounted for by the classic HLA-DPB1*04 allele. An independent single SNP, rs26595, near SEMA6A (the gene for semaphorin 6A) on chromosome 5, was also associated with GPA, reaching genome-wide significance in a combined analysis of the GWAS and replication cohorts (P = 2.09 × 10(-8) ). CONCLUSION We identified the SEMA6A and HLA-DP loci as significant contributors to risk for GPA, with the HLA-DPB1*04 allele almost completely accounting for the MHC association. These two associations confirm the critical role of immunogenetic factors in the development of GPA.

A Randomized, Double-Blind Trial of Abatacept (CTLA-4Ig) for the Treatment of Giant Cell Arteritis: ABATACEPT FOR THE TREATMENT OF GCA

To compare the efficacy of abatacept to that of placebo for the treatment of Takayasu arteritis (TAK).

Exposure to ACE inhibitors prior to the onset of scleroderma renal crisis-results from the international scleroderma renal crisis survey

OBJECTIVE To determine whether exposure to angiotensin-converting enzyme (ACE) inhibitors prior to the onset of scleroderma renal crisis (SRC) leads to worse outcomes of SRC. METHODS Prospective cohort study of incident SRC subjects. The exposure of interest was ACE inhibitors prior to the onset of SRC. The outcomes of interest were death or dialysis during the first year after the onset of SRC. RESULTS A total of 87 subjects with incident SRC were identified and 1-year follow-up data were obtained in 75 (86%) subjects. Overall, 27 (36%) subjects died within the first year and an additional 19 (25%) remained on dialysis 1 year after the onset of SRC. In adjusted analyses, exposure to ACE inhibitors prior to the onset of SRC was associated with an increased risk of death (hazard ratio 2.42, 95% CI 1.02, 5.75, p < 0.05 in the primary analysis and 2.17, 95% CI 0.88, 5.33, p = 0.09 after post-hoc adjustment for pre-existing hypertension). CONCLUSION Overall, the 1-year outcomes of SRC were poor. Prior exposure to ACE inhibitors was associated with an increased risk of death after the onset of SRC, although there was uncertainty around the magnitude of the risk and the possibility of residual confounding could not be ruled out. Further studies will be needed to confirm these findings.

IgA and IgG antineutrophil cytoplasmic antibody engagement of Fc receptor genetic variants influences granulomatosis with polyangiitis

Granulomatosis with polyangiitis (Wegeners) is a rare autoimmune neutrophil-mediated vasculitis that can cause renal disease and mucosal manifestations. Antineutrophil cytoplasmic antibodies (ANCA) are present in many patients, vary in level over time, and induce neutrophil activation through engagement with Fc receptors (FcRs). Given roles for FcRs in ANCA-mediated neutrophil activation and IgA antibodies in mucosal immunity, we hypothesized that FcR genetics and previously unappreciated IgA ANCA affect clinical presentation. We assembled a total of 673 patients and 413 controls from two multicenter cohorts, performed ELISA and immunofluorescence assays to determine IgA and IgG ANCA positivity, and used Illumina, TaqMan, or Pyrosequencing to genotype eight haplotype-tagging SNPs in the IgA FcR (FCAR) and to determine NA1/NA2 genotype of FCGR3B, the most prevalent neutrophil IgG FcR. We evaluated neutrophil activation by measuring degranulation marker CD11b with flow cytometry or neutrophil extracellcular trap formation with confocal microscopy. Functional polymorphisms in FCGR3B and FCAR differed between patient groups stratified by renal involvement. IgA ANCA were found in ∼30% of patients and were less common in patients with severe renal disease. Neutrophil stimulation by IgA or IgG ANCA led to degranulation and neutrophil extracellcular trap formation in a FcR allele-specific manner (IgA:FCAR P = 0.008; IgG:FCGR3B P = 0.003). When stimulated with IgA and IgG ANCA together, IgG ANCA induced neutrophil activation was reduced (P = 0.0001). FcR genotypes, IgA ANCA, and IgG ANCA are potential prognostic and therapeutic targets for understanding the pathogenesis and presentation of granulomatosis with polyangiitis (Wegeners).

An Open-label, Phase II Study of the Safety and Tolerability of Pirfenidone in Patients with Scleroderma-associated Interstitial Lung Disease: the LOTUSS Trial

Objective. Systemic sclerosis-associated interstitial lung disease (SSc-ILD) shares a number of clinical features and pathogenic mechanisms with idiopathic pulmonary fibrosis (IPF). This study was designed to evaluate the tolerability of the IPF treatment pirfenidone in SSc-ILD. The known gastrointestinal, skin, and liver adverse events (AE) of pirfenidone are of importance given the involvement of these organs in SSc. Methods. All patients received pirfenidone and were randomized 1:1 to either a 2- or 4-week titration starting at 801 mg/day and finishing at a maintenance dose of 2403 mg/day. Patients received pirfenidone for 16 weeks in total. Assessments included treatment-emergent AE (TEAE) and exploratory disease outcomes. Results. Sixty-three patients were randomized; 96.8% experienced a TEAE and more patients reported TEAE during the titration versus the maintenance period. The most commonly reported TEAE were consistent with those observed for pirfenidone in IPF (nausea, headache, fatigue) and were similar regardless of titration schedule. More patients discontinued treatment because of TEAE in the 2- versus 4-week titration group (5 vs 1, respectively); all discontinuation events occurred > 3 weeks after reaching the full dose of pirfenidone. Mycophenolate mofetil (MMF), taken by 63.5% of patients in addition to pirfenidone, did not appear to affect tolerability. Exploratory disease outcomes remained largely unchanged. Conclusion. Pirfenidone showed an acceptable tolerability profile in SSc-ILD, although a longer titration may be associated with better tolerability. Tolerability was not affected by concomitant MMF. The present findings support further investigation of pirfenidone in future clinical trials in patients with SSc-ILD. Trial registration: ClinicalTrials.gov; www.clinicaltrials.gov NCT01933334.