Brief report: candidate gene study in systemic sclerosis identifies a rare and functional variant of the TNFAIP3 locus as a risk factor for polyautoimmunity

OBJECTIVE

Systemic lupus erythematosus (SLE) and systemic sclerosis (SSc) share some pathophysiologic bases as evidenced by individual and familial polyautoimmunity and common susceptibility genetic factors. With regard to the latter, there has been a recent shift from the "common variant" to the "rare variant" paradigm, since rare variants of TNFAIP3 and TREX1 with large effect sizes have recently been discovered in SLE. The present study was undertaken to investigate whether rare variants of TNFAIP3 and TREX1 are also associated with SSc.

METHODS

TREX1 single-nucleotide polymorphisms (SNPs) rs3135946, rs7626978, rs3135943, and rs11797 and TNFAIP3 SNPs rs9494883, rs72063345, rs5029939, rs2230926, rs117480515, and rs7749323 were genotyped in a discovery set (985 SSc patients and 1,011 controls), and replication analysis of the most relevant results was performed in a second set (622 SSc patients and 493 controls).

RESULTS

No association between TREX1 variants and SSc was observed. For TNFAIP3, we first demonstrated that a low-frequency variant, rs117480515, tagged the recently identified TT>A SLE dinucleotide. In the discovery sample, we observed that all tested TNFAIP3 variants were in linkage disequilibrium and were associated with SSc and various SSc subsets, including the polyautoimmune phenotype. We subsequently genotyped rs117480515 in the replication sample and found it to be associated solely with the SSc polyautoimmune subset (odds ratio 3.51 [95% confidence interval 2.28-5.41], P = 8.58 × 10(-9) ) in the combined populations. Genotype-messenger RNA (mRNA) expression correlation analysis revealed that the TNFAIP3 rs117480515 risk allele was associated with decreased mRNA expression.

CONCLUSION

The present findings establish the TNFAIP3 locus as a susceptibility factor for the subset of SSc with a polyautoimmune phenotype. Our results support the implication of rare/low-frequency functional variants and the critical role of A20 in autoimmunity.

Imatinib mesylate in scleroderma-associated diffuse skin fibrosis: a phase II multicentre randomized double-blinded controlled trial

BACKGROUND

Imatinib mesylate is a potent inhibitor of platelet-derived growth factor and transforming growth factor-β signalling pathways which may play a role in systemic sclerosis (SSc)-associated skin changes.

OBJECTIVES

We aimed primarily at assessing the efficacy of imatinib mesylate in scleroderma skin fibrosis.

METHODS

We performed a phase II double-blinded trial on patients with scleroderma with either morphoea involving > 20% of body surface area or SSc with extensive skin involvement: modified Rodnan Skin Score (mRSS) ≥ 20/51. Each patient was randomized to receive either imatinib mesylate 400 mg or placebo daily for a total of 6 months, and then was followed up 6 months after therapy discontinuation. Skin fibrosis was assessed by mRSS and measurement of the dermal thickness using skin biopsies performed at inclusion and at 6 months of treatment. In addition, quality of life (Dermatology Life Quality Index and modified Health Assessment Questionnaire for Scleroderma) was recorded at each visit, and pulmonary function before and after intervention.

RESULTS

Twenty-eight patients were included in the study with a mean age of 48·9 years (range 30-71): 25 had a diagnosis of a SSc and three of diffuse cutaneous scleroderma. Demographic data, frequency of organ involvement of SSc and mRSS were comparable between groups. At 6 months, the proportion of variation of mRSS from inclusion was not statistically significantly different between the two groups (median +0·10 in imatinib group vs. -0·16 in placebo group, P = 0·098). Similarly, changes in dermal thickness, quality of life and diffusion capacity for carbon monoxide were not significantly different between groups.

CONCLUSIONS

This study failed to demonstrate the efficacy of imatinib 400 mg daily to improve skin fibrosis of diffuse scleroderma after 6 months of treatment based on validated outcome measurements.

Comparison of long-term outcome between anti-Jo1- and anti-PL7/PL12 positive patients with antisynthetase syndrome

The aims of the present study were to: compare the characteristics between antisynthetase syndrome (ASS) patients with anti-Jo1 antibody and those with anti-PL7/PL12 antibody. The medical records of 95 consecutive patients with ASS were reviewed. Seventy-five of these patients had anti-Jo1 antibody; the other patients had anti-PL7 (n=15) or anti-PL12 (n=5) antibody. At ASS diagnosis, the prevalence of myalgia (p=0.007) and muscle weakness (p=0.02) was significantly lower in the group of anti-PL7/PL12-positive patients than in those with anti-Jo1 antibody; median value of CK (p=0.00003) was also lower in anti-PL7/PL12 patients. Anti-Jo1 positive patients developed more rarely myositis resolution (21.3% vs. 46.2%); in addition, the overall recurrence rate of myositis was higher in anti-Jo1 positive patients than in patients with anti-PL7/PL12 antibody (65.9% vs. 19.4%). Anti-Jo1-positive patients, compared with those with anti-PL7/PL12 antibody, more often experienced: joint involvement (63.3%vs. 40%) and cancer (13.3% vs. 5%). By contrast, anti-PL7/PL12 positive patients, compared with those with anti-Jo1 antibody, more commonly exhibited: ILD (90% vs. 68%); in anti-PL7/PL12 positive patients, ILD was more often symptomatic at diagnosis, and led more rarely to resolution of lung manifestations (5.6% vs. 29.4%). Finally, the group of anti-PL7/PL12 positive patients more commonly experienced gastrointestinal manifestations related to ASS (p=0.02). Taken together, although anti-Jo1 positive patients with ASS share some features with those with anti-PL7/PL12 antibody, they exhibit many differences regarding clinical phenotype and long-term outcome. Our study underscores that the presence of anti-Jo1 antibody results in more severe myositis, joint impairment and increased risk of cancer. On the other hand, the presence of anti-PL7/PL12 antibody is markedly associated with: early and severe ILD, and gastrointestinal complications. Thus, our study interestingly indicates that the finding for anti-Jo1 and anti-PL7/PL12 antibodies impacts both the long-term outcome and prognosis of patients with ASS.

Evidence of the contribution of the X chromosome to systemic sclerosis susceptibility: association with the functional IRAK1 196Phe/532Ser haplotype

OBJECTIVE

Several autoimmune disorders, including systemic sclerosis (SSc), are characterized by a strong sex bias. To date, it is not known whether genes on the sex chromosomes influence SSc susceptibility. Recently, an IRAK1 haplotype that contains the 196Phe functional variant (rs1059702), located on Xq28, was found to confer susceptibility to systemic lupus erythematosus (SLE). This study was undertaken to test for an association between SSc and the IRAK1 SLE risk haplotype.

METHODS

We tested for an association with the IRAK1 SLE risk haplotype in a discovery set of 849 SSc patients and 625 controls. IRAK1 rs1059702 was further genotyped in a replication set, which included Caucasian women from Italy (493 SSc patients and 509 controls) and Germany (466 SSc patients and 1,083 controls).

RESULTS

An association between the IRAK1 haplotype and SSc was detected in the discovery set. In both the discovery and replication sets, the rs1059702 TT genotype was found to be associated with specific SSc subsets, highlighting a potential contribution to disease severity. A meta-analysis provided evidence of an association of both the T allele and TT genotype with the overall disease, with an odds ratio (OR) of 1.20 and 95% confidence interval (95% CI) of 1.06-1.35 for the T allele (P = 0.003) and an OR of 1.49 and 95% CI of 1.06-2.10 for the TT genotype (P = 0.023). However, the most notable associations were observed with the diffuse cutaneous, anti-topoisomerase I antibody positive, and SSc-related fibrosing alveolitis subsets (OR 2.35 [95% CI 1.51-3.66], P = 1.56 × 10(-4), OR 2.84 [95% CI 1.87-4.32], P = 1.07 × 10(-6), and OR 2.09 [95% CI 1.35-3.24], P = 9.05 × 10(-4), respectively).

CONCLUSION

Our study provides the first evidence of an association between IRAK1 and SSc, demonstrating that a sex chromosome gene directly influences SSc susceptibility and its phenotypic heterogeneity.

Association of Fcγ receptor IIIA variant with a subset of anti-topoisomerase I-positive patients in systemic sclerosis: a descriptive pilot study

Hypothesizing a pathophysiological role of anti-topoisomerase I antibodies (anti-topo I) through autoantibody-dependent cell-mediated cytotoxicity (ADCC) and cytotoxic effectors expressing receptors for the Fc portion of IgG in systemic sclerosis (SSc), 267 SSc patients (56 with anti-topo I and 102 with anti-centromere antibodies (ACA)) were genotyped for the functional FCGR3A-V158F polymorphism. A descriptive analysis of patients according to their clinical and immunological status and FCGR3A-158 V/F genotypes was performed using multiple correspondence analysis. This descriptive analysis revealed an association between the FCGR3A-158 VV genotype and the presence of anti-topo I. By contrast, no relationship was found between FCGR3A polymorphism and the presence of ACA. SSc patients with anti-topo I appear to be more frequently homozygous for the high-affinity FcγRIIIA-coding allele, suggesting that some autoantibodies may be pathogenic through ADCC.

NLRP1 influences the systemic sclerosis phenotype: a new clue for the contribution of innate immunity in systemic sclerosis-related fibrosing alveolitis pathogenesis

BACKGROUND

Recent evidence has highlighted a potential role of interleukin 1β (IL-1β) in systemic sclerosis (SSc). NLRP1 provides a scaffold for the assembly of the inflammasome that promotes the processing and maturation of pro-IL-1β. In addition, NLRP1 variants were found to confer susceptibility to autoimmune disorders.

OBJECTIVE

/st> To study a possible association of the NLRP1 rs6502867, rs2670660 and rs8182352, rs12150220 and rs4790797 with SSc in the European Caucasian population.

METHODS

NLRP1 single nucleotide polymorphisms were genotyped in 3227 individuals comprising a discovery set (870 SSc patients and 962 controls) and a replication set including individuals from Germany (532 SSc patients and 324 controls) and Italy (527 SSc patients and 301 controls), all individuals being of European Caucasian origin.

RESULTS

Conditional analyses revealed a significant association for the NLRP1 rs8182352 variant with both anti-topoisomerase-positive and SSc-related fibrosing alveolitis (FA) subsets under an additive model: p=0.0042, OR 1.23 (95% CI 1.07 to 1.41) and p=0.0065 OR 1.19 (95% CI 1.05 to 1.36), respectively. Logistic regression analysis showed an additive effect of IRF5 rs2004640, STAT4 rs7574865 and NLRP1 rs8182352 risk alleles on SSc-related FA.

CONCLUSIONS

Our results establish NLRP1 as a new genetic susceptibility factor for SSc-related pulmonary fibrosis and anti-topoisomerase-positive SSc phenotypes. This provides new insights into the pathogenesis of SSc, underlining the potential role of innate immunity in particular in the FA-positive SSc subphenotype, which represents a severe subset of the disease.