Clinical correlates of a subset of anti-CENP-A antibodies cross-reacting with FOXE3p53-62 in systemic sclerosis

Clinical correlates of a subset of anti-fibroblast antibodies in systemic sclerosis

Anti-fibroblast antibodies (AFA) have been reported in systemic sclerosis (SSc) and are known to promote fibroblast activation. Aim of this study was to characterize the fine specificity of AFA and to analyze any correlations with clinical parameters associated to fibrosis. To this end, AFA were affinity-purified from a patient with diffuse cutaneous SSc (dcSSc) and interstitial lung disease (ILD). Panning of a phage display peptide library with purified AFA identified the motif . The peptide p121, bearing the AFA-specific motif, was used in ELISA to screen sera from 186 SSc patients and 81 healthy donors. Anti-p121 Ab serum levels were statistically higher in SSc than in healthy groups, and directly associated with dcSSc, reduced FVC (FVC < 70), and ILD. Given these clinical correlates, this study lays the groundwork for the identification of the antigen recognized by anti-p121 Ab, which might represent a novel therapeutic target for ILD.

Approach to Systemic Sclerosis Patient Assessment

Systemic sclerosis (SSc) is a heterogeneous disease comprising of a wide spectrum of ages of onset, sex-based differences, ethnic variations, disease manifestations, differential serologic profiles, and variable response to therapy resulting in reduced health-related quality of life, disability, and survival. The ability to subset groups of patients with SSc can assist with refining the diagnosis, guide appropriate monitoring, inform aggressiveness of immunosuppression, and predict prognosis. The ability to subset patients with SSc has several important practical implications for patient care.

Systematic Analysis of the Literature in Search of Defining Systemic Sclerosis Subsets

OBJECTIVE

Systemic sclerosis (SSc) is a multisystem disease with heterogeneity in presentation and prognosis.An international collaboration to develop new SSc subset criteria is underway. Our objectives were to identify systems of SSc subset classification and synthesize novel concepts to inform development of new criteria.

METHODS

Medline, Cochrane MEDLINE, the Cumulative Index to Nursing and Allied Health Literature, EMBASE, and Web of Science were searched from their inceptions to December 2019 for studies related to SSc subclassification, limited to humans and without language or sample size restrictions.

RESULTS

Of 5686 citations, 102 studies reported original data on SSc subsets. Subset classification systems relied on extent of skin involvement and/or SSc-specific autoantibodies (n = 61), nailfold capillary patterns (n = 29), and molecular, genomic, and cellular patterns (n = 12). While some systems of subset classification confer prognostic value for clinical phenotype, severity, and mortality, only subsetting by gene expression signatures in tissue samples has been associated with response to therapy.

CONCLUSION

Subsetting on extent of skin involvement remains important. Novel disease attributes including SSc-specific autoantibodies, nailfold capillary patterns, and tissue gene expression signatures have been proposed as innovative means of SSc subsetting.

Bicaudal D2 is a novel autoantibody target in systemic sclerosis that shares a key epitope with CENP-A but has a distinct clinical phenotype

We studied the clinical correlations and epitopes of autoantibodies directed to a novel autoantigen, Bicaudal D (BICD2), in systemic sclerosis (SSc) and reviewed its relationship to centromere protein A (CENP-A). 451 SSc sera were tested for anti-BICD2 using a paramagnetic bead immunoassay and then univariate and multivariate logistic regression was used to study the association between anti-BICD2 and demographic and clinical parameters as well as other SSc-related autoantibodies. Epitope mapping was performed on solid phase matrices. 25.7% (116/451) SSc sera were anti-BICD2 positive, of which 19.0% had single specificity anti-BICD2 and 81.0% had other autoantibodies, notably anti-CENP (83/94; 88.3%). Compared to anti-BICD2 negative subjects (335/451), single specificity anti-BICD2 subjects were more likely to have an inflammatory myopathy (IM; 31.8% vs. 9.6%, p=.004) and interstitial lung disease (ILD; 52.4% vs. 29.0%, p=.024). Epitope mapping revealed a serine- and proline-rich nonapeptide SPSPGSSLP comprising amino acids 606-614 of BICD2, shared with CENP-A but not CENP-B. We observed that autoantibodies to BICD2 represent a new biomarker as they were detected in patients without other SSc-specific autoantibodies and were the second most common autoantibody identified in this SSc cohort. Our data indicate that the major cross-reactive epitope is associated with anti-CENP-A but, unlike anti-CENP, single specificity anti-BICD2 antibodies associate with ILD and IM.

Subspecificities of anticentromeric protein A antibodies identify systemic sclerosis patients at higher risk of pulmonary vascular disease

Patients with systemic sclerosis (SSc) who express autoantibodies to centromeric proteins (CENPs) are at risk of developing pulmonary vascular disease and pulmonary arterial hypertension without fibrosis. Currently no biomarkers are available to predict these complications. We previously characterized the fine specificity of anti-CENP-A antibodies in SSc by screening a phage display library (expressing random 12-mer peptides), and identified phage clones whose peptides were differentially recognized by patients' autoantibodies. Here, we examined if subgroups of SSc patients with different anti-CENP-A antibody subspecificities also differ clinically, and if serum reactivity to phage-displayed peptides can predict pulmonary vascular disease.Clinical data and serum samples were collected from 84 anti-CENP-A-positive SSc patients. Indirect ELISAs were used to test serum reactivity. Pulmonary vascular disease was defined as high systolic pulmonary arterial pressure (sPAP) and low diffusing lung capacity for carbon monoxide (DLCO; percent of predicted values).Sera were screened for reactivity to peptides expressed by phage clones pc4.2 and pc14.1, confirming our earlier observation of differential specificities. Linear regression showed that the levels of antibodies specific for the 2 phage clones were associated with clinical features of pulmonary vascular disease, but in opposite ways: anti-pc4.2 antibodies were positively associated with sPAP and inversely associated with DLCO, whereas anti-pc14.1 antibodies were inversely associated with sPAP and positively associated with DLCO. Anti-pc4.2 and anti-pc14.1 antibody levels predicted sPAP independently of DLCO. These associations were confirmed by logistic regression using antibodies as predictors and dichotomized sPAP (cutoff, 45 mm Hg) as outcome. The ratio of the 2 antibody levels was a useful marker in predicting high sPAP.This study demonstrates that some SSc clinical features associate with subspecificities of anti-CENP-A antibodies. Moreover, it shows that a simple, inexpensive phage-based assay can predict which SSc patients have high sPAP and low DLCO, hence who are at greater risk of developing pulmonary arterial hypertension. The ability to identify these at-risk patients can contribute to clinical efficiency and effectiveness. Further research into the peptides expressed by the phage clones may reveal the molecular mechanisms that put some anti-CENP-A-positive patients at greater risk than others for pulmonary vascular disease.

Anti-centromere protein A antibodies in systemic sclerosis: Significance and origin

Systemic sclerosis (SSc) is systemic, autoimmune, connective tissue disorder characterized by vascular abnormalities, collagen deposition (fibrosis), and the production of autoantibodies to nuclear proteins. About 20%-40% of patients have antibodies to centromere protein (CENP)-A or -B. Despite the known association of anti-CENP antibodies with certain clinical features of SSc, the role of these antibodies in SSc physiopathology is still poorly understood. To better understand the clinical significance and origin of these antibodies, we and others have been studying the epitopic motifs (amino acid contact sites) on CENP-A with the aim of determining whether other proteins can prime or be targeted by them. Here, we review published and ongoing studies aimed at defining the fine specificity and origin of anti-CENP-A antibodies. We describe progress made in identifying the CENP-A epitopic motif amino acids, and the discovery of one of these motifs in forkhead box protein E3 (FOXE-3), a transcription factor previously studied only for its role in the development of lens fiber cells. Moreover, we discuss preliminary evidence for a possible role of FOXE-3 in SSc pathogenesis and for the association of different subsets of anti-CENP-A antibodies, heterogeneously expressed among SSc patients, with some clinical correlates.