Anti-centromere antibodies target centromere-kinetochore macrocomplex: a comprehensive autoantigen profiling

[Clinical and immunological features of primary Sjögren's syndrome patients with positive anti-centromere protein B antibody]

OBJECTIVE

To investigate the clinical and immunological features of primary Sjögren's syndrome (pSS) patients with positive anti-centromere protein B (CENP-B) antibody.

METHODS

In this cross-sectional study, the general clinical data, radiographic examination and labial salivary gland biopsy data, and serum immunological and biochemical data of patients diagnosed with pSS from January 2016 to August 2022 were evaluated. The included patients were divided into the anti-CENP-B antibody positive and negative groups. Intergroup differences were analyzed with SPSS 23.0 software. Subgroup analysis was further performed by dividing the anti-CENP-B antibody positive group into the single anti-CENP-B antibody positive and with other auto-antibodies positive groups to determine the characters related to anti-CENP-B antibody.

RESULTS

In this study, 288 patients with pSS were evaluated, including 75 patients with anti-CENP-B antibody positive and 213 with anti-CENP-B antibody negative. Univariate analysis showed that compared with the anti-CENP-B antibody negative group, the patients of the anti-CENP-B antibody positive group were older, had lower proportion of the patients with salivary gland enlargement and higher proportion of autoimmune liver disease. As for immunological indicators, the positive proportions of anti-SSA/Ro60, anti-Ro52, and anti-SSB antibodies were significantly lower. Moreover, the immunoglobulin (Ig) G and rheumatoid factor levels were significantly lower, while the IgM level was significantly higher in the patients of the anti-CENP-B antibody positive group. As for serum biochemical indicators, for the patients of the anti-CENP-B antibody positive group, the level of total protein (TP) was lower, the albumin/globulin ratio was higher, and the levels of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), gamma glutamyl transferase (GGT), lactate dehydrogenase (LDH) were higher. Subgroup analysis showed that the levels of TP and IgA in the patients of the single anti-CENP-B antibody positive group were significantly lower than those of the patients with other autoantibodies positive group.

CONCLUSION

The pSS patients with anti-CENP-B antibody positive have unique clinical and immunological features of lower disease activity, less likely to involve salivary gland, higher risk for autoimmune liver disease, and higher levels of liver function indicators. Anti-CENP-B antibody may be a marker for a distinct subset of polyautoimmunity in Sjögren's syndrome.

Uncovering potential new biomarkers and immune infiltration characteristics in primary Sjögren's syndrome by integrated bioinformatics analysis

Primary Sjögren's syndrome (pSS) is known as autoimmune disease characterized by damage to endocrine glands, such as the salivary and lacrimal glands. This study aimed to identify potential biomarkers for pSS using integrated bioinformatics analysis and explore the relationship between differentially expressed genes (DEGs) and immune infiltration. Three pSS datasets (GSE7451, GSE23117, and GSE40611) from the gene expression omnibus database were integrated. All the datasets were processed in R (version 4.0.3). A total of 16 immune cells and 13 immune functions were obtained. The top immune cell and immune function were "activated" dendritic cells and major histocompatibility complex class I. Correlation analysis showed the top correlation among 16 immune cells were B cells and tumor infiltrating lymphocytes, check-point and T cell co-stimulation, respectively. In comparisons of immune score, "activated" dendritic cells (.657 vs 594, P < .001), B cells (.492 vs 434, P = .004), macrophages (.631 vs 601, P = .010), inflammation-promoting (.545 vs 478, P < .001), Type I interferon Reponse (.728 vs 625, P < .001) and so on were higher in pSS than control group. In correlation analysis, the up-regulation of interferon induced protein with tetratricopeptide repeats 1 gene was strongly correlated with Type I interferon response with a correlation coefficient of .87. The receiver operating characteristic curve of 5 genes showed that the area under curve was.891. In the verification model, the area under curve was.881. In addition, disease ontology analysis supported the association between DEGs and pSS. In summary, pSS has a variety of DEGs in immune infiltration, which is worthy of the attention from clinicians.

Annals of the Rheumatic Diseases collection on autoantibodies in the rheumatic diseases: new insights into pathogenesis and the development of novel biomarkers

The rheumatic diseases are a diverse group of conditions that can display autoantibody production, functional immune disturbances and systemic disease manifestations. These autoantibodies can serve as markers for classification, diagnosis, prognosis and disease activity. Among specificities prominently expressed by patients, those directed to nuclear antigens (antinuclear antibodies or ANAs) are markers for specific rheumatic diseases. ANAs can bind to DNA, RNA and complexes of proteins with nucleic acids. Other autoantibodies expressed in the rheumatic diseases are directed to proteins, including IgG, post-translational modifications of proteins and soluble mediators such as cytokines. While autoantibodies have been investigated for over 50 years, recent studies published in the Annals of the Rheumatic Diseases (ARD) have provided an exciting perspective on the mechanisms of autoantibody production and the power of new technologies to identify novel autoantibody targets to elucidate aetiology and underpin patient evaluation. Furthermore, in-depth serological studies have demonstrated a phenomenon known as clustering; clustering defines sets of autoantibodies that are commonly expressed together in patients with a given rheumatic disease. Other research reported in ARD has used B cell phenotyping and genotypic analysis to subtype patients, and has explored the relationship of autoantibodies, complement activation and patterns of gene expression as exemplified by the interferon gene signature. Together, these studies provide important new insights into disease mechanisms as well as actionable information to facilitate personalised patient care.

Outline of Salivary Gland Pathogenesis of Sjögren's Syndrome and Current Therapeutic Approaches

Sjögren's syndrome (SS) is an autoimmune disease characterized by the involvement of exocrine glands such as the salivary and lacrimal glands. The minor salivary glands, from which tissue samples may be obtained, are important for the diagnosis, evaluation of therapeutic efficacy, and genetic analyses of SS. In the onset of SS, autoantigens derived from the salivary glands are recognized by antigen-presenting dendritic cells, leading to the activation of T and B cells, cytokine production, autoantibody production by plasma cells, the formation of ectopic germinal centers, and the destruction of salivary gland epithelial cells. A recent therapeutic approach with immune checkpoint inhibitors for malignant tumors enhances the anti-tumor activity of cytotoxic effector T cells, but also induces SS-like autoimmune disease as an adverse event. In the treatment of xerostomia, muscarinic agonists and salivary gland duct cleansing procedure, as well as sialendoscopy, are expected to ameliorate symptoms. Clinical trials on biological therapy to attenuate the hyperresponsiveness of B cells in SS patients with systemic organ involvement have progressed. The efficacy of treatment with mesenchymal stem cells and chimeric antigen receptor T cells for SS has also been investigated. In this review, we will provide an overview of the pathogenesis of salivary gland lesions and recent trends in therapeutic approaches for SS.

Laboratory risk factors for coexistent primary biliary cholangitis in patients with Sjögren's syndrome: a retrospective study

BACKGROUND

Limited research exists on the laboratory characteristics of coexistent primary biliary cholangitis (PBC) and Sjögren's syndrome (SS). This study aimed to investigate the laboratory risk factors for the coexistence of PBC in patients with SS.

METHODS

Eighty-two patients with coexistent SS and PBC (median age 52.50 years) and 82 age- and sex-matched SS controls were retrospectively enrolled between July 2015 and July 2021. The clinical and laboratory characteristics of the two groups were compared. Laboratory risk factors for the coexistence of PBC in patients with SS were analyzed using logistic regression analysis.

RESULTS

Both groups had a similar prevalence of hypertension, diabetes, thyroid disease, and interstitial lung disease. Compared with the SS group, patients in the SS + PBC group had higher levels of liver enzymes, immunoglobulins M (IgM), G2, and G3 (P < 0.05). The percentage of patients with an antinuclear antibody (ANA) titre > 1:10000 in the SS + PBC group was 56.1%, higher than that in the SS group (19.5%, P < 0.05). Additionally, cytoplasmic, centromeric, and nuclear membranous patterns of ANA and positive anti-centromere antibody (ACA) were observed more frequently in the SS + PBC group (P < 0.05). Logistic regression analysis showed that elevated IgM levels, high ANA titre, cytoplasmic pattern, and ACA were independent risk factors for PBC coexistence in SS.

CONCLUSIONS

In addition to established risk factors, elevated IgM levels, positive ACA, and high ANA titre with cytoplasmic pattern provide clues to clinicians for the early screening and diagnosis of PBC in patients with SS.

Anti-SSA/SSB-negative primary Sjögren's syndrome showing different clinical phenotypes: a retrospective study of 934 cases

BACKGROUND

Currently, only a few studies have described the general characteristics of patients with primary Sjögren's syndrome (pSS) who tested negatives for anti-SSA and anti-SSB antibodies. We aimed to further investigate the clinical characteristics of these patients in a large sample.

METHODS

Data from patients with pSS who were treated at a tertiary hospital in China between 2013 and 2022 were retrospectively analyzed. Clinical characteristics of the patients were compared between those with and without anti-SSA and anti-SSB antibody negativity. Factors associated with anti-SSA and anti-SSB negativity were identified by logistic regression analysis.

RESULTS

Overall, 934 patients with pSS were included in this study, among whom 299 (32.0%) tested negative for anti-SSA and anti-SSB antibodies. Compared with patients testing positive for anti-SSA or anti-SSB antibodies, that testing negative for the two antibodies had a lower proportion of females (75.3% vs. 90.6%, p < 0.001) and thrombocytopenia (6.7% vs. 13.6%, p = 0.002), but a higher proportion of abnormal Schirmer I tests (96.0% vs. 89.1%, p = 0.001) and interstitial lung disease (ILD) (59.2% vs. 28.8%, p = 0.001). Anti-SSA and anti-SSB negativity was positively associated with male sex (odds ratio [OR] = 1.86, 95% confidence interval [CI]: 1.05, 3.31), abnormal Schirmer I tests (OR = 2.85, 95% CI: 1.24, 6.53), and ILD (OR = 2.54, 95% CI: 1.67, 3.85). However, it was negatively related to thrombocytopenia (OR = 0.47, 95% CI: 0.24, 0.95).

CONCLUSION

Approximately one third of pSS patients had anti-SSA and anti-SSB negativity. pSS patients testing negative for anti-SSA and anti-SSB showed a higher risk of abnormal Schirmer I tests and ILD, but a lower risk of thrombocytopenia.

Uncommon types of autoantibodies - Detection and clinical associations

Immunofluorescence is a basic method for detection of autoantibodies in serum. It is used as screening for people with symptoms suggesting autoimmune process and disease. Antinuclear antibodies (ANA) assay detecting antibodies against nuclear proteins used commonly for diagnosis of systemic autoimmune disease, although antibodies against cytoplasmic components and mitotic structures are usable in clinic. The majority of ANA nuclear patterns have been comprehensively studied with increasing data. However, the cytoplasmic and mitotic patterns are underestimated and still require further assessment. In this review the clinical associations and significance of uncommon types of autoantibodies are presented and discussed.

Autoreactive B cell responses targeting nuclear antigens in systemic sclerosis: Implications for disease pathogenesis

A hallmark of disease pathogenesis of systemic sclerosis (SSc) is the presence of autoreactive B cell responses targeting nuclear proteins. Almost all SSc-patients harbour circulating antinuclear autoantibodies of which anti-topoisomerase 1, anti-centromere protein, anti-RNA polymerase III and anti-fibrillarin autoantibodies (ATA, ACA, ARA and AFA, respectively) are the most common and specific for SSc. In clinical practice, autoantibodies serve as diagnostic biomarkers and can aid in the identification of clinical phenotypes of the disease. However, factors driving disease progression in SSc are still poorly understood, and it is difficult to predict disease trajectories in individual patients. Moreover, treatment decisions remain rather empirical, with variable response rates in clinical trials due to patient heterogeneity. Current evidence has indicated that certain patients may benefit from B cell targeting therapies. Hence, it is important to understand the contribution of the antinuclear autoantibodies and their underlying B cell response to the disease pathogenesis of SSc.

Centromere defects, chromosome instability, and cGAS-STING activation in systemic sclerosis

Centromere defects in Systemic Sclerosis (SSc) have remained unexplored despite the fact that many centromere proteins were discovered in patients with SSc. Here we report that lesion skin fibroblasts from SSc patients show marked alterations in centromeric DNA. SSc fibroblasts also show DNA damage, abnormal chromosome segregation, aneuploidy (only in diffuse cutaneous (dcSSc)) and micronuclei (in all types of SSc), some of which lose centromere identity while retaining centromere DNA sequences. Strikingly, we find cytoplasmic "leaking" of centromere proteins in limited cutaneous SSc (lcSSc) fibroblasts. Cytoplasmic centromere proteins co-localize with antigen presenting MHC Class II molecules, which correlate precisely with the presence of anti-centromere antibodies. CENPA expression and micronuclei formation correlate highly with activation of the cGAS-STING/IFN-β pathway as well as markers of reactive oxygen species (ROS) and fibrosis, ultimately suggesting a link between centromere alterations, chromosome instability, SSc autoimmunity, and fibrosis.

Autoantibodies in Primary Biliary Cholangitis

Primary biliary cholangitis (PBC) is a chronic immune-mediated liver disease characterized by a lymphocytic cholangitis, with subsequent cholestasis, progressive liver fibrosis, and ultimately complications arising from end-stage liver disease. Testing for autoantibodies is important in the diagnosis of PBC, as well as stratifying prognosis. This review focuses on the role of autoantibodies in the diagnosis of PBC, as well as the relationship between autoantibodies with pathophysiology and prognostication, along with a discussion regarding novel and other related disease autoantibodies.

Innate Immunity in Calcinosis Cutis

Calcinosis cutis is the deposition of calcium salts in the skin and subcutaneous tissue, manifesting as variably shaped papules, nodules, and plaques that can substantially impair quality of life. The pathophysiology of calcinosis cutis involves dysregulation of proinflammatory cytokines, leukocytes, and other components of the innate immune system. In some conditions associated with calcinosis cutis, elevated serum calcium, phosphate, and vitamin D may also perturb innate immunity. The mechanisms by which these lead to cutaneous and subcutaneous calcification likely parallel those seen in vascular calcification. The role of aberrant innate immunity is further supported by the association between various autoantibodies with calcinosis cutis, such as anti-MDA5, anti-NXP2, anti-centromere, and anti-topoisomerase I. Treatments for calcinosis cutis remain limited and largely experimental, although mechanistically many therapies appear to focus on dampening innate immune responses. Further research is needed to better understand the innate immune pathophysiology and establish treatment options based on randomized-controlled trials.

Can Antinuclear Antibodies Have a Pathogenic Role in Systemic Sclerosis?

Systemic sclerosis (SSc) is a connective tissue disease characterized by extensive fibrosis of the skin and internal organs, associated with vasculopathy and autoimmune features. Antinuclear antibodies (ANA) are found in almost all SSc patients and constitute strong diagnosis and prognosis biomarkers. However, it remains unclear whether ANA are simple bystanders or if they can have a role in the pathophysiology of the disease. One might think that the nuclear nature of their targets prevents any accessibility to autoantibodies. Nevertheless, recent data suggest that ANA could be pathogenic or at least contribute to the perennation of the disease. We review here first the indirect clues of the contribution of ANA to SSc: they are associated to the disease subtypes, they may precede disease onset, their titer correlates with disease activity and severity, there is an association between molecular subsets, and some patients can respond to B-cell targeting therapy. Then, we describe in a second part the mechanisms of ANA production in SSc from individual genetic background to post-transcriptional modifications of neoantigens. Finally, we elaborate on the potential mechanisms of pathogenicity: ANA could be pathogenic through immune-complex-mediated mechanisms; other processes potentially involve molecular mimicry and ANA penetration into the target cell, with a focus on anti-topoisomerase-I antibodies, which are the most probable candidate to play a role in the pathophysiology of SSc. Finally, we outline some technical and conceptual ways to improve our understanding in this field.

Contribution of HLA and KIR Alleles to Systemic Sclerosis Susceptibility and Immunological and Clinical Disease Subtypes

Systemic sclerosis (SSc) is an autoinflammatory, fibrotic condition of unknown aetiology. The presence of detectable autoantibodies against diverse nuclear antigens, as well as strong HLA associations with disease, suggest autoimmune involvement, however the links between endogenous and exogenous risk factors and SSc pathology remain undetermined. We have conducted a genetic analysis of HLA inheritance in two independent and meta-analysed cohorts of 1,465 SSc cases and 13,273 controls, including stratified association analyses in clinical and autoantibody positive subgroups of disease. Additionally, we have used patient genotypes to impute gene dosages across the KIR locus, encoding paired activating and inhibitory lymphocyte receptors for Class I HLA ligands, to conduct the largest analysis of KIR-HLA epistatic interactions in SSc to date. We confirm previous Class II HLA associations with SSc risk and report a new Class I association with haplotype HLA-B*44:03-HLA-C*16:01 at genome-wide significance (GWS). We further report statistically significant HLA associations with clinical and serological subtypes of disease through direct case-case comparison, and report a new association of HLA-DRB1*15:01, previously shown to bind topoisomerase-1 derived peptides, with anti-topoisomerase (ATA) positive disease. Finally, we identify genetic epistasis between KIRs and HLA class I ligands, suggesting genetic modulation of lymphocyte activation may further contribute to an individual’s underlying disease risk. Taken together, these findings support future functional investigation into endogenous immunological and environmental stimuli for disrupted immune tolerance in SSc.

Pathogenetic Aspects of Systemic Sclerosis: A View Through the Prism of B Cells

Systemic sclerosis (SSc) is a rare fibrotic rheumatic disease, associated with psychological distress and increased morbidity and mortality due to skin involvement and internal organ damage. The current understanding of the complex pathogenesis is yet incomplete and disease therapeutic algorithms are far from optimal. Immunologic aberrations are considered key factors for the disease, along with vascular involvement and excess fibrosis. Adaptive immunity and its specialized responses are an attractive research target and both T and B cells have been extensively studied in recent years. In the present review, the focus is placed on B cells in SSc. B cell homeostasis is deranged and B cell subsets exhibit an activated phenotype and abnormal receptor signaling. Autoantibodies are a hallmark of the disease and the current perception of their diagnostic and pathogenetic role is analyzed. In addition, B cell cytokine release and its effect on immunity and fibrosis are examined, together with B cell tissue infiltration of the skin and lung. These data support the concept of targeting B cells as part of the therapeutic plan for SSc through well designed clinical trials.