Antigen-driven selection of antibodies against SSA, SSB and the centromere 'complex', including a novel antigen, MIS12 complex, in human salivary glands

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.

Current Views on Pathophysiology and Potential Therapeutic Targets in Sjögren's Syndrome: A Review from the Perspective of Viral Infections, Toll-like Receptors, and Long-Noncoding RNAs

Sjögren's syndrome (SS) is a rheumatic disease characterized by sicca and extraglandular symptoms, such as interstitial lung disease and renal tubular acidosis. SS potentially affects the prognosis of patients, especially in cases of complicated extraglandular symptoms; however, only symptomatic therapies against xerophthalmia and xerostomia are currently included in the practice guidelines as recommended therapies for SS. Considering that SS is presumed to be a multifactorial entity caused by genetic and environmental factors, a multidisciplinary approach is necessary to clarify the whole picture of its pathogenesis and to develop disease-specific therapies for SS. This review discusses past achievements and future prospects for pursuing the pathophysiology and therapeutic targets for SS, especially from the perspectives of viral infections, toll-like receptors (TLRs), long-noncoding RNAs (lncRNAs), and related signals. Based on the emerging roles of viral infections, TLRs, long-noncoding RNAs and related signals, antiviral therapy, hydroxychloroquine, and vitamin D may lower the risk of or mitigate SS. Janus-kinase (JAK) inhibitors are also potential novel therapeutic options for several rheumatic diseases involving the JAK-signal transducer and activator of transcription pathways, which are yet to be ascertained in a randomized controlled study targeting SS.

Diagnostic value of the saliva immunoglobulin free light chains concentrations measured in primary Sjцgren's syndrome

Proliferation and hyperactivation of B-lymphocytes in the salivary glands is a feature of primary Sjцgren's syndrome (pSS). Detection in saliva of proteins synthesized by B-lymphocytes may be important in the diagnosis of this disease.Objective: to evaluate the diagnostic value of measuring the concentration of immunoglobulin free light chains (FLC) in saliva in patients with pSS.Material and methods. The cross-sectional study included 24 patients with pSS over the age of 18 years. PSS was diagnosed according to the 2016 ACR/EULAR classification criteria. The control group consisted of 11 healthy volunteers. Blood-salivary glands histohematic barrier permeability ratio for albumin, FLC was measured. Quantitative determination of FLC and in blood and saliva was performed by enzyme immunoassay. An immunohistochemical study of biopsies of minor salivary glands (MSG) was carried out with a quantitative assessment of CD3+, CD4+, CD8+, CD20+, CD21+, CD68+, CD138+ cells. The Mann–Whitney U-test was used to compare quantitative traits. Identification of diagnostic thresholds for the concentration of FLC in saliva for the diagnosis of pSS was carried out using the ROC analysis method. An operating characteristic curve was plotted, the area under the curve, indicators of diagnostic specificity, diagnostic sensitivity, and diagnostic accuracy were calculated.Results and discussion. The obtained values corresponded to the low permeability of the histohematic barrier of the salivary glands for albumin and FLC in patients with pSS and healthy individuals. The median concentrations of FLC ê and ë in the saliva of patients with pSS and healthy volunteers were 1.08 [0.58; 1.91], 1.038 [0.55; 2.03] mg/l and 0.36 [0.32; 0.54], 0.35 [0.21; 0.52] mg/l, respectively. The concentration of FLC in the saliva of patients with pSS was statistically significantly higher than in the control group (p<0.01). The amount of FLC ê and ë in saliva correlated with the rate of unstimulated saliva flow: rs=-0.483 (p=0.02), rs=-0.491 (p=0.017), respectively.A relationship was found between the concentration of ê-chains in saliva and the specific number of CD138+ cells: rs=0.733 (p=0.025). Statistically significant correlations between the concentration of ë-chains and the number of mononuclear cells in the MSG have not been established.Based on the results of ROC analysis, diagnostic thresholds for FLC concentrations in the saliva of patients with pSS were determined. Concentrations of ê- and ë-type FLC in saliva of 0.56 and 0.68 mg/l correspond to area under the curve values of 0.84 (95% confidence interval, CI 0.69–0.98) and 0.83 (95% CI 0.71–0.97), sensitivity 79.2% (95% CI 59.5–90.8) and 75% (95% CI 55.1–88), specificity 81.8% (95% CI 52.3–96.8) and 90.9% (95% CI 62.3–99.5), respectively.Salivary FLC concentrations were compared in patients with pSS receiving and not receiving glucocorticoids (GC). The groups did not differ in a statistically significant way in terms of clinical and laboratory parameters. The median daily dose of GC was 10 [5; 10] mg in prednisolone equivalent. There were no significant differences between the concentrations of saliva FLC in patients of these groups.Conclusion. Salivary-fixed FLCs are most likely produced by cells localized in the stroma of the salivary glands. Determination of the concentration of FLC in saliva can be proposed as a diagnostic test for the pSS. The concentration of free ê-chains in saliva can be considered as a surrogate marker of benign B-cell proliferation in the MSG. Therapy with low and medium doses of GC in pSS does not affect the concentration of FLC in saliva.

Potent SARS-CoV-2 neutralizing antibodies with therapeutic effects in two animal models

The use of therapeutic neutralizing antibodies against SARS-CoV-2 infection has been highly effective. However, there remain few practical antibodies against viruses that are acquiring mutations. In this study, we created 494 monoclonal antibodies from patients with COVID-19-convalescent, and identified antibodies that exhibited the comparable neutralizing ability to clinically used antibodies in the neutralization assay using pseudovirus and authentic virus including variants of concerns. These antibodies have different profiles against various mutations, which were confirmed by cell-based assay and cryo-electron microscopy. To prevent antibody-dependent enhancement, N297A modification was introduced. Our antibodies showed a reduction of lung viral RNAs by therapeutic administration in a hamster model. In addition, an antibody cocktail consisting of three antibodies was also administered therapeutically to a macaque model, which resulted in reduced viral titers of swabs and lungs and reduced lung tissue damage scores. These results showed that our antibodies have sufficient antiviral activity as therapeutic candidates.

Impact of KMN network genes on progression and prognosis of non-small cell lung cancer

The Knl1-Mis12-Ndc80 (KMN) network genes (including KNL, MIS12 and NDC80 complexes) encode a highly conserved network of protein complexes that act in cell mitosis. In recent years, multiple studies revealed that KMN network genes also play a vital role in tumor appearance and growth. However, the role of the KMN gene network in non-small cell lung cancer (NSCLC) remains unknown. In this study, we analyzed the effects of KMN genes expression and clinical phenotype in patients with lung adenocarcinoma (LUAD). The expression of KMN network genes and related clinical information was extracted from The Cancer Genome Atlas. The samples were classified into cluster I and II by consistent clustering. We analyzed the gene distribution by principal component analysis, and the potential risk characteristics were analyzed using the least absolute shrinkage and selection operator Cox regression algorithm. Univariate and multivariate Cox regression analyses were used to analyze the clinical information. The Database for Annotation, Visualization, and Integrated Discovery, Gene MANIA and gene set enrichment analysis were used to analyze function and correlation among genes of the KMN network. The expression levels of nine out of ten KMN genes were significantly up-regulated in LUAD and were associated with poor overall survival (OS). Higher expression of NDC80 and KNL1 was related to low OS in both univariate and multivariate analyses. According to two independent prognostic KMN network genes (KNL1 and NDC80), a risk signature was established to predict the prognosis of patients with LUAD. Additionally, the genes NDC80 and KNL1 were considerably enriched in pathways associated with signaling pathways, biological processes, and the cell cycle. The results indicate that KMN network genes are intimately related to lung adenocarcinoma. KMN network genes are involved in the malignant process of LUAD. Assessment of NDC80 and KNL1 might be helpful for prognostic stratification and treatment strategy development.

Clinical influences of anticentromere antibody on primary Sjögren's syndrome in a prospective Korean cohort

BACKGROUND/AIMS

This study was performed to clarify influences of anticentromere antibody (ACA) on clinical phenotypes of primary Sjögren's syndrome (pSS) patients in Korea.

METHODS

We assessed 318 patients who met the 2016 American College of Rheumatology/European League Against Rheumatism classification criteria for pSS. All patients were selected from the Korean Initiative of primary Sjögren's Syndrome (KISS), a prospective cohort. Among them, 53 patients were positive for ACA, while another 265 patients were not. We compared various clinical data including demographic features, extra-glandular manifestations (EGMs), clinical indices, and laboratory values available from the KISS database between the two groups.

RESULTS

Patients in the ACA-positive pSS group were older (p = 0.042), and had higher xerostomia inventory scores (p = 0.040), whereas glandular dysfunction represented with Schirmer I test was more severe in the ACA-negative group. More frequent Raynaud's phenomenon and liver involvement (both p < 0.001) and less articular involvement (p = 0.037) were observed among the EGMs in the ACA-positive group. Less frequency of leukopenia (p = 0.021), rheumatoid factor (p < 0.001), anti-Ro/SSA antibody positivity (p < 0.001), and hypergammaglobulinemia (p = 0.006), as well as higher positivity rates of anti-nuclear antibody and anti-topoisomerase antibody (p < 0.001 and p = 0.006, respectively) were found in the laboratory data in the ACA-positive pSS group.

CONCLUSION

Considering distinct phenotypes in hematological and serological features and EGMs, we should monitor the occurrence of these clinical features among pSS patients with ACA in caution.

Increased Expression of the lncRNA NRON Along With NFATc1/PIM-1 in Labial Salivary Glands of Sjögren's Syndrome Patients

The aim of our study was to analyze the expressions of nuclear factor of activated T cells (NFAT)-related substances including long noncoding RNA NRON which participates in pathophysiology of Sjögren's syndrome (SS), and to assess the histologic findings in individuals with SS. In this study, the expressions of NRON, NFATc1, CD3/CD4, and proviral integration site for Moloney murine leukemia virus (PIM)-1 were examined by in situ hybridization, immunohistochemical analysis, and immunofluorescence in labial salivary glands (LSGs) obtained from 16 patients with SS and five controls. The microcell count method has been applied to calculate the NFATc1-positive area/infiltrating cell area in LSGs, and we compared those results to the infiltrating cell area, focus score, serum immunoglobulin G, and the European League Against Rheumatism Sjögren's Syndrome Disease Activity Index. The NRON expression in the nuclei of cell-infiltration lesions of the SS patients were prominent. The NFATc1 expression was strong in the cytoplasm of infiltrating mononuclear cells and weak in ducts of both SS and controls. In SS, the NFATc1-positive area/infiltrating cell area was positively correlated with the infiltrating cell area and focus score. CD3/CD4 was expressed in infiltrating mononuclear cells, and PIM-1 colocalized with NFATc1 in the cytoplasm. These results suggest NRON along with NFATc1/PIM-1 in SS LSGs might participate in SS pathophysiology.

Immune-Intrinsic Myd88 Directs the Production of Antibodies With Specificity for Extracellular Matrix Components in Primary Sjögren's Syndrome

Primary Sjögren's syndrome is an autoimmune disease that is predominantly seen in women. The disease is characterized by exocrine gland dysfunction in combination with serious systemic manifestations. At present, the causes of pSS are poorly understood. Pulmonary and renal inflammation are observed in pSS mice, reminiscent of a subset of pSS patients. A growing body of evidence indicates that inflammation mediated by Damage-Associated Molecular Patterns (DAMPs) contributes to autoimmunity, although this is not well-studied in pSS. Degraded extracellular matrix (ECM) constituents can serve as DAMPs by binding pattern-recognition receptors and activating Myd88-dependent signaling cascades, thereby exacerbating and perpetuating inflammatory cascades. The ECM components biglycan (Bgn) and decorin (Dcn) mediate sterile inflammation and both are implicated in autoimmunity. The objective of this study was to determine whether these ECM components and anti-ECM antibodies are altered in a pSS mouse model, and whether this is dependent on Myd88 activation in immune cells. Circulating levels of Bgn and Dcn were similar among pSS mice and controls and tissue expression studies revealed pSS mice had robust expression of both Bgn and Dcn in the salivary tissue, saliva, lung and kidney. Sera from pSS mice displayed increased levels of autoantibodies directed against ECM components when compared to healthy controls. Further studies using sera derived from conditional knockout pSS mice demonstrated that generation of these autoantibodies relies, at least in part, on Myd88 expression in the hematopoietic compartment. Thus, this study demonstrates that ECM degradation may represent a novel source of chronic B cell activation in the context of pSS.

Combining multi-antigenic immunodot with indirect immunofluorescence on HEp-2 cells improves the diagnosis of systemic sclerosis

Systemic sclerosis (SSc) is associated, in nearly all patients, with autoantibodies (Ab). Accordingly, and in order to identify major (anti-CEN A/B and anti-Topo I) but also minor Abs, the usefulness of combining indirect immunofluorescence (IIF) on HEp-2 cells with an 11 multi-antigenic SSc immunodot was explored. 1689 samples tested at the request of clinicians, were evaluated retrospectively. The positivity rate was 28.8% and the diagnosis of SSc was supported for 232 samples. Two groups of Abs were considered: group 1, Abs (anti-CENP A/B, anti-Topo I) present at elevated levels in SSc patients; group 2, Abs for which the Ab specificity (odds ratio and/or positive predictive value) was improved by using IIF on HEp-2 cells (RNA-Polymerase III, fibrillarin, Th/T0, PM-Scl). Altogether, this study highlights the utility of combining IIF on HEp-2 cells with the SSc immunodot as the first line of an SSc Abs detection/SSc diagnostic strategy.

Antigen-driven autoantibody production in lungs of interstitial lung disease with autoimmune disease

Interstitial lung disease (ILD) sometimes becomes a life-threatening complication of systemic autoimmune diseases; however, little is known about the immune response in lung lesions. We aimed to investigate humoural immunity in ILD associated with rheumatoid arthritis (RA), sjögren's syndrome (SjS), and mixed connective tissue disease (MCTD), using bronchoalveolar fluid (BALF) and serum samples from 15 patients with autoimmune disease associated-ILD. We first showed that BALF contained higher titers of disease-related autoantibodies than serum, suggesting the possibility of autoantibody production in lungs. Next, we produced 326 monoclonal antibodies from antibody-secreting cells in BALF, and the reactivity and their revertants, in which somatic hypermutations were reverted to germline, were analyzed. Among 123 antibodies from RA-ILD, 16 disease-related antibodies (anti-modified protein antibodies and rheumatoid factors) were identified, of which one antibody had both properties. The revertant antibodies changed their target modification in a complicated manner, suggesting that the antibodies were selected against various modifications in lungs. Among 146 antibodies from SjS-ILD and/or MCTD-ILD, seven anti-SSA/Ro60 antibodies and 15 anti-RNP antibodies were identified. Some of the anti-RNP antibodies recognized multiple RNP constituent proteins simultaneously, indicating that epitope spreading may progress in lungs. Our results revealed the existence of an active autoimmunity in the lungs of autoimmune disease associated-ILD.

Clinical manifestations in anti-Ro52/SS-A antibody-seropositive patients with Sjögren's syndrome

Background: The relationship between anti-Ro52/SS-A antibody (anti-Ro52) and the clinical manifestations of Sjögren's syndrome (SS) has not been fully clarified. We determined the clinical factors relevant to SS patients with anti-Ro52.Methods: We conducted a retrospective study of 149 subjects suspicious for SS and 50 healthy control subjects. We analyzed items of the American-European Consensus Group (AECG) criteria and the EULAR Sjögren's Syndrome Disease Activity Index (ESSDAI).Results: SS was documented in 115 subjects. Anti-Ro52 was observed in 70 SS patients. Anti-Ro52 positivity showed a significantly higher association with anti-Ro60 positivity than with anti-centromere antibody (ACA) positivity (p < 0.05). Regarding the difference in the anti-Ro52 concentration, we observed six significantly relevant components: two AECG components and four non-AECG components. The anti-Ro52 concentration well-discriminated three clinical factors (ROC AUC >0.75), i.e., ACA seropositivity, ESSDAI score ≥1, and RF, and it moderately discriminated high serum IgG, focus score ≥1, and anti-La/SS-B antibody seropositivity (ROC AUC >0.7). A linear relationship between the ESSDAI score and the anti-Ro52 concentration was observed.Conclusion: A significant association between clinical factors (including the ESSDAI) and the anti-Ro52 concentration were revealed. Anti-Ro52 was more highly associated with anti-Ro60 positivity than with ACA positivity.

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

OBJECTIVES

Anti-centromere antibodies (ACAs) are detected in patients with various autoimmune diseases such as Sjögren's syndrome (SS), systemic sclerosis (SSc) and primary biliary cholangitis (PBC). However, the targeted antigens of ACAs are not fully elucidated despite the accumulating understanding of the molecular structure of the centromere. The aim of this study was to comprehensively reveal the autoantigenicity of centromere proteins.

METHODS

A centromere antigen library including 16 principal subcomplexes composed of 41 centromere proteins was constructed. Centromere protein/complex binding beads were used to detect serum ACAs in patients with SS, SSc and PBC. ACA-secreting cells in salivary glands obtained from patients with SS were detected with green fluorescent protein-fusion centromere antigens and semiquantified with confocal microscopy.

RESULTS

A total of 241 individuals with SS, SSc or PBC and healthy controls were recruited for serum ACA profiling. A broad spectrum of serum autoantibodies was observed, and some of them had comparative frequency as anti-CENP-B antibody, which is the known major ACA. The prevalence of each antibody was shared across the three diseases. Immunostaining of SS salivary glands showed the accumulation of antibody-secreting cells (ASCs) specific for kinetochore, which is a part of the centromere, whereas little reactivity against CENP-B was seen.

CONCLUSIONS

We demonstrated that serum autoantibodies target the centromere-kinetochore macrocomplex in patients with SS, SSc and PBC. The specificity of ASCs in SS salivary glands suggests kinetochore complex-driven autoantibody selection, providing insight into the underlying mechanism of ACA acquisition.

Incomplete humoral response including neutralizing antibodies in asymptomatic to mild COVID-19 patients in Japan

The pandemic of COVID-19 is still ongoing, and many studies on serum antibodies have been reported, however, there are few studies about asymptomatic and mild patients. In this study, we enrolled 44 COVID-19 patients with relatively mild disease and 48 pre-pandemic controls. We measured serum antibodies against extracellular domain, S1 domain, and receptor-binding domain of Spike and N protein, examined neutralization titers by authentic virus neutralization assay and newly-developed bead/cell-based Spike-ACE2 inhibition assay, and compared them with clinical features. Most of these antibodies, including neutralizing titers, were mutually correlated, and the production of antibodies were associated with low Ct values of PCR test, disease severity, symptoms especially pneumonia, lymphopenia, and serological test including CRP, LD, D-dimer, and procalcitonin. Notably, 87.5% of asymptomatic and 23.5% of mild patients did not have antibody against SARS-CoV-2. Our results revealed the inadequate acquisition of humoral immunity in patients with asymptomatic and mild COVID-19 patients.

Sjögren's Syndrome: The Clinical Spectrum of Male Patients

Background: To compare the clinical, serological and histologic features between male and female patients with Sjögren’s syndrome (SS) and explore the potential effect of gender on lymphoma development. Methods: From a multicenter population (Universities of Udine, Pisa and Athens, Harokopion and Ioannina (UPAHI)) consisting of consecutive SS patients fulfilling the 2016 ACR/EULAR criteria, male patients were identified, matched and compared with female controls. Data-driven multivariable logistic regression analysis was applied to identify independent lymphoma-associated factors. Results: From 1987 consecutive SS patients, 96 males and 192 matched female controls were identified and compared. Males had a higher frequency of lymphoma compared to females (18% vs. 5.2%, OR = 3.89, 95% CI: 1.66 to 8.67; p = 0.0014) and an increased prevalence of serum anti-La/SSB antibodies (50% vs. 34%, OR = 1.953, 95% CI: 1.19 to 3.25; p = 0.0128). No differences were observed in the frequencies of lymphoma predictors between the two genders. Data-driven multivariable logistic regression analysis revealed negative association of the female gender with lymphoma and positive association with lymphadenopathy. Conclusion: Male SS patients carry an increased risk of lymphoma development. Although statistics showed no difference in classical lymphoma predictors compared to females, data-driven analysis revealed gender and lymphadenopathy as independent lymphoma-associated features.

Salivary Gland Mucosa-Associated Lymphoid Tissue-Type Lymphoma From Sjögren's Syndrome Patients in the Majority Express Rheumatoid Factors Affinity-Selected for IgG

Objective

Patients with Sjӧgren's syndrome (SS) have an increased risk of developing malignant B cell lymphomas, particularly mucosa‐associated lymphoid tissue (MALT)–type lymphomas. We have previously shown that a predominant proportion of patients with SS‐associated salivary gland MALT lymphoma express somatically hypermutated IgM with strong amino acid sequence homology with stereotypic rheumatoid factors (RFs). The present study was undertaken in a larger cohort of patients with SS‐associated MALT lymphoma to more firmly assess the frequency of RF reactivity and the significance of somatic IGV‐region mutations for RF reactivity.

Methods

B cell antigen receptors (BCRs) of 16 patients with SS‐associated salivary gland MALT lymphoma were analyzed. Soluble recombinant IgM was produced of 12 MALT lymphoma samples, including 1 MALT lymphoma sample that expressed an IgM antibody fitting in a novel IGHV3‐30–encoded stereotypic IGHV subset. For 4 of the 12 IgM antibodies from MALT lymphoma samples, the somatically mutated IGHV and IGKV gene sequences were reverted to germline configurations. Their RF activity and binding affinity were determined by enzyme‐linked immunosorbent assay and surface plasmon resonance, respectively.

Results

Nine (75%) of the 12 IgM antibodies identified in patients with SS‐associated salivary gland MALT lymphoma displayed strong monoreactive RF activity. Reversion of the IGHV and IGKV mutations to germline configuration resulted in RF affinities for IgG that were significantly lower for 3 of the 4 somatically mutated IgM antibodies. In stereotypic IGHV3‐7/IGKV3‐15–encoded RFs, a recurrent replacement mutation in the IGKV3‐15–third complementarity‐determining region was found to play a pivotal role in the affinity for IgG‐Fc.

Conclusion

A majority of patients with SS‐associated salivary gland MALT lymphoma express somatically mutated BCRs that are selected for monoreactive, high‐affinity binding of IgG‐Fc. These data underscore the notion that soluble IgG, most likely in immune complexes in inflamed tissues, is the principal autoantigen in the pathogenesis of a variety of B cell lymphomas, particularly SS‐associated MALT lymphomas.