New coupled-particle light-scattering assay for detection of Ro/SSA (52 and 60 kilodaltons) and La/SSB autoantibodies in connective tissue diseases

The clinical and immunological characteristics related to salivary gland enlargement in primary Sjögren's syndrome: a retrospective cross-sectional study

Background

Salivary gland enlargement (SGE) is one of the common manifestations in primary Sjögren's syndrome (pSS) patients who are first referred to the hospital of stomatology. Whether the characteristics of the pSS patients with SGE differ from those of the ones without SGE remains unclear. Therefore, this study aimed at investigating the clinical and immunological characteristics related to SGE in pSS, to provide a comprehensive understanding of the clinical phenotype of pSS with SGE.

Methods

In this retrospective cross-sectional study, medical records of patients diagnosed with pSS from 2016 to 2021 were evaluated. The included patients were divided into the SGE and non-SGE groups. Patient data including general clinical data, radiographic and B-ultrasound examination data, and immunological data were extracted. Intergroup differences were analyzed using the chi-square test, Fisher's exact test, and non-parametric tests with SPSS 23.0. Binary logistic regression analysis was further performed to determine the factors related to SGE in pSS.

Results

Two hundred and three patients with pSS were included, including 126 and 77 patients with and without SGE, respectively. Univariate analysis showed that compared to the non-SGE group, the SGE group was younger, had dry eye symptom for a longer duration, and had a higher proportion of patients with severe conditions on salivary gland radiography (P<0.05). Regarding immunological indicators, the levels of anti-Ro52, anti-SSA (Ro60), and anti-SSB antibodies; immunoglobulin (Ig)G; IgA; and rheumatoid factor (RF) and erythrocyte sedimentation rate (ESR) were significantly higher in the SGE group (P<0.05). Binary logistic regression analysis showed that younger age and high anti-Ro52 levels were independent factors related to SGE in pSS.

Conclusions

SGE is highly consistent with increased immunological indicators, reflecting disease activity. pSS patients with SGE were younger than those without. Special attention should be paid to the changes in the anti-Ro52 level since it is an independent factor related to SGE in pSS.

Anti-Ro52 antibodies in clinical practice: A single-centre experience

INTRODUCTIONS

To analyse the clinical significance of anti-Ro52 autoantibodies that target TRIM21 protein and occur in a variety of connective tissue diseases (CTD), 4782 cases with blood tested positive for anti-Ro52 antibodies between January 2016 and September 2017 in Drum Tower Hospital were enrolled.

METHODS

Anti-Ro52 and anti-Ro60 were measured using the immunoblotting method together with antibodies against other extractable nuclear antigens at the time of the patient's first visit.

RESULTS

In this cohort, females accounted for the majority of all subjects (75.9%) and the average age was 47.25 years old. About 97.4% were diagnosed as having various diseases, in which around 2/3 were CTDs. The incidence of CTD in patients with merely anti-Ro52 was lower than those with both anti-Ro52 and anti-Ro60 (54.7% vs 85.5% for all patients and 53.3% vs 87.1% for inpatients, both P < .0001). Amongst CTDs, the incidence of systemic lupus erythematosus was significantly decreased, while the incidence of inflammatory myositis as well as undifferentiated connective tissue diseases was increased in anti-Ro52 single-positive group. For patients with either CTDs or non-CTDs, respiratory involvement was more common in patients with merely anti-Ro52 (67.6% vs 34.7%, P < .0001 and 53.2% vs 36.3%, P < .01). Sub-analysis revealed that both interstitial lung disease and pulmonary infection were related to anti-Ro52 in CTD inpatients (P < .0001 and P < .05).

CONCLUSIONS

Our study shows that anti-Ro52 could occur in various clinical conditions. These antibodies may appear in the early stage of CTD with the lung an important target organ, thus their presence warrants long-term follow-up.

Diagnostic Utility of Separate Anti-Ro60 and Anti-Ro52/TRIM21 Antibody Detection in Autoimmune Diseases

Anti-SS-A antibodies are often sought for in autoimmune diseases diagnosis. Two different target proteins have actually been identified: Ro52 and Ro60. Clinical and immunological associations seem different depending on anti-Ro52 or anti-Ro60 antibodies presence. However, due to a heterogeneous presentation in the literature, some immunology laboratories in France have stopped providing anti-Ro52 antibody findings. We report here a new hospital study designed to determine the diagnostic utility of the separate detection of anti-Ro52 and anti-Ro60 antibodies. We conducted a retrospective, observational study, including every adult patient with positive antinuclear antibodies (ANA) tested in our immunology laboratory, and associated with anti-Ro52 and/or anti-Ro60 antibodies, between 2011 and 2014. Out of 13032 sera tested for ANA, 399 adults had antibodies to Ro52 and/or Ro60; 81.7% were female, with a mean age of 54.5 ± 17.0 years. Anti-Ro52 antibodies were found in 75.7% of the patients and anti-Ro60 antibodies in 56.9%. Among them, 43.1% were classified in the Ro52 + Ro60- group, 32.6% in the Ro52 + Ro60 + group and 24.3% in the Ro52-Ro60+ group. In the Ro52-Ro60+ group, systemic lupus was the most frequent diagnosis (48.5%), with a possible association with antiphospholipid antibodies (anti-cardiolipin antibodies: OR 2.5 (CI95 [1.0-5.0], p = 0.05) and lupus anticoagulant {OR 3.6 (CI95 [1.10-10.0] p = 0.02)}. In the Ro52+Ro60+, primary Sjögren Syndrome was the most likely (OR 4.2 95% CI [2.1-8.3] p < 10^-4), especially in patients Ro52+Ro60+La+. Patients with isolated anti-Ro52 had a wider variety of diseases associated, but among auto-immune diseases they were more prone to inflammatory myositis (OR 10.5 [1.4-81.7], p = 0.02) and inflammatory rheumatism (OR 4.6 [1.6-13.8], p = 0.006) in contrast to systemic lupus (OR 0.2 [0.1-0.3], p < 10^-4) or primary Sjögren's syndrome (OR 0.1 [0.06-0.2], p < 10^-4). We therefore suggest that, when anti-ENA antibodies are prescribed, it should include separate anti-Ro52 and anti-Ro60 antibodies determination. To go even further, we would like to suggest a change in ENA nomenclature to avoid confusion, abandoning the anti-SS-A label in favor of the anti-Ro52/TRIM21 or anti-Ro60 antibody for a clearer designation.

Autoantibody Detection Using Multiplex Technologies

Measurement of multiple antibodies has been possible for years using labor-intensive methods such as counterimmunoelectrophoresis and radioimmunoprecipitation. Recently, simpler methods that are more practical for routine analysis, often described as multiplex technologies, have been introduced. One common technique, the line assay, uses nitrocellulose strips that are precoated at different locations with more than a dozen recombinant proteins or peptides. Detection of results may be performed visually or with scanning instrumentation. A second technique uses families of polystyrene beads that are dyed to establish a unique identity; each bead type is then coated with a specific affinity-purified or recombinant protein. Detection is performed by flow cytometry. There have been multiple descriptions of the use of these techniques for measuring antibodies associated with the antinuclear antibody screen. More recent reports describe applications to antibodies associated with hypothyroidism, ANCA, anti-phospholipid syndrome, and celiac disease. This review summarizes the work that has been performed to date and examines the potential benefits of multiplexing to both the laboratory and the physician.

Current state of diagnostic technologies in the autoimmunology laboratory

The methods for detecting and measuring autoantibodies have evolved markedly in recent years, encompassing three generations of analytical technologies. Many different immunoassay methods have been developed and used for research and laboratory practice purposes, from the early conventional (or monoplex) analytical methods able to detect single autoantibodies to the more recent multiplex platforms that can quantify tens of molecules. Although it has been in use for over 50 years, indirect immunofluorescence remains the standard method for research on many types of autoantibodies, due to its characteristics of diagnostic sensitivity and also to recent technological innovations which permit it a greater level of automation and standardization. The recent multiplex immunometric methods, with varying levels of automation, present characteristics of higher diagnostic accuracy, but are not yet widely diffused in autoimmunology laboratories due to the limited number of autoantibodies that are detectable, and due to the high cost of reagents and systems. Technological advancement in autoimmunology continues to evolve rapidly, and in the coming years new proteomic techniques will be able to radically change the approach to diagnostics and possibly also clinical treatment of autoimmune diseases. The scope of this review is to update the state of the art of technologies and methods for the measurement of autoantibodies, with special reference to innovations in indirect immunofluorescence and in multiple proteomic methods.

Myositis-specific autoantibodies: detection and clinical associations

In recent years, the detection and characterization of (novel) autoantibodies is becoming increasingly important for the early diagnosis of autoimmune diseases. The idiopathic inflammatory myopathies (IIM, also indicated with myositis) are a group of systemic autoimmune disorders that involve inflammation and weakness of skeletal muscles. One of the hallmarks is the infiltration of inflammatory cells in muscle tissues. A number of myositis-specific autoantibodies have been identified and these may be associated with distinct IIM subclasses and clinical symptoms. Here, we review all myositis-specific autoantibodies identified today as well as their target proteins, together with their clinical associations in IIM patients. Post-translational modifications that might be associated with the generation of autoantibodies and the development of the disease are discussed as well. In addition, we describe well established autoantibody detection techniques that are currently being used in diagnostic laboratories, as well as novel multiplexed methods. The latter techniques provide great opportunities for the simultaneous detection of distinct autoantibodies, but may also contribute to the identification of novel autoantibody profiles, which may have additional diagnostic and prognostic value. The ongoing characterization of novel autoantibody specificities emphasizes the complexity of processes involved in the development of such autoimmune diseases.

Recent advances in diagnostic technologies for autoimmune diseases

The investigation of autoimmunity provides an interest challenge in "omics" research and, particularly, proteome research, as autoimmune diseases are common disorders of unsolved etiology that occur in a wide range of manifestations, in all of which tissues and organs are attacked by the body's own immune system. Autoantibodies are a hallmark of many autoimmune diseases and the presence of autoantibodies is a distinctive and key characteristic of autoimmune diseases. Conventionally, the study of autoimmune response has always been conducted by analysing the presence and/or concentration of individual antibodies in biological fluids. New proteomic techniques allow the simultaneous identification/measurement of different autoantibodies in sera of patients suffering from autoimmune diseases. The possibility of simultaneously measuring a number of correlated analytes appears to be very interesting for analytical reasons (reduced volumes of biological samples, reagents and low costs), logistical/managerial reasons, and pathophysiological reasons (combination of markers in disease-oriented or organ-oriented profiling). In particular, we describe data collected by using high-throughput techniques such as antigen microarrays and mass spectrometry for antibody profiling. While recently collected data demonstrate satisfactory analytical sensitivity and reproducibility, some issues such as standardization and data interpretation have to be solved before the introduction of these new and promising techniques into clinical practice.

Recent advances in diagnostic technologies and their impact in autoimmune diseases

Conventional immunological methods for the detection of serum autoantibodies have been an essential tool for the diagnosis of autoimmune diseases for 40 years: in the last decade autoantibody tests have become accepted criteria for the diagnosis and classification of the main systemic and organ-specific autoimmune diseases. The high degree of purification reached by the autoantigens used in these methods has allowed high diagnostic sensitivity and specificity, especially in the case of some new autoantibodies of particular clinical significance, such as anti-nucleosome, anti-transglutaminase, anti-TSH receptor and anti-citrullinated protein autoantibodies. In the last 5 years the advent of proteomic technology, which allows the simultaneous measurement of a number of autoantibodies (multiplexing), has opened up new horizons in the diagnosis of autoimmune diseases. Multiplexing is particularly interesting for clinical laboratories, for organisational, logistical/managerial, physiopathological and research reasons. The emerging technologies are represented by systems based on planar or non-planar (suspension) arrays: the latter include methods which use addressable microbeads or nanobarcoded particles. Within a few years, the new methods will allow testing of individual autoantibody profiles, which will probably improve understanding of the physiopathology of autoimmunity, allow early diagnosis (due to the predictive value of autoantibodies), and drive the diffusion of antigen-specific therapies in autoimmune diseases.

Multiplex bead array assays: performance evaluation and comparison of sensitivity to ELISA

The measurement of soluble cytokines and other analytes in serum and plasma is becoming increasingly important in the study and management of many diseases. As a result, there is a growing demand for rapid, precise, and cost-effective measurement of such analytes in both clinical and research laboratories. Multiplex bead array assays provide quantitative measurement of large numbers of analytes using an automated 96-well plate format. Enzyme-linked immunosorbent assay (ELISAs) have long been the standard for quantitative analysis of cytokines and other biomarkers, but are not well suited for high throughput multiplex analyses. However, prior to replacement of ELISA assays with multiplex bead array assays, there is a need to know how comparable these two methods are for quantitative analyses. A number of published studies have compared these two methods and it is apparent that certain elements of these assays, such as the clones of monoclonal antibodies used for detection and reporting, are pivotal in obtaining similar results from both assays. By careful consideration of these variables, it should be possible to utilize multiplex bead array assays in lieu of ELISAs for studies requiring high throughput analysis of numerous analytes.