Reactivity in ELISA with DNA-loaded nucleosomes in patients with proliferative lupus nephritis

Coexistence of antinucleosome and anti-double-stranded DNA antibodies is associated with severe systemic lupus erythematosus in Tunisian patients

INTRODUCTION

We sought to compare clinical features among distinct antibody profiles defined by the presence or absence of antinucleosome (anti-NCS) and anti-double-stranded DNA (anti-dsDNA) antibodies in Tunisian patients with systemic lupus erythematosus (SLE).

METHODS

The study enrolled 131 patients with SLE meeting at least 4 American College of Rheumatology or SLICC criteria. Participants were recruited from the Department of Internal Medicine and Rheumatology at the university teaching hospital of Monastir between January 2000 and December 2022. The patients were divided into 4 groups: Group 1 with neither anti-dsDNA nor anti-NCS; Group 2 with anti-dsDNA and no anti-NCS; Group 3 with anti-NCS lacking anti-dsDNA; and Group 4 with both anti-NCS and anti-dsDNA.

RESULTS

The mean (SD) age at the time of diagnosis for the 131 participants with SLE was 38.7 (15.1) years; the ratio of female to male individuals was 7.2. Thirty-four (26%) patients were positive for anti-NCS and anti-dsDNA (group 4: antinuclear antibody pattern AC-1, 72%; pattern AC-5, 16%), and 30 (22.9%) were positive for anti-NCS and negative for anti-dsDNA (group3: pattern AC-1, 53.6%; pattern AC-5, 32.1%). The group 3 patients showed higher peripheral neuropsychiatric SLE (P =.034) and lower rates of disease activity (P =.01). The comparison between the 4 groups showed that group 4 patients had the highest frequency of lupus nephritis (P ≤.001) and the highest rate disease activity (P =.013).

DISCUSSION

Patients with both anti-NCS and anti-dsDNA at the time of diagnosis are likely to have severe SLE, while anti-NCS was associated with nonsevere disease in patients with SLE who lack anti-dsDNA.

A reverse translational study on the effect of rituximab, rituximab plus belimumab, or bortezomib on the humoral autoimmune response in SLE

Objectives

SLE is a severe autoimmune disease characterized by autoreactive B cells and IC formation, which causes systemic inflammation. B cell–targeted therapy could be a promising treatment strategy in SLE patients; nevertheless, randomized clinical trials have not always been successful. However, some groups have demonstrated beneficial effects in severe SLE patients with off-label rituximab (RTX) with belimumab (BLM), or bortezomib (BTZ), which targeted different B cells subsets. This study assembled sera from SLE cohorts treated with RTX+BLM (n = 15), BTZ (n = 11) and RTX (n = 16) to get an in-depth insight into the immunological effects of these therapies on autoantibodies and IC formation.

Methods

Autoantibodies relevant for IC formation and the avidity of anti-dsDNA were determined by ELISA. IC-mediated inflammation was studied by complement levels and ex vivo serum-induced neutrophil extracellular trap formation.

Results

Reductions in autoantibodies were observed after all approaches, but the spectrum differed depending upon the treatment. Specifically, only RTX+BLM significantly decreased anti-C1q. Achieving seronegativity of ≥1 autoantibody, specifically anti-C1q, was associated with lower disease activity. In all SLE patients, the majority of anti-dsDNA autoantibodies had low avidity. RTX+BLM significantly reduced low-, medium- and high-avidity anti-dsDNA, while RTX and BTZ only significantly reduced medium avidity. IC-mediated inflammation, measured by C3 levels and neutrophil extracellular trap formation, improved after RTX+BLM and RTX but less after BTZ.

Conclusion

This study demonstrated the impact of different B cell–targeted strategies on autoantibodies and IC formation and their potential clinical relevance in SLE.

A leukocyte activation test identifies food items which induce release of DNA by innate immune peripheral blood leucocytes

Background

Leukocyte activation (LA) testing identifies food items that induce a patient specific cellular response in the immune system, and has recently been shown in a randomized double blinded prospective study to reduce symptoms in patients with irritable bowel syndrome (IBS). We hypothesized that test reactivity to particular food items, and the systemic immune response initiated by these food items, is due to the release of cellular DNA from blood immune cells.

Methods

We tested this by quantifying total DNA concentration in the cellular supernatant of immune cells exposed to positive and negative foods from 20 healthy volunteers. To establish if the DNA release by positive samples is a specific phenomenon, we quantified myeloperoxidase (MPO) in cellular supernatants. We further assessed if a particular immune cell population (neutrophils, eosinophils, and basophils) was activated by the positive food items by flow cytometry analysis. To identify the signaling pathways that are required for DNA release we tested if specific inhibitors of key signaling pathways could block DNA release.

Results

Foods with a positive LA test result gave a higher supernatant DNA content when compared to foods with a negative result. This was specific as MPO levels were not increased by foods with a positive LA test. Protein kinase C (PKC) inhibitors resulted in inhibition of positive food stimulated DNA release. Positive foods resulted in CD63 levels greater than negative foods in eosinophils in 76.5% of tests.

Conclusion

LA test identifies food items that result in release of DNA and activation of peripheral blood innate immune cells in a PKC dependent manner, suggesting that this LA test identifies food items that result in release of inflammatory markers and activation of innate immune cells. This may be the basis for the improvement in symptoms in IBS patients who followed an LA test guided diet.

Performance analysis of automated evaluation of Crithidia luciliae-based indirect immunofluorescence tests in a routine setting - strengths and weaknesses

BACKGROUND

Antibodies directed against dsDNA are a highly specific diagnostic marker for the presence of systemic lupus erythematosus and of particular importance in its diagnosis. To assess anti-dsDNA antibodies, the Crithidia luciliae-based indirect immunofluorescence test (CLIFT) is one of the assays considered to be the best choice. To overcome the drawback of subjective result interpretation that inheres indirect immunofluorescence assays in general, automated systems have been introduced into the market during the last years. Among these systems is the EUROPattern Suite, an advanced automated fluorescence microscope equipped with different software packages, capable of automated pattern interpretation and result suggestion for ANA, ANCA and CLIFT analysis.

METHODS

We analyzed the performance of the EUROPattern Suite with its automated fluorescence interpretation for CLIFT in a routine setting, reflecting the everyday life of a diagnostic laboratory. Three hundred and twelve consecutive samples were collected, sent to the Central Diagnostic Laboratory of the Maastricht University Medical Centre with a request for anti-dsDNA analysis over a period of 7 months.

RESULTS

Agreement between EUROPattern assay analysis and the visual read was 93.3%. Sensitivity and specificity were 94.1% and 93.2%, respectively. The EUROPattern Suite performed reliably and greatly supported result interpretation.

CONCLUSIONS

Automated image acquisition is readily performed and automated image classification gives a reliable recommendation for assay evaluation to the operator. The EUROPattern Suite optimizes workflow and contributes to standardization between different operators or laboratories.