Performance of commercial SARS-CoV-2 wild-type and Omicron BA.1 antibody assays compared with pseudovirus neutralization tests.

BACKGROUND: Commercially available ELISA-based antibody tests are used to approximate vaccination success against SARS-CoV-2 in at-risk patients, but it is unclear whether they correlate with neutralization of the Omicron variant. METHODS: 269 serum samples of a cohort of 44 non-immunosuppressed participants and 65 MTX-treated rheumatic patients taken before and after COVID-19 booster vaccinations were measured using COVID-19 antibody testing systems with wild-type and Omicron BA.1 antigens developed by three different manufacturers (surrogate virus neutralization test cPass, and binding antibody tests QuantiVac and SeraSpot), as well as with a pseudovirus neutralization test (pVNT). The pVNT was considered the gold standard for determining the presence and level of anti-SARS-CoV-2 antibodies. RESULTS: All three wild-type ELISAs showed excellent test performance compared with wild-type neutralization in pVNT. However, out of 56 samples without Omicron BA.1 neutralization in pVNT, 71.4% showed positive results in at least one and 28.6% in all three wild-type ELISAs at the manufacturer-defined cut-offs. Omicron ELISAs showed either decreased specificity (57.1% and 55.4% for binding ELISAs) or sensitivity (51.2% in cPass) compared to Omicron neutralization in pVNT. The proportion of any false positive results among all samples decreased from 26.5% before to 3.2% after booster vaccination, however binding antibody test specificities remained below 70%. CONCLUSIONS: We found a poorer test performance of new Omicron antibody test systems compared to wild-type tests in detecting neutralizing antibodies against the corresponding SARS-CoV-2 variants. Decisions for booster vaccination or passive immunization of at-risk patients should not be based solely on antibody test results.

Refractory mixed proliferative and membranous lupus nephritis treated with the topoisomerase I inhibitor irinotecan as add-on therapy.

OBJECTIVE: To evaluate the safety and effects of irinotecan, an inhibitor of topoisomerase I, on refractory lupus nephritis. METHOD: A patient with refractory lupus nephritis under medication with mycophenolic acid, prednisolone, and hydroxychloroquine was treated with add-on low-dose irinotecan. Irinotecan was applied every fourth week at a dose of 50 mg/m2 for four cycles followed by 100 mg/m2 for another eight cycles. Renal function and anti-double-stranded DNA antibodies as well as blood count for evaluation of side effects were assessed during the treatment with irinotecan. RESULTS: Before starting the treatment with irinotecan, a urine protein/creatinine ratio of 1298 mg/g was determined. This declined to 613 mg/g after four cycles with 50 mg/m2 irinotecan and was further reduced to 198 mg/g when using the higher dose of irinotecan. Kidney function remained stable, with creatinine levels of 1.66 mg/dL at the beginning and 1.76 mg/dL at the end of treatment with irinotecan. Importantly, no side effects, such as diarrhoea or neutropenia, were observed during the entire course of treatment. CONCLUSION: Administration of low-dose irinotecan as add-on medication for the treatment of refractory lupus nephritis was shown to be safe. Clinical trials are needed to determine whether irinotecan can improve kidney function and the outcome of patients with refractory lupus nephritis.

Autoantibodies, complement and type I interferon as biomarkers for personalized medicine in SLE.

Systemic lupus erythematosus (SLE) can be a mysterious disease, presenting with extremely divergent clinical phenotypes. Already, biomarkers are very helpful tools for diagnosis, assessment and monitoring of disease activity, differential diagnosis of clinical manifestations, prediction of the disease course and stratified therapy, and they hold the key to personalized medicine in SLE. We summarize the clinical information that can only be supplied by autoantibodies, complement components and interferon biomarkers in this diverse disease.

Serum antibodies to human leucocyte antigen (HLA)-E, HLA-F and HLA-G in patients with systemic lupus erythematosus (SLE) during disease flares: Clinical relevance of HLA-F autoantibodies.

T lymphocyte hyperactivity and progressive inflammation in systemic lupus erythematosus (SLE) patients results in over-expression of human leucocyte antigen (HLA)-Ib on the surface of lymphocytes. These are shed into the circulation upon inflammation, and may augment production of antibodies promoting pathogenicity of the disease. The objective was to evaluate the association of HLA-Ib (HLA-E, HLA-F and HLA-G) antibodies to the disease activity of SLE. The immunoglobulin (Ig)G/IgM reactivity to HLA-Ib and ß2m in the sera of 69 German, 29 Mexican female SLE patients and 17 German female controls was measured by multiplex Luminex(®)-based flow cytometry. The values were expressed as mean flourescence intensity (MFI). Only the German SLE cohort was analysed in relation to the clinical disease activity. In the controls, anti-HLA-G IgG predominated over other HLA-Ib antibodies, whereas SLE patients had a preponderance of anti-HLA-F IgG over the other HLA-Ib antibodies. The disease activity index, Systemic Lupus Erythematosus Disease Activity Index (SLEDAI)-2000, was reflected only in the levels of anti-HLA-F IgG. Anti-HLA-F IgG with MFI level of 500-1999 was associated with active SLE, whereas inactive SLE revealed higher MFI (>2000). When anti-HLA-F IgG were cross-reactive with other HLA-Ib alleles, their reactivity was reflected in the levels of anti-HLA-E and -G IgG. The prevalence of HLA-F-monospecific antibodies in SLE patients was also associated with the clinical disease activity. Anti-HLA-F IgG is possibly involved in the clearance of HLA-F shed from lymphocytes and inflamed tissues to lessen the disease's severity, and thus emerges as a beneficial immune biomarker. Therefore, anti-HLA-Ib IgG should be considered as a biomarker in standard SLE diagnostics.

[Rheumatoid factor or antinuclear antibodies as incidental finding]. / Positiver Rheumafaktor oder positive ANA als Zufallsbefund.

Rheumatoid factor and antinuclear antibodies are detectable in many different conditions and are ordered by various specialities. The interpretation of results, however, is quite complex.The objective of this article is to help apply these tests correctly and enable an accurate interpretation of the test results. Furthermore, we describe the steps in the differential diagnostics for selecting those patients who need to be referred to a rheumatologist.

[DNA microarrays]. / DNA-Microarrays.

Since their development in the 1990s DNA microarrays have advanced to one of the most important technologies for biomedical research. Miniaturization enables up to 1 million different sequence-specific DNA hybridization tests to be performed on an area of less than 2 cm². Depending on the selection of oligonucleotide sequences, which are assembled on a microarray and on the treatment of samples prior to hybridization, up to genome-wide analyses for genotypes, gene expression, epigenetic changes or promoter activation can be performed. Increasing knowledge about the human genome advances commercial pre-assembly of DNA microarrays with selected oligonucleotide sequences for specialized applications. In clinical rheumatology gene expression analyses in treatment studies are of increasing importance. Similarly, this technique also identified new biomarkers that allow even better assessment of the current disease activity. The varieties of application enable the possibility of systematic research on the immunological response to specific patterns after stimulation. This opens up opportunities to detect and differentiate immunological reaction patterns better.

[Systemic lupus erythematosus. Target criteria for treatment]. / Systemischer Lupus erythematodes. Zielkriterien der Behandlung.

Systemic lupus erythematosus (SLE) is a chronic systemic intermittent autoimmune disease, which can affect nearly all organ systems. The disease is characterized by the detection of more than 100 different auto-antibodies. For the clinical practice as well as in controlled clinical studies it is absolutely necessary to define target criteria which allow the evaluation of the effectiveness of therapy. Many instruments are available for measuring the activity of the disease, the quality of life, the extent of irreversible damage and the individual manifestation in organs. There are also now various biomarkers to characterize the pathophysiologic aspects, clinical activity, therapeutic effectiveness and prognosis.

CXCR3+CD4+ T cells are enriched in inflamed kidneys and urine and provide a new biomarker for acute nephritis flares in systemic lupus erythematosus patients.

OBJECTIVE: The high frequency of CD4+ T cells in interstitial infiltrates of patients with lupus nephritis suggests a contribution of these cells to local pathogenesis. The aim of this study was to examine the role of CXCR3 and the chemokine CXCL10 in recruiting these cells into the kidney and to determine whether the infiltrating T cells could be monitored in the urine to provide a reliable biomarker for acute lupus nephritis. METHODS: The frequencies of CD3+ T cells, CXCR3+ cells, and CXCL10+ cells were determined by immunohistochemical and immunofluorescence analyses of kidney sections from 18 patients with lupus nephritis. The frequency of CXCR3+CD4+ T cells was determined by flow cytometry of peripheral blood and urine from 38 patients with systemic lupus erythematosus (SLE), and the values were compared with disease activity as determined by the Systemic Lupus Erythematosus Disease Activity Index. RESULTS: In renal biopsy tissues from patients with lupus nephritis, a mean of 63% of the infiltrating cells expressed CXCR3, approximately 60% of them were T cells, and the CXCR3+ cells colocalized with CXCL10-producing cells. In biopsy tissues from SLE patients with acute nephritis, approximately 50% of the urinary CD4+ T cells were CXCR3+, as compared with 22% in the peripheral blood, and the frequency of urinary CXCR3+CD4+ T cells correlated with disease activity. Moreover, the number of urinary CD4+ T cells reflected nephritis activity, and elevation above 800 CD4+ T cells per 100 ml of urine sharply delineated active from inactive nephritis. CONCLUSION: CXCR3+ T cells are recruited into the inflamed kidneys, are enriched in the urine, and are a valuable marker of nephritis activity in SLE. They also present a potential target for future therapies.