| 1. |
- Kharlamova, N., et al.
(författare)
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False Positive Results in SARS-CoV-2 Serological Tests for Samples From Patients With Chronic Inflammatory Diseases
- 2021
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Ingår i: Frontiers in Immunology. - : Frontiers Media SA. - 1664-3224. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Patients with chronic inflammatory diseases are often treated with immunosuppressants and therefore are of particular concern during the SARS-CoV-2 pandemic. Serological tests will improve our understanding of the infection and immunity in this population, unless they tests give false positive results. The aim of this study was to evaluate the specificity of SARS-Cov-2 serological assays using samples from patients with chronic inflammatory diseases collected prior to April 2019, thus defined as negative. Samples from patients with multiple sclerosis (MS, n=10), rheumatoid arthritis (RA, n=47) with or without rheumatoid factor (RF) and/or anti-cyclic citrullinated peptide antibodies (anti-CCP2) and systemic lupus erythematosus (SLE, n=10) with or without RF, were analyzed for SARS-CoV-2 antibodies using 17 commercially available lateral flow assays (LFA), two ELISA kits and one in-house developed IgG multiplex bead-based assay. Six LFA and the in-house validated IgG assay correctly produced negative results for all samples. However, the majority of assays (n=13), gave false positive signal for samples from patients with RA and SLE. This was most notable in samples from RF positive RA patients. No false positive samples were detected in any assay using samples from patients with MS. Poor specificity of commercial serological assays could possibly be, at least partly, due to interfering antibodies in samples from patients with chronic inflammatory diseases. For these patients, the risk of false positivity should be considered when interpreting results of the SARS-CoV-2 serological assays.
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| 2. |
- Valstar, A., et al.
(författare)
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Heat-set bovine serum albumin-sodium dodecyl sulfate gels studied by fluorescence probe methods, NMR, and light scattering
- 2001
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 17:11, s. 3208-3215
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Tidskriftsartikel (refereegranskat)abstract
- In this work, concentrated protein-surfactant solutions and their corresponding heat-set gels; were studied by fluorescence probe methods, NMR, and light scattering. Bovine serum albumin (BSA) was used as the protein, and sodium dodecyl sulfate (SDS) as the surfactant. Heating concentrated BSA solutions gives turbid gels. Heat-setBSA-SDS gels are transparent. From fluorescence measurements it was concluded that SDS forms micelle-like clusters on BSA, both in solution and in the corresponding heat-set gel. Aggregation numbers were found to be similar in solution and gel. Also, I-1/I-3 values in solution and gel were similar. H-2 NMR relaxation measurements of specifically deuterated SDS at the ct-carbon position next to the headgroup were performed, and the longitudinal relaxation rates R-1 were found to be the same in solution and gel. High values for the transverse relaxation rate R-2 (indicating slow motions of SDS bound to large aggregates) were obtained, and the largest R-2 value was found for the gel. Dynamic light scattering on BSA-SDS gels was used to obtain the correlation length xi, which defines a mean distance between two points of entanglements. The decrease of xi with increasing [SDS]/[BSA] molar ratio was explained by the size of the BSA-SDS complex and the possibility that micelle-like structures might form cross-links between different BSA molecules. With static light scattering the extent of inhomogeneities in BSA and BSA-SDS gels was found to decrease with increasing SDS concentration. Also, the gel region in the ternary phase diagram BSA-SDS-3.1 mM NaN3 at room temperature and constant pressure (1 atm) was determined.
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