Counting of single prion particles bound to a capture-antibody surface (surface-FIDA)

ArticleinVeterinary Microbiology 123(4):294-304 · September 2007with17 Reads
DOI: 10.1016/j.vetmic.2007.04.001 · Source: PubMed
Abstract
Hitherto accredited prion tests use the PK resistance of PrP(Sc), the pathogenic isoform of the prion protein, as a marker for the disease. Because of variations in the amount of disease-related aggregated PrP, which is not PK-resistant, these prion tests offer only limited sensitivity. Therefore, a prion detection method that does not rely on PK digestion would allow for the detection of both PK-resistant as well as PK-sensitive PrP(Sc). Furthermore, single particle counting is more sensitive than methods measuring an integrated signal. Our new test system is based on dual-colour fluorescence correlation spectroscopy (FCS). This method quantifies the number of protein aggregates that have been simultaneously labelled with two different antibodies using dual-colour fluorescence intensity distribution analysis (2D-FIDA). This only counts PrP aggregates, and not PrP monomers. To increase the sensitivity, PrP(Sc) was concentrated in a two-dimensional space by immobilizing it so that the antibodies could be captured on the surface of the slide (surface-FIDA). When the surface was systematically scanned, even single prion particles were detected. Using this new technique, the sensitivity to identify samples from scrapie-infected hamster as well as BSE-infected cattle can be dramatically increased in comparison with identification using FIDA in solution.
    • "More recent data indicate that oligomeric Aβ is the most toxic species and is therefore of interest both as drug target and candidate biomarker (Haass and Selkoe, 2007; Blennow et al., 2015). On that account, we developed a highly sensitive oligomer-specific diagnostic assay designated surface-based fluorescence intensity distribution analysis (sFIDA) (Birkmann et al., 2006; Birkmann et al., 2007; Funke et al., 2007; Funke et al., 2010; Bannach et al., 2012; Wang-Dietrich et al., 2013; Kühbach et al., 2016). In sFIDA, Aβ is captured to a functionalized glass surface by Aβ specific antibodies which recognize the N-terminus of the molecule. "
    [Show abstract] [Hide abstract] ABSTRACT: Early diagnostics at the preclinical stage of Alzheimer’s disease is of utmost importance for drug development in clinical trials and prognostic guidance. Since soluble Aβ oligomers are considered to play a crucial role in the disease pathogenesis, several methods aim to quantify Aβ oligomers in body fluids such as cerebrospinal fluid (CSF) and blood plasma. The highly specific and sensitive method surface-based fluorescence intensity distribution analysis (sFIDA) has successfully been established for oligomer quantitation in CSF samples. In our study, we explored the sFIDA method for quantitative measurements of synthetic Aβ particles in blood plasma. For this purpose, EDTA, citrate and heparin treated blood plasma samples from five individual donors were spiked with Aβ coated silica nanoparticles (Aβ-SiNaPs) and were applied to the sFIDA assay. Based on the assay parameters linearity, coefficient of variation and limit of detection, we found that EDTA plasma yields the most suitable parameter values for quantitation of Aβ oligomers in sFIDA assay with a limit of detection of 16 fM.
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    • "The method discriminates aggregated PrP forms from monomeric PrP without the use of the proteinase K (PK) digestion step and therefore recognizes both PK-resistant and PK-sensitive PrPTSE. Surface-FIDA enabled the counting of bovine and hamster PrP aggregates in brain homogenates and in bovine cerebrospinal fluid [47]. PrP aggregates were also blind-detected in blood of scrapie-infected sheep (n = 15) with high specificity and sensitivity [46], although it remains unsettle whether the detection of PrP aggregates correlates with infectivity. "
    [Show abstract] [Hide abstract] ABSTRACT: Transmissible spongiform encephalopathy (TSE) or prion diseases are fatal rare neurodegenerative disorders affecting man and animals and caused by a transmissible infectious agent. TSE diseases are characterized by spongiform brain lesions with neuronal loss and the abnormal deposition in the CNS, and to less extent in other tissues, of an insoluble and protease resistant form of the cellular prion protein (PrP(C)), named PrP(TSE). In man, TSE diseases affect usually people over 60 years of age with no evident disease-associated risk factors. In some cases, however, TSE diseases are unequivocally linked to infectious episodes related to the use of prion-contaminated medicines, medical devices, or meat products as in the variant Creutzfeldt-Jakob disease (CJD). Clinical signs occur months or years after infection, and during this silent period PrP(TSE), the only reliable marker of infection, is not easily measurable in blood or other accessible tissues or body fluids causing public health concerns. To overcome the limit of PrP(TSE) detection, several highly sensitive assays have been developed, but attempts to apply these techniques to blood of infected hosts have been unsuccessful or not yet validated. An update on the latest advances for the detection of misfolded prion protein in body fluids is provided.
    Full-text · Article · Aug 2013
    • "Starting from the basic principle of the " sFIDA " assay [17, 18], which has been developed to detect and quantify prion protein aggregates from scrapieinfected hamster as well as BSE-infected cattle, and an earlier version of this assay adapted to detect A aggregates [20, 21], we optimized the assay to an even more sensitive and highly specific A oligomer detection and quantification assay. The details are described in the methods section and a general scheme of the procedure is shown in Fig. 1. "
    [Show abstract] [Hide abstract] ABSTRACT: Recent studies indicate that small amyloid-β peptide (Aβ) oligomers are the major toxic species responsible for development and progression of Alzheimer's disease (AD). Therefore, we suggest that the number of Aβ oligomers in body fluids is the most direct and relevant biomarker for AD. Determination of the Aβ oligomer content of cerebrospinal fluid (CSF) samples from 14 AD patients and 12 age-matched controls revealed a clear distinction between both groups. All samples of the control group showed homogenously low numbers of Aβ oligomers, while the samples of the AD group exhibited significantly higher levels of Aβ oligomers. The Aβ oligomer numbers correlated with the patients' Mini-Mental State Examination scores. This indicates that the quantity of Aβ oligomers in CSF reflects the severity of the disease and that Aβ oligomers play a crucial role in AD pathology and in turn can be used as a diagnostic biomarker.
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