title: Optimisation of the quantification of glutamine synthetase and myelin basic protein in cerebrospinal fluid by a combined acidification and neutralisation protocol.
abstract: The measurement of proteins in cerebrospinal fluid (CSF) by enzyme-linked immunosorbent assays (ELISAs) is becoming increasingly important in the diagnosis of many neurodegenerative diseases such as Alzheimer's Disease. However, detection of proteins in these immunoassays can be hampered by confounding factors either present in the sample matrix or inherent to the protein of interest. These confounding factors may, for example, include protein aggregation or binding to other proteins resulting in epitope masking. Furthermore, the pH of CSF may vary considerably amongst different samples which may limit standardisation of CSF analysis. Pre-treatment of CSF to liberate epitopes or optimise conditions for antibody binding may enhance protein detection. In the current study we investigated whether CSF acidification followed by neutralisation (in short: AFBN) or neutralisation alone prior to measurement might improve the detection of a panel of brain-specific proteins. We demonstrate that the AFBN pre-treatment protocol for CSF significantly enhances the measurement of glutamine synthetase (GS) and myelin basic protein (MBP) in CSF but does not affect detection of glial fibrillary protein (GFAP), amyloid β 42 (Aβ₄₂), total tau (t-tau) or phosphorylated tau (p-tau). Neutralisation alone did not improve detection of any of the proteins tested. Based on our results, we suggest including the AFBN protocol in the evaluation of new biomarker development protocols to avoid confounders such as CSF pH or epitope-masking of the target protein.
authors.affiliation: Radboud University Nijmegen Medical Centre, Department of Neurology, Department of Laboratory Medicine, Donders Institute for Brain, Cognition and Behaviour, Alzheimer Centre Nijmegen, Nijmegen, The Netherlands.
authors.forename: Megan K
authors.initials: MK
authors.lastname: Herbert
authors.forename: H Bea
authors.initials: HB
authors.lastname: Kuiperij
authors.forename: Marcel M
authors.initials: MM
authors.lastname: Verbeek
mesh_terms: D000544:Alzheimer Disease / Q000134:cerebrospinal fluid / Q000175:diagnosis; D016229:Amyloid beta-Peptides / Q000134:cerebrospinal fluid / Q000276:immunology; D002555:Cerebrospinal Fluid / Q000737:chemistry* / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005904:Glial Fibrillary Acidic Protein / Q000134:cerebrospinal fluid / Q000276:immunology; D005974:Glutamate-Ammonia Ligase / Q000134:cerebrospinal fluid* / Q000276:immunology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D004676:Myelin Basic Protein / Q000134:cerebrospinal fluid* / Q000276:immunology; D019636:Neurodegenerative Diseases / Q000134:cerebrospinal fluid / Q000175:diagnosis; D009500:Neutralization Tests; D010766:Phosphorylation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016875:tau Proteins / Q000134:cerebrospinal fluid / Q000276:immunology / Q000378:metabolism
chemical_list: D016229:Amyloid beta-Peptides; D005904:Glial Fibrillary Acidic Protein; D004676:Myelin Basic Protein; D016875:tau Proteins; D005974:Glutamate-Ammonia Ligase