30 ANALYTICAL AND LABORATORY EQUIPMENT
Alzheimer’s disease: Sensitive and specific one-step ELISA assays
Véronique Mainfroid and Benoît Wolf report on highly sensitive and economic assays to measure β-amyloid (1-40) and (1-42) in body fluids and tissue lysates.
A
lzheimer’s disease (AD), the most common cause of dementia afflicts
more than 36 million people worldwide. Currently there is no cure for AD and researchers are still looking for new treatments to alter the course of the disease.
Characteristic features of AD include the presence of senile plaques and neurofibrillary tangles, surrounded by damaged neurons.
Senile plaques are mainly constituted of 39-42 amino acid β-amyloid peptides (Aβ) formed after sequential cleavage of the transmembrane Amyloid Precursor Protein (APP) by β and g-secretases1-3
.
Toxic oligomers Many studies suggest that these peptides can form toxic oligomers and fibrils under physiological conditions and rapidly aggregate. Tis aggregation is an essential event
in the pathogenesis of AD. Even if it represents less than
10 per cent of the secreted Aβ, Aβ42 is the predominant component of senile plaques4-5
.
Te decrease of Aβ42 in cerebro- spinal fluid (CSF) indicates that it begins to form plaques in the brain.
Terefore, soluble Aβ peptides in CSF and blood plasma represent promising candidates for biological markers of AD.
However, the Aβ42 concentration measurement in biological fluids is not sufficient alone because the Aβ load in the brain has a large inter-individual variability. Te Aβ42/Aβ40 ratio may represent a more reliable biomarker.
To further facilitate detection and quantification of Aβ40 and Aβ42 peptides in biological fluids, Eurogentec has developed sensitive and specific one-step ELISA assays.
Sandwich ELISA method SensoLyte anti-human β-Amyloid (1-40) and (1-42) Quantitative ELISA assay kits are based on the sandwich ELISA method in which the antigen is captured between a highly specific pre-coated mouse monoclonal anti-Aβ40 or anti-Aβ42 and the detection Horseradish peroxidase (HRP) labeled rabbit anti-Aβ N-terminal specific antibody (Fig. 1).
SensoLyte anti-human β-Amyloid (1-40) & (1-42) ELISA kits offer a high sensitivity and a large dynamic range (3.9-250pg/ml of human Aβ). Tey were optimised to achieve 100 per cent recovery of spiked analytes for Aβ40 and Aβ42 in classical matrices such as human CSF and plasma (Fig. 2). Fig. 3 shows quantification data of Aβ40 and Aβ42 in transgenic mice brain lysates successfully.
Statistical analysis Statistical analysis demonstrate
Fig. 1. Assay Principle - Aβ peptides are captured between a pair of highly specific mouse monoclonal anti-Aβ40 or anti-Aβ42 capture antibodies and HRP labeled rabbit anti-Aβ (N-terminal specific) detection antibodies. Plate is incubated overnight at 4ºC, washed, and developed with colorimetric tetramethylbenzidine (TMB) substrate. Reaction is stopped with 1M HCl and signal is read at 450nm using ELISA plate reader.
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