Development of a Protofibril-Selective Sandwich ELISA to Analyze Alzheimer’s Amyloid-β Levels

Protein aggregation is recognized as an important contributing factor to several neurodegenerative diseases such as Alzheimer’s disease (AD). One of the peptide involved is amyloid-β (Aβ), a 40-42-residue peptide and the primary component of the senile plaques found in AD brains. Aβ aggregations can be found in the form of protofibrils, monomers, and fibrils intermediates. However, only protofibrils have been shown to be a crucial factor in pathogenicity due to their toxicity. This research involves the development of a novel protofibril-selective sandwich ELISA to determine Aβ levels in AD so it can be used for further research as a biomarker, detection agent, research tool, or potential therapy for Alzheimer’s disease. In the sandwich ELISA developed, monoclonal-antibody mAbSL 113 is used as the detection antibody and biotinylated-affinity-purify-antibody apAbSL 40-4 is used as the capture antibody. ApAbSL 40-4 is conjugated with Streptavidin-HRP, which consist of streptavidin protein that is covalently conjugated to horseradish peroxidase (HRP). Streptavidin binds to biotin in apAbSL 40-4 and the conjugated HRP provides enzyme activity for detection using an appropriate substrate system, allowing us to quantify the specificity of such antibody for the different Aβ intermediates. The results obtained show that mAbSL 113 has higher affinity for protofibrils over fibrils and monomers, and for fibrils over monomers. This makes mAbSL 113 a protofibril-selective antibody that can be used in either sandwich and indirect ELISA to analyze Aβ protofibril intermediates in Alzheimer’s disease