A Sensitive and Cost-Effective Chemiluminescence ELISA for Measurement of Amyloid-β 1-42 Peptide in Human Plasma

Abstract

Background:

Amyloid-β₄₂ (Aβ₄₂) is associated with plaque formation in the brain of patients with Alzheimer’s disease (AD). Studies have suggested the potential utility of plasma Aβ₄₂ levels in the diagnosis, and in longitudinal study of AD pathology. Conventional ELISAs are used to measure Aβ₄₂ levels in plasma but are not sensitive enough to quantitate low levels. Although ultrasensitive assays like single molecule array or immunoprecipitation-mass spectrometry have been developed to quantitate plasma Aβ₄₂ levels, the high cost of instruments and reagents limit their use.

Objective:

We hypothesized that a sensitive and cost-effective chemiluminescence (CL) immunoassay could be developed to detect low Aβ₄₂ levels in human plasma.

Methods:

We developed a sandwich ELISA using high affinity rabbit monoclonal antibody specific to Aβ₄₂. The sensitivity of the assay was increased using CL substrate to quantitate low levels of Aβ₄₂ in plasma. We examined the levels in plasma from 13 AD, 25 Down syndrome (DS), and 50 elderly controls.

Results:

The measurement range of the assay was 0.25 to 500 pg/ml. The limit of detection was 1 pg/ml. All AD, DS, and 45 of 50 control plasma showed measurable Aβ₄₂ levels.

Conclusion:

This assay detects low levels of Aβ₄₂ in plasma and does not need any expensive equipment or reagents. It offers a preferred alternative to ultrasensitive assays. Since the antibodies, peptide, and substrate are commercially available, the assay is well suited for academic or diagnostic laboratories, and has a potential for the diagnosis of AD or in clinical trials.