A sandwich enzyme immunoassay for detecting and measuring Alzheimer's disease--associated proteins in human brain tissue.

A simple, fast, and reliable immunoassay has been developed to detect and measure Alzheimer's disease-associated proteins (ADAPs) in human brain tissue. This assay, called ALZ-EIA (brain), was developed for Abbott's quantum system, in which 1/4-in. beads are used as solid phase. The beads were coated with polyclonal IgG purified from sera obtained from rabbits immunized with a highly enriched Alzheimer's disease brain protein fraction for ADAP. The antigen (ADAP) is effectively captured by the polyclonal IgG coated on the beads. ALZ-50 (a mouse monoclonal IgM) is used as the detection antibody, and bound ALZ-50 is subsequently quantified by a horseradish peroxidase-linked goat antimouse IgM and appropriate substrate. The assay is linear up to 0.5 absorbance units (r = 0.9), reproducible (CV less than 10%), sensitive, and specific. With preformulated reagents and standard supplies, the assay is simple and rapid; 120 data points can readily be generated in about 4 hr.