Characterisation of two antibodies to oligomeric Aβ and their use in ELISAs on human brain tissue homogenates

Abstract

Oligomeric forms of Aβ are believed to be the major toxic species of this peptide in Alzheimer's disease (AD). Although the characterisation of oligomer-specific antibodies has been reported, these have not been successfully incorporated into an enzyme-linked immunosorbent assay (ELISA), and measurement of the levels of oligomeric Aβ in brain tissue has remained problematic. We have examined the specificity of two monoclonal antibodies, 7A1a and 1G5, for synthetic oligomers of Aβ 1–42 and for oligomeric Aβ 1–42 in human brain homogenates, and the utility of these two antibodies for measuring oligomeric Aβ 1–42 by sandwich ELISA. Both antibodies were found to recognise a range of synthetic oligomers of Aβ 1–42 but to cross-react in Western blots with a 34 kDa protein, shown by two-dimensional gel electrophoresis and mass spectrometry to be tropomyosin. However, by using 7A1a and 1G5 in combination with an Aβ 1–42 capture antibody, we were able specifically to detect and to measure the levels of oligomeric Aβ 1–42 in brain homogenates by ELISA. The development of a simple ELISA for measurement of oligomeric Aβ should facilitate further studies of the role of oligomeric species of Aβ in AD.