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

Oligomeric forms of A beta 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 A beta in brain tissue has remained problematic. We have examined the specificity of two monoclonal antibodies, 7A1 a and 1G5, for synthetic oligomers of A beta(1-42) and for oligomeric A beta(1-42) in human brain homogenates, and the utility of these two antibodies for measuring oligomeric A beta(1-42) by sandwich ELISA. Both antibodies were found to recognise a range of synthetic oligomers of A beta(1-42) but to cross-react in Western blots with a 34kDa protein, shown by two-dimensional gel electrophoresis and mass spectrometry to be tropomyosin. However, by using 7A1a and 1G5 in combination with an A beta(1-42) capture antibody, we were able specifically to detect and to measure the levels of oligomeric A beta(1-42) in brain homogenates by ELISA. The development of a simple ELISA for measurement of oligomeric A beta should facilitate further studies of the role of oligomeric species of A beta in AD. (C) 2008 Elsevier B.V. All rights reserved.