Preparation and Characterization of a Monoclonal Antibody with High Affinity for Soluble Aβ Oligomers

Amyloid beta-protein (A beta) has been causally implicated in the neurodegenerative processes that accompany Alzheimer's disease. Soluble oligomers of the A beta(1-42) fragment are thought to be significantly more neurotoxic than higher molecular weight aggregates. We report the isolation and characterization of a mouse monoclonal antibody (MAb) directed against soluble A beta(1-42) oligomers. Synthetic A beta(1-42) oligomers were assembled in vitro; these were used to immunize mice, and hybridomas were isolated following myeloma fusion of splenocytes from immunized animals. Screening for reactivity against A beta(1-42) resulted in the identification of MAb A8 with high affinity for soluble oligomers. The isotype of A8 was found to be IgG(2b). Experiments using sub-peptides of A beta(1-42) revealed that the epitope identified by A8 lies within the 1-6 region of Ab. The antibody displays high affinity for soluble A beta(1-42) oligomers in the molecular weight range of 16.5-25 kDa, and detected target antigen in brain sections from senescence-accelerated SAMP 8 mice. The sensitivity and optimal titers for the detection of soluble A beta(1-42) oligomers were determined to be 0.625 mu g/mL in indirect ELISA, and 1:10(6), 1:4000, and 1:150 for ELISA, Western blotting, and immunohistochemistry, respectively. The A8 antibody specific for soluble A beta(1-42) oligomers will provide a valuable tool for Alzheimer's disease research.