High-affinity rabbit monoclonal antibodies specific for amyloid peptides amyloid-β40 and amyloid-β42.

Antibodies that specifically bind to either amyloid-β peptide (Aβ) isoform Aβ₄₀ or Aβ₄₂ contribute to the study of Alzheimer's disease (AD) pathology and to the development of cerebrospinal fluid-based tests for the probable diagnosis of AD. Polyclonal rabbit anti-Aβ antibodies possess high affinity and specificity, but their generation requires a long immunization period, and the resulting antibodies exhibit variable specificities and affinities. To secure a continuing supply of antibodies with uniform properties, we generated and partially characterized rabbit monoclonal antibodies specific for either Aβ₄₀ or Aβ₄₂. These antibodies possess nanomolar or sub-nanomolar dissociation constants and are at least 3,000-fold more selective for one isoform over the other. These antibodies are suitable for immunoblotting and, in a sandwich ELISA, RabmAb42 (anti-Aβ₄₂) is sensitive enough to measure plasma levels of Aβ₄₂. In addition, these antibodies have been applied to the immunohistology of Down syndrome and AD brain tissues, where they reveal fibrillar and diffuse amyloid deposits and are almost free of non-specific staining. The data indicate that diffuse amyloid deposits contain only minute amounts of Aβ₄₀. Thus these rabbit monoclonal anti-Aβ antibodies can be widely applied in AD and Down syndrome research and diagnosis.