Generation and Partial Characterization of Rabbit Monoclonal Antibody to Pyroglutamate Amyloid-ß3-42 (pE3-Aß).

N-terminally truncated pyroglutamate amyloid-ß (Aß) peptide starting at position 3 represents a significant fraction of Aß peptides (pE3-Aß) in amyloid plaques of postmortem brains from patients with Alzheimer's disease (AD) and older persons with Down syndrome (DS). Studies in transgenic mouse models of AD also showed that pE3-Aß is a major component of plaques, and mouse monoclonal antibody to pE3-Aß appears to be a desirable therapeutic agent for AD. Since small peptides do not typically elicit a good immune response in mice, but do so favorably in rabbits, our aims were to generate and partially characterize a rabbit monoclonal antibody (RabmAb) to pE3-Aß. The generated RabmAb was found to be specific for pE3-Aß, since it showed no reactivity with Aß16, Aß40, Aß42, Aß3-11, and pE11-17 Aß peptides in an enzyme linked immunosorbent assay (ELISA). The isotype of the antibody was found to be IgG class. The antibody possesses high affinity to pE3-Aß with dissociation constant (KD) for the antibody of 1 nM. The epitope of the antibody lies within the sequence of pE3-FRHD. In dot blotting, the optimal detection of pE3-Aß was at an antibody concentration of 0.5 µg/ml. The threshold of pE3-Aß detection was 2 fmol. The antibody was sensitive enough to detect 10 pg/ml of pE3-Aß in sandwich ELISA. pE3-Aß was detected in AD and DS brain extracts in ELISA and immunoblotting. Immunohistological studies showed immunolabeling of plaques and blood vessels in brains from patients with AD, and DS showing AD pathology. Thus, the antibody can be widely applied in AD and DS research, and therapeutic applications.

Generation and Partial Characterization of Rabbit Monoclonal Antibody to Amyloid-ß Peptide 1-37 (Aß37).

Secreted soluble amyloid-ß 1-37 (Aß37) peptide is one of the prominent Aß forms next to Aß40, and is found in cerebrospinal fluid (CSF) and blood. Recent studies have shown the importance of quantitation of CSF Aß37 levels in combination with Aß38, Aß40, and Aß42 to support the diagnosis of patients with probable Alzheimer's disease (AD), and the value of antibody to Aß37 to facilitate drug discovery studies. However, the availability of reliable and specific monoclonal antibody to Aß37 is very limited. Our aims were: 1) to generate and partially characterize rabbit monoclonal antibody (RabmAb) to Aß37, and 2) to determine whether the antibody detects changes in Aß37 levels produced by a γ-secretase modulator (GSM). Our generated RabmAb to Aß37 was found to be specific to Aß37, since it did not react with Aß36, Aß38, Aß39, Aß40, and Aß42 in an ELISA or immunoblotting. The epitope of the antibody was contained in the seven C-terminal residues of Aß37. The antibody was sensitive enough to measure CSF and plasma Aß37 levels in ELISA. Immunohistological studies showed the presence of Aß37-positive deposits in the brain of AD, and Down syndrome persons diagnosed with AD. Our studies also showed that the antibody detected Aß37 increases in CSF and brains of rodents following treatment with a GSM. Thus, our antibody can be widely applied to AD research, and in a panel based approach it may have potential to support the diagnosis of probable AD, and in testing the effect of GSMs to target AD.

Generation of Rabbit Monoclonal Antibody to Amyloid-ß38 (Aß38): Increased Plasma Aß38 Levels in Down Syndrome.

Secreted soluble amyloid-ß (Aß)38 is the second most prominent Aß form next to Aß40, and is found in cerebrospinal fluid (CSF) and blood. Recent studies have shown the importance of quantitation of CSF Aß38 levels in combination with those of Aß40 and Aß42 to support the diagnosis of Alzheimer's disease (AD), and other neurodegenerative diseases, and to facilitate drug discovery studies. However, the availability of reliable and specific Aß38 monoclonal antibody is limited. Our first aim was to generate and partially characterize rabbit monoclonal antibody (RabmAb) to Aß38. The antibody was specific to Aß38, since it did not react with Aß37, Aß39, Aß40, or Aß42 in ELISA or immunoblotting. The antibody was sensitive enough to measure Aß38 levels in plasma. Our second aim was to quantitate Aß38 levels in plasma from older Down syndrome (DS) persons and age-matched controls. Persons with DS (35 years and older) have neuropathological changes characteristic of AD. Studies have shown that plasma Aß40 and Aß42 levels are higher in older persons with DS than in controls. However, none examined Aß38 levels in DS. Our quantitation data showed that, like Aß40 and Aß42 plasma levels, Aß38 plasma levels were higher in DS than in controls. Longitudinal studies will determine whether plasma Aß38 levels in combination with levels of Aß40 and Aß42 are useful to predict early signs of AD in DS.