Identification of the shortest Aß-peptide generating highly specific antibodies against the C-terminal end of amyloid-ß42.

Alzheimer's disease (AD) is characterized by neurofibrillary tangles, consisting of hyperphosphorylated tau protein and senile plaques, which are consisting mainly of amyloid-ß (Aß). Attempts to generate a safe vaccine against Aß rely on both B- and T-cell epitopes within the neurotoxic peptide Aß1-42. This, however, poses a risk for an inflammatory and/or autoimmune response against Aß-peptides in the brain. To overcome such risks we wanted to identify the shortest C-terminal Aß-peptide that would induce antibodies selectively recognizing the C-terminal end of Aß42. Immunization with this antigen should result in a non-inflammatory Th2 immune response and the T-cell response should be against a T-cell epitope covalently attached to the small Aß-peptide. Antigen constructs were made by the ligand presenting assembly (LPA) technology, comprising dimeric presentation of short Aß-peptides ending at amino acid 42 in connection with potent T-cell epitopes. Mice were immunized with antigen constructs using different adjuvants, and sera from mice were tested to characterize the generated immune response. Immunization with Keyhole limpet hemocyanin (KLH)-Aß(37-42) resulted in generation of IgG1 antibodies specific for the Aß42 C-terminal end, indicating a Th2-response. The T-cell mediated response was predominantly against T-cell epitopes in KLH. The antibodies stained senile plaques specifically in brain tissue from AD patients. Thus, KLH-Aß(37-42) was able to induce a non-inflammatory and highly specific antibody response against Aß42.

Specific recognition of the C-terminal end of A beta 42 by a high affinity monoclonal antibody.

The neurotoxic peptide A beta(42) is derived from the amyloid precursor protein by proteolytic cleavage and is deposited in the brain of patients suffering from Alzheimer's disease (AD). In this study we generate a high affinity monoclonal antibody that targets the C-terminal end of A beta(42) with high specificity. By this is meant that the paratope of the antibody must enclose the C-terminal end of A beta(42) including the carboxy-group of amino acid 42, and not just recognize a linear epitope in the C-terminal part of A beta. This has been accomplished by using a unique antigen construct made by the Ligand Presenting Assembly technology (LPA technology). This strategy results in dimeric presentation of the free C-terminal end of A beta(42). The generated Mab A beta1.1 is indeed specific for the C-terminal end of A beta(42) to which it binds with high affinity. Mab A beta1.1 recognizes the epitope in human AD tissue and stains plaques with high specificity. Therefore the monoclonal antibody can thus be useful in the histological investigations of the AD pathology.