Development of human antibody fragments directed towards synaptic acetylcholinesterase using a semi-synthetic phage display library.

Current Alzheimer's disease therapies suppress acetylcholine hydrolysis by inhibiting acetylcholinesterase (AChE) at cholinergic synapses. However, anticholinesterases promote alternative splicing changing the composition of brain AChE variants. To study this phenomenon we developed monoclonal antibodies to acetylcholinesterase synaptic peptide (ASP), a synthetic peptide with the C-terminal sequence unique to the human synaptic variant AChE-S. Screening of a phage display human antibody library allowed the isolation of single-chain Fv (scFv) antibodies that were highly specific for ASP, and displayed closely related third complementarity determining regions of the variable heavy chain domain (V(H)-CDR3). BIAcore analysis demonstrated dissociation constants at the micromolar range: 1.6 x 10(-6) and 2.0 x 10(-6) M for ASP and the complete AChE-S protein, respectively. The anti-ASP antibodies provide a novel tool for studying the synaptic AChE-S variant, the expression of which is altered in ageing and dementia.