Engineering a Dimeric Single-Domain Antibody for Improved Detection and neutralization of Amyloid-β oligomers

Soluble Aβ oligomers are regarded as major neurotoxic agents in Alzheimers disease. Several monoclonal antibodies have been developed to target Aβ oligomers, but most of them show limited specificity binding also to monomers and fibrils. To generate an antibody with high specificity for the oligomers, we aimed to increase the efficiency and sensitivity of a humanized Aβ-oligomer-specific single domain antibody, called DesAb-O. We engineered a dimeric DesAb-O variant, DiDesAb-O, which showed a significantly improved binding properties for Aβ oligomers as compared to the monomeric sdAb. Furthermore, DiDesAb-O detected Aβ42 oligomers in cells, prevented their binding to cell membranes and the Aβ42 oligomers-induced neurotoxicity from both synthetic Aβ42 samples and cerebrospinal fluid of Alzheimer's patients at lower concentrations compared to DesAb-O. Overall, our findings indicate that the rational engineering of dimeric sdAb variants is an effective strategy to improve their binding properties offering new opportunities for the development of clinical molecules in the early diagnosis and cure of Alzheimers disease.