Antibodies that preferentially and specifically target pathological oligomeric
protein and
peptide assemblies, as opposed to their monomeric and
amyloid counterparts, provide therapeutic and diagnostic opportunities for
protein misfolding diseases. Unfortunately, the molecular properties associated with oligomer-specific
antibodies are not well understood, and this limits targeted design and development. We present here a generic method that enables the design and optimisation of oligomer-specific
antibodies. The method takes a two-step approach where discrimination between oligomers and fibrils is first accomplished through identification of cryptic
epitopes exclusively buried within the structure of the fibrillar form. The second step discriminates between monomers and oligomers based on differences in avidity. We show here that a simple divalent mode of interaction, as within e.g. the
IgG isotype, can increase the binding strength of the antibody up to 1500 times compared to its monovalent counterpart. We expose how the ability to bind oligomers is affected by the monovalent affinity and the turnover rate of the binding and, importantly, also how oligomer specificity is only valid within a specific concentration range. We provide an example of the method by creating and characterising a spectrum of different
monoclonal antibodies against both the Aβ
peptide and α-
synuclein that are associated with Alzheimer's and Parkinson's diseases, respectively. The approach is however generic, does not require identification of oligomer-specific architectures, and is, in essence, applicable to all
polypeptides that form oligomeric and fibrillar assemblies.