Molecular and cellular characterization of nanobodies directed against Tau – ToNIC

The aggregation of neuronal Tau protein to form fibrilar structures inside neurons is associated with tauopathies, notably Alzheimer’s disease (AD). A trans-synaptic transfer of Tau may participate in the spatio-temporal progression of the disease and this supposes that Tau is secreted into the interstitial fluids. Molecular and cellular mechanisms behind these processes, aggregation and transfer, are still unknown. Additionally, although Tau immunotherapy is a potential therapeutic strategy in AD, fundamental knowledge is still lacking to implement this strategy. The objective of ToNIC (Tau Nanobodies Interaction Characterization) is to identify, optimize and evaluate potent and selective VHHs (nanobodies) targeting Tau, as well as to generate novel basic knowledge on the pathophysiology of tauopathies to validate, in the long term, immune-targets in the treatment of tauopathies. Nanobodies correspond to the variable domains of camelid heavy-chain antibodies (VHHs). The antigen binding capacity of VHHs relies on a single domain and therefore VHHs correspond to the smallest antigen-binding fragment of an antibody.
A unique and original multi-disciplinary strategy will be implemented to reach our objectives thanks to the year-long expertise in Tau biology of both partners, Partner 1 I. Landrieu UMR8576 and Partner 2 L. Buée UMR- S 1172. Complementary approaches will be used to transfer the in vitro experimental biophysical data into cellular contexts. VHHs directed against soluble, phosphorylated or aggregated Tau protein will be selected from a validated synthetic library (sub-contracting Hybrigenics services, Paris) by phage-display. These VHHs will be fully characterized for their specificity, affinity and capacity to recognize their target in a cellular context. Selected VHHs, based on these criteria, will be further assayed to evaluate their capacity to inhibit Tau aggregation, both in vitro and in a cellular model of aggregation, and/or their capacity to block Tau transfer using microfluidic devices. These experiments should provide novel knowledge on which pathway(s) might preferentially be altered in Tau immune strategy. Preliminary data show the feasibility of our approaches which combine high resolution Nuclear Magnetic Resonance spectroscopy, with other biophysical methods (partner 1) and in cell studies (partner 2) as one of our VHH, directed against soluble Tau, was found to inhibit Tau aggregation, both in vitro and in a cellular context. This project of fundamental interest, aiming at answering key questions in Tau biology, has potential exciting perspectives in human health.