Abstract: The invention relates to generation, optimization and characterisation of VHH targeted against Tau MTBD (microtubule-binding domain) with high affinity, obtained by screening from a naïve synthetic library. The inventors optimized version of a lead VHH which is able to inhibit Tau aggregation in vitro and in HEK 293 aggregation-reporting cellular model, providing a new tool in Tau immunotherapies. Accordingly the invention relates to new VHH antibody that specifically binds with high affinity Tau species, especially the epitope region involved in Tau aggregation. Moreover, the inventors found that immunization with the optimized version of this lead VHH prevented the formation of neurofibrillary tangles induced by injection of extracellular h-AD in mouse model. Thus, these specific antibodies can be used for the therapy of tauopathy disorders such as Progressive supranuclear palsy (PSP).