Neuronally expressed anti-tau scFv prevents tauopathy-induced phenotypes in Drosophila models

We have derived single-chain variable fragments (scFv) from tau antibody hybridomas and previously shown their promise as imaging diagnostic agents. Here, we examined the therapeutic potential of anti-tau scFv in transgenic Drosophila models that express in neurons wild-type (WT) human tau (htau) or the human tauopathy mutation R406W. scFv expressing flies were crossed with the tauopathy flies and analyzed. Overall, the survival curves differed significantly (p < .0001). Control flies not expressing htau survived the longest, whereas R406W expressing flies had the shortest lifespan, which was greatly prolonged by co-expressing the anti-tau scFv (p < .0001). Likewise, htau WT expressing flies had a moderately short lifespan, which was prolonged by co-expressing the anti-tau scFv (p < .01). In addition, the htau expression impaired wing expansion after eclosion (p < .0001), and caused progressive abdomen expansion (p < .0001). These features were more severe in htau R406W flies than in htau WT flies. Importantly, both phenotypes were prevented by co-expression of the anti-tau scFv (p < .01-0.0001). Lastly, brain analyses revealed scFv-mediated tau clearance (p < .05-0.01), and its prevention of tau-mediated neurotoxicity (p < .05-0.001). In summary, these findings support the therapeutic potential of an anti-tau scFv, including as gene therapies, and the use of Drosophila models for such screening.