Anti-Aß scFvs prevent the progressive dysfunction of motor neurons. (A and B) Locomotor activity of flies expressing LacZ or Aß42 constructs under the control of elav-Gal4. (A) Snapshot of the locomotor assay at Day 12 showing all the genotypes covered. Only one vial (#6, Aß42; LacZ) contains flies with impaired climbing ability. Flies co-expressing anti-Aß scFvs show similar locomotor activity (#3, #4, #5) as negative control flies (#1, LacZ). (B) Longitudinal study of locomotor performance, each genotype is shown in duplicate. Flies expressing LacZ alone (green lines) reach 50% climbing index by Day 12 (arrow), whereas flies expressing Aß42 and LacZ (red) reach 50% climbing by Day 5. Flies co-expressing Aß42 and scFv9 (yellow) reach 50% climbing by Day 12. Flies co-expressing Aß42 and scFv42.2 (black) reach 50% climbing by Day 16. Flies co-expressing Aß42 and scFv9+42.2 (blue) reach 50% climbing by Day 13. ****P < 0.0001.