RESUMO
In Alzheimer's disease (AD), amyloid-ß (Aß) peptides accumulate in the brain in different forms, including fibrils and oligomers. Recently, we established three distinct conformation-dependent human single-chain Fv (scFv) antibodies, including B6 scFv, which bound to Aß42 fibril but not to soluble-form Aß, inhibiting Aß42 fibril formation. In this study, we determined the mimotopes of these antibodies and found a common mimotope sequence, B6-C15, using the Ph.D.-C7C phage library. The B6-C15 showed weak homology to the C-terminus of Aß42 containing GXXXG dimerization motifs. We synthesized the peptide of B6-C15 fused with biotinylated TAT at the N-terminus (TAT-B6-C15) and characterized its biochemical features on an Aß42-fibrillation reaction in vitro. We demonstrated that, first, TAT-B6-C15 inhibited Aß42 fibril formation; secondly, TAT-B6-C15 bound to prefibril Aß42 oligomers but not to monomers, trimers, tetramers, fibrils, or ultrasonicated fragments; thirdly, TAT-B6-C15 inhibited Aß42-induced cytotoxicity against human SH-SY5Y neuroblastoma cells; and, fourthly, when mice were administered B6-C15-phages dissolved in phosphate-buffered saline, the anti-Aß42 conformer IgG antibody response was induced. These results suggested that the B6-C15 peptide might provide unique opportunities to analyze the Aß42 fibrillation pathway and develop a vaccine vehicle for Alzheimer's disease.
