Generation and Study of Antibodies against Two Triangular Trimers Derived from Aß.

Monoclonal antibodies (mAbs) that target the P-amyloid peptide (Aß) are important Alzheimer's disease research tools and are now being used as Alzheimer's disease therapies. Conformation-specific mAbs that target oligomeric and fibrillar Aß assemblies are of particular interest, as these assemblies are associated with Alzheimer's disease pathogenesis and progression. This paper reports the generation of rabbit mAbs against two different triangular trimers derived from Aß. These antibodies are the first mAbs generated against Aß oligomer mimics in which the high-resolution structures of the oligomers are known. We describe the isolation of the mAbs using single B-cell sorting of peripheral blood mononuclear cells (PBMCs) from immunized rabbits, the selectivity of the mAbs for the triangular trimers, the immunoreactivity of the mAbs with aggregated Aß42, and the immunoreactivity of the mAbs in brain tissue from the 5xFAD Alzheimer's disease mouse model. The characterization of these mAbs against structurally defined trimers derived from Aß enhances understanding of antibody-amyloid recognition and may benefit the development of diagnostics and immunotherapies in Alzheimer's disease.

Antibodies Raised Against an Aß Oligomer Mimic Recognize Pathological Features in Alzheimer's Disease and Associated Amyloid-Disease Brain Tissue.

Antibodies that target the ß-amyloid peptide (Aß) and its associated assemblies are important tools in Alzheimer's disease research and have emerged as promising Alzheimer's disease therapies. This paper reports the creation and characterization of a triangular Aß trimer mimic composed of Aß17-36 ß-hairpins and the generation and study of polyclonal antibodies raised against the Aß trimer mimic. The Aß trimer mimic is covalently stabilized by three disulfide bonds at the corners of the triangular trimer to create a homogeneous oligomer. Structural, biophysical, and cell-based studies demonstrate that the Aß trimer mimic shares characteristics with oligomers of full-length Aß. X-ray crystallography elucidates the structure of the trimer and reveals that four copies of the trimer assemble to form a dodecamer. SDS-PAGE, size exclusion chromatography, and dynamic light scattering reveal that the trimer also forms higher-order assemblies in solution. Cell-based toxicity assays show that the trimer elicits LDH release, decreases ATP levels, and activates caspase-3/7 mediated apoptosis. Immunostaining studies on brain slices from people who lived with Alzheimer's disease and people who lived with Down syndrome reveal that the polyclonal antibodies raised against the Aß trimer mimic recognize pathological features including different types of Aß plaques and cerebral amyloid angiopathy.

Probing differences among Aß oligomers with two triangular trimers derived from Aß.

The assembly of the ß-amyloid peptide (Aß) to form oligomers and fibrils is closely associated with the pathogenesis and progression of Alzheimer's disease. Aß is a shape-shifting peptide capable of adopting many conformations and folds within the multitude of oligomers and fibrils the peptide forms. These properties have precluded detailed structural elucidation and biological characterization of homogeneous, well-defined Aß oligomers. In this paper, we compare the structural, biophysical, and biological characteristics of two different covalently stabilized isomorphic trimers derived from the central and C-terminal regions Aß. X-ray crystallography reveals the structures of the trimers and shows that each trimer forms a ball-shaped dodecamer. Solution-phase and cell-based studies demonstrate that the two trimers exhibit markedly different assembly and biological properties. One trimer forms small soluble oligomers that enter cells through endocytosis and activate capase-3/7-mediated apoptosis, while the other trimer forms large insoluble aggregates that accumulate on the outer plasma membrane and elicit cellular toxicity through an apoptosis-independent mechanism. The two trimers also exhibit different effects on the aggregation, toxicity, and cellular interaction of full-length Aß, with one trimer showing a greater propensity to interact with Aß than the other. The studies described in this paper indicate that the two trimers share structural, biophysical, and biological characteristics with oligomers of full-length Aß. The varying structural, assembly, and biological characteristics of the two trimers provide a working model for how different Aß trimers can assemble and lead to different biological effects, which may help shed light on the differences among Aß oligomers.