N‐terminal heterogeneity of parenchymal and vascular amyloid‐β deposits in Alzheimer’s disease

• DOI: 10.1111/nan.12637
• Publication Date: 2020-06-04T20:30:00Z
• Authors: S. Zampar; H. W. Klafki; K. Sritharen; T. A. Bayer; J. Wiltfang; A. Rostagno; J. Ghiso; L. A. Miles; O. Wirths
• Keywords: N-terminal truncation; metabolism [Amyloid beta-Peptides]; Plaque, Amyloid; Antibodies, Monoclonal, Humanized; pharmacology [Antibodies, Monoclonal, Humanized]; Article; 03 medical and health sciences; 0302 clinical medicine; Alzheimer Disease; antibody; metabolism [Peptide Fragments]; Animals; Humans; ddc:610; Aged; Aged, 80 and over; Amyloid beta-Peptides; amyloid; Brain; metabolism [Plaque, Amyloid]; Peptide Fragments; 3. Good health; Disease Models, Animal; capillary isoelectric focusing immunoassay; metabolism [Brain]; Abeta; Alzheimer disease; metabolism [Alzheimer Disease]

AimsThe deposition of amyloid‐β (Aβ) peptides in the form of extracellular plaques in the brain represents one of the classical hallmarks of Alzheimer’s disease (AD). In addition to ‘full‐length’ Aβ starting with aspartic acid (Asp‐1), considerable amounts of various shorter, N‐terminally truncated Aβ peptides have been identified by mass spectrometry in autopsy samples from individuals with AD.MethodsSelectivity of several antibodies detecting full‐length, total or N‐terminally truncated Aβ species has been characterized with capillary isoelectric focusing assays using a set of synthetic Aβ peptides comprising different N‐termini. We further assessed the N‐terminal heterogeneity of extracellular and vascular Aβ peptide deposits in the human brain by performing immunohistochemical analyses using sporadic AD cases with antibodies targeting different N‐terminal residues, including the biosimilar antibodies Bapineuzumab and Crenezumab.ResultsWhile antibodies selectively recognizing Aβ1–x showed a much weaker staining of extracellular plaques and tended to accentuate cerebrovascular amyloid deposits, antibodies detecting Aβ starting with phenylalanine at position 4 of the Aβ sequence showed abundant amyloid plaque immunoreactivity in the brain parenchyma. The biosimilar antibody Bapineuzumab recognized Aβ starting at Asp‐1 and demonstrated abundant immunoreactivity in AD brains.DiscussionIn contrast to other studied Aβ1–x‐specific antibodies, Bapineuzumab displayed stronger immunoreactivity on fixed tissue samples than with sodium dodecyl sulfate‐denatured samples on Western blots. This suggests conformational preferences of this antibody. The diverse composition of plaques and vascular deposits stresses the importance of understanding the roles of various Aβ variants during disease development and progression in order to generate appropriate target‐developed therapies.