Glycosylation profiles of epitope-specific anti-beta-amyloid antibodies revealed by liquid chromatography mass spectrometry

Abstract

Alzheimer's disease (AD) is the most prevalent form of age-related neurodementia. The accumulation of β-amyloid polypeptide (Aβ) in brain is generally believed to be a key event in AD. The recent discovery of physiological β-amyloid autoantibodies represents a promising perspective for treatment and early diagnosis of AD. The mechanisms by which natural β-amyloid autoantibodies prevent neurodegeneration are currently unknown. The aim of the present study was to analyze the N-linked glycosylation of a plaque-specific, monoclonal antibody (clone 6E10) relevant for immunotherapy of AD, in comparison with the glycosylation pattern of an Aβ autoantibody isolated from an IgG source. Liquid chromatography in combination with tandem mass spectrometry was used to analyze the glycopeptides generated by enzymatic degradation of the antibodies reduced and alkylated heavy chains. The oligosaccharide pattern of the 6E10 antibody shows primarily core-fucosylated biantennary complex structures and, to a low extent, tri- and tetragalactosyl glycoforms, with or without terminal sialic acids. The glycans associated with the serum anti-Aβ autoantibodies are of the complex, biantennary-type, fucosylated at the first N-acetyl glucosamine residue of the trimannosyl chitobiose core and contain zero to two galactose residues, and zero to one terminal sialic acid, with or without bisecting N-acetyl glucosamine. Glycosylation analysis of the Aβ-autoantibody performed at the peptide level revealed all four human IgG subclasses, with IgG1 and IgG2 as the dominant subclasses.