Assessment of the Bioactivity of Antibodies against β-Amyloid Peptide in vitro and in vivo

Abstract

The accumulation of the β-amyloid peptide (Aβ) is a central event in the pathogenesis of Alzheimer’s disease (AD). Aβ removal from the brain by immune therapy shows promising potential for the treatment of patients with AD, although the mechanisms of the antibody action are incompletely understood. In this study we compared the biological activities of antibodies raised against various Aβ fragments for Aβ reduction in vitro and in vivo. Antibodies against Aβ enhanced the uptake of Aβ₄₂ aggregates up to 6-fold by primary microglial cells in vitro. The kinetics of Aβ₄₂ uptake varied considerably among antibodies. Based on the activity to mediate Aβ₄₂ uptake by microglial cells, we identified a bioactive antibody that significantly reduced Aβ₄₂ levels in the brains of transgenic mice with neuronal expression of an AD-related mutated amyloid precursor protein. This effect depended on the epitopes recognized by the antibody. Our data suggest that the ability to facilitate Aβ₄₂ uptake by primary microglia cells in vitro can be used to predict the biological activity of the antibody by passive immunization in vivo. This protocol may prove useful for the rapid validation of the activity of antibodies designed to be used in immune therapy of AD.

Modulation of Alzheimer's pathology by cerebro‐ventricular grafting of hybridoma cells expressing antibodies against Aβ in vivo

“…treated mice. This finding is in line with data that mostly antibodies directed against the midportion of Ab were able to bind the soluble peptide and prevent its oligomerization and fibrillogenesis [5], and the fact Mice were treated with antibodies for three weeks (for application details see [15]). Ab 42 concentrations in brain homogenates and sera are expressed in percent relative to a 100% baseline of the corresponding values obtained from averaging readings from a control group of four agematched, non-implanted SwAPP littermates (* P 6 0.05, *** P 6 0.001).…”

“…In this study, the efficacy of intra-ventricular grafting of antibody producing cells to reduce Ab levels in brain and periphery was tested. These data are compared to the results obtained in a parallel experiment subjecting the same AD model to intravenous injections of same antibodies [15]. Our accumulative data verify the bioactivity of anti-Ab antibodies with two different immunization protocols in vivo.…”

“…In a previous study, only 8G7 promoted a continuous uptake of Ab 42 by primary microglial cells in vitro [15]. All antibodies used in both studies recognize and bind the transgenically expressed Ab as was shown by Western blotting and have facilitated Fc receptor-mediated microglial uptake of fibrillar Ab 42 in vitro [15].…”

“…All antibodies used in both studies recognize and bind the transgenically expressed Ab as was shown by Western blotting and have facilitated Fc receptor-mediated microglial uptake of fibrillar Ab 42 in vitro [15]. Furthermore, SwAPP mice treated in both protocols were littermates and the duration of treatment was identical for both immunization protocols.…”

“…Moreover, concentrations of Ab 42 and levels of anti-Ab antibodies were also determined in sera of mice as previously described [15,16].…”