Evaluating the transmission risk of amyloid beta peptide via ingestion

Abstract

Recent reports suggest that amyloid beta (Aβ) peptides can exhibit prion-like pathogenic properties. Transmission of Aβ peptide and the development of associated pathologies after surgeries with contaminated instruments and intravenous or intracerebral inoculations have now been reported across fish, rodents, primates, and humans. This raises a worrying prospect of Aβ peptides also having other characteristics typical of prions, such as evasion of the digestive process. We asked if such transmission of Aβ aggregates via ingestion was possible. We made use of a transgenic Drosophila melanogaster line expressing human Aβ peptide prone to aggregation. Fly larvae were fed to adult zebrafish under two feeding schemes. The first was a short-term, high-intensity scheme over 48 hours to determine transmission and retention in the gut. The second, long-term, lower-intensity scheme specifically examined accumulation in the brain. The gut and brain tissues were examined through histological, Western blotting, and mass spectrometric analyses. None of the analyses could detect Aβ aggregates in the guts of zebrafish following ingestion, despite it being easily detectable in the feed. Additionally, there was no detectable accumulation of Aβ in the brain tissue or development of associated pathologies after prolonged feeding. While Aβ aggregates do not appear to be readily transmissible by ingestion across species, two prospects remain open. First, this mode of transmission, if occurring, may stay below a detectable threshold and may take much longer to manifest. A second possibility is that the human Aβ peptide may not be able to trigger self-propagation or aggregation of non-mammalian amyloid. Either possibility requires further investigation but suggests that Alzheimer′s Disease (AD) preventive measures to account for such transmission in humans are at present unwarranted.