Antibodies to potato virus Y bind the amyloid beta peptide: immunohistochemical and NMR studies

Studies in transgenic mice bearing mutated human Alzheimer disease (AD) genes show that active vaccination with the amyloid beta (Abeta) protein or passive immunization with anti-Abeta antibodies has beneficial effects on the development of disease. Although a trial of Abeta vaccination in humans was halted because of autoimmune meningoencephalitis, favorable effects on Abeta deposition in the brain and on behavior were seen. Conflicting results have been observed concerning the relationship of circulating anti-Abeta antibodies and AD. Although these autoantibodies are thought to arise from exposure to Abeta, it is also possible that homologous proteins may induce antibody synthesis. We propose that the long-standing presence of anti-Abeta antibodies or antibodies to immunogens homologous to the Abeta protein may produce protective effects. The amino acid sequence of the potato virus Y (PVY) nuclear inclusion b protein is highly homologous to the immunogenic N-terminal region of Abeta. PVY infects potatoes and related crops worldwide. Here, we show through immunocytochemistry, enzyme-linked immunosorbent assay, and NMR studies that mice inoculated with PVY develop antibodies that bind to Abeta in both neuritic plaques and neurofibrillary tangles, whereas antibodies to material from uninfected potato leaf show only modest levels of background immunoreactivity. NMR data show that the anti-PVY antibody binds to Abeta within the Phe4-Ser8 and His13-Leu17 regions. Immune responses generated from dietary exposure to proteins homologous to Abeta may induce antibodies that could influence the normal physiological processing of the protein and the development or progression of AD.