Schenk et al.,92 using aggregated Aβ as an immunogen, first investigated Aβ vaccination in PDAPP mice. They started immunizing mice at 6 weeks of age (well before the age when plaque deposition begins in this line) with a vaccine that was injected on a monthly basis for 11 months. High titers of anti-Aβ antibodies developed, and at 12 months of age, the mice showed dramatic reductions in plaque loads in comparison with saline-injected controls. In an additional set of studies, 11-month-old mice with already existing plaque loads received monthly injections and were examined pathologically at 15 and 18 months. At both ages, plaque burdens were dramatically less in the immunized animals, suggesting that Aβ vaccination might be beneficial even after parenchymal deposits are present.
