Peripherally administered sera antibodies recognizing amyloid-β oligomers mitigate Alzheimer's disease-like pathology and cognitive decline in aged 3× Tg-AD mice.

Active and passive immunotherapy targeting amyloid-β (Aβ) may be the most promising strategy to prevent or treat Alzheimer's disease (AD). Previously, immunization with the recombinant 6Aβ15-T antigen generated robust anti-Aβ serum antibodies that strongly recognized Aβ42 oligomers in different mice, markedly reduced the amyloid burden, and improved behavioral performance of immunized older AD mice. Here, we further determined that these anti-6Aβ15-T serum antibodies from different strains of mice displayed anti-Aβ antibody responses against the same epitopes in the Aβ1-15 region. Peripheral administration of anti-6Aβ15-T serum antibodies was also effective to mitigate AD-like pathology and cognitive decline in aged 3× Tg-AD mice. Specifically, the levels of Aβ and tau in the brains of 3× Tg-AD mice were significantly reduced after passive immunotherapy, which seemed necessary or beneficial to ameliorate memory impairment. In addition, our results showed that this immunotherapy also prevented presynaptic dynamin 1 degradation, which might help to further protect synaptic functions and allow functional recovery of cognition. Moreover, immunization with 6Aβ15-T in rabbits induced a similar antibody response as that in mice, and the rabbit serum antibodies reacted strongly with Aβ42 oligomers and inhibited oligomer-mediated neurotoxicity. We concluded that passive immunization with Aβ42 oligomer conformation-sensitive anti-6Aβ15-T serum antibodies is effective in providing potentially therapeutic effects in aged 3× Tg-AD mice by reducing Aβ and tau.