A vaccine with Aß oligomer-specific mimotope attenuates cognitive deficits and brain pathologies in transgenic mice with Alzheimer's disease.

ABSTRACT

BACKGROUND: ß-Amyloid peptide (Aß) oligomers are initial factors used to induce Alzheimer's disease (AD) development, and Aß monomers have normal physiological function. The antibodies or vaccines against Aß monomers have serious problems, such as side effects and low curative effects. Therefore, it is essential to specifically target Aß oligomers rather than monomers for the treatment of AD. METHODS: The mimotopes of Aß oligomers were obtained by panning the phage-displayed random peptide libraries using oligomer-specific antibodies as targets and expressed on the surface of EBY100 Saccharomyces cerevisiae to generate yeast cell base vaccines. One vaccine (AOE1) induced antibodies specifically against Aß oligomers and was selected for further study. The APP/PS1 mice were subcutaneously immunized with AOE1 eight times. The levels and characteristics of antibodies induced by AOE1 were determined by enzyme-linked immunosorbent assay. The effect of AOE1 on the cognitive deficits of AD mice was tested by novel object recognition (NOR) and Y-maze. Dot blot analysis, Western blot analysis, and immunohistochemistry were applied to measure the effects of AOE1 on Aß pathologies, neuroinflammation, and microhemorrhages in the brains of AD mice. RESULTS: Eight mimotope candidates of Aß oligomers were selected and expressed on EBY100 S. cerevisiae. Only AOE1 vaccine containing mimotope L2 induced antibodies that specifically recognized Aß42 oligomers rather than monomers. AOE1 immunization significantly increased the AD mice's exploration times for the novel object in the NOR test and the choices for new arms in the Y-maze test, and it reduced levels of Aß oligomers and glial activation in the AD mouse brains. No activation of Aß-specific T cells and microhemorrhages was observed in their brains following AOE1 vaccination. CONCLUSIONS: AOE1 is the first vaccine applying the oligomer-specific mimotope as an immunogen, which could induce antibodies with high specificity to Aß oligomers. AOE1 immunization attenuated Aß pathologies and cognitive deficits in AD mice, decreased the overactivation of glial cells, and did not induce microhemorrhage in the brains of AD mice. These findings suggest that AOE1 may be a safer and more effective vaccine for AD treatment.