Active full-length DNA Aβ immunization in 3xTg-AD mice reduces not only amyloid deposition but also tau pathology.

BACKGROUND

Alzheimer's disease (AD) is the most well-known and most common type of age-related dementia. Amyloid deposition and hyperphosphorylation of tau protein are both pathological hallmarks of AD. Using a triple-transgenic mouse model (3xTg-AD) that develops plaques and tangles in the brain similar to human AD, we provide evidence that active full-length DNA amyloid-β peptide 1-42 (Aβ) trimer immunization leads to reduction of both amyloid and tau aggregation and accumulation.

METHODS

Immune responses were monitored by enzyme-linked immunosorbent assay (ELISA) (antibody production) and enzyme-linked immunospot (cellular activation, cytokine production). Brains from 20-month-old 3x Tg-AD mice that had received DNA Aβ immunotherapy were compared with brains from age- and gender-matched transgenic Aβ peptide-immunized and control mice by histology, Western blot analysis, and ELISA. Protein kinase activation and kinase levels were studied in Western blots from mouse hemibrain lysates.

RESULTS

Quantitative ELISA showed a 40% reduction of Aβ peptide and a 25-50% reduction of total tau and different phosphorylated tau molecules in the DNA Aβ trimer-immunized 3xTg-AD mice compared with nonimmunized 3xTg-AD control animals. Plaque and Aβ peptide reductions in the brain were due to the anti-Aβ antibodies generated following the immunizations. Reductions of tau were likely due to indirect actions such as less Aβ in the brain resulting in less tau kinase activation.

CONCLUSIONS

The significance of these findings is that DNA Aβ trimer immunotherapy targets two major pathologies in AD-amyloid plaques and neurofibrillary tangles-in one vaccine without inducing inflammatory T-cell responses, which carry the danger of autoimmune inflammation, as found in a clinical trial using active Aβ peptide immunization in patients with AD (AN1792).