A vaccine against Alzheimer's has come a step closer to reality, as scientists have managed to prevent the accumulation of toxic brain proteins associated with the disease.
Experiments in mice showed that the DNA vaccine, injected into the skin, could delay the onset of Alzheimer's disease without serious side effects.
Scientists have said that the findings, published in Alzheimer's research and treatment, could pave the way for clinical trials with human patients.
Two types of toxic proteins or proteinaceous components are thought to play an important role in Alzheimer's, β-amyloid and tau.
Β-amyloid accumulates in sticky clusters in the brain and is a hallmark of the disease observed in post-mortem examinations of patients.
Tau is a protein that produces devastating "tangles" in nerve cells. Some studies suggest that the two are linked, with beta-amyloid promoting the formation of tau langs.
The new vaccine contains DNA encoding a portion of the beta-amyloid protein building block or peptide.
In the study, the vaccine caused an immune response that not only resulted in a 40% decrease in β-amyloid accumulation, but also in a 50% reduction in tau formation.
The study was conducted in mice that were genetically engineered to develop a rodent equivalent of Alzheimer's disease.
A major hurdle to developing effective anti-Alzheimer's vaccines is to find safe ways of introducing them to the body.
A previous experimental vaccine developed in the early 2000s caused brain edema in some patients when tested in humans.
The new vaccine is injected into the skin instead of muscle, which leads to a different kind of immune response.
If it is repeated in humans, the effects observed in mice will have "great healing value," the researchers said.
"If the onset of the disease could be delayed for even five years, that would be enormous for patients and their families," said co-author of the study, Dr. Doris Lambracht-Washington.
"The number of cases of dementia could be halved," he said.