A new study in mice has suggested that chronic inflammation, as a result of infection, could contribute to the development of Alzheimer’s disease. The research is published on Monday 2 July in the Journal of Neuroinflammation.
While age is the biggest known risk factor for the development of Alzheimer’s, there is evidence that activation of the body’s immune system in the brain, called neuroinflammation, may also contribute to the development of the disease.
A team of scientists based in Switzerland investigated this further by activating the immune system in mice in the womb using a chemical called PolyI:C, which simulates a viral infection. They followed these mice as they aged and compared them to mice which weren’t given an injection. The scientists looked for any changes in behaviour or in brain features which could be characteristic of Alzheimer’s disease.
The study found that large-scale activation of the immune system during development predisposed mice to signs of Alzheimer’s as they aged. The scientists observed that these mice performed less well on memory tasks and had changes in amyloid and tau – hallmark proteins of the disease in humans. The researchers also found that if a second injection was given later in life, the changes were even more marked.
In mice which were bred to already have some features of Alzheimer’s disease in the brain, activation of the immune system using PolyI:C caused the disease to progress more rapidly. These mice showed a dramatic increase in amyloid plaques – toxic bundles of amyloid protein – compared to mice which did not receive the injection.
Dr Marie Janson of Alzheimer’s Research UK, the UK’s leading dementia research charity, said:
“The results of this study suggest that repeated or severe infections may contribute to the development of Alzheimer’s disease in mice. While we know that the immune system plays a role in human Alzheimer’s disease, clinical trials with anti-inflammatory drugs have not yet shown conclusive benefits in treating the disease and so more research is needed to fit these pieces of the puzzle together.
“Understanding the risk factors for Alzheimer’s disease is essential, especially if some of these factors are things that we can actively change or avoid. This understanding can only come through research, yet research into dementia remains hugely underfunded. With around half a million people in the UK living with Alzheimer’s, and this number expected to increase, the need for this research has never been greater.”