Viral and bacterial infections can trigger a series of changes in the body, paving the way for the eventual development of Alzheimer’s disease, according to a new study. The study builds on previous evidence linking this type of dementia to inflammation, and found that when the immune system is triggered by an invading pathogen, it can cause this type of neuro-inflammation. The key to the findings is the link between this inflammation and the deposition of amyloid plaques in the brain.
The new study, from memorial Sloan-Kettering Cancer Center, found that viral and bacterial infections, the immune system, nerve inflammation, and plaque build-up that causes Alzheimer’s disease may all be linked. According to the institute, the study represents a “direct link” between the build-up of these plaques and the body’s immune response to these infections.
The study linked the IFITM3 protein to the build-up of beta-amyloid plaques in the brain, triggered by the activation of the immune system against infection. In past studies, these plaques have been closely linked to Alzheimer’s disease, although work is still under way to fully understand them, what triggers their accumulation, and their overall role in this type of dementia.
The latest study, involving mice, found that as they grew older, levels of THEFITM3 protein and inflammatory markers increased in mice. Similarly, an increase in IFITM3 levels was found in a particular subset of patients with late-onset Alzheimer’s disease, suggesting that this may be a biomarker of the disease. Researchers have found that removing IFITM3 in mice reduces the activity of an enzyme and ultimately the accumulation of Plaques in the brain associated with Alzheimer’s disease.
Li Yuming, a chemical biologist at memorial Sloan-Kettering Cancer Center, said:
We already know that the immune system plays a role in Alzheimer’s disease — for example, it helps clean up beta-amyloid plaques in the brain. But this is the first direct evidence that the immune response promotes the production of beta-amyloid plaques – a major feature of Alzheimer’s disease.