Alzheimer’s disease could appear following an infection by a very common virus

Researchers from Tufts University in the United States present recent findings that support the hypothesis that Alzheimer’s disease may be triggered by a virus.

Nearly 225,000 people in France declare Alzheimer’s disease each year, most after age 65. Although this form of dementia is common, its origin is still hotly debated among specialists. There are, however, points of consensus: the amyloid plaques and the aggregates of tau protein in the neurons are involved in the occurrence of symptoms typical of the Alzheimer’s diseaseand theinflammation who seizes the brain patients exacerbates this toxicity.

To explain these observations, several hypotheses are proposed by scientists. Factors genetic seem to have an important role in the most frequent sporadic cases of Alzheimer’s, but a deregulation of the synthesis of amyloid proteins or the intervention of a micro-organism – a virus most of the time – could also have an implication.

Experiences in vitro on cultured neurons

A team from Tufts University, in the United States, presents results falling within the framework of the “viral hypothesis” on the origin of Alzheimer’s disease. The latter stipulates that a virus dormant in the brain – most often herpes virus 1 or HSV-1 – is “awakened” by factors that are still poorly defined, and induces the symptoms of Alzheimer’s disease. ” Our results suggest a pathway that leads to Alzheimer’s disease, caused by infection with the virus VZV that triggers inflammation waking up the HSV-1 virus in the brain “says Dana Cairnsfirst author ofstudy published in Journal of Alzheimer’s Disease.

To corroborate this hypothesis, they infected human neural stem cells with the two viruses and looked for the presence of markers specific to Alzheimer’s: amyloid plaques and Tau aggregates, gliosis (proliferation of glial cells in the brain) and neuroinflammation. Their results show that the VZV virus alone does not cause the formation of amyloid plaques and Tau aggregates, like HSV-1, but rather neuroinflammation and gliosis. This suggests, according to scientists, an indirect action of the VZV virus. In addition, they observed that infection of cells, in which HSV-1 is dormant, by the VZV virus reactivates the latter and causes changes typical of Alzheimer’s. ” It’s a double punch of two viruses that are very common and generally harmless, but lab studies suggest that if further exposure to VZV awakens dormant HSV-1, it could cause problems. “says Dana Cairns.

These experiments alone are not robust enough to confirm a causal link between Alzheimer’s disease and the VZV and HSV-1 viruses, even if the observations point in this direction. Moreover, the different hypotheses being studied on the origin of Alzheimer’s disease are not necessarily mutually exclusive. Viral infection could be a factor to consider in Alzheimer’s disease, among others.