Examination of brain tissue samples from patients who died of Alzheimer’s disease has revealed biomarkers supporting the idea that viral infections affecting the olfactory system accelerate the development of this condition.
Exploring the potential role of viral nasal infections in disease progression d’Alzheimer
In recent years, a growing body of work has established links between brain diseases and acute viral infections. However, the exact way in which virus are likely to influence the dementia remains obscure.
Published in the journal Neurobiology of Aging, the new study specifically focused on the olfactory system. As the loss of the sense of smell has been regularly presented as an early marker of the neurodegeneration observed in people suffering from Alzheimer’s disease, researchers have explored the potential role of nasal viral infections in its progression.
Comparison of postmortem brain tissue from several patients with this form of dementia to that of cognitively healthy, age-matched individuals revealed the presence of clear markers of viral infection and inflammation of the olfactory tract ( key pathway leading to the hippocampus) in subjects with Alzheimer’s disease.
« Overall, the transcriptional profile observed in this study might be representative of an olfactory system regularly assaulted by pathogens and the resulting pathological ramifications, such as amyloid deposition, microglia activation and, potentially, alterations. myelination write the researchers.
Worsening of brain damage
According to Andrew Bubak, lead author of the new study, the various elements highlighted suggest that the loss of smell is not the result of brain damage caused by Alzheimer’s disease, as initially thought, but the consequence of viral infections, participating in the aggravation of the lesions observed in patients suffering from this form of dementia.
« Supporting a parallel body of literature indicating that early Alzheimer’s is characterized by loss of smell, amyloid deposition in the olfactory epithelium, and dysfunction of olfactory sensory neurons, our study raises the possibility that a viral infection of the olfactory bulb /of the olfactory pathways accelerates its development », Details the researcher.
The study did not look at specific pathogens that might be responsible for persistent infections. However, researchers believe that herpes simplex virus type 1 (HSV-1) and varicella/zoster virus (VZV), already implicated in the onset of Alzheimer’s diseaseare the most likely culprits.