Herpes may play role in pathogenesis of Alzheimer’s

Herpes may play role in pathogenesis of Alzheimer’s

"We saw a key virus, HHV 6A, regulating the expression of quite a few Alzheimer's risk genes and genes known to regulate the processing of amyloid, a key ingredient in Alzheimer's neuropathology".

Scientists have found up to two times higher level of human herpes virus among people with Alzheimer's disease, suggesting the potential role of the viruses in the development of the progressive brain disorder.

Results of the study were published online in Neuron on June 21. However, one controversial theory asserts that Alzheimer's may be caused by numerous viruses that affect the brain. "This research reinforces the complexity of Alzheimer's disease, creates opportunities to explore Alzheimer's more thoroughly, and highlights the importance of sharing data freely and widely with the research community". Alzheimer's is characterised by building up of amyloid sticky plaques in the brain.

Dudley notes that this study could potentially translate to the identification of virus, or virus-related, biomarkers that could improve patient risk stratification and diagnosis, as well as implying novel viral targets and biological pathways that could be addressed with new preventative and therapeutic drugs.

Herpes virus causes contagious sores, most often around the mouth or on the genitals.

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The researchers found that the viruses, particularly the types that infect humans during infancy and then become comatose for years, interact with the genes that cause Alzheimer's. To evaluate the robustness of their findings, the team incorporated a further 800 RNA sequencing samples collected by the Mayo Clinic and Rush Alzheimer's Disease Center, observing a persistent increase of HHV-6A and HHV-7 abundance in samples from individuals with Alzheimer's, thus replicating their main findings in two additional, independent, geographically dispersed cohorts.

David Reynolds, chief scientific officer of Alzheimer's Research UK, said this element was significant. Still, it's unclear exactly how the viruses are interacting with the brain. Researchers also found in the new study that the herpes virus was involved in networks that regulate the generation of amyloid proteins.

Viruses acquired early in life could play a role in Alzheimer's disease.

"Similar to other studies in this area, while this is robust research, it could not prove that the viruses actually were responsible for the disease", said James Pickett, the head of research at Alzheimer's Society. While determining the role of the viruses, the researches checked to see if either of the virus was affecting the proteins and genes commonly implicated in Alzheimer's disease. "If viral infections are playing a part, they are not the sole actor".

"All these Alzheimer's brains in these separate, major brain banks have previously unsuspected substantial populations of herpesvirus genomes and that deserves an explanation wherever it falls in the pathogenesis", Gandy said.

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