Published: Sat, June 23, 2018
Medical | By Vernon Walton

Harder Evidence Builds That Viruses Play a Role in Alzheimer's

Harder Evidence Builds That Viruses Play a Role in Alzheimer's

The loss of cognitive functioning in Alzheimer's disease, an irreversible and progressive brain disorder, has been found to be a mix of different disease processes in the brain, rather than just one, such as buildup of amyloid or tau proteins.

They found that viruses called human herpes virus 6 (HHV-6) and HHV-7 were more abundant in the brains of people who died with Alzheimer's.

Researchers in the United States believe the disease may trigger an immune "cascade" which encourages the growth of amyloid plaques.

These results could provide a new avenue of research aimed at preventing and treating Alzheimer's, said Keith Fargo, director of scientific programs and outreach for the Alzheimer's Association.

The research group, including experts from Icahn School of Medicine at Mount Sinai and Arizona State University, performed RNA sequencing on four brain regions in more than 600 samples of postmortem tissue from people with and without Alzheimer's to quantify which genes were present in the brain. "The title of the talk that I usually give is, 'I Went Looking for Drug Targets, and All I found Were These Lousy Viruses, ' " he said.

"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".

"We know from several large population-based studies that nutrition is a key factor in the development of Alzheimer's disease, but attempts to identify an exact combination of nutrients that can positively impact on brain health have failed up until now", he said.

"Thus while these data are very interesting and important for future research, they do not definitively support the idea that people with herpes are more likely to develop Alzheimer's." says Spires-Jones. And now, not only is the viral hypothesis resurrected: "it has specific testable pathways and networks and interactions that can be explored and reconciled with the rest of the work emerging in Alzheimer's", says Dudley. Using techniques in bioinformatics, the study integrates high-throughput data into probabilistic networks that are postulated to account for the associations between herpesviruses and the telltale effects of AD.

"The hypothesis that viruses play a part in brain disease is not new, but this is the first study to provide strong evidence based on unbiased approaches and large data sets that lends support to this line of inquiry", Dr. Richard J. Hodes, the National Institute on Aging director, said in a press release by the National Institutes of Health, the parent agency. Their results found a number of common viruses in normal aging brains, but more specifically identified increased levels of HH-6A and HH-7 in AD brains, a finding that was subsequently validated in the additional patient cohorts. It was also a chance for others in the community to donate and become part of the cause to help find a cure for Alzheimer's.

HAMILTON: Levels of two human herpes viruses were up to twice as high in brain tissue from people with Alzheimer's. "'But what's clear is that they're perturbing networks and participating in networks that directly accelerate the brain towards the Alzheimer's topology". While a group of dedicated scientists continued to toil away at investigations correlating viral infections with Alzheimer's, the general research community began to focus on the amyloid hypothesis as the fundamental causal explanation behind the disease.

There may be some new clues as to what lead to Alzheimer's Disease. Rather, the findings show viral DNA sequences and activation of biological networks-the interrelated systems of DNA, RNA, proteins and metabolites-may interact with molecular, genetic and clinical aspects of Alzheimer's.

"We were able to build a social network of the virus and the host genes, to see who is friends with who", Dudley said.

Readhead is an assistant research professor in the NDRC, housed at ASU's Biodesign Institute.

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