Published: Fri, June 22, 2018
Medical | By

Alzheimer's 'may be caused by a virus'

Alzheimer's 'may be caused by a virus'

Their findings add to a controversial theory that viruses might play a role in starting or fueling Alzheimer's, a progressive, incurable brain disease that robs people of their personalities, memory and ability to care for themselves.

Using computational tools to analyze these large datasets, the researchers were able to generate a picture of the genetic, transcriptional, and molecular networks that underpin AD development and progression and how viruses are potentially involved.

They found that human herpesvirus DNA and RNA were more abundant in the brains of those diagnosed postmortem with Alzheimer's disease and that abundance correlated with clinical dementia scores. "We are excited about the chance to capitalize on this approach to help in the scientific understanding, treatment and prevention of Alzheimer's and other neurodegenerative diseases".

More on this research is available in announcements from the Icahn School of Medicine at Mount Sinai, Arizona State University and Cell Press, the publisher of Neuron.

The nature and significance of viruses and other pathogens in the brain are now hot topics in neuroscience, though the exploration is still in its early stages.

The question remained, OK, in the Alzheimer brain what are the microbes that matter, what are the microbes that trigger the plaque?
"This is the first study to provide evidence based on multiple, large data sets that lends support to this idea", says Keith Fargo, director of scientific programs and outreach at the Alzheimer's Association. The data suggested that viruses directly interact with known AD risk genes.

Suzanne Miller Allen, with BCBS, says it's all to raise awareness by dedicating June 21, the longest day of the year, to brain health in the midst of Alzheimer's and Brain Awareness Month. RNA of both HHV-6A and HHV-7 were also higher in the Alzheimer's brains than in healthy brains, and viral RNA levels tracked with the severity of clinical symptoms. These viruses can cause encephalitis and other chronic conditions.

Instead, scientists say further work will test whether herpes virus activity is one of the causes of Alzheimer's. Nationwide, there are 5.7 million Americans living with the disease, a number that is expected to grow to 14 million by 2050. The constructed virus-host protein networks also suggested that herpesvirus interaction perturbed cell nucleotide pools, tRNA synthesis, and protein translation, "which suggested a picture of virally induced dysregulation of nucleotide pool metabolism, especially purine bases, consistent with several metabolomics studies in AD".

But people should not be anxious by the findings.

If the findings pan out, they could change how scientists look for new ways to treat or prevent Alzheimer's, said Dr. Miroslaw Mackiewicz of NIH's National Institute on Aging.

This is especially true because HHV-6A and HHV-7 are extremely common and often latent or asymptomatic: in North America, nearly 90% of children have one of these viruses circulating in their blood by the time they're a few years old.

"This kind of analysis was only possible because the consortium had coordinated for all of these other groups to put their sequencing data in the AMP-AD Knowledge Portal in a precompetitive environment that let us very quickly replicate our work across all these different cohorts".

A new study links certain viruses, called HHV-6 and HHV-7, with Alzheimer's disease.

Prof Dudley said: "We didn't have a horse in this virus race whatsoever". It's the data that took us there. They identified specific testable pathways and biological networks.

Sam Gandy, professor of neurology and psychiatry, and co-author of the study, said: "This is the most compelling evidence ever presented that points to a viral contribution to the cause or progression of Alzheimer's".

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