Inflammation can reawaken dormant viruses in the brain, which may help to explain why concussions often precede dementia, a new study finds.
Brain injuries like concussions raise the risk of dementia, and the more blows someone takes to the head, the higher that risk becomes, evidence suggests. Scientists are investigating what happens in the brain after injury that might lead to changes tied to dementia — for instance, a buildup of abnormal proteins and the malfunction and death of brain cells. Such changes are seen in Alzheimer’s disease and chronic traumatic encephalopathy (CTE), a disorder that’s recently gained recognition in high-impact sports.
Some scientists think these changes may be linked to a common virus: herpes simplex virus 1 (HSV-1), the germ behind cold sores.
Herpesviruses — a broader group that also includes the viruses behind chickenpox and mono — have an ability to go dormant in the body and then later reactivate. “They can remain latent in your body forever,” said lead study author Dana Cairns, a postdoctoral research fellow at Tufts University. There’s evidence that HSV-1 can somehow weasel its way into the brain and then lie there in wait, Cairns told Live Science.
Related: Lab-grown ‘minibrains’ help reveal why traumatic brain injury raises dementia risk
What’s new here is that the researchers have demonstrated that physical injury can activate latent viruses in the brain, said Dr. Gorazd Stokin, who leads a neuroscience lab at the Institute of Molecular and Translational Medicine in the Czech Republic and was not involved in the new study.
The new research relied on miniature laboratory models of the brain, so more work will be needed to show that the results are relevant to people. “But it’s a good first step to show something interesting,” said Stokin, who is also a consultant neurologist at the Gloucestershire Hospitals NHS Foundation Trust in the U.K.
Viruses in dementia
The idea of viruses sparking dementia isn’t new; Ruth Itzhaki, a co-author of the new paper, raised the notion in 1991. Itzhaki and colleagues had found the virus in the brains of older adults who had died of Alzheimer’s. They later found that people who carry both the virus and ApoE4 — a gene variant that raises Alzheimer’s risk — have a higher risk of the disease than those with ApoE4 alone. They also found that latent HSV-1 can be reawakened by stress or…
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