Concussions may activate dormant viruses in the brain

Concussions and repeated head injuries are no longer seen as mere occupational hazards of contact sports; they are now recognized as serious health concerns. 

Recent research from Tufts University and the University of Oxford reveals a potential link between head trauma and the activation of dormant viruses in the brain, which may lead to long-term neurodegenerative diseases such as Alzheimer’s. 

The findings, published in the journal Science Signaling, suggest that early preventive treatments using antiviral drugs could help mitigate these risks.

Hidden threat of dormant viruses

Our bodies host many dormant viruses, including herpes simplex virus 1 (HSV-1) and varicella-zoster virus, which commonly reside in neurons and glial cells without causing harm. 

Dana Cairns, lead author and research associate in Tufts University’s Department of Biomedical Engineering, explained her previous findings.

“In that study, another virus – varicella – created the inflammatory conditions that activated HSV-1. We thought, what would happen if we subjected the brain tissue model to a physical disruption, something akin to a concussion? Would HSV-1 wake up and start the process of neurodegeneration?” 

This question drove the new study, which investigates how concussions might trigger these latent viruses.

Mimicking brain trauma in the lab

To explore this, the researchers developed a unique brain tissue model. This model is a 6mm wide, donut-shaped sponge made of silk protein and collagen, infused with neural stem cells. 

The stem cells matured into neurons and glial cells, forming a network similar to that of a real brain, and some even harbored dormant HSV-1. The team simulated a concussion by enclosing the model in a cylinder and delivering a sudden jolt with a piston.

After subjecting the tissue to this controlled shock, Cairns observed that in models containing HSV-1, the virus reactivated. 

Following this reactivation, the tissue began to exhibit key markers of Alzheimer’s disease: amyloid plaques, tau protein tangles, inflammation, neuronal death, and a surge in glial cells – a condition known as gliosis. Repeated shocks intensified these effects. 

In contrast, tissue models without HSV-1 showed only minor gliosis and no other Alzheimer’s indicators.

Concussions and dormant viruses 

The results strongly indicate that concussions might awaken dormant viruses in the brain, potentially leading to neurodegenerative conditions over time. 

“This opens the question as to whether antiviral drugs or anti-inflammatory agents might be useful as early preventive treatments after head trauma to stop HSV-1 activation in its tracks, and lower the risk of Alzheimer’s disease,” Cairns said. 

This points to a potential new direction in post-concussion care, aiming to prevent the long-term damage often linked to repeated head injuries.

A breakthrough brain model

David Kaplan, Stern Family Endowed Professor of Engineering at Tufts and co-author of the study, highlighted the significance of their lab-based brain model. 

“The brain tissue model takes us to another level in investigating these connections between injury, infection, and Alzheimer’s disease,” he said. 

This model allows researchers to recreate a realistic brain environment in which they can monitor virus behavior, plaque formation, and inflammatory responses in response to simulated trauma.

“There is a lot of epidemiological evidence about environmental and other links to the risk of Alzheimer’s. The tissue model will help us put that information on a mechanistic footing and provide a starting point for testing new drugs,” he added. 

The model thus serves as a crucial tool in bridging the gap between large-scale health data and the specific biological processes that underlie neurodegenerative diseases.

Targeted interventions for concussions

The study’s findings underscore the potential for antiviral or anti-inflammatory treatments following head injuries to prevent the reactivation of latent viruses like HSV-1. 

This approach could reduce the risk of developing neurodegenerative diseases later in life. Moreover, the research highlights the broader importance of understanding how environmental factors and bodily responses interplay after trauma.

As scientists continue to refine these brain models and further investigate how concussions affect brain chemistry, they hope to develop targeted interventions. 

Such advancements could not only benefit athletes but also countless individuals worldwide who suffer from traumatic brain injuries, potentially transforming post-injury care and long-term health outcomes.

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