New research has revealed a connection between ancient viral DNA embedded in the human genome and the genetic risk for a major disease that affects the central nervous system. The researchers said their findings offer evidence that specific viral sequences within our genome contribute to the risk of neurodegenerative diseases.

The study, conducted by researchers from King’s College London and Northwell Health, focused on human endogenous retroviruses — remnants of ancient retroviral infections that are now fixed features within our DNA. The team identified specific HERV gene expression signatures linked to multiple sclerosis. These findings suggest that viral elements within our DNA may play a role in the development of the disease. 

Neurodegenerative diseases are characterized by progressive degeneration and loss of neurons, resulting in the deterioration of the nervous system’s structure and function. MS is amongst the most common neurodegenerative diseases affecting young adults. 

The study marks an important advance in understanding the complex genetic architecture of neurodegenerative diseases. While previous studies hinted at a connection between HERVs and these conditions, this is amongst the first to pinpoint specific HERVs that are linked to disease susceptibility. These sequences are not just static fossils derived from ancient viral infections — they must be actively influencing brain function in ways we are only beginning to understand.

The researchers analyzed data from hundreds of brain samples to map out the relationship between HERV gene expression and genetic risk factors for four neurodegenerative diseases: Parkinson’s disease, Alzheimer’s disease, amyotrophic lateral sclerosis and MS. They identified a robust HERV signature linked to amyotrophic lateral sclerosis, and another linked to MS. These viral sequences appear to be involved in homophilic cell adhesion — a process essential for communication between cells in the brain. No robust signatures were observed for Alzheimer’s and Parkinson’s disease, although the authors highlight that larger studies may uncover novel associations in the future.

As the global burden of neurodegenerative diseases continues to grow — with more than 50 million people currently affected worldwide, a number projected to nearly triple by 2050 — these insights offer a promising direction for future research and treatment development. This discovery opens up new possibilities for therapeutic interventions targeting HERVs. By better understanding how these viral elements drive disease, researchers hope this could aid the development of novel treatments that could mitigate the effect of neurodegenerative diseases.

The researchers said they now need to better understand how these HERVS affect brain function, and whether or not targeting HERVs could offer new therapeutic opportunities.

The findings were published in the journal Brain, Behavior, and Immunity.