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A study has unveiled a chilling possibility: Common viruses, including SARS-CoV-2 that causes COVID-19 and the Herpes Simplex Virus-1 (HSV-1), may be stealthily invading our brains, potentially laying the groundwork for devastating diseases like Alzheimer’s.
These viruses can induce protein clumping in the brain — a hallmark of neurodegenerative diseases, stated the article published in the journal ACS Chemical Neuroscience. These conditions occur when nerve cells gradually lose their function and die, impacting movement, balance, speech, breathing, and heart function.
Scientists have long suspected that COVID-19 can affect the brain, as evidenced by symptoms like fatigue, persistent headaches, and “brain fog,” which impairs memory and concentration. Millions of individuals continue to experience long-term neurological issues, commonly referred to as “long COVID,” the paper noted.
“The large and increasing number of people with post-COVID neurological symptoms has renewed the interest in the link between viruses and neurodegenerative brain disorders. There have been similar findings with other post-viral syndromes, including HSV-1 and its link to Alzheimer’s disease,” the researchers wrote.
A 2022 study published in the Journal of Alzheimer’s Disease reported that older adults with COVID-19 had a significantly higher risk of developing Alzheimer’s disease within a year of their diagnosis. The findings underscored the need to investigate the mechanisms underlying this potential link.
To explore this connection, the researchers analysed cerebrospinal fluid (CSF) — a clear, protective fluid surrounding the brain — from healthy participants. They incubated the fluid with live HSV-1 and ultraviolet-inactivated SARS-CoV-2 viruses.
CSF exposed to these viruses triggered protein aggregation, meaning clumping together of proteins. Meanwhile, the samples without viral exposure showed no such activity over time.
Many of the proteins identified in these clumps are known to play roles in neurodegenerative diseases and have been detected in amyloid plaques (protein clumps found in the tissue between the nerve cells) from patients.
The components of amyloid plaques have also been linked to other neurodegenerative diseases that affect movement like kuru and Creutzfeldt-Jakob disease.
The researchers speculated that viruses may catalyse protein aggregation, depleting essential proteins and their functions. This, they suggest, could be one way in which viruses contribute to neurodegeneration.
The study called for further research into protein levels in the CSF of patients with neurological symptoms following viral infections. Such investigations could provide deeper insights into the mechanisms at play.
The researchers also emphasised the need for robust patient databases and more sensitive methods to detect viruses in the brain. “Understanding the mechanisms by which viruses may cause neurological disorders is especially important due to the SARS-CoV-2 pandemic which has led to a large number of people suffering from long-COVID neurological symptoms post infection,” the experts wrote.
