The common cold sore is a more serious illness than most think. According to a new study, the virus causing the cluster of blisters can take hold of the brain's most important regions and trigger neurological diseases.
It was previously found that herpes simplex virus type 1 (HSV-1), the virus that causes cold sores, can infect the brain and central nervous systems. However, a new study by researchers from the University of Colorado and the University of Bourgogne in France shows how it infiltrates the central nervous system after entering through the nasal passages, what parts of the brain it affects most, and the other diseases it may initiate.
"Identifying how HSV-1 can get into the brain and what brain regions are vulnerable is key in understanding how it initiates disease," explained Christy Niemeyer, neurology assistant professor at the University of Colorado Anschutz Medical Campus and corresponding author of the study.
Published in the Journal of Virology, the study used mice's brains to map out the regions affected by the virus. They found that HSV-1 enters the central nervous system through the trigeminal nerve or the olfactory nerve.
Once it enters the brain, it penetrates vital sections, including the brainstem which connects the brain to the spinal cord and regulates breathing, heart rate, and blood pressure; and the hypothalamus, controlling hormone release, appetite, mood, and body temperature.
The cold sore virus also caused an inflammation of microglia, resident cells of the brain that regulate brain development and maintenance of neuronal networks. Notably, the inflammation persisted even after the virus had gone.
In the most rare and serious cases, the virus may cause encephalitis or the inflammation of the brain caused by viral or bacterial infections. Johns Hopkins Medicine reports that 10% of patients die of the condition, although HSV-1 may only cause a mild case of the illness.
"Persistently inflamed cells can lead to chronic inflammation, a known trigger for a number of neurological and neurodegenerative diseases. This research offers important takeaways in better understanding how viruses interact with overall brain health as well as the onset of pervasive neurological diseases," Niemeyer added.
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