Herpes virus may easily enter brains, causing damage

A new study on mice suggests that the herpes simplex virus (HSV) could be entering the brain more easily than previously thought. Researchers found that when HSV type 1 infects through the nose, it can cause rapid nerve damage and inflammation in the brain. Months after infection, the mice displayed increased anxiety, motor problems, and cognitive issues. Dr. Deepak Shukla from the University of Illinois Chicago (UIC) highlighted the alarming long-term effects of this infection route. It is still unknown if humans face the same severe consequences, as they typically have better defenses against herpes. However, in rare cases, HSV has been known to infect human eyes, noses, and brains, causing serious neurological problems. Researchers believe the nasal pathway might allow the virus to bypass the blood-brain barrier, which normally protects the brain from infections. They propose that the virus could reach the brain more directly from the nasal cavity through tears. Dr. Shukla pointed out that the neurological effects of herpes infections are often underdiagnosed and more serious than those from typical oral or genital sores. In mice with HSV-1 eye infections, an enzyme called heparanase (HPSE) was found to increase, contributing to inflammation in the brain. When mice's brains were infected via the nose, those with HPSE showed worse cognitive outcomes. Conversely, mice lacking HPSE had less inflammation and performed better cognitively. This suggests that targeting HPSE could help in treating HSV-1's effects on the brain. The study raises concerns that HSV-1 might play a role in cognitive decline. Research has linked the virus to higher chances of developing dementia. While severe infections in humans are rare, their long-lasting impact may be more common. Ongoing research aims to understand why HSV can reactivate and what triggers these flare-ups, especially as they may lead to conditions like Alzheimer’s. The findings emphasize that HSV, a widespread infection affecting two-thirds of the global population, might contribute to brain health issues more than previously realized. These insights offer potential avenues for new therapies to reduce neuroinflammation and limit brain damage caused by viral infections. The study was published in the journal mBio.