A “Harmless” Virus May Be Linked to Parkinson's

Scientists at Northwestern Medicine have uncovered surprising evidence linking a common virus—previously thought completely harmless—to Parkinson's. In a small study, they found this virus in the brains and spinal fluid of people with Parkinson's but not in those without it, hinting it could play a role in the condition. The Virus: Human Pegivirus (HPgV) HPgV is a blood-borne virus, related to hepatitis C, but has never been known to cause any illness. Using a tool called ViroFind, which scans for all known human viruses, researchers looked at post-mortem brain samples from 10 people with Parkinson's and 14 without. They found HPgV in 50% of the Parkinson's samples, and none of the controls. Brain Changes & Immune Responses The people whose brains tested positive for HPgV showed more advanced or distinct brain changes, including increased accumulation of tau proteins and altered levels of other critical brain proteins. Blood tests from over 1,000 participants (part of the Parkinson’s Progression Markers Initiative) mirrored these unusual immune signs seen in the brain. Genes May Change How the Body Reacts The study also looked at a common genetic mutation linked to Parkinson's, called LRRK2. In people with this mutation, the immune system reacted differently to HPgV compared to those without the mutation. This suggests genes may influence how the immune system handles viral infections and potentially affect disease development. Why This Matters Parkinson's often appears out of nowhere, with only a small portion explained by known genetic causes. Finding an environmental factor like a virus opens up new paths for understanding and potentially treating the condition. And since HPgV is closely related to hepatitis C, there's even a possibility that existing medications might be adapted to target it if future research supports that approach. What Still Isn’t Known It’s unclear whether HPgV is a cause of Parkinson's or simply appears more often in its presence. That is, did the virus trigger the condition, or did the brain changes caused by Parkinson's allow the virus in? We also don’t know how common HPgV is in the brains of people both with and without Parkinson's. More research with larger groups is needed to answer this.