Could a virus be causing Parkinson’s disease?
New research is raising the possibility that a virus that is seemingly otherwise harmless to humans could possibly trigger the onset of Parkinson’s disease.
The data from Northwestern Medicine published in July shows that some cases are linked to genetics but that most are not, and the cause is still not known. However, one clue in some of the cases shows a common thread. Post-mortem analysis of the brains of some Parkinson’s patients detected the Human Pegivirus (HPgV) which is a blood-borne virus in the same family as hepatitis C. Researchers were surprised to find the virus in many cases and at how the immune system responded to it.
The study examined brains from 10 people with Parkinson’s and 14 without, with researchers finding HPgV in half the people with Parkinson’s and none in those without it. They then examined nearly 1,000 blood samples of people with and without Parkinson’s and found similar results. Those with a Parkinson’s-related gene mutation showed different immune system responses to HPgV compared to those without the mutation. That could suggest the virus may enter the human brain through the nose, damaging neurons related to motor function.
“We don’t know what any of this stuff actually means, we don’t know what the underlying trigger in Parkinson’s disease is just yet,” says Dr. Timothy Leichliter, a neurologist with Allegheny Health Network (AHN). “It’s always been, well, there’s some sort of genetic underlying component to this, there’s some sort of environmental trigger component to this, but we’ve never really been able to pinpoint either very well. Now, we’re starting to make some headway here in genetics by picking up some abnormal genes and mutations, and now in the realm of environmental triggers.”
Those environmental triggers are especially concerning as Southwestern Pennsylvania lies in what’s known as the “Parkinson’s Belt,” where there’s as much as a 56% greater risk of developing the disease due to pollution and pesticides. This area is heavily related to the Rust Belt across parts of the Midwest and Great Lakes where Parkinson’s disease rates are significantly higher than the national average.
With more than one million people in the U.S. living with Parkinson’s and no known cure, the possibility of a viral trigger opens new avenues for prevention and early detection.
“Now, we’re starting to kind of wrap our heads around, could there be these other triggers, which is why some people get Parkinson’s disease, and some people don’t,” says Leichliter. “We haven’t quite unraveled it. We’re still trying to figure it out.”
If you’re never heard of this virus, you’re not alone. Even Leichliter admits he had to look it up himself.
“It doesn’t cause any medical problems or infectious problems that we know of, and all of a sudden, now we find people with Parkinson’s disease seem to have this virus more than people who don’t,” he says. “When you look at that, it seems like, could there be something here? I’ll be interested to see where we take this and see if we can actually come up with some underlying cause.”
The Parkinson’s Belt idea comes from the fact that states within each have or have had their own toxic industrial pollutant problems.
“We think it’s all the pollution that when these people now in their 60s and 70s, when they were kids were exposed to when there was high industry here and there was a lot of pollutants here, and what kind of chemicals were they using?”
He went on to discuss trichloroethylene, which is the biggest chemical discussed in Parkinson’s disease research, even though no link has been established yet.
When it comes to the research involving the pegivirus, doctors are still trying to put together the pieces of the puzzle and determine whether it truly can cause the disease.
“We’re still trying to figure out why people get this and how can we prevent it,” says Leichliter. “If we can figure it out, can we stop it? Can we slow it down? Can we cure it? That’s probably the take-home message that we’re learning through all of this is kind of that Parkinson’s disease is not one thing. It’s really a syndrome.”
He explains that Parkinson’s itself is a collection of symptoms and the more we can find underlying causes or genetic variants or specific environmental triggers, the closer we’ll be to answers.
“The more we can unravel and figure out these underlying causes or triggers or potential types of Parkinson’s disease, I think the closer we’ll be to curing it or at least finding disease-modifying medications.”