Clinical trials of parasitic worms to treat MS, related to the "hygiene hypothesis"

13 July 2010 - National MS Society (USA)

At least two small clinical trials are currently underway - one supported with funding from the National MS Society - to test the idea that infection with intestinal parasites may reduce immune attacks in MS.

This idea relates to the "hygiene hypothesis," which states that MS is less common in underdeveloped regions because early exposure to common infectious agents may stimulate the immune response in a positive way and help offset the attack on the brain and spinal cord in MS. These cutting-edge clinical trials should provide important information as to whether this unique approach has the potential to benefit those with MS.

Background: Scientists have noted that autoimmune diseases and allergies are less common in underdeveloped regions. Some researchers have noted that early exposure to common infectious agents - such as that which occurs to people in regions with poor sanitation - may stimulate immune regulation in a positive way and aid healthy immune responses. Because MS is more prevalent in regions with high standards of hygiene, researchers have been testing the hygiene hypothesis - the idea that lack of exposure to common innocuous agents at an early age may cause the immune system to over-react and cause MS.

Studies in MS-like disease in lab rodents and preliminary clinical trials in Crohn's disease, an autoimmune disease of the bowel, suggest that drinking a concoction containing eggs from parasitic worms might alter immune attacks and improve these conditions.

The studies

Based on these and other studies, John Fleming, MD, and colleagues at the University of Wisconsin, Madison, are conducting a small, novel study using the eggs of a harmless parasitic worm - called a helminth - to determine whether the treatment can reduce relapses in people with relapsing-remitting MS.

In the first phase, five participants who declined to take medications approved to treat MS (and who met other study criteria) were given drinks of a solution containing the tiny eggs of the helminth for three months. The eggs hatch and mature inside the body, reaching about the size of an eyelash. When they reach the large intestine, the larvae interact with the immune system and are then killed. MRI scans were taken to determine increases in MS disease activity. In a preliminary report presented at the American Academy of Neurology Meeting in 2009, Dr Fleming noted no safety concerns. There was some indication of benefit on MRI activity, although no conclusions can be drawn from such a small study. The team is submitting a manuscript about these findings for publication.

A second, follow-up study is underway. Dr Fleming's team is recruiting 18 patients at two sites (University of Wisconsin; Marshfield Clinic). Participants are drinking the egg solution every two weeks for 10 months, and are undergoing MRI scans to determine the effects on MS disease activity.

In a separate study using a similar approach, investigators at Rigshospitalet in Denmark are conducting a small study in 10 people with relapsing-remitting MS or secondary-progressive MS (who are still experiencing relapses). The team also is administering the eggs of a helminth to participants every two weeks for 12 weeks, and using MRI to determine if MS disease activity increases during treatment. This study is not yet recruiting participants; read more about it on clinicaltrials.gov.