Massachusetts researchers are beginning a clinical trial using eggs from the pig whipworm parasite Trichuris suis to modulate the autoimmune attack that produces Crohn's disease, a severe form of bowel inflammation. Preliminary results suggest that the harmless worms can tamp down the immune responsethat produces Crohn's without the side effects of existing drugs, which leave patients more susceptible to infectious diseases. The eggs are also being tested against other forms of autoimmune disease, including irritable bowel syndrome and multiple sclerosis.
The concept was developed at the University of Iowa by Dr. Joel Weinstock, a gastroenterologist who is now at Tufts Medical Center in Boston. It is based on what is known as the "hygiene hypothesis," an idea formulated by many researchers. Epidemiologists have noted that autoimmune diseases are more common in countries with the highest levels of sanitation; in such countries, the rates are even higher in the richest classes. The hygiene hypothesis suggests that poor children are more likely to be in contact with parasites and other infectious agents during childhood and that these organisms modulate the immune system somehow, making an autoimmune attack less likely.
Weinstock chose to work with T. suis because it does not appear to produce any ill effects in pigs. In humans, the worms grow for about two weeks before dying off, also without producing any apparent harm. Previous small trials have shown that the eggs can modulate the human immune system and ameliorate the symptoms of inflammatory bowel disease.