In 2007, parasite immunologist P'ng Loke sat down for lunch at a University of California, San Francisco, cafeteria with an inquisitive man who had called him earlier that week. Their chosen topic of conversation would deprive many people of an appetite, but the scientist and his guest shared an intellectual hunger for a stomach-churning subject: gut worms—specifically, tiny worm-like parasitic organisms called helminths that live nestled in the gastrointestinal tracts of their hosts.
Loke was fully prepared to answer the man's questions about the parasites he knew so well, but what he did not realize was that his companion had more than just questions—he had worms burrowed in his intestinal walls, worms he had deliberately swallowed. Together, Loke and the worm-wrangler embarked on a research project, the results of which appear today in the December 2010 issue of Science Translational Medicine.
The 35-year-old man who had lunch with Loke was quite healthy in 2007. But only a few years earlier he was in the throes of an inflammatory bowel disease known as ulcerative colitis. An autoimmune disease, ulcerative colitis inflames the colon and leaves it rife with open sores; patients experience intense abdominal pain, vomiting, diarrhea, rectal bleeding and weight loss. While searching for treatments, the man discovered the work of Joel Weinstock, a gastroenterologist, parasitologist and immunologist at Tufts University who has pioneered research on helminthic therapy—treating autoimmune diseases by deliberately infesting patients with parasitic worms, such as whipworm and hookworm.
The results of Loke's new case study—the most recent of only five studies that investigate helminthic therapy in people instead of animals—suggest that helminths may ease the symptoms of autoimmune diseases by increasing mucus production.
"It's a unique study—there's nothing like it before," says Weinstock, who was not involved in the new research. "In this case they had a very unique patient—one who was self-infecting with helminths." Clinical trials on helminthic therapy are particularly difficult to arrange because helminths are live pathogens and have not been officially approved as therapeutic agents by any governmental agency, although the U.S. Food and Drug Administration has granted pig whipworm (Trichuris suis) the status of Investigational New Drug. In contrast to human whipworm (Trichuris trichiura), the porcine variety cannot survive inside the human gut for very long.
"The researchers noticed a specific pattern of behavior, cycling between remission and active disease depending on when the patient infected himself with helminths," Weinstock adds. "This is not a double-blind study, but the pattern is highly suggestive that the worms helped this patient. The major point of this paper is the potential mechanism—mucus production—which has not been looked at properly before."