Eat your worms
It's hard to imagine that infection with a parasitic worm could be good for you, but there's evidence to show that such a treatment may be useful in IBD. Microscopic worm eggs, mixed into a drink and swallowed by the patient, hatch in the intestine and grow into small organisms. Then the immune system reacts to these organisms, eventually getting rid of them. Researchers believe that the interaction between the worms and the immune system triggers regulatory pathways to stop the rampant inflammation that is the hallmark of IBD.
But how does treatment with worms really work? This question captivates AHFMR Scientist Dr. Derek McKay: It is the focus of one of the major research programs in his lab at the University of Calgary. His group works with parasitic helminths, a scientific classification for various types of parasitic worms that live in the intestines of humans and animals.
"We want to understand how treatment with a parasite can block inflammation," explains Dr. McKay. "The idea is to identify all the cells, mediators, and pathways that are involved. Pilot studies to date have shown that having people ingest helminth eggs is feasible. But there's always a risk in introducing any species where it is not meant to be. If we understand how the worms actually interact with the immune system, we may be able to identify molecules that could be used as drugs to treat IBD."
Experiments on animal models in Dr. McKay's lab show that the immune system of the host responds to the worms by producing an anti-inflammatory molecule. But clinical trials using this molecule in humans have been unsuccessful. Dr. McKay's results in animals suggest that success may depend on eliciting this anti-inflammatory response naturally, in the right place and at the right time.
Asked to speculate about how this might translate to people, Dr. McKay gives this scenario: It might be possible to give IBD patients a helminth infection to trigger the interleukin-10 response on purpose. The patients would then be treated with drugs to clear the worm infection. But their immune systems would "remember" the infection. Subsequently, if the IBD flared up, the patients could be treated with a worm antigen rather than the live worm. The antigen—a substance that, by definition, prompts the immune response—would trigger the appropriate reaction and treat the inflammation.
"This is very exciting, but it is some ways down the road," notes Dr. McKay. "That's the beauty of model systems; they can give you clues to what's happening in humans."