The researchers found that people with parasitic infections have these unique protein fragments in their bloodstreams, while unaffected people have few or none. “We think the worm modifies this protein as an immune invasion tactic,” says Ganley-Leal, who presented the research at a conference in Boston earlier this week. “By blocking IgE’s ability to bind to cells, we think the worm is protecting itself, and that also seems to protect the host.” Her team is now producing this modified protein, which they plan to test in mice that have the human version of IgE receptors. Ganley-Leal has formed a company called Epsilon Therapeutics to commercialize the technology.
This mechanism is just one possible explanation for parasites’ protective effects. Because parasitic worms coevolved with us for the vast majority of human history (even mummies have them), they likely evolved ways to turn down the immune system just enough to permit their survival without severely harming their hosts. “I think the consensus, if there is one, is that chronic worm infections induce an immunoregulatory response in the body,” says Mitre. “Exactly how that immunoregulatory milieu is set up remains unknown.”
In fact, the IgE system may have evolved as a way to keep parasites in check. As our environment became cleaner and infection more rare, at least in rich countries, pollen and food allergies may have developed as collateral damage. By studying these organisms, “we may be getting at the basic pathophysiology of these diseases,” says Weinstock. “In terms of drug discovery, this is a major unexplored area. But it’s hard to know if a single component of worms will ever work as well as worms themselves.”
At this point, worm-based treatments are further along in clinical development than worm-inspired ones. A study found that infecting inflammatory bowel disease sufferers with pig whipworms helped alleviate symptoms, although a similar study with allergic rhinitis sufferers showed no effect. (This may be due to the choice of worm–pig whipworms live in the gut and thus may not exert a strong enough effect on the respiratory system.) A handful of other clinical trials are currently under way.