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“Nematodes may someday be used to 'vaccinate' people susceptible to immunological diseases to lower their risk of developing one or more diseases.”
If you have allergies or immune problems, one reason may be that as a child you failed to get a nematode. Nearly all of the several billion people living in developing countries house nematodes, but in developed countries these pale, parasitic worms are more scarce, rare even. The idea that the loss of parasites has had negative effects on our health is old. What is new is the growing understanding of the mechanisms underlying these effects. Nematodes could save your life—and now we are beginning to know how.
Worms, it turns out, could play a role in treating allergies. It had previously been an unexplained paradox: Globally, allergies and autoimmune diseases are spreading rapidly in the developed world yet not in the developing world. In a paper published in November in the “Letters” section of the journal Nature Medicine, a group of researchers led by Alirio Melendez at the National University of Singapore and William Harnett at Glasgow University offered a resolution. They discovered that some worms can inhibit allergies in some people. Specifically, filarial nematodes, threadlike parasitic worms transmitted by flies and mosquitoes, use a protein, ES-62, to reduce our allergic response, albeit apparently more with their own benefit in mind than our own.
But humans can certainly reap the benefits. As Joel Weinstock, a biologist at Tufts University who was not involved in the study, puts it, nematodes “may someday be used to ‘vaccinate’ people susceptible to immunological diseases to lower their risk of developing one or more diseases.”
Make no mistake, playing with filarial nematodes, a diverse group of worms found in the blood and tissue of the host, can have a cost. Some species, for example, cause elephantiasis, in which men’s testicles swell to the size of grapefruits. But your body is also home to hundreds of species of bacteria, archaea, and protists, and may also have been infected by a dozen or so of the hundreds of thousands of nematode species on earth, most of which are harmless or even beneficial.
But over the last 100 years, “modernity” has changed which species we find in our faunas. We have done away with some—nematodes included—and added others (think drug-resistant staph). We made these changes without much knowledge of what the consequences might be. What happens when we, for example, are deprived of nematodes and other parasites?
Health problems including asthma, diabetes, multiple sclerosis, and acute bowel autoimmune diseases such as Crohn’s disease are far more common where nematodes are rare in humans. Experiments suggest these results may be causative: a nematode a day keeps the doctor at bay. In more and more studies, the presence of nematodes has been shown to reduce autoimmune and allergy problems. Clinical trials are under way in which Crohn’s patients are being given pig nematodes to help alleviate the symptoms of the disease. There is even a new “pharmaceutical nematode,” a treatment containing nematode ova, winding its way through regulatory approval in Europe and the United States.
To figure out how filarial nematodes affect our bodies, Melendez and colleagues tested the effects of a protein produced by some nematodes, ES-62, on mouse and human mast cells. (Mast cells play a key role in allergic responses.) They found that the ES-62 protein blocked the pathway inside mast cells that links anti-parasite antibodies (IgE) to the allergic responses and increased parasite defense. ES-62 kills, or at least gums up, the messenger. In the end, the nematodes’ effect is both to reduce allergic responses and save their own butts.
For Harnett, the biggest immediate implications seem to be that “you can explain the lack of allergy” in individuals with nematodes “by the effects of ES-62 on mast cells and that this has therapeutic implications.” But these new results and research on the effects of other nematodes on our immune system bear implications for treating not just allergies, but also autoimmune diseases ranging from Crohn’s to diabetes.
There is perhaps a broader implication. We have, in the developed world, extricated ourselves from the part of the food web that includes nematodes. While our brains are sure we would rather do without them, our bodies seem unconvinced. You can take man out of nature, but it is harder to take the nature out of man.
March 11, 2008
http://www.burrillreport.com/article-saved_by_worms.html
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