Thursday, December 27, 2012

The price of not having worms

It seems we may be missing out on the benefits of worm infection in our too-clean world. For a long while in human evolution, gut worms helped to train and balance our immune systems, and their absence may make some of us more likely to develop an oversensitive gut-based immune reactions.  

For instance, developed nations have the highest rates of inflammatory bowel disease or IBD, where the immune system mistakenly attacks intestinal cells. Such autoimmune diseases occur when processes meant to attack foreign invaders (e.g., viruses, bacteria, parasites) mistakenly attack healthy tissue and cause inflammation. Crohn's disease and ulcerative colitis are the two main kinds of IBD.  

The Mix chose to broach this somewhat nauseating subject because researchers just published a study in the journal PLOS Pathogens that found giving worm eggs to monkeys protected them from the simian version of IBD.  

That article, covered by Scientific American, also mentioned that worm-based IBD treatments will soon be tested in human trials. Specifically, researchers are looking at whether or not whipworm eggs that infect pigs (but never humans) could trigger a worm-specific immune response that counters human IBD. Worm eggs may be able to trick the immune system into thinking it has a worm infection, and to trigger a specific kind of worm-related response that happens to counter gut inflammation. 

We asked UAB’s Peter Mannon, M.D., professor in the UAB School of Medicine’s Division of Gastroenterology and Hepatology, for his take on the study and on the rise of worm-based medical therapies to counter gut inflammation.

One benefit of living in a world where we are regularly infected by viruses, bacteria and parasites is that they teach our immune system what to attack, and what to ignore, says Mannon.  The immune systems of mice raised in germ-free conditions never mature, and become less capable of fighting off infection in their intestines.

Mannon is also an expert in the gut microbiome, the complete set of bacteria inhabiting the human gut. Many are commensal, having co-evolved alongside the human body to help it digest foods. Interestingly, the abnormal gut inflammation in IBD not only damages human cells, but also the helpful bacteria we keep in our guts on purpose. Thus, studies underway seek to describe specific changes that take place in gut microbiomes when they are exposed to inflammation.  

“I think, given the strong consumer interest in products like probiotics, that the potential use of such worm-egg therapies would be acceptable to most patients, as long as they know the cannot possibly get worms from them," said Mannon.

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