Going beyond probiotics: will pathogenic bacteria help us fight eczema in the future?

The human microbiome was the star of this week's science news. In seventeen papers in the journals Nature and PLoS, the Human Microbiome Consortium published the genetic sequences for virtually all the microbes that live in or on the human body. I can't be alone in feeling overwhelmed by the volume of data and analysis. It's clear that the coming years will bring much research into how our body partners with, benefits from, and combats our microbial tenants--which outnumber our cells by a factor of ten.

In a Wall Street Journal story, Michael Fischbach, a professor at the University of California, San Francisco, was quoted as saying "It's likely this work will lead to new treatments for [the inflammatory bowel disorder] Crohn's disease, new treatments for diabetes and metabolic diseases, new treatments for even other diseases, like eczema."

Considering the various locations in the body, the gut and intestines contain the majority of microbes, as you can see in this graphic. A lot of recent work has shown connection between gut flora & systemic inflammation, particularly that involved in asthma and eczema.

A graduate student who reads this blog told me about one of these microbes: Helicobacter pylori. H. pylori has long  lived in the human gut--until the twentieth century, it was apparently the most numerous microbe in the stomach. But it seems that antibiotics have since largely killed it off.

A lot of people would say this was a good thing: only about a decade ago, scientists discovered that H. pylori was the cause of stomach ulcers. But Martin Blaser, a prominent researcher at NYU who made a career out of studying H. pylori, has controversially claimed that it's not just a pathogen but can also do some good. Blaser says H. pylori used to protect us from developing allergic disease. The reason that allergic, atopic diseases are increasing in Western society, Blaser says, is that H. pylori isn't around any more.

The graduate student who wrote me gave me a link to a recent paper in which scientists prevent asthma from developing in lab mice by infecting newborn pups with H. pylori. They show that the way H. pylori is most likely working is that it stimulates the body to produce more regulatory T cells--a class of T cells that put a damper on the activity of other T cells.

In a 2008 story in the Economist, Blaser is portrayed as envisioning a future in which doctors colonize babies' digestive tracts with (presumably) non-pathogenic strains of H. pylori to protect the infants against atopic disease. Certainly a more aggressive form of probiotics than kimchi or yogurt! (Am I allowed to say "probiotics on steroids"?)

I could imagine, also, that there may be no need to use H. pylori at all. If you could arrange things so that a patient grew more Treg cells, that might have the same effect as a H. pylori infection, but a reduced risk of disease caused by the bacteria. Perhaps it will be possible to take a drug that increases the number of Treg cells. Or a patient could donate blood so that Treg cells could be extracted and grown in culture before being reinjected.

I'm excited about this area--admittedly only as speculation about what medicine may hold for us in the distant future. Whenever you're talking about altering the developing immune system, you have to be very careful. Of course, what do antihistamines and steroids do but alter the immune response?