Archive for March, 2012

Our “old friends” in a brand new world – a tale about worms and microbes

Tuesday, March 27th, 2012

The topic of this blog post is controversial and I would say “intriguing”. I just came back from Europe and watched some presentations of different researchers in a very “cozy” city called Bergamo in Italy. The most interesting talk was about the “hygiene hypothesis”. Well, humans have a very strong aversion to worms in general and one of these are helminths (the so-called “old friends” in the title of this post) that colonize our gastrointestinal tract. These worms can be pathogenic, cause digestion discomfort and they are uncommon in the developed countries but still occur in poor countries and the ones under development. In fact, there is an inverse correlation between the percentages of autoimmune disease incidences in the world and helminth infestation (see figure above). Recent research by several epidemiologists has shown a paradox with an opposite view of helminths suggesting that the recent increase in allergic and autoimmune diseases such as, for example, Multiple Sclerosis, occurred mainly because of increased improvement in sanitation (see the editorial “Helminths and multiple sclerosis: Will old friends give us new treatments for MS?” for more details). Even more disturbing is the suggestion that helminths may protect humans from autoimmune diseases and also allergic reactions. To prove this hypothesis, researchers did an experiment with Multiple Sclerosis (MS) patients. One group of patients was infected with helminths and the other wasn’t. After some time, the symptoms of MS patients infected with helminths disappeared and the ones without the worms worsened. These results are unexpected but have a scientific explanation: the improved control of the MS patients’ symptoms was associated with cellular immune responses characterized by decreases in immunomodulators and increase in other factors with concomitant induction of imunne regulatory cells (for more information see “Helminth-derived immunomodulators: can understanding the worm produce the pill?”). Essentially, in the infected MS patients it was if gastrointestinal helminth infection acted as a virtual immunological “switch”: when present helminths significantly turned off MS activity; however when helminths were removed by drug treatment, MS activity was turned on again. These results are controversial and more research is needed to understand why the worms can turn the MS activity off, but they are indeed intriguing. If the increase in autoimmune disorders and allergic reactions is associated to the elimination of worms in the developed countries, the “hygiene hypothesis” could explain more than we think about this increase in autoimmune diseases. Another fact worth to mention is the increased use of antibiotics in the developed world: in fact, microbiome research is showing that the microbes in people with autoimmune diseases such as Crohn’s and IBD is different from people without the disease. These new insights and theories that are emerging will be very important for a better understanding of why there has been an increase in autoimmune diseases in the developed world. The answer could be in the worm and microbe population that were always in “symbiosis” with our body and now we are “killing” them. New studies are warranted, but the worms are more important than we have thought for sure…