Helminths, or gut worms, are native inhabitants of our microbiome that are known to have substantial immunosuppressive effects. Some scientists believe they are a keystone species in the microbiome and that their absence in people following a Western lifestyle may be contributing to the rise in autoimmune diseases, such as celiac disease. In fact, scientists have recently shown that hookworm infection leads to higher gluten tolerance in individuals with celiac disease. The cause of hookworm’s broad immunosuppression is unknown, but those same scientists investigated the possibility that it may be caused by the worms’ ability to modulate the bacteria in the gut. The researchers recently tested this hypothesis and published their results in Nature Scientific Reports.
First, the researchers measured the fecal microbiota of eight human subjects with celiac disease, all of whom had followed a gluten free diet for at least five years prior to the trial. Compared to a control group that hadn’t followed a gluten free diet, the trial subjects had a greater abundance of Bacteroidetes, while the control group showed greater abundance of Firmicutes. Next, the subjects were successfully infected with hookworm and gluten was slowly reintroduced into their diets over a period of 44 weeks. The scientists measured the subjects gut microbiota at different time points and discovered that the hookworms, in conjunction with the gluten introduction, restored levels of Firmicutes in the celiac disease patients. By the end of the study all of the remaining participants had rich abundances of both Bacteroidetes and Firmicutes.
It should be noted, and the authors admit, that the study is limited by its small sample size. Still though, the results lead one to believe that helminths are modulating the microbiome, and that this may contribute to the overall immunosuppressive effects of these worms. People have been known to practice helminth therapy to achieve immunosuppression in the gut, however this is dangerous for a number of reasons. Instead researchers, such as the ones that performed this study, are in search of the mechanism for this immunosuppression. There is certainly some very interesting biology that occurs during a helminth infection, and hopefully sometime soon scientists can turn these helminths into therapies.