Gut bacteria have been linked to an ever-increasing number of diseases. Research is now going beyond establishing a link between a disorder and the community of gut microbes, and has begun to identify specific organisms that are responsible for certain conditions. Scientists have now shown that a strain of bacteria in the Subdoligranulum genus can lead to the production of autoantibodies, which appears to cause the development of rheumatoid arthritis. The findings have been reported in Science Translational Medicine.
Rheumatoid arthritis is an autoimmune disease in which the joints are erroneously attacked by the immune system, and the inflammation and damage that occurs in affected joints causes pain, the loss of mobility, and other serious problems. Disruption of mucosal immunity, in the gut, has been proposed to be one cause of rheumatoid arthritis.
In this work, the researchers obtained blood samples from people who are at risk of developing RA, and the autoantibodies were isolated from those samples.
The scientists found that the autoantibodies were causing a response in certain bacteria in the Lachnospiraceae/Ruminococcaceae families. Further work revealed that bacteria of the genus Subdoligranulum, a member of those families that was isolated from the feces of people ate risk for RA, could bind to the autoantibodies and cause the activation of CD4+ T cells. This was occurring in individuals with RA, but not in healthy people.
The Subdoligranulum bacteria was put in an animal model, and the animals began to develop the same RA risk markers found in the blood of people who are at risk for RA. Some of the animals also developed RA.
"Through studies in humans and animal models, we were able to identify these bacteria as being associated with the risk for developing RA. They trigger an RA-like disease in the animal models, and in humans, we can show that this bacterium seems to be triggering immune responses specific to RA," said study leader Kristine Kuhn, MD, Ph.D., an associate professor at CU School of Medicine.
This microbe could be a good therapeutic target for RA treatment, noted Kuhn. Now, the scientists want to assess large populations of people who are at risk for RA to see if the Subdoligranulum microbes are also linked to other factors like genetics, mucosal immunity, and environmental conditions that can lead to RA. It may help scientists find prevention strategies or other ways to stop the microbes from causing disease, added Kuhn.
Sources: CU Anschutz Medical Campus, Science Translational Medicine
