Enterococcus gallinarum, a species of bacterium found in the small intestines of humans and mice, can travel to other organs and trigger an autoimmune response, according to a new study published in the journal Science. The findings suggest new approaches for treating chronic autoimmune conditions, including systemic lupus and autoimmune liver disease.
Gut bacteria have been linked to a range of diseases, including autoimmune conditions characterized by immune system attack of healthy tissue.
To shed light on this link, Dr. Martin Kriegel from the Yale School of Medicine and co-authors focused on Enterococcus gallinarum, which is able to spontaneously ‘translocate’ outside of the gut to lymph nodes, the liver, and spleen.
In models of genetically susceptible mice, the researchers observed that in tissues outside the gut, this bacterium initiated the production of auto-antibodies and inflammation — hallmarks of the autoimmune response.
They confirmed the same mechanism of inflammation in cultured liver cells of healthy people, and the presence of Enterococcus gallinarum in livers of patients with autoimmune disease.
Through further experiments, the scientists found that they could suppress autoimmunity in mice with an antibiotic or a vaccine aimed at Enterococcus gallinarum.
With either approach, they were able to suppress growth of the bacterium in the tissues and blunt its effects on the immune system.
“When we blocked the pathway leading to inflammation, we could reverse the effect of this bug on autoimmunity,” Dr. Kriegel said.
“The vaccine against Enterococcus gallinarum was a specific approach, as vaccinations against other bacteria we investigated did not prevent mortality and autoimmunity.”
“The vaccine was delivered through injection in muscle to avoid targeting other bacteria that reside in the gut.”
While the researchers plan further research on Enterococcus gallinarum and its mechanisms, the findings have relevance for systemic lupus and autoimmune liver disease.
“Treatment with an antibiotic and other approaches such as vaccination are promising ways to improve the lives of patients with autoimmune disease,” Dr. Kriegel said.
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S. Manfredo Vieira et al. 2018. Translocation of a gut pathobiont drives autoimmunity in mice and humans. Science 359 (6380): 1156-1161; doi: 10.1126/science.aar7201