AUTOIMMUNE responses can be initiated by bacteria residing in the small intestine that are able to translocate to other regions of the body, according to researchers from Yale University, Connecticut, USA. The study, which showed that such an autoimmune reaction can be suppressed by targeting the bacteria, suggests fresh approaches for treating chronic autoimmune conditions such as systemic lupus and autoimmune liver disease.
In their research, the team focussed on the bacterium Enterococcus gallinarum to analyse its role in autoimmune conditions associated with immune attack of healthy tissue. As well as discovering that E. gallinarum was able to travel from the gut to lymph nodes, the liver, and spleen, they observed in genetically susceptible mice that when in tissues outside of the gut, the bacterium triggered the production of auto-antibodies and inflammation, which are features of the autoimmune response. The same mechanism of inflammation was then found in cultured liver cells of healthy people, and the team also confirmed the presence of the bacterium in the livers of patients with autoimmune disease.
Following these findings, the researchers were able to suppress autoimmunity in mice by targeting E. gallinarum with an antibiotic or vaccine, restraining its growth in the tissues and its effects on the immune system. This vaccine was injected in muscle to specifically target E. gallinarum and avoid other bacteria that live in the gut.
“When we blocked the pathway leading to inflammation, we could reverse the effect of this bug on autoimmunity,” explained senior author Dr Martin Kriegel, Yale University. “The vaccine against E. gallinarum was a specific approach, as vaccinations against other bacteria we investigated did not prevent mortality and autoimmunity.”
The team believe that the findings have relevance for systemic lupus and autoimmune liver disease and that the use of antibiotics and other treatment approaches like vaccination can improve outcomes in patients with these conditions. Further research is now planned to better understand E. gallinarum and its mechanisms.
James Coker, Reporter
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