June 18, 2019
A common type of bacteria living in the gut may spark a common lupus complication called antiphospholipid syndrome, a study partly funded by the Lupus Research Alliance shows. Antiphospholipid syndrome can lead to blood clots and miscarriages. Led by Dr. Martin Alexander Kriegel of Yale School of Medicine, the research may also help explain why patients’ symptoms recur.
The immune system makes a mistake in lupus and produces proteins called antibodies that damage the kidneys, joints, and other parts of the body. Close to half of people with lupus have antiphospholipid antibodies that target molecules in the outer layer of the body’s cells.
Researchers think that in patients with lupus, the immune system tries to destroy molecules from healthy cells because they look like molecules from bacteria. Dr. Kriegel and colleagues found that a tiny organism called Roseburia intestinalis, which is one of the most common bacteria in the intestines, may cause some of these attacks. The researchers found that these bacteria contain parts of molecules that are very much like the parts of a blood protein targeted in patients with antiphospholipid syndrome. They discovered that patients with antiphospholipid syndrome make antibodies that hone in on the same piece of the bacterium as in the blood protein and that these antibodies correlate with each other. When the scientists gave the bacterium to mice prone to lupus, the animals showed signs of antiphospholipid syndrome.
“Our results suggest that Roseburia intestinalis may be a chronic trigger for antiphospholipid syndrome,” says Dr. Kriegel. “Because the bacteria are so common and stable in the human gut, they may keep sparking attacks by the immune system and cause patients’ symptoms to return again and again. Dr. Kriegel and his colleagues revealed their findings in the journal Cell Host & Microbe.
“The microbiome is of great interest in lupus, and we are excited to see Dr. Kriegel’s results fulfill the promise of his LRA grant,” noted Kenneth M. Farber, President and CEO, Lupus Research Alliance. “This work points to a new approach to treating antiphospholipid syndrome, a dangerous complication of lupus.”