Gut bacterium R. gnavus linked to lupus flares



New York University researchers have found a ninefold increase of the bacterium Ruminococcus gnavus in the intestines of particularly ill lupus patients.

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Not only that, but those patients also had highly elevated antibodies to an endotoxin-like antigen released by one particular R. gnavus strain.

That antigen is “very proinflammatory, very immunogenic. We are wondering if this is actually [what drives] the immune activation that results in immune complexes in the glomeruli” of patients with lupus nephritis, said investigator Gregg Silverman, MD, a professor of medicine and pathology and head of the laboratory of B-cell immunobiology at New York University.

R. gnavus is an obligate anaerobe found in the guts of most people, but in lupus, it might be a problem.

“We are finding a very specific relationship with lupus patients and this bacteria – and this particular antibody,” Dr. Silverman explained in an interview at an international congress on systemic lupus erythematosus. “There’s an expansion of this particular bug, but also a contraction of others” as disease activity progresses.

“It speaks to an imbalance,” he added, and it suggests a role for probiotics or even fecal transplants to restore order.

“What if instead of killing the immune system” in lupus treatment, “we should be reducing or removing a single bacterium or a single molecule?” he asked.

Dr. Silverman is one of many researchers working to unravel the role of the human microbiome in both disease and health. His findings are preliminary, and, as he cautioned, correlation is not causation. But the implications are remarkable, Dr. Silverman noted.

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