Biofilms consist of surface-associated bacteria surrounded by an extracellular matrix (think dental plaque). Biofilms often form on urinary catheters and orthopedic implants, where the bacteria may infect bone or enter the blood stream. However, researchers at Temple University Health System have now implicated gut biofilms in the development of systemic lupus erythematosus, an autoimmune disease. Cagla Tukel, PhD, and Stefania Galluci, MD, report their findings in the journal Immunity.
Lupus is a systemic inflammatory disease, and flare-ups can cause joint pain and swelling, skin lesions, fatigue, fever, and the characteristic "butterfly" facial rash. Tukel and Galluci knew that lupus flares also coincided with bacterial infections, particularly Salmonella, and questioned whether gut-resident biofilms play a role. The group showed that Escherichia coli and Salmonella typhimurium, common gut bacteria, form biofilms containing extracellular DNA and amyloid fibers (curli).
When they exposed dendritic cells to E. coli or Salmonella DNA/curli complexes, they produced pro-inflammatory cytokines, such as type-1 interferon. Then, when lupus-prone mice were injected with the DNA/curli complexes, they produced auto-antibodies typical of lupus within two weeks. Such a response to other bacterial products, like lipopolysaccharide, generally takes up to five months.
Tukel and Galluci are now collaborating with Roberto Carrichio, MD, Director of the Temple Lupus Clinic, to probe for DNA/curli complexes in lupus patients. They also plan to develop a mouse model to understand just how the DNA/curli complexes move to the bloodstream from biofilms in the gut.
Sources: Science Daily, Mayo Clinic, Amyloid-DNA Composites of Bacterial Biofilms Stimulate Autoimmunity. Immunity, 2015; 42 (6): 1171