A common feature in many chronic inflammatory diseases is dysbiosis – alterations in the type and number of microbes that typically reside in the human gut. Some of these microbes are highly motile due to the presence of flagella, which contributes to the microbes' pathogenic qualities. A new study suggests that immunization against the protein flagellin may confer protection against some chronic inflammatory diseases.

Flagellins are structural components of the flagella of gram-negative bacteria. Flagella provide bacteria motility, which facilitates penetration of the gut mucosa and drives the activation of pro-inflammatory responses.

The study involved wild type mice that received weekly peritoneal injections of purified bacterial flagellin for 10 weeks. The injections elicited a robust immune response to the flagellin, manifested in elevated antibody counts that lasted approximately three months after the injections ceased. Furthermore, the gut microbial composition of the mice was changed to a more favorable makeup, and the mice were protected against mucosal penetration, experimentally-induced colitis, and the negative effects of diet-induced obesity.

These findings suggest that repeated exposure to flagellin proteins immunizes mice against chronic diseases by reducing immune response-related inflammation.

• Link to press release.
• Link to full study.