|This image shows massive aggregates of the bacterium (purple) in the skin of hepcidin-deficient mice with lethal septicemia.
Graphic: Courtesy of João Arezes
Every summer, there are people who sicken, and some die, after eating raw shellfish that is tainted with a bacterium called Vibrio vulnificus or who have an open wound and come in contact with bacteria-laden saltwater. People with a weakened immune system, chronic liver disease or iron-overload disease are most at risk for severe illness.
Researchers at UCLA have figured out why those with iron-overload disease are so vulnerable: The overabundance of iron in their blood and tissue provides prime growth conditions for Vibrio vulnificus. The study also found that minihepcidin, a medicinal form of hepcidin — the iron-regulating hormone that is deficient in people with the disease hereditary hemochromatosis — that lowers iron levels in blood could cure the infection by restricting bacterial growth.
Researchers compared the fatality of Vibrio vulnificus infection in healthy mice with mice that lacked hepcidin, modeling human hereditary hemochromatosis. The results showed that the infection was much more lethal in hepcidin-deficient mice because they could not decrease iron levels in the blood in response to infection.
Giving minihepcidin to susceptible hepcidindeficient mice to lower the amount of iron in the blood prevented infection if the hormone was given before the Vibrio vulnificus was introduced. Additionally, mice given minihepcidin three hours after the bacterium was introduced were cured of any infection.
The next stage of research is to understand why Vibrio vulnificus bacteria become so lethal when iron levels are high.
“Hepcidin-Induced Hypoferremia Is a Critical Host Defense Mechanism against the Siderophilic Bacterium Vibrio vulnificus,” Cell Host and Microbe, January 2015