Anthrax toxin can lurk for days in cells as a lingering threat

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Anthrax toxin can lurk for days in cells as a lingering threat The deadly toxin produced by anthrax bacteria can hide out in human cells for days, invisible both to our immune systems and to the cellular machinery responsible for destroying proteins. The findings reported in the Cell Press journal Cell Reports on November 14th explain why antibiotics aren't always enough to cure anthrax infections.

"The anthrax bacteria kills people in a very short period of time, and this is in large part due to the production of the anthrax lethal toxin," said Gisou van der Goot of the École Polytechnique Fédérale de Lausanne. "This toxin disarms our immune system, but also, as very recently shown, affects our heart."

"Many years ago, we had noticed that the effect of anthrax lethal toxin was detectable for more than a week in cells that had been exposed to the toxin for less than one single hour," she added. "We wanted to understand how this was possible."

To find out just how the anthrax toxin could do its damage over time and space, in the new study the researchers examined the toxin's complex delivery route. The toxin itself has two main ingredients: the damaging lethal factor itself and a protective antigen required for cells to take up and move that killer protein.

Protective antigen helps the lethal factor enter cells by forming channels. Van der Goot and her colleagues now confirm their earlier suspicion that those channels might be capable of delivering toxin not just into cells themselves, but also into smaller sacs or vesicles within the larger cell.

Once safely inside those vesicles, the lethal factor can persist for days without degradation, the researchers show. They were surprised to find that while sheltered inside those vesicles, the toxin can also be passed on from one cell to its daughters and from one cell to another.

The findings help to explain why anthrax infection is so devastatingly deadly, but this new understanding of these bacterial weapons and their sneaky behavior does come with an upside for science.

"By studying these interactions, we can learn more than how to fight anthrax infection," van der Goot said. "We also learn a lot about how cells work. "

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Cell Reports, Abrami et al.: "Hijacking multivesicular bodies enables long-term and exosome-mediated long-distance action of anthrax toxin."

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