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Using an animal model, scientists have
discovered a way to inactivate the lethal toxin produced by
the anthrax bacterium.
The findings provide a potential
route to therapy of anthrax that could complement antibiotics.
Anthrax infection -- lately in the news
because of its potential for use as a biological weapon --
can be contracted by humans through the skin or by inhalation.
Antibiotics can treat the infection,
but they must be given quickly.
And while they may kill the anthrax bacterium, they cannot
inactivate the lethal toxin it produces.
By the time symptoms of anthrax contracted
by inhalation have appeared, it is generally too late to rescue
an individual with antibiotics, because he or she will succumb
to the toxin the bacteria has already produced.
Anthrax releases three nontoxic proteins
that assemble themselves into the toxin. Investigators have
identified a protein,
known as a polyvalent inhibitor, that blocks
this assembly.
The researchers have tested the polyvalent
inhibitor of toxin action by mixing it with a potentially
lethal dose of the lethal toxin and injecting the mixture
into rats.
Normally, the lethal dose of toxin will
kill the animal within 90 minutes. In the presence of the
polyvalent inhibitor, the animals survived
and showed no symptoms.
This finding supports the notion that
this inhibitor could be used to block toxin action in infected
humans and rescue them. According to the researcher, inhalation
anthrax is the most deadly form of the disease.
It is contracted by inhaling anthrax spores -- durable, hard-shelled
"seeds" containing the bacterium.
The spores begin to grow in the lungs
and enter the bloodstream, where they produce the anthrax
toxin. The toxin acts by killing certain immune system cells
that normally guard against bacterial invaders. In so doing
it also causes changes in metabolism that lead to death.
Nature
Biotechnology October 2001;19:958-961
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