Anthrax stopper
Travis, John
Science News
08-24-2002
SCIENCE NEWS
This Week
Viral enzyme detects, kills bacterium
Last fall, envelopes full of anthrax-causing spores killed 5 people,
sickened about a dozen, and struck fear in millions. Researchers funded by the
The enzyme, called lysin, prevented the death of most mice that the
researchers had infected with a bacterial relative of B. anthracis, Raymond
Schuch of Rockefeller University in New York and his colleagues there report in
the Aug. 22 Nature. The investigators also used the enzyme to create a
prototype handheld instrument that quickly detects the anthrax bacterium, even
in its spore form.
"This is avery clever exploitation" of lysin, says biowarfare
researcher Stephen Morse of
Bacteriophages, or phages, infect bacteria in order
to reproduce inside. Once they do, phages use lysin to
break apart their hosts cell walls so the new phages can
infect other bacteria "They cause the [bacterium] to explode," says
study coauthor Vincent A. Fischetti.
Discovered nearly a century ago, bacteriophages have long attracted the interest of physicians seeking to control bacterial infections. Antibiotics stole the spotlight from phage therapy for many decades, but there's renewed interest in the strategy, given the rise of antibiotic-resistant bacteria (SN: 6/1/96, p. 350; 6/3/00, p. 358).
Over the past few years, Fischetti and his colleagues have exploited the
bacteria-- killing talent of phages in a different way.
They've shown that lysin itself represents a new way to destroy bacteria. For
example, they've successfully used lysin to treat animals infected with
bacteria that cause strep throat and pneumonia in people (SN: 6/10/00, p. 376).
Fischetti's group recently turned its attention to potential biowarfare
agents, starting with the anthrax bacterium. While conventional antibiotics can
treat many strains of B. anthracis, there's concern that resistant strains
could evolve or be created, says Fischetti.
He and his colleagues began working with a phage that
infects the anthrax bacterium almost exclusively and identified the gene
encoding its lysin. In test-tube experiments, the enzyme destroyed strains ofB.
anthracis collected from around the world but left most other bacteria
unscathed.
Next, the scientists tested the enzyme on mice infected with a strain of
Bacillus cereus closely related to the anthrax bacterium. This strain serves as
an initial testing ground for anthrax therapies because
B. anthracis is so dangerous to work with. The B. cereus strain typically kills
infected mice, but treatment with lysin saved up to 76 percent of infected
animals, Fischetti's team reports.
The researchers now plan to test the enzyme against B. anthracis, first in
rodents and then in a nonhuman primate. If those experiments prove successfull,
physicians would then assess the safety of the viral protein in human
volunteers. If lysin passes muster, the
Fischetti's group also built a B. anthracis detector. The investigators
mixed lysin with chemicals that emit a flash of light when exposed to a
substance released by dead bacteria. They also added an agent that induces B.
anthracis spores to germinate, making them susceptible to lysin. Finally, they
engineered a handheld light meter to monitor this broth and found it could
detect a signal produced by as few as 100 spores within an hour of adding them
to the broth.
"It's an innovative and promising strategy," says Morse.
Copyright Science Service, Incorporated Aug
24, 2002
