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1-Proteins: Volcanic pool enzyme kills prions

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TITLE:  Volcanic pool enzyme kills prions
SOURCE: New Scientist, UK, by Gaia Vince
DATE:   Jul 29, 2003

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Volcanic pool enzyme kills prions

A new disinfectant, based on enzymes collected from a volcanic pool, is
showing promise in destroying the mutated prion proteins that cause vCJD,
the human form of BSE.

These prions are notoriously difficult to break down, and because an
unknown number of people in the UK have vCJD, there is a theoretical risk
that surgical instruments could transmit the disease. The disinfectant
could also be effective against the prions that cause sporadic CJD, which
occurs spontaneously and has been spread surgically.

Standard decontamination procedures, such as detergents, UV inactivation
and high-pressure boiling at 137 C, have proven unsuccessful at
destroying all the prions on contaminated equipment.

But now researchers at the UK's Centre for Applied Microbiology and
Research (CAMR) in Porton Down and biotechnology company Genencor believe
they have developed a prion eradication agent.

"Essentially it's a protease enzyme, which is active at high alkalinity -
pH 12 to 14 - and a temperature of between 60 and 80 C," says CAMR's
Phil Luton. "It requires an incubation period of less than one hour under
the enzymes' optimal conditions to degrade the prions."

Bond breaker

The researchers tested a variety of different enzymes, before selecting
the most effective. This was a genetically modified version of a
naturally occurring, thermostable enzyme found in volcanic pools and was
produced by Genencor.

"The enzyme appears to be very promising from the preliminary research
findings, although it will need to undergo further tests," says UK-based
prion expert John Stephenson. "It works by chemically breaking down the
bonds between amino-acids in the protein."

He told New Scientist: "We don't know why prions are so highly stable,
but they are extremely hard to destroy. Indeed, one standard method of
decontamination - soaking in fomaldehyde - actually stabilises the prions."

Stephenson notes that several other research groups are exploring similar
ways of decontaminating surgical instruments.

Tonsil trouble

Safety procedures issued by the UK Department of Health (DoH) in 1999
require surgical instruments used on patients with suspected vCJD to be
quarantined until diagnosis is confirmed or discounted.

"The surgery of highest risk is brain or eye surgery, although
tonsillectomy also carries risk," says Stephenson. "Studies have shown
that tonsils removed from patients with vCJD have quite high levels of
infected prions, although infection has never been found in tonsils from
those with the sporadic CJD."

In January 2001, the DoH ordered the use of disposable tonsillectomy
kits, but this was reversed in December 2001 after the kits caused a rise
in surgical complications.

Since 1990, 132 people have died of vCJD in the UK, with 659 succumbing
to sporadic CJD. The number of people infected with vCJD remains unknown
and there is no diagnostic test. Epidemiological data suggest the
epidemic is still growing, with a final death toll as high as several


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