http://news.independent.co.uk/uk/science/story.jsp?dir=64&story=99903&host=3&printable=1
Government scientists are developing a new anthrax vaccine after
encountering problems with the existing preparation, which was designed by military
personnel.
Side-effects and the ineffectiveness of the current vaccine to provide
long-term immunity have led scientists to experiment with a genetically
engineered version.
Clinical trials of the vaccine are scheduled to begin next year, according
to a spokesman for the Defence Science and Technology Laboratory (DSTL) at
Porton Down in Wiltshire.
Studies at the military arm of the Porton Down research facility are
understood to have identified potentially serious difficulties with the
existing vaccine, which is based on a dead strain of the bacteria.
Research presented by scientists to the Fourth International Conference on
Anthrax, held in Annapolis, Maryland, earlier this year, said a genetically
modified vaccine could solve many difficulties, such as side-effects and the
need for regular booster injections.
The vaccine is made by extracting the DNA of the anthrax microbe to isolate
the gene for its protective antigen – which stimulates the human immune system
– and then injecting this gene into a harmless bacterium which can be grown in
fermenters to manufacture the vaccine.
A genetically engineered vaccine would be "cleaner" than the
existing vaccine, which contains extraneous components of the anthrax cell that
are believed to be involved in causing the side-effects seen in some inoculated
people.
A Porton Down spokesman said the existing vaccine is probably able to
protect against infection for a year before a booster is needed. But a clinical
trial to test the ability of the British vaccine to protect humans against
anthrax has never been carried out.
The spokesman said: "We've done animal studies with the anthrax vaccine
and it works but it's an impossible clinical trial to do [now]. There's no
objective clinical trial in individuals who otherwise would have got anthrax.
"The current vaccine works [but] it will give side-effects, and a small
proportion of people will get sore arms. It needs regular boosting to remind
the immune system what it looks like."
Animal studies and laboratory experiments involving tests for human
antibodies suggest the current vaccine will protect most people, but the only
clinical trial on humans at risk of anthrax involved an American vaccine and
took place in the US in 1962.
Workers in a wool mill were involved in this trial, which compared several
hundred vaccinated individuals against an equal number of unvaccinated
"controls". The vaccine was found to offer effective protection
against respiratory anthrax, the form of the disease that is most likely to
result from a terrorist attack.
"The other problem with producing the existing vaccine is that you are
fermenting anthrax bacteria," the DSTL spokesman said. The production
process of a genetically modified vaccine would be safer because harmless
microbes would be cultured instead.
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