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- An international team of microbiologists have taken the
first steps in developing a completely new type of vaccine to combat tuberculosis.
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- The treatment uses fragments of DNA from the TB microbe
to stimulate the immune system and ward off infection. It is a novel approach
that is currently being tried with a range of diseases including Aids and
malaria.
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- TB kills about three million people every year. It is
estimated that the bacterium that causes the disease, Mycobacterium tuberculosis,
is carried by over a third of the world's population.
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- Although there are antibiotics available, problems of
drug resistance, and the sheer cost and availability of long-term medication
in many parts of the world, mean that new strategies for tackling the disease
are being sought.
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- Disabled bacterium
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- The best approach, of course, is prevention, by means
of vaccination, and many people will be familiar with the BCG injection.
But such vaccines are not always entirely effective.
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- The research team are hoping for even better results
from their new DNA vaccine. Unlike the BCG, which is based on a disabled
version of the whole bacterium, the new vaccine incorporates just specific
pieces of DNA taken from the microbe.
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- The proteins which are created in the body using these
bits of DNA will hopefully trigger an attack on the disease by the immune
system, and provide the desired protection against future infection.
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- In research published in the Journal Nature, mice infected
with TB showed a marked decline in their levels of infection after being
given the DNA vaccine. There was evidence that the mice's bodies started
to employ a far more effective type of immune response.
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- Better protection
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- Dr Doug Lowrie, from the UK's National Institute for
Medical Research, says the studies undertaken by the team suggest they
are on the trail of an improved treatment for existing infections as well
as a promising new method of vaccination.
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- "We had in mind that we might be heading towards
something that would prevent infection," he says. "But during
the studies, it became apparent that we'd stumbled on something which would
actually change the immune system in infected animals and possibly infected
people. This would enhance their resistance to the disease and improve
their treatment."
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- If all goes well, the vaccine could be used in clinical
trials for humans early in the next millennium.
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- "If we were are extremely lucky and the vaccine
that we have at the moment does not need much modifcation, we might be
in clinics within one or two years, perhaps," he told the BBC.
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- "The first application is likely to be in those
patients who are dying of a multidrug-resistant tuberculosis where there
is really nothing else on offer."
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- Clinical trials
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- DNA vaccines are a new idea, and are not yet in general
use.
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- But they are seen as a tool of great potential that could
provide a means of combating many illnesses for which there are, at present,
few effective treatments.
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- "There are about half a dozen different clinical
trails, in different parts of the world, against a range of different diseases,
things like influenza, malaria, HIV which causes AIDS, hepatitis B, and
herpes.
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- "There is some caution about how effective they're
likely to be. Perhaps the most encouraging results have come from potential
vaccine candidates against malaria, where the immune response has looked
very encouraging"
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