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Thursday, 31 August, 2000, 10:55 GMT 11:55 UK
HIV vaccine trials
Vaccine
The vaccine should be safe for the volunteers
Liberal Democrat MP Dr Evan Harris is to test an experimental vaccine for Aids. BBC News Online examines what the scientists are hoping to achieve.


Scientists hope the vaccine on which they are working could eventually save millions of lives.

However, it could be ten years before the vaccine is made widely available.

It is being developed by team based at the Human Immunology Unit of the Medical Research Council.

The vaccine works by stimulating the body's immune system to produce T cells which attack foreign invaders.

The hope is that T cells can be produced in sufficient quantity to kill off HIV-infected cells fast enough to stop the infection growing and spreading to other parts of the body.

They may even be able to rid the body of the virus completely.

The vaccine contains enough DNA from the HIV virus to stimulate the immune system into action.

This genetic material is housed in the shell of a modified vaccina virus which has been weakened so that it cannot spread within the tissues of the recipient.

The vaccina virus was widely used in the 1970s as a component of the smallpox vaccine without any ill effects.

It has also been shown in animal experiments to be non-toxic, and effective at stimulating the production of T cells.

Safe

The scientists are confident that the vaccine is perfectly safe. There is no possibility that the volunteers will be infected by HIV, as there is no live HIV material in the vaccine.

Professor Andrew McMichael
Professor Andrew McMichael is testing the vaccine

Volunteers such as Dr Harris have been carefully selected because they are at very low, or no risk of contracting the HIV virus.

At this stage, the aim of the tests is to measure the strength of the immune system response to the vaccine.

Lead researcher Professor Andrew McMichael said: "The candidate vaccine that we have made tests one concept: that killer T cells will be able to protect against HIV infection.

"Until we do the trial we do not know whether this will work or not."

If the first phase of tests are successful, more extensive tests will be carried out on volunteers in Nairobi. The vaccine was originally developed after scientists noticed that several Kenyan prostitues appeared immune to HIV.

It has proved extremely difficult to produce a vaccine for HIV, as the virus has the ability to conceal itself in organs such as the eyes, brain and testicles.

When conventional blood tests have failed to detect the virus, doctors and patients have been given the false impression that so-called anti-retroviral drugs have stopped the virus spreading.

But all too often the virus has merely hidden and bursts out of the organs and tissues where it is quietly replicating to trigger a relapse.

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31 Aug 00 | Health
MP tests Aids vaccine
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