Monday, April 26, 1999 Published at 21:52 GMT 22:52 UK
'Safe' Aids vaccine developed
Harmless fragments of DNA from HIV are the key to the vaccine
A "safe" HIV vaccine has been successfully tested, in what researchers say is a major breakthrough in the fight against the virus.
The only vaccines that previously showed any promise were "live" vaccines, in which the virus is partly disabled. However, widespread fears that the vaccine could mutate and cause infection has meant this approach is unpopular.
"We challenged the vaccine using a highly virulent virus which normally kills the monkeys in six months, but the vaccine was still effective," research leader Dr Harriet Robinson told BBC News Online.
The scientific advance was welcomed by the UK's biggest Aids charity, the Terrence Higgins Trust.
"This is great news," says Andrew Ridley, the charity's director of operations. "This is clearly a step on the way to finding a vaccine for HIV and a vaccine is the only way to end the scourge of HIV."
However, Dr Robinson points out: "We didn't completely prevent infection, but we contained it below the level that we could detect it using very sensitive tests."
Dr Robinson says that everyone eventually wants to have a foolproof vaccine, but that this new work represents significant progress: "Now, 16,000 people a day around the world get HIV, if we can change that to one person a week, that would be tremendous."
Work has begun on the next phase of pre-clinical trials, again using macaque monkeys, and focussing on the doses required. Dr Robinson says her "dream" is to see phase one clinical trials in humans begin within a year.
The final vaccine should be "relatively inexpensive", an important consideration given that the most devastating epidemics of HIV are frequently in poorer countries. At present, the vaccination requires two separate injections of different materials.
The second part uses the same DNA but packs it inside a pox virus. The virus is excellent at invading cells and this helps produce very high levels of the HIV proteins inside the cell. The pox virus used was part of the smallpox eradication programme and is known to be safe.
The development of an HIV vaccine has been extremely difficult. HIV eludes the antibodies which should capture viruses invading the body. It also destroys the helper T cells which are vital in co-ordinating the body's immune response.
The new vaccination method, published in Nature Medicine, shows that this formidable foe can be beaten.