Important note: Information in this article was accurate in 1997. The state of the art may have changed since the publication date.

Reuters NewMedia, Inc. - Friday November 28 10:51 AM EST
Patricia Reaney

As news that AIDS cases soared to 30 million worldwide hit the headlines and amid preparations for World Aids Day on Monday, doctors in Britain said a small trial of a potential vaccine had proved promising.

Researchers at Britain's Medical Research Council who tested a vaccine based on a manufactured protein called rgp120 on 30 healthy volunteers found it was 10 times more potent than other experimental therapies.

Tests on animals in the Netherlands showed it protected them from an AIDS-type virus.

"We should be cautiously optimistic," Dr. Tim Peto told BBC television.

"We've got lots of drugs to test. There may be 15 or 16 drugs good enough to actually prolong life 10-15 years. The challenge is to do trials on different mixtures and find out how to give them, what order to give them and how many to give at once.

Rgp 120 is similar to one of the components in the outer shell of the human immunodeficiency virus (HIV) that causes AIDS. The vaccine uses new additives, known as adjuvants, which are combinations of compounds that are designed to increases the response of the immune system to the HIV-like protein.

"We think rgp120 is an important component of any potential HIV vaccine. It stimulates the immune system into responding to the coating of HIV, even though there is no virus there," said Professor Jonathan Weber, who conducted the study.

"The results of the study are that the new adjuvants containing three chemicals, triple adjuvants called SBAS2, is very potent," he added in an interview.

If further tests on animals are successful large-scale trials with human AIDS patients could follow.

Doctors in the United States have already volunteered to test a live virus vaccine on themselves but the National Institutes of Health say it is too dangerous.

The U.S. researchers believe that if the vaccine works -- it is made up of a genetically weakened but live strain of the AIDS virus -- an AIDS vaccine could be developed within 10 years.

Since the AIDS virus was identified in 1984, medical developments to combat the deadly disease have been swift.

First the drug AZT, then combination drug therapy and the celebrated protease inhibitor compounds have offered hope to sufferers, but "real world" conditions have shown they are not as effective as clinical trials had suggested.

After promising early results, patients often develop resistance to the drugs.

The problem in finding an effective treatment is the virus's complexity. HIV is the most variable virus ever studied.

"The high rates of replication, mutation, and recombination of HIV enable the virus to evolve rapidly in the host and so outstrip immune responses evoked by natural immunity or a vaccine," Professor Charles Bangham, of Imperial College School of Medicine in London, explained in The Lancet medical journal on Friday.

HIV replicates in the body very quickly. It makes mistakes when it makes copies of its genetic code and these mutations allow it to evade the immune system and antiviral drugs. The virus is also latent in some cells and infection can re-emerge when, for whatever reason, it becomes reactivated.

So for any vaccine to be effective it needs to protect against more than one strain of the virus.

Bangham and his colleague, Professor Rodney Phillips of John Radcliffe Hospital in Oxford, believe hope for a vaccine lies in the fact that the human immune system seems to suppress HIV in early infection.

Animal studies have also shown that infection with a weakened virus -- what the U.S. doctors want to try -- may protect against more virulent strains.

"The reason there is some cause for optimism in vaccine development is that there are clearly conserved parts of the virus. The body can mount an immune response to these bits of the virus that do not change and are relatively constant over time," said Weber.

"Things are going in the right direction. There has been a lean period in the last few years but there is progress once again."

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