AIDS vaccines must be combined with prevention

BARCELONA, Spain, July 9 (Reuters) - Vaccines are considered the best hope for defeating AIDS but experts emphasised the continued need for traditional prevention methods and drugs to stop the illness that kills someone every 10 seconds.

"HIV vaccine development is not a sprint. HIV vaccines need to be developed within the context of a larger prevention effort," Dr Lawrence Corey, of the HIV Vaccine Trials Network in the United States, told an AIDS conference on Tuesday.

Many scientists and AIDS activists believe predictions of a vaccine within five years are too optimistic, and Corey said education and methods to prevent sexual and blood transmission of the virus are vitally important.

The need for a vaccine has never been more urgent -- 40 million people have AIDS and nearly 600 are infected with HIV every hour.

Many different vaccine approaches have been tried, but progress has not been as quick as many had hoped because of HIV's continually changing outer envelope and its use of many different strategies to evade the immune system.

Economic issues have also played a part because vaccine development is a risky venture and drug and biotech companies can make more money developing drugs to treat diseases than making vaccines to prevent them.

"Vaccines still do very poorly when you look at the economic realities of it," said Corey.

Vaccines have to be not only highly effective but also inexpensive and have negligible toxicity.

NEW DEVELOPMENTS

California-based VaxGen's (VXGN) AIDSVax vaccine is the most advanced vaccine and will have preliminary results from human safety and efficacy trials in early 2003. If it proves successful the company hopes to make it available by 2005.

But many AIDS experts believe the vaccine, which uses a protein from HIV's outer surface to produce antibodies against the virus, will not work on its own.

The International AIDS Vaccine Initiative (IAVI), a global non-profit organisation spearheading vaccine development, is backing a dual vaccine developed by Oxford University to produce a cellular immune response, which is the basis of most AIDS vaccines in clinical trials.

IAVI also launched a consortium to speed up development of vaccines to stimulate the immune system to make broadly neutralising antibodies against HIV.

Combining the killer instincts of cell-mediated immune defences and virus-blunting neutralising antibodies is thought to be one of the best vaccine approaches.

There have been some advances in cell-mediated immunity but stimulating broadly neutralising antibodies has been more difficult.

"We believe this is a solvable problem, because broadly neutralising antibodies that block HIV have been isolated from a few rare humans. We just do not yet know what it takes to get the body to make them," said Seth Berkley, president and CEO of IAVI.