New AIDS vaccine blueprint calls for more focus

By Maggie Fox, Health and Science Editor

WASHINGTON, Aug 5 (Reuters) - AIDS vaccine researchers should move to smaller, more focused trials and dump any vaccines that do not show strong promise, the International AIDS Vaccine Initiative said on Tuesday.

The group, known as IAVI, released a blueprint for how to proceed at an international meeting of AIDS experts and activists in Mexico City.

Dr. Seth Berkley, president and chief executive officer of IAVI, said the failure last year of a high-profile Merck and Co (MRK.N) experimental shot should not mean the end of the quest -- even though some experts have been calling for an end to expensive AIDS vaccine trials.

"Developing an AIDS vaccine may take more time and innovation than we might have once imagined, but we are confident that science will prevail. The necessary direction for the field is clear," Berkley said.

More than 25 years since the AIDS epidemic started, there is no vaccine against the fatal and incurable virus, although more than 20 drugs are on the market to help control its symptoms.

The human immunodeficiency virus that causes AIDS is especially tricky to vaccinate against because it easily evades immune defenses and mutates constantly.

Berkley said it is not unexpected for a vaccine to take decades to develop and he thinks HIV can be beaten.

"We have got to create this new mechanism to be able to turn the AIDS vaccine into a normal product development initiative so that every time there a failure, it doesn't raise the question of whether this is the end of the line," Berkley said in a telephone interview.

For instance, the IAVI blueprint notes it took 25 years to create a vaccine against the human papilloma virus or HPV, which causes cervical cancer, and there are still no vaccines against tuberculosis or malaria.

"Strong scientific evidence in both humans and animal models suggests that developing an AIDS vaccine is possible," said IAVI's Dr. Wayne Koff.

SHIFTING RESOURCES

If money is steered away from testing vaccines just to see if they work, an expensive proposition, it might free up resources to solve the trickier scientific roadblocks, Berkley said.

IAVI'S plan calls for solving the scientific challenges to make an AIDS vaccine, such as finding a way to activate the two arms of the human immune system against the virus.

The vaccine must generate neutralizing antibodies -- immune system proteins that flag and attack invaders such as viruses, as well as so-called cell-mediated immunity -- the T-cells that directly attack invaders.

"Before vaccines go into efficacy trials they need to go through a set of screenings to look at evidence they are significantly better," Berkley said.

It might be possible to improve a vaccine's power by using things like another type of virus to carry the vaccine into the body, Berkley said.

"We are pushing a whole new generation of vectors. We have got candidates coming down the pipeline on that," he said.

The approach mirrors one being taken by the National Institute of Allergy and Infectious Diseases, part of the U.S. government's National Institutes of Health, to funnel spending more to lab work and animal tests rather than expensive large-scale vaccine trials on humans.

The nonprofit IAVI is helping to test five vaccines along with the National Institutes of Health, academic research institutions and companies such as Targeted Genetics (TGEN.O), Therion Biologics, Crucell NV (CRCL.AS) and GlaxoSmithKline Biologicals (GSK.L). (Editing by Julie Steenhuysen and John O'Callaghan)