JOHANNESBURG, South Africa – Each day, 13,000 people worldwide contract the virus that causes AIDS, the United Nations estimates. But two decades after the disease was first identified, scientists are still struggling to find a vaccine that could help contain its spread.

More than 70 AIDS vaccines have reached human trials. But only one has made it to advanced testing, and it has shown little sign of being effective, according to the International AIDS Vaccine Initiative, an advocacy organization.

“Making a vaccine has turned out to be much more difficult than we ever believed,” Barton Haynes, a leading vaccine researcher at Duke University, said back in 1999. Today, he and other equally frustrated scientists around the globe have abandoned their race to be first to create an effective vaccine and decided to try something new: cooperation.

Using a model pioneered by the Human Genome Project, AIDS researchers worldwide are joining forces and sharing labs, data, technology and funding to try to solve some of the most intractable mysteries surrounding HIV infection, with the aim of finally producing a vaccine that works.

With 40 million people now infected with the virus and 45 million more expected to get it by 2010 without intervention, “we all feel a sense of extraordinary urgency,” said Haynes, who leads one of the first two investigative centers created under the new Global HIV Vaccine Enterprise, which was launched last year.

The centers, one based at the U.S. National Institute of Allergy and Infectious Disease and the other at Duke University, will pull together AIDS experts from throughout the world – including from India, South Africa, Thailand and China – to do what Haynes calls “desperately needed” basic research on HIV infection in clinics and laboratories in major infection zones, particularly sub-Saharan Africa.

At public clinics in South Africa, Malawi, Uganda and Tanzania, for instance, researchers will use RNA tests to try to find between 600 and 1,000 people who are in their first few days of HIV infection and who have not yet begun producing antibodies to the virus. Then they will track them in an effort to understand, for the first time, how the virus behaves in its first few days in the human body and how the body responds.

The data produced from such studies and other research information – including, potentially, the genetic sequencing of the virus itself – will be put on a public Web site for use by all AIDS researchers and members of the “virtual consortium.” Scientists will use the data to try to come up with new ideas for a vaccine, with the aim of getting vaccine candidates in human testing by 2009.

Basic research should help “tackle the big questions,” said Dr. Salim Abdool-Karim, director of the Center for the AIDS Program of Research in South Africa, one of the members of the new consortium. But “the roadblocks are so large and fundamental it’s impossible to predict when we’ll overcome this hurdle,” he said.

South Africa, with one of the largest AIDS epidemics in the world, has more than 5 million people infected with the virus, which means “South Africa and Africa have the most to gain” from a vaccine, said Carolyn Williamson, an AIDS researcher at the Institute of Infectious Disease and Molecular Medicine at the University of Cape Town.

South Africa already is involved in creating and testing potential AIDS vaccines, but its vaccine candidates – like most of those worldwide – show promise only in limiting the level of virus in the bloodstream of those who become infected, rather than curing their infection altogether.

The problem, scientists say, is that most vaccines – for diseases such as measles, for instance – help a newly infected person clear the virus or bacteria from the blood, ensuring the disease never develops. With HIV, however, there is no known case of an infected person ever clearing the virus from his body, which means an effective vaccine would have to prevent infection in the first place to be effective.

“We’re trying to do something that has not been accomplished for any vaccine yet,” Haynes said.

Nearly all the HIV vaccines currently in human trials – about 30 – focus on achieving a particular kind of immune response in the bloodstream to the virus. The first results from those studies should be released next year. The new research effort, however, will also focus on some neglected areas of study, including the possibility that a nasal-spray vaccine could stimulate the body’s mucus linings – including in the genitals – to neutralize HIV before it enters the bloodstream and causes infection.

Researchers warn that finding such a vaccine will take time, even with a cooperative effort.

“The vaccine will not be a “Eureka!’ moment. It will be a very slow process,” Williamson said.

South African scientists say that even a lesser vaccine that keeps the level of the virus low in people who become infected would be a help. Although it would not necessarily save their lives, it could help lower the likelihood they pass the disease to others, slowing the rapid transmission of the disease in sub-Saharan Africa.

Essentially such a virus would mean “not curing individuals but curing a population,” said Dr. Clive Gray of the National Institute of Communicable Diseases in Johannesburg.

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