About 2880 candles are seen lit during a World AIDS Day event in Jakarta

About 2880 candles are seen lit during a World AIDS Day event in Jakarta (Dadang Tri, Reuters)

Michael said it has been a major effort to secure new research partners and funding, including support from host countries, as well as to persuade rivals Novartis and Sanofi to work together. The teams still need to retool the vaccines to work in South Africa, where the strain of HIV is different.

"We're really working as fast as we can," said Michael, who expects large-scale effectiveness studies to start in 2016.

The hope is to have at least 50 percent effectiveness, a level that mathematical modelers say could have a major impact on the epidemic. Michael thinks this might be the pathway for getting the first HIV vaccine licensed, possibly by 2019.

Vaccine experts are equally excited about a vaccine that Michael's team is developing with Harvard University and Johnson & Johnson's Crucell unit, which uses weakened versions of a common cold virus and a smallpox virus.

A study published in February showed this vaccine protected monkeys from a virulent strain of HIV. Animals that did become infected after repeated exposure also had low levels of virus in their blood. Safety studies in human patients are just starting, with large-scale efficacy studies slated for 2016.

NEXT-GENERATION VACCINES

The current crop of vaccines is largely designed to train immune system cells known as T-cells to recognize and kill cells already infected with HIV. While these trials progress, scientists are working on even more advanced vaccines that activate powerful antibodies to prevent HIV from infecting cells in the first place. Both would be administered before a person becomes exposed to the virus.

Most modern vaccines use this antibody approach, but HIV's extreme skill at mutating makes it difficult for specifically targeted antibodies to identify and neutralize the virus.

Teams led by Dr. Dennis Burton of the Scripps Research Institute in La Jolla, California, Dr. Michel Nussenzweig at Rockefeller University in New York, Dr. Gary Nabel of NIAID's Vaccine Research Center, Haynes at Duke and others have focused on rare antibodies made by 10 to 20 percent of people with HIV that can neutralize a broad array of strains.

Researchers think a vaccine that can coax the body into making these antibodies before HIV exposure would offer a powerful foil to many forms of the virus.

Such antibodies seek out and latch on to regions of the virus that are highly "conserved," meaning they are so critical to the virus that they appear in nearly every HIV strain. By attaching to the virus they make it incapable of infecting other cells.

Until 2009, scientists had identified only a few broadly neutralizing antibodies, but in the past few years teams have found dozens.

So far, scientists have isolated the antibodies, identified what part of HIV they target and even know the exact shape they make, Koff said. Researchers are now using this information to design vaccines that prompt the immune system to make them.

"We're not there yet," Nabel said.

NIAID this month said it will spend up to $186 million over the next seven years to fund the Centers for HIV/AIDS Vaccine Immunology & Immunogen Discovery. The new consortium is focused on making vaccines that induce these protective antibodies, with major grants going to Duke and Scripps.

Nabel said no vaccine being tested today "is likely to hit it out of the park," but many researchers do feel advances in broadly neutralizing antibodies are key to developing a highly successful HIV vaccine.

"It's really a new day when we start to think about where we are with AIDS vaccines," Nabel said.

(Editing by Michele Gershberg and Prudence Crowther)