In a decade-long effort, Johnson, K. Reed Clark of Nationwide Children's Hospital in Columbus, Ohio, and their team developed immunoadhesins, antibody-like proteins designed to attach to SIV and block it from infecting cells.

Then they needed a way to get the immunoadhesins into the cells.

The researchers selected the widely used adeno-associated virus as the carrier because it is an effective way to insert DNA into the cells of monkeys or humans. That virus was injected into muscles, where it carried the DNA of the immunoadhesins. The muscles then began producing the protective proteins.

Scientists first tested the idea in mice and then turned to monkeys because SIV is closely related to HIV and would be a good test model.

A month after administering the AAV, the nine treated monkeys were injected with SIV, as were six not treated in advance.

None of the immunized monkeys developed AIDS and only three showed any indication of SIV infection. Even a year later they had high concentrations of the protective antibodies in the blood.

All six unimmunized monkeys became infected; four died during the experiment.

The next step is moving toward human trials, Johnson said. He said he is working with the International AIDS Vaccine Initiative in hopes of getting tests in humans under way in the next few years.

At the same time of this new development, contrary to what some are saying, studies continue and not everyone has given up on a more ordinary vaccine approach. A minority of HIV-infected individuals, called elite controllers, suppress the amount of virus in their bodies indefinitely, without needing drug therapy. Scientists are trying to determine the precise immune responses that protect elite controllers, in order to devise a vaccine that would replicate those responses.

There are documented cases of individuals who have been repeatedly exposed to HIV but have not become infected. These individuals, known as exposed seronegatives, were first described among female sex workers in Nairobi, Kenya. Some research has indicated that some of these exposed seronegatives have immune responses against HIV, suggesting the immune system is at least partly responsible for their protection. If it is, they may hold the key to an effective vaccine.

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Nearly 7,500 people a day are infected with HIV. A vaccine with only 30% efficacy and 20% coverage could avert 5.5 million infections by 2015.

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Don't become a statistic. Practice Safe Sex.

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