An experimental vaccine developed by a Johnson & Johnson (JNJ) unit and the U.S. military protected monkeys against an animal version of the AIDS virus, a study found.

Monkeys that got the vaccine were as much as 83 percent less likely than those that got a dummy shot to become infected with simian immunodeficiency virus, or SIV, researchers from Harvard Medical School and the U.S. Military HIV Research Program said in a study published online in the journal Nature today. They now plan to test the vaccine in humans.

While previous vaccine trials have helped to keep AIDS at bay by controlling the virus in infected monkeys, this is the first to prevent monkeys from becoming infected, said Dan Barouch, a professor of medicine at Harvard’s Beth Israel Deaconess Medical Center who led the study.

“There’s more hope now than ever before that the development of a safe and effective HIV vaccine is indeed possible,” Barouch said in a telephone interview today.

The research builds on the first partially successful HIV vaccine trial in Thailand in 2009, which showed that two inoculations that hadn’t worked on their own offered some patients protection when given in combination. The first prompts the immune system to produce so-called killer T-cells that are primed to hunt and destroy infected cells, and antibodies that go after the virus itself. The second repeats the dose, boosting the body’s defenses.

The results in that trial showed about a 31 percent reduction in infections compared with placebo, though the benefit waned after a year.

The search for a vaccine to prevent HIV has eluded scientists since the early 1980s. While there are treatments for HIV that limit the virus in the body, holding AIDS at bay for years, there is no cure. AIDS, which is caused by HIV, killed 1.8 million people in 2010, and new infections with the virus fell to 2.7 million, according to a November report by the Joint United Nations Programme on HIV/AIDS.

Barouch and colleagues experimented with four different combinations of the so-called prime-boost approach, using disabled cold viruses and pox viruses as Trojan horses to ferry SIV proteins into the monkeys. Unlike other vaccine trials, they then exposed the animals to a strain of the virus that was genetically different to the one used to design the vaccine.

 “That’s called stacking the cards against yourself,” said Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health, which helped to fund the research.

After the first of six exposures, as few as 12 percent of the vaccinated monkeys became infected, compared with 75 percent of those that got a placebo. While most of the animals were infected by the sixth exposure, that doesn’t mean the same would be seen in humans because the virus used in the trial was about 100 times more infectious than that to which humans are typically exposed, Barouch said.

The scientists also found that the vaccines worked best when they contained a viral protein called Env, which is used to build the outer shell of the virus. That indicates

The most promising of the combinations was one that featured a prime vaccine developed by Crucell NV, the Leiden, Netherlands-based company that Johnson & Johnson, of New Brunswick, New Jersey, bought last year, and a booster developed by the U.S military and NIAID. The researchers plan to test that combination in people “in the near future” Barouch said.

The research was funded by the National Institutes of Health, the U.S. military, the Bill and Melinda Gates Foundation and the Ragon Institute at Harvard, the Massachusetts Institute of Technology and Massachusetts General Hospital. (Bloomberg)