Four years ago, a potential HIV vaccine showed promise against the virus that causes AIDS, but it fell short of providing the broad protection necessary to stem the spread of disease.
Now researchers -- led by Duke Medicine and including team members from the National Institute of Allergy and Infectious Diseases of the National Institutes of Health, the U.S. Military HIV Research Program and the Thailand Ministry of Health -- have gained additional insights into the workings of the vaccine that help explain why it benefited a third of recipients and left others vulnerable. The findings, reported in the Jan. 10, 2013, issue of the journal Immunity, are providing new options for vaccine designers to strengthen the drug.
"This study shows what types of antibodies the vaccine induced and gives us information that can guide the study of future vaccine trials," said senior author Barton Haynes, M.D., director of the Duke Human Vaccine Institute. "Understanding how this vaccine works is important to develop strategies to make it better."
The research team focused on an HIV vaccine candidate tested in Thailand called ALVAC. In 2009, AIDS researchers reported that the vaccine protected 31.2 percent of study participants from HIV infection. It was an encouraging protection rate, but short of the minimum 50-percent efficacy required to slow the epidemic, which afflicts an estimated 34 million people worldwide.
Since that time, researchers have been studying the vaccine for clues to its successes and failures in the hopes of making improvements. Haynes and colleagues reported last year they had found a correlation between a key antibody response to the drug and a lower risk of infection.
"But that was a correlation of risk, not necessarily a correlation of protection," Haynes said. "We couldn't prove that the antibody was the cause of protection."