In 2009, the HIV research field was rocked by the results of a vaccine study conducted in Thailand, the first HIV vaccine success in the epidemic’s 30 years of existence. Finally, scientists had a real starting point to fight this devastating disease.
The vaccine in the RV144 HIV study — often called the "Thai Trial" — protected 31 percent of heterosexuals from new HIV infections, a huge step forward in the hunt for a successful vaccine against the virus that causes AIDS.
But the trial’s partial success meant nothing without understanding why this vaccine succeeded where others had failed. This year, Fred Hutchinson Cancer Research Center scientists helped answer that question.
The Hutchinson Center has the largest team of infectious disease researchers of any U.S. cancer center and is a global leader in HIV research. Our scientists manage the world’s largest HIV vaccine program, the HIV Vaccine Trials Network.
Statistician Dr. Peter Gilbert is an expert at detecting “correlates of protection” in HIV vaccine trials. These correlates are signals from our immune system that it is successfully protecting us from infection. Identifying correlates of protection could dramatically speed up trials to test new candidate HIV vaccines and enable scientists to build a vaccine that specifically elicits those signals.
Gilbert, collaborating with a team of HIV vaccine researchers, including the Hutchinson Center’s Dr. Julie McElrath and scientists at Duke University, led an effort to compare the immune signals of Thai Trial participants who had become infected and those who had not. The team found that uninfected people had higher levels of an antibody that binds to one tiny spot in HIV’s bumpy outer shell.
Gilbert and his Hutchinson Center collaborators also found the HIV strains that slipped past the Thai Trial vaccine had mutations in the exact spot where the antibody would normally bind.
The team’s findings are the first evidence of this kind of weakness in HIV’s seemingly bullet-proof armor.
"If this is, indeed, a real correlate of protection, then it changes everything," Gilbert said.
Our vaccine researchers are already designing their upcoming trials to focus on this important antibody.
"This is not just academic data," Gilbert said. "This is changing the science of HIV vaccines."