An experimental vaccine appears to give monkeys some protection against a version of HIV, the virus that leads to AIDS. Scientists say the research gives big clues about the most essential elements needed to develop a successful HIV vaccine for humans.
In the study, published today in the journal Nature, scientists gave rhesus monkeys a vaccine against SIV, the monkey version of HIV. The monkeys were then exposed to a strain of the SIV, a difficult-to-treat strain that was different than the one used to create the vaccine. The monkeys that were vaccinated seemed to be partially protected against the virus, which reduced their susceptibility to infection by 80 percent.
When the monkeys did become infected, the amount of the virus that appeared in their blood was substantially lower than monkeys that were not vaccinated.
The successful vaccines all contained an essential element, called Env, which helps the virus bind to the antibodies that can destroy it.
“The study demonstrates very clearly that in order to prevent acquisition of the virus, a vaccine needs to have an Env glycoprotein component,” said Eric Hunter, professor of pathology and co-director of the Center for AIDS Research at Atlanta’s Emory University who was not involved with the study. “I would say this is significant progress in the process of trying to develop a protective HIV vaccine.”
That a vaccine that was made using one strain of the virus protected the monkeys from a different and difficult strain is also a major advancement, scientists say. Dr. Carl Dieffenbach, director of the division of AIDS for the National Institute of Allergy and Infectious Diseases, the government agency that funded the study, said that’s because there are multiple versions of the HIV virus that attack humans.
“There’s so much variability in the population of viruses that are circulating. When you have viruses that are different, can the immune system use the response it’s made against virus A to mount a successful repulsion of a related virus,” Dieffenbach said. “That’s one of the major things this study did.”
The scientists were testing elements of HIV vaccines that were successful in humans in a 2009 trial. Dieffenbach said their findings now give some idea as to what made those vaccines work.
“We’re trying to bring those human findings full circle, and this gets us about half way around the loop,” Dieffenbach said.