New, Genetically-Modified HIV Vaccine Enters Next Phase of Trials

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Image: U.S. Army Corps of Engineer/Flickr

A new possible HIV vaccine that uses a genetically-modified version of the virus is heading into Phase II trials. The results of an earlier trial showed it provoked an immune response against the virus, but now we need to see if that response is strong enough to protect someone from getting infected with HIV in the first place.

The vaccine uses an inactivated—or “dead”—version of the HIV virus, the first vaccine of this type for HIV. Previously, inactivated vaccines haven’t been attempted for HIV because it was considered too risky, but this candidate uses a version of the virus that has been genetically modified—swapping out some of the genes with genetic material from honey bees—to make it less virulent and easier to mass produce.

This week, the researchers published the results of the Phase I trial in the journal Retrovirology. Using a group of 33 participants who were already HIV-positive, they doled out the vaccine to half and a placebo to half, then measured whether the vaccine group started to produce extra antibodies. They found it “significantly increased” the pre-existing antibodies in the vaccine group, a good sign that it could produce similar antibodies in people without HIV.

Now, they’ve started plans for a Phase II trial, the researchers from Western University in Canada announced Thursday, which also happens to be World AIDS Day. For this phase, they’ll test out the vaccine on 300 participants from the general population, as well as 300 people from high-risk groups, intravenous drug users and sex workers. They’ll be looking to see if the vaccine not only provokes an immune response, but also does so well enough to prevent people who are exposed to HIV from getting infected.

Scientists have been trying to find a vaccine for HIV for decades. Just three years after HIV was conclusively identified as the cause of AIDS, researchers launched the first clinical trial of an HIV vaccine. In the 30 years that have passed, many vaccine candidates have gone through clinical trials, but none have been effective enough to get approval for widespread use.

Part of the problem is that our usual strategy for making vaccines doesn’t quite work with HIV. Typically, when making a new vaccine, researchers figure out how the immune system naturally fights off the infection and then looks for ways to provoke that same fight response with a vaccine, instead of the pathogen. But HIV is trickier.

“With HIV, of course, the immune response doesn’t clear the infection,” Col. Nelson Michael, a medical doctor and a researcher who works on developing HIV vaccines at the Walter Reed Army Institute of Research, told me in a previous interview. “People go on to develop a disease that can kill them. Therapy will keep them alive a lot longer, in some cases a lot longer. But the natural immune response to HIV does not provide you that blueprint [for a vaccine].”

But the researchers are hopeful that because this vaccine uses a different approach than previous attempts, it may be more effective.

“If we can show that this vaccine is effective in preventing people from contracting HIV, we can stop the AIDS epidemic and that would be tremendous,” said Chil-Yong Kan, one of the researchers at Western, in a press release. “It would be a tremendous contribution to humankind, and it would make all of our efforts worthwhile.”

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