A new study has shown promise for an experimental HIV vaccine, when combined with compounds that stimulate the immune system. The study successfully used such a combination to suppress the equivalent of HIV in rhesus monkeys, without the need for continued antiretroviral treatment.

While antiretroviral therapy (ART) has allowed patients with HIV to live healthy lives, by controlling the levels of the virus, it is a treatment that has to be taken every day, indefinitely. If a patient stops taking it, the virus can immediately return to dangerous levels. Even when ART is able to lower HIV to undetectable levels, the virus can essentially hide, and return with force as soon as it has the chance. Dan Barouch, director for the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center and Harvard Medical School, says that one approach to cure HIV would be to suppress these levels without the need for daily ART treatments, creating what he calls a “functional” cure.

According to Barouch, the study could mean we are one step closer to finding a true cure for HIV.

Aiming to determine if an experimental HIV vaccine, an immune system stimulant, or a combination of both would be most effective, Barouch infected 36 rhesus monkeys with simian immunodeficiency virus. He first tried treating them with ART to suppress levels of the virus, and after 6 months of these treatments, divided the monkeys into four groups.

The first group was treated with the vaccine alone, the second with just the immune system stimulant, the third with a combination of both, and the fourth received only a placebo. Barouch then stopped the ART for all of the groups.

In most of the monkeys, the virus bounced back fully at that point. However, this rebound took 2.5 times as long in the monkeys who had been treated with a combination of both. This group of monkeys also had levels of the virus in their bloodstream 50 times lower than the other groups.

Most importantly, however, three out of nine of the monkeys treated with the combination had undetectable levels of the virus, as if they were still undergoing ART.

According to Barouch, “If all the animals went undetectable in the absence of [ART], that would have been a home run. I would say that what we achieved was a solid base hit, and it’s something that we can work from.”

While each treatment individually is already being tested by the companies that produce them, (Johnson and Johnson makes the vaccine, while the immune system stimulant is made by Gilead Sciences Inc.) Barouch hopes to run a trial using the combination of both to treat humans with HIV.

“We do see this as an advance in terms of increasing our understanding of the ability of vaccines or innate immune stimulators to provide antiviral effects,” Barouch said. “We hope the results in humans will allow us to continue to improve this strategy.”

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