Monkey Experiments Boost Hope For Human AIDS Vaccine | WAMU 88.5 - American University Radio

NPR : News

Filed Under:

Monkey Experiments Boost Hope For Human AIDS Vaccine

Researchers trudging down the long and twisted path toward an AIDS vaccine are encouraged by new studies that show an experimental vaccine protects monkeys against infection with a virus that is very similar to HIV.

The vaccine protected 80 percent of monkeys from infection with SIV, the simian version of HIV. By comparison, an experimental HIV vaccine was 31 percent effective in protecting people against infection in a large-scale study unveiled in 2009.

Dr. Anthony Fauci, director of the National Institute on Allergies and Infectious Diseases, tells Shots the monkey studies, published online in Nature, are important for several reasons.

First, the virus used to challenge the monkeys after vaccination was "a pretty hefty, robust" virus, as Fauci puts it. In the past many studies used the same virus both to vaccinate animals and then to infect them. "That's stacking the cards in your favor," Fauci says.

The new study is more of a real-world test of a vaccine, because people are likely to encounter viruses that are not genetically identical to the ones used in the vaccine.

Another stand-out aspect of the new study — arguably the most important one — is that it nails down what sort of immune response an AIDS vaccine will need to prevent infection. Specifically, the vaccine must stimulate the immune system to make antibodies against a specific part of the virus's envelope, or outer coating, called the V2 loop.

This is not the classic type of antibody that scientists generally think is necessary to "neutralize" a virus. The 2009 human vaccine trial hinted that antibodies against the V2 loop were important, but the evidence for that was sketchy.

"This study makes it very, very clear," Fauci says.

The monkey paper also shows clearly that a vaccine must stimulate two different kinds of immunity — one to guard against infection, the other to damp down the virus if infection occurs anyway.

The new studies were led by Dan Barouch, a vaccine researcher at Beth Israel Deaconess Medical Center in Boston.

One note about the 80 percent protection seen in the monkeys: It means the vaccine reduced infection by that much when the researchers inoculated the animals with a single relatively high dose of the virus. After repeated exposures, virtually all the monkeys eventually got infected despite vaccination.

In the real world, of course, humans get exposed repeatedly to HIV, so a vaccine would need to protect over time. But Fauci points out that in the real world, each exposure would involve far lower doses of HIV.

In the end, the only way to know how protective an experimental AIDS vaccine is for humans is to test it in people. The Boston group is raising the $22 million it will take to do the initial safety testing in humans. It might begin next year.

Copyright 2012 National Public Radio. To see more, visit http://www.npr.org/.

NPR

Rod McKuen, The Cheeseburger To Poetry's Haute Cuisine

Poet Rod McKuen was loved by millions but mocked by literary critics. He died this week at age 81.
NPR

Shake Shack Sizzles With IPO As McDonald's Fizzles

Shares of the burger chain shot up Friday, its first trading day. Shake Shack and other fast-casual joints are taking a bite out of McDonald's, which can't recast itself to fit the current trend.
NPR

What Romney's Retreat Means For GOP Hopefuls

NPR's Scott Simon speaks with senior Washington editor Ron Elving about the narrowing Republican presidential field for 2016 and what we've seen so far in the first month of the new Congress.
NPR

The Infinite Whiteness Of Public Radio Voices

The hashtag #publicradiovoices, about the "whiteness" of public radio, trended on Twitter this week. NPR's Scott Simon speaks with Gene Demby of NPR's Code Switch team about the conversation.

Leave a Comment

Help keep the conversation civil. Please refer to our Terms of Use and Code of Conduct before posting your comments.