AVI and affiliated researchers have discovered two powerful new antibodies to HIV that reveal what may be an Achilles heel on the virus. The findings are the result of a worldwide effort launched by IAVI in 2006 to find new antibodies that neutralize a wide variety of strains of HIV circulating in the world. The study was published in the journalScience. 

HIV, the virus that causes AIDS, is the most mutable pathogen everencountered by modern science. It changes at a furious rate, which helps it evade the body’s immune system. Today, countless variations of the virus infect people around the world. To be effective an AIDS vaccine would have to work against many versions of HIV. 

The two new broadly neutralizing antibodies are the first to be discovered in more than a decade, and the first to be isolated from donors in developing countries where the pandemic is raging. Now researchers will try to exploit the newfound vulnerability on the virus to craft new approaches to designing an AIDS vaccine. 

 “The findings are an exciting advance because now we’ve got a new, potentially better target on HIV to focus our efforts for vaccine design,” said Wayne Koff, senior vice president of research and development at IAVI. “And having identified this one, we’re set up to find more.” 

What are broadly neutralizing antibodies? 

Antibodies are infection-fighting protein molecules that tag, neutralize and help destroy toxins and invading pathogens. They are secreted by immune cells known as B lymphocytes (a kind of white blood cell) in response to stimulation by antigens, which are molecules found on the invading pathogen. Each antibody binds only to the specific antigen that stimulated its production. HIV attacks and quickly overwhelms the body’s immune system, but a minority of people naturally producebroadly neutralizing antibodiesones that target multiple strains of HIV and prevent the virus from infecting cells. Isolating these antibodies gives vaccine researchers valuable insight into fighting the virus. 

Why is this discovery important? 

Before this discovery, researchers had found just four antibodies widely considered to be broadly neutralizing, and those four were associated with a strain of the virus circulating primarily in the Americas, Europe and Australia. The new antibodies came from a donor in the developing world, where 95% of new infections occur. 

They also reveal a new vulnerable spot on HIV, binding to a potentially easier-to-reach patch on the virus that no previously known antibodies targeted. This is extremely importantit provides a new target for vaccine designers to exploit. And the antibodies appear to be highly potent as well, which means they bind to the virus tightly.  This is important becauseif they can be elicited by vaccinationthe body might not have to produce large amounts of the antibodies to gain protection from HIV. 

What’s the next step? 

The new antibodies will now be closely studied by researchers in IAVI’sNeutralizing Antibody Consortium, who will work out the molecular structure and the precise mechanism by which the antibodies bind to HIV. With this information in hand, they will begin working to design novel immunogensthe active ingredient in vaccinesto elicit these antibodies in all people. If they succeed, the immunogens will be put through the preclinical process to produce an industrially viable vaccine candidate for further development. 

How were the antibodies found? 

The discovery of the new antibodies is the result of a global collaboration among IAVI, the Scripps Research Institute, private biotech firms and more than a dozen clinical research centers around the world.