The work identifies “a new and much more efficient method to generate broadly active antibodies against HIV,” says immunologist Justin Bailey of Johns Hopkins University School of Medicine, who was not involved in the study.
Making an HIV vaccine has proved difficult because the virus changes all the time. Different strains exist throughout the world, and the virus even mutates within an infected person’s body. Most often, people develop antibodies that are specific to one strain but ineffective against others. HIV vaccines tested so far have not led to the production of broadly neutralizing antibodies.
About 1 percent of HIV-infected people eventually generate broadly neutralizing antibodies that are especially potent and effective against many types of HIV. The development of these antibodies doesn’t seem to help infected people. But when given to monkeys before exposure to a virus similar to HIV, the antibodies prevent infection.
Broadly neutralizing antibodies specific to HIV have a few quirky features, one of which is the presence of a long stretch of amino acids that sticks out from the antibody surface. This protruding part of the antibody binds to a viral site that remains the same between strains, because the virus needs it to gain entry to a cell. HIV’s thick coat of surface sugars makes the viral binding site difficult to access. A longer stretch of amino acids seems to be able to pierce through “and reach in, almost like the long arm of the law,” says Vaughn Smider, a molecular immunologist at the Scripps Research Institute in La Jolla, Calif.
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