Neutralizing antibodies are soluble proteins that are secreted by adaptive immune cells into the bloodstream, following exposure to a virus. In the bloodstream, antibodies bind to viral particles in circulation, prevent them from infecting human cells, and lead to the viral particles' destructionthus neutralizing them.
Because neutralizing antibodies attack the virus before it enters cells, they can prevent HIV infection if they are present prior to exposure to the virus. An HIV vaccine would seek to elicit these neutralizing antibodies -- just as existing vaccines against diseases such as measles, polio, hepatitis B, and hepatitis A elicit neutralizing antibodies against those viruses.
However, this is easier said than done. The body makes many antibodies against HIV, but they are almost always unable to neutralize the virus. Nonetheless, the immune systems of some patients with HIV have beaten the odds and have produced effective neutralizing antibodies. The structure of one of these, called 4E10, is described in the latest issue of the journal Immunity.
"This antibody is very broadly active," says Scripps Research Professor Dennis Burton, Ph.D., who led the research with Scripps Research Professor Ian Wilson, D.Phil. "It neutralized nearly 100 different viral strains of HIV from all over the world. [During tests in the laboratory], every one of them was neutralized."
4E10 was isolated from an HIV-positive individual about a decade ago by Burton and Wilson's collaborator Hermann Katinger, a doctor at the Institute for Applied Microbiology of the University of Agriculture in Vienna, Austria, and one of the authors of the paper.