Antibodies are proteins that are part of the immune system. Antibodies are specific for each different foreign “invader,” such as flu, measles, or chickenpox. For example, an HIV antibody will not recognize or work against the flu virus. In fact, most HIV antibodies are very specific for one strain of HIV and maybe a few close relatives.
Researchers have found that some people have rare HIV antibodies, called broadly neutralizing antibodies, which work against many different strains of HIV. Scientists can learn a lot about preventing HIV infection in studies using these broadly neutralizing antibodies. There are two different ways that these antibodies can be given to people. Both methods for giving people antibodies have been tested and found to be safe for other diseases.
Passive Immunity
Antibodies can be given through injections or infusions into a vein, a muscle, or the fatty tissue under the skin (subcutaneous). Copies of the antibodies are made in the lab. These copies are called monoclonal antibodies. Studies are testing whether giving people monoclonal antibodies before they are exposed to HIV can prevent an infection, because these antibodies will already be circulating in the person’s blood stream, ready to fight HIV. Whereas a vaccine teaches your body how to make antibodies, passive immunization skips that step and gives a person the antibodies directly. These lab-made antibodies do not last very as long in the body, so people need to continue to get infusions or injections on a schedule.
bnAbs
Some antibodies are known as Broadly Neutralizing Antibodies, or bnAbs for short (pronounced bee-nabs). These antibodies are able to block many of the global strains of HIV. Studies with broadly neutralizing antibodies may lead directly to a strategy to prevent HIV. We call this prevention method antibody mediated prevention, or AMP. In the two recent AMP Studies, it was proved that one bnAb called VRC01 was able to block about 30% of the HIV that was sensitive to this antibody, proving the concept that bnAbs can be used for HIV prevention, but that one bnAb is likely not enough by itself. Current and future studies are looking at combinations of antibodies that bind to different parts of HIV, as well as how often the bnAbs need to be given to people. Vaccine studies are also being done to see if the immune system can be trained to produce bnAbs directly.