Using Antibodies for HIV Prevention

Antibodies are proteins that are part of the immune system. Antibodies are specific for each different foreign invader. So for example, an HIV antibody will not recognize or work against a 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 2 different ways that these antibodies can be given to people. Both methods for giving people antibodies have been tested and found to be safe in other diseases, for example as a way to treat certain cancers.

Injecting the antibodies

One way involves giving the antibodies through injections or infusions. 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. The downside of this method is that the antibodies do not last very long in the body. People would have to get regular injections or infusions of these antibodies.

Delivering antibody genes

Another method that can provide lasting antibodies is gene transfer. This method involves using DNA or a viral vector to deliver a gene for the monoclonal antibody into a person’s cells. The DNA or vector carries instructions for making the antibody inside a person’s cells, allowing them to make the HIV-specific antibodies on their own, rather than getting injections of them. This method is similar to that used with DNA vaccines and viral vector vaccines. The major difference is that in this case a copy of an antibody gene is delivered and for vaccines, a copy of an HIV gene is delivered (see DNA vaccines and Viral vector vaccines).

Studies with broadly neutralizing antibodies may lead directly to a strategy to prevent HIV. We call this prevention method antibody mediated prevention, or AMP. These studies could also tell us which antibodies work and what amounts are needed to prevent HIV infection. From there, scientists can work to develop future vaccines to reproduce this response.