Ever since the AIDS epidemic began 30 years ago, researchers have been unable to develop a vaccine to protect vulnerable populations against HIV, the virus that causes AIDS.  Now, scientists are exploring an alternative approach to fighting HIV that could prove even more effective than a vaccine.

In the more than 200 years since vaccines were developed to protect people against disease, smallpox being the first, HIV has been among the disease organisms against which scientists have been unable to develop an effective vaccine.  But some scientists believe vaccines might not be the best answer.

Researcher Alejandro Balazs of the California Institute of Technology in Pasadena is working on alternatives to an AIDS vaccine.

Balazs says Caltech scientists are developing a way to kill the virus that is very different from how traditional vaccines work.

Vaccines stimulate the body's production of protective antibodies, infection-fighting proteins, by injecting harmless bits of a virus or bacterium so that later on, if the real thing shows up uninvited, the immune system can quickly recognize and attack the pathogen.  Balazs says this strategy provides immunity to many dangerous disease organisms.

?In the case of HIV, however, that traditional approach to vaccination does not really work, because the body tends to make antibodies that are not neutralizing, and so that they do not actually prevent the infection.  And so in this case we can specify this monoclonal antibody that we already know to be effective against HIV directly.  And so we do not have to hope the immune system will produce the right one," Balazs said.

Balazs says Caltech researchers did not engineer the monoclonal antibody targeted specifically against HIV.  That had already been done by many scientists around the world.

But the Caltech team broke new ground by inserting the antibody into a harmless cold virus, and then injecting that into the muscle tissue of experimental mice.  Those mice, bred to develop a human-like immune system, then produced large amounts of the virus-killing antibodies.

Balazs says the technique, which is called VIP for vectored immuno-prophylaxis, prevented infection when the mice were exposed to high doses of HIV. "They were essentially protected from HIV-induced depletion of their immune systems, which mimics the process that happens in humans.  When humans are infected with HIV, their immune systems are, over time, killed by the virus.  And so we found that our prophylaxis prevented that," Balazs said.

Balazs says researchers hope to begin human clinical trials of the VIP treatment in the next two to three years.

An article by researchers on vectored antibody-based protection against HIV is published in the journal Nature.