Salmonella is a successful germ because it can adapt to overcome the body’s defenses. But the king of adapting may be HIV, the virus that causes AIDS. Twenty-five years after the first AIDS case was reported, there is still no cure or vaccine for this deadly infection. The virus is a tricky target for several reasons.

With most diseases, at least some people recover fully. The survivors are immune to future infections from the same virus. Scientists study these survivors to figure out how their bodies fought off the disease. Then they create a vaccine that produces the same immune response.

“In all research on vaccines from the time of Edward Jenner, one of the key things to create immunity is to look for natural cases of immunity,” explains Tsafrir Mor, an ASU biologist. But scientists don't have anyone who has completely recovered from the AIDS to study.

To make matters worse, HIV attacks the immune system, the very system that should be fighting it. Once the virus gets into a body, it hitches a ride on the immune cells and uses them to sneak into the lymph nodes, the immune system’s “headquarters.” HIV can hide out in the immune system for a long time—sometimes for years—before it starts replicating and causing damage.

“The virus is making a fool of our immune systems,” says Mor.

These problems and others have slowed down attempts to develop a vaccine against HIV. Mor is trying a new approach. He wants to cut off HIV before it even gets started.

Most vaccines are delivered by injection. They cause the immune system to make antibodies in the blood. These antibodies fight off viruses after they have entered the body. Unfortunately, once HIV gets into the body, it is almost impossible to get rid of.

Mor wants to turn HIV away at the gates. The body’s first line of defense is its epithelial cells. These cells line the outside and inside of the body. Your skin is made up of epithelial cells. So are the mucous linings of your mouth, nose, lungs, anus, and urinary and reproductive tracts.

HIV is usually spread when the virus comes in contact with those mucous linings. Normally, these mucosal cells form a wall that won’t let anything pass through. However, the body needs to let some molecules in.

HIV gets through this wall by passing itself off as a friendly molecule. It slips through the body’s borders like a traveler with a fake passport. Once inside, the virus gets busy finding host cells to infect so that it can start replicating.

The researchers want to stop the virus before it can get inside the body. They plan to deliver their vaccine by mouth instead of through a shot.

Traditional vaccines only produce antibodies in the blood, not the mucosal surfaces. However, when a vaccine is delivered by mouth or inhaled through the nose, it can produce antibodies in both the blood and the mucosal system. This kind of vaccine would block the virus from entering the body and also neutralize it inside the body if it slips though.

So far, the scientists have tested their vaccine on mice. The mice were able to block HIV after receiving the vaccine. The results are promising, but there is still a long way to go. More animal trials are needed to ensure that the vaccine is safe. Only then can it be tested on humans.

“Every minute, 10 people are infected with HIV, and five people die of AIDS,” says Noboyuke Matoba, a researcher who works with Mor. “We have to stop it.”

(first published in 2008)