16 Mar 2007

Clues to HIV's trickery

Researchers report that they've found more evidence of how the Aids virus escapes the immune system.

While the findings could help in the development of an HIV vaccine, they suggest that it will be far from simple to figure out how the virus will react in specific people.

"There aren't just easy, predictable patterns," said study co-author Bette Korber, a laboratory fellow at Los Alamos National Laboratory, in New Mexico. "The virus is changing in response to our immune system, but it's not always changing in one direction."

At issue is the Aids virus's ability to evolve as it learns about the weaponry that the human immune system tries to throw at it. "In the human population, we all have different immune response teams," Korber said. "We inherit them from our parents - half of our response is from Mom, half from Dad. The question is: Are those responses really predictable? If I know your (genetic profile), could I predict how the virus would escape from you?"

How HIV escapes immune system
Korber and her colleagues decided to try to find out. In their study, they statistically analysed how the Aids virus mutates into new forms and "escapes" from the immune system. Their findings appear in the March 16 issue of Science.

The researchers found that the immune system is important in pushing the virus to mutate in response to it, but the genetic heritage of the virus itself also plays a major role. All this combines to make it difficult to predict what the virus will do when it needs to mutate to get away from the immune system, Korber said.

According to her, this suggests that a successful HIV vaccine would have to cover a wide number of "escape routes" that the virus might take in the body.

Scientists have long been trying to develop a vaccine against HIV, but the disease has turned out to be extremely stubborn. Among other things, the virus' ability to mutate into new forms has made it difficult to develop a vaccine that can keep up with all the changes. Other types of germs don't adjust so rapidly to the immune system.

In an accompanying commentary, two British scientists speculate that it may be possible to design a "complex" vaccine that would anticipate mutations in the Aids virus.

Focus on fixed target
Another alternative would be to develop a vaccine that would focus on killing parts of the virus that don't mutate as rapidly, they said. In February, researchers at the US National Institute of Allergy and Infectious Diseases announced in the journal Nature that they had found this type of non-mutating "site of vulnerability" on the surface of HIV, renewing hopes for an effective vaccine.

Ultimately, Korber is hopeful about the possible effects of her research, as well. It may bring scientists "one tiny nudge closer to a vaccine," she said. – (HealthDayNews)