LONDON, (Reuters) – The AIDS virus is quickly adapting across large groups of people to avoid triggering the human immune system, posing another challenge in the search for  a potential vaccine, researchers said yesterday.
Scientists know the human immunodeficiency virus, or HIV,  constantly mutates within individual people to find ways to  attack cells.

But the study published in the journal Nature suggests  changes that help the virus do this are increasingly passed on  in the wider population.

“What was previously clear is the virus could evolve within  each infected person but that doesn’t really matter from a  vaccine perspective if the virus at the population level is  staying the same,” said Philip Goulder, an immunologist at  Oxford University who led the study.

“The implication is that once we have found an effective  vaccine, it would likely need to be changed to keep pace with  the rapidly evolving virus.”

There is no cure for AIDS and 33 million people globally are  infected with HIV. Cocktails of drugs can control the virus and  keep patients healthy. AIDS has killed more than 25 million  people since the early 1980s, mostly in sub-Saharan Africa.
Researchers are trying to find vaccines that either prevent  infection or would control the virus so that patients are less  likely to transmit it — a so-called therapeutic vaccine.

“The process of the virus adapting is happening before our  eyes at quite a speed, and it is something we need to take into  account when making our vaccines,” Goulder said.

HIV attacks the immune system, the body’s natural defences.  Like other viruses, it cannot replicate on its own but must  hijack a cell and turn it into a virus factory.

HIV must evade several genes to do this, including an  immunity gene called HLA.