AIDS virus is ‘changing to evade human immune system’

RAPID evolution of the AIDS virus could make it more difficult to fight HIV with a vaccine, experts have warned.

A new study led by researchers at Oxford University shows that the virus is changing to evade the human immune system.

The scientists looked at the genetic codes of HIV viruses from more than 2,800 people around the world. They compared them with human leucocyte antigen (HLA) genes from the same group. HLA enables the immune system to recognise and kill infected cells, including those invaded by the AIDS virus. Everyone has his or her own unique set of HLA genes.

HIV mutations that allow the virus to evade certain versions of HLA were found more often in populations with those HLA genes. This was strong evidence HIV was adapting to the human immune system at population level.

One of the HLA genes most successful at controlling HIV is known as HLA-B*51. But in people with this gene, HIV tends to change into a mutant form that is immune to it.

About 96% of HIV positive people with the HLA-B*51 gene were found to have the mutation. “We saw similar effects in every mutation that we looked at,” said Professor Philip Goulder. “This shows HIV is extremely adept at adapting to the immune responses in human populations that are most effective at containing the virus.”

Co-author Professor Rodney Phillips, also from Oxford University, said: “The virus is out-running human variation, you might say.”

The findings are published today in the journal, Nature and could be important to the development of anti-HIV vaccines, the researchers said.

“The implication is that, once we have found an effective vaccine, it would need to be changed on a frequent basis to catch up with the evolving virus, much like we do today with the flu vaccine,” Prof Goulder said. “In this anniversary year of Darwin’s birth, we are accustomed to think of evolution happening over thousands, tens of thousands and even millions of years. But we are seeing changes in HIV, and our immune response to the virus, in just a couple of decades.”

HIV/AIDS has already killed 25 million people around the world and an estimated 33 million are currently infected. However, people do not succumb to the virus at the same rate. On average, an untreated adult with HIV will live for 10 years without progressing to AIDS. But some individuals will progress to AIDS within 12 months while others survive without any therapy for more than 20 years.