HIV evolving rapidly to evade human immune system

In a study published in Nature, researchers have shown that HIV mutates rapidly in a way that allows it to avoid being destroyed by the human immune system. They stress, however, that this will not affect the way that antiretroviral drugs work.

It is well known that HIV does not progress at the same rate in everyone. Some people progress quickly to AIDS, while other, known as long-term slow progressors live with the virus for many years before their immune system starts to break down. The key to this difference in progression are genes that control production of key immune system molecules called human leucocyte antigens (HLAs).

Humans differ in the exact HLA genes they have, and even small differences can have a big impact on how quickly AIDS develops. The researchers examined HIV genetic sequences and HLA genes in over 2800 people in countries, including the UK, Australia, South Africa, Canada and Japan.

They found mutations that enabled HIV effectively to neutralise the effect of a particular HLA gene were more frequent in populations with a high prevalence of that specific gene.

For example, a HLA gene called B*51 is particularly effective at controlling HIV - unless the virus is carrying an "escape" mutation in its genetic make-up.

The researchers found that in Japan, where the B*51 gene is common, two-thirds HIV-positive people without the gene carry HIV armed with the "escape" mutation.
In contrast, in the UK, where the gene is much less common, just 15%-25% of this group of patients are infected with HIV which carries the same key mutation.

These rapid changes may mean that any HIV vaccine that is produced would have to be changed regularly, in much the same way as the flu vaccine changes annually.