Sunday, March 1, 2009

HIV is evolving to evade human immune responses

HIV is evolving rapidly to escape the human immune system, an international study led by Oxford University has shown. The findings, published in Nature, demonstrate the challenge involved in developing a vaccine for HIV that keeps pace with the changing nature of the virus.

‘The extent of the global HIV epidemic gives us a unique opportunity to examine in detail the evolutionary struggle being played out in front of us between an important virus and humans,’ says lead researcher Professor Philip Goulder of the Peter Medawar Building for Pathogen Research at Oxford University.

‘Even in the short time that HIV has been in the human population, it is doing an effective job of evading our best efforts at natural immune control of the virus. This is high-speed evolution that we’re seeing in the space of just a couple of decades.’

HIV has already killed 25 million people, and an estimated 33 million are currently infected. However, HIV does not kill all people at the same rate. On average, an adult with HIV will survive for ten years without anti-HIV drugs before developing AIDS. But some people will progress to AIDS within 12 months while others can make effective immune responses to the virus and survive without any anti-HIV therapy for over 20 years.

Genes encoding a key set of molecules in the human immune system called the human leucocyte antigens (HLA) are critically important. HLA determine the progress of many infectious diseases including HIV, and enable the recognition and killing of HIV-infected cells. Humans differ from each other in the exact HLA genes they have, and small differences can make the difference in how long it takes to progress to AIDS.

The research team set out to determine whether HIV is adapting to human immune responses. They looked at HIV genetic sequences in different countries around the world, including the UK, South Africa, Botswana, Australia, Canada, and Japan, wanting to see whether the HIV sequences could be related to the different HLA genes present in the different populations.

The collaboration between Oxford University, the Ragon Institute at Massachusetts General Hospital, Kumamoto University in Japan, the Royal Perth Hospital and Murdoch University in Australia and others analysed the genetic sequences of the HIV virus and human leucocyte antigen (HLA) genes in over 2,800 people. The work was funded by a number of organisations including the Wellcome Trust, the Medical Research Council, the US National Institutes of Health, and Oxford’s James Martin 21st Century School.

VIA : Physorg