Keeping it in the room: health, happiness and living in Berlin
Researchers from the Wellcome Trust and has found that the rapid evolution of HIV – which has allowed the virus to develop resistance to people’s natural immunity to disease – is at the same time slowing the virus’s ability to cause Aids.
The study also indicates that people infected by HIV are likely to progress to Aids more slowly – in other words the virus becomes less ‘virulent’ – because of widespread access to antiretroviral therapy (ART).
The study, published today in the journal Proceedings of the National Academy of Sciences (PNAS), was led by researchers at the University of Oxford, along with scientists from South Africa, Canada, Tokyo, Harvard University and Microsoft Research.
The research was carried out in Botswana and South Africa, two countries that have been worst affected by the HIV epidemic. Across those countries, researchers enrolled over 2,000 women with chronic HIV infection to take part in the study.
The first part of the study looked at whether the interaction between the body’s natural immune response and HIV leads to the virus becoming less virulent.
Central to this investigation are proteins in our blood called the human leukocyte antigens (HLA), which enable the immune system to differentiate between the human body’s proteins and the proteins of pathogens. People with a gene that expresses a particular HLA protein, called HLA-B*57, are known to benefit from a protective effect against HIV. HIV-infected patients with the HLA-B*57 gene progress more slowly than usual to Aids.
In Botswana, HIV has evolved to adapt to this protective gene more than in South Africa, so that patients no longer benefit from its protective effect. However, the cost to HIV of this adaptation is that its ability to replicate is significantly reduced, making the virus less virulent – and thereby contributing to the virus’s own elimination.
In the second part of the study, the authors examined the impact of HIV medication on the virus’s virulence. They concluded that by treating some people with low CD4 counts, these weaker HIV variants with a weaker ability to replicate will evolve even faster.
The study’s lead scientist, Professor Phillip Goulder from the University of Oxford, said: ‘This research highlights the fact that HIV adaptation to the most effective immune responses we can make against it comes at a significant cost to its ability to replicate. Anything we can do to increase the pressure on HIV in this way may allow scientists to reduce the destructive power of HIV over time.’
Dr Mike Turner, Head of Infection and Immunobiology at the Wellcome Trust, said: ‘The widespread use of ART is an important step towards the control of HIV. This research is a good example of how further research into HIV and drug resistance can help scientists to eliminate HIV.’
However, Dr Michael Brady, Medical Director at Terrence Higgins Trust, sounded a warning bell: ‘This study gives an interesting insight into how viruses adapt to their environment and evolve over time. However, if left untreated HIV still leads to Aids and death. Effective drug treatments mean people living with HIV today can have a near normal life expectancy and be non-infectious to others. Our efforts should remain focused on encouraging the quarter of people with HIV in the UK who remain undiagnosed to come forward for testing, and ensuring they have access to treatment and care as early as possible.’
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