HIV's adaptation to immune system may slow its AIDS-causing ability

Like many viruses, HIV has evolved to become resistant to genes that provide natural immunity in the human body. But a new study finds that this evolution may be the virus' downfall; it is also curbing its ability to cause AIDS.

As HIV evolves to adapt to the human immune system, its virulence may be slowing.

The research team - led by Prof. Phillip Goulder of the University of Oxford in the UK - also found that an increase in access to antiretroviral therapy (ART) has meant that progression to AIDS among people with HIV is slowing.

The researchers say their findings - recently published in the Proceedings of the National Academy of Sciences (PNAS) - bring us one step closer to tackling the HIV pandemic that is responsible for around 39 million deaths worldwide.

Prof. Goulder and his team enrolled more than 2,000 women with chronic HIV to the study. The women were from two countries worst hit by the HIV epidemic - South Africa and Botswana.

First, the researchers set out to see how the body's natural immune response impacts the virulence of HIV, or its ability to progress to AIDS.

In particular, the team investigated blood proteins called human leukocyte antigens (HLA). These proteins allow the immune system to distinguish between friendly and harmful proteins. The researchers explain that some people have a gene that expresses a protein called HLA-B*57, which is known to have a "protective effect" against HIV.

The researchers found, however, that in some cases HIV has evolved to become resistant to the protective effects of HLA-B*57 - particularly among women in Botswana. But they also found that this evolution has impaired the ability of HIV to replicate, meaning its progression to AIDS is being slowed.

According to the researchers, the way HIV is evolving to resist protective gene variants is hampering the virulence of transmitted HIV. This means that HIV is playing a part in its own eradication.

Commenting on this finding, Prof. Goulder says:

"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."

ART causing HIV to evolve, impairing its virulence

The team then developed a mathematical model to assess how ART affects the virulence of HIV.

ART usually involves a combination of three antiretroviral drugs to slow progression of HIV. According to the World Health Organization (WHO), 2.3 million new people received antiretroviral treatment last year, compared with 1.6 million in 2012. This represents the largest ever annual increase in uptake of ART.

The researchers found that administering ART to people with HIV who have low levels of CD4 cells (types of white blood cells that fight infection) is causing HIV to evolve, which is impairing the virus' ability to replicate.

This finding highlights the importance of ART in the fight against HIV. Mike Turner, head of infection and immunobiology at the Wellcome Trust in the UK - who funded the study - adds:

"The widespread use of ART is an important step toward 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."

In line with World AIDS Day yesterday, Medical News Today reported on a study claiming that the world has reached a "tipping point" in the worldwide AIDS pandemic, in that more people are signing up for ART than are becoming infected with HIV.

Written by Honor Whiteman

Link to article: http://www.medicalnewstoday.com/articles/286321.php