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Gene therapy could be 'functional cure' for HIV

10 March 2014

By Dr Lanay Griessner

Appeared in BioNews 745

A potential HIV therapy where patients have their blood cells genetically modified to help them resist the virus is safe and promising as a treatment, say researchers after a small clinical trial.

The phase I study, published in the New England Journal of Medicine, was designed to evaluate the safety of the 'gene editing' approach.

Dr Bruce Levine, from the University of Pennsylvania, a study co-author, told The Guardian the team was 'absolutely encouraged' by the results which, he said, showed gene editing to be 'potentially a new therapy for HIV'.

Scientists collected white blood cells from 12 HIV-positive patients and modified them to carry a mutation in the gene for CCR5, a protein which acts as a 'docking station' for the virus and allows it to infect cells. The modified cells were then injected back into the patients in the hope that they would spread and confer resistance.

The approach mimics a rare natural mutation in the CCR5 gene that makes about one percent of the population resistant to the most common strains of HIV. HIV primarily infects T-cells, white blood cells that fight viral infections, and it is these cells that are genetically modified in the new therapy.

When the patients in the study were taken off their anti-viral medication, there was a brief increase in the amount of HIV virus in the body. However, once the modified cells began to multiply and circulate, the level began to drop. The trial began in 2009 and some of the modified cells survived for several years. Today, all of the participants in the trial are back on antiretroviral drugs.

'This study shows that we can safely and effectively engineer an HIV patient's own T-cells to mimic a naturally occurring resistance to the virus, infuse those engineered cells, have them persist in the body, and potentially keep viral loads at bay without the use of drugs', said senior author Professor Carl June.

The researchers hope gene editing could be a 'functional cure' for HIV: the virus would still be present in the body, but it would no longer infect cells.

All the same, Dr Levine told the Guardian, '"cure" is a four-letter word. We don't like to use it, particularly with HIV. We are looking at improving the health and immune function of people with HIV'.

In 2012, the World Health Organisation estimated that 35.3 million people were infected with HIV worldwide, with 1.5 million dying from AIDS-related complications. Although anti-viral treatments now have the ability to control the disease for decades, there is no cure. Side-effects associated with these drugs and their considerable financial cost remain a significant concern.

Researchers have been investigating the use of genetically-modified immune cells since 2008 when Timothy Brown, also known as the Berlin patient, was functionally cured of his HIV. His recovery occurred after a bone marrow transplant for leukaemia from a donor who had the rare protective CCR5 mutation in both alleles. Since then, Brown has apparently been HIV-free.

Scientists are now attempting to replicate Brown's story without bone marrow transplants as they carry a high risk of death and require lengthy hospitalisation.

RELATED ARTICLES FROM THE BIONEWS ARCHIVE

09 November 2015 - by Lone Hørlyck 
An experimental cell-based treatment using gene editing, previously only tested on mice, has successfully reversed advanced leukaemia in a one-year-old girl...
19 October 2015 - by Darius Khalid 
This book is an impressive examination of the CCR5 gene, which provides a carefully detailed interdisciplinary understanding involving biochemistry, genetics and biotechnology, as well as the historical and contemporary aspects of patenting and intellectual property laws...
01 June 2015 - by Dr Lanay Griessner 
Part of a gene that protects against the progression of HIV in humans has been identified in Tanzanian chimps...
23 February 2015 - by Dr Lanay Griessner 
A kind of gene therapy has been shown to protect monkeys against HIV infection. The potential treatment instructs muscle cells to produce a protein that effectively neutralises the virus...
10 November 2014 - by Arit Udoh 
Scientists claim to have discovered the genetic mechanism by which two patients developed immunity to HIV infection...

08 July 2013 - by Dr James Heather 
Two HIV patients that received bone marrow transplants have been able to stop taking their anti-viral drugs without any detectable reappearance of the virus, scientists have announced....
08 April 2013 - by Matthew Thomas 
For the first time, scientists have observed how the human immune system makes antibodies capable of neutralising the human immunodeficiency virus (HIV), confirming the belief that their production occurs only after the virus has started to diversify....
30 July 2012 - by Dr Daniel Grimes 
Scientists have discovered that an anti-cancer drug can revive dormant HIV thereby allowing therapies to act upon the low level inactive virus particles that hide in patients' immune cells and have, until now, been unsusceptible to treatment...
08 May 2012 - by Helen Brooks 
HIV patients treated over a decade ago with genetically modified immune cells have suffered no serious side effects from the treatment. Although the cells may not have been successful in targeting and killing HIV-infected cells, the results are promising as they bolster the safety credentials of gene therapy for clinical use...

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