Gene therapy could be 'functional cure' for HIV

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.