Yahoo – AFP,
Brigitte Castelnau, 4 Nov 2014
Paris (AFP) - French scientists said Tuesday they had found the genetic mechanism by which two HIV-infected men may have experienced a "spontaneous cure", and said it offered a new strategy in the fight against AIDS.
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| French scientists have unveiled the genetic mechanism by which they believe two men were cured of HIV (AFP Photo/Leon Neal) |
Paris (AFP) - French scientists said Tuesday they had found the genetic mechanism by which two HIV-infected men may have experienced a "spontaneous cure", and said it offered a new strategy in the fight against AIDS.
Both men
were infected by the human immunodeficiency virus (HIV), one of them 30 years
ago, but never developed AIDS symptoms.
The
AIDS-causing virus remained in their immune cells but was inactivated because
its genetic code had been altered, the scientists said.
The change
appeared to be linked to increased activity of a common enzyme named APOBEC,
they theorised.
The
"apparent spontaneous cure" throws up an intriguing avenue for drug
engineers, the team said in a statement.
"The
work opens up therapeutic avenues for a cure, using or stimulating this enzyme,
and avenues for identifying individuals among newly-infected patients who have
a chance of a spontaneous cure."
The work,
published in the journal Clinical Microbiology and Infection, was carried out
by scientists at France's Institute of Health and Medical Research (Inserm).
HIV
replicates by invading human CD4 immune cells, which it reprogrammes to become
virus factories.
A rare
group of people -- fewer than one percent of those infected -- are naturally
able to rein in viral replication and keep the virus at clinically undetectable
levels.
They are
known as "elite controllers", but the mechanism by which they keep
the virus at bay remains a mystery.
The French
group looked at two such individuals, a 57-year-old man diagnosed HIV-positive
in 1985, and a 23-year-old diagnosed in 2011, and sequenced their virus
genomes.
Though they
remained infected, standard tests could not detect the virus in their blood.
The team
found that in both cases, the virus was unable to replicate in immune cells due
to mutations in its genetic code.
The
researchers suggested spontaneous evolution between humans and the virus, a
process called "endogenisation" that is believed to have neutralised
other viruses in humans in the past.
A similar
process has been witnessed in a population of koalas that has integrated an
AIDS-like virus into their genes, neutralised it, and were passing resistance
on to their offspring.
"We
propose that HIV cure may occur through HIV endogenisation in humans," the
team wrote.
"These
findings suggest that without therapeutic and prophylactic strategies, after
several decades of HIV/host integrations and millions of deaths, it is likely
that a few individuals might have endogenised and neutralised the virus and
transmitted it to their progeny," they added.
"We
believe that the persistence of HIV DNA can lead to cure, and protection, from
HIV."
The
approach hitherto has been the opposite: to try and clear all traces of HIV
from human cells and from cell reservoirs where they hide.
"We
suggest that persistence of integrated HIV DNA is not a barrier, but on the
contrary, may be a prerequisite to HIV cure," said the study authors.
"We
propose a new vision of HIV cure through integration, inactivation and
potential endogenisation of a viral genome into the human genome."
Not
unique
The team
said they did not believe the two patients were unique or that the phenomenon
was new.
And they called
for "massive sequencing" of human DNA, particularly from Africans who
had been exposed to HIV for longest, to find further proof.
Only one
person is thought to have ever been cured of HIV: Timothy Ray Brown who had
bone marrow transplants as a treatment for leukaemia, from a donor with
resistance to HIV.
A baby
given anti-AIDS drugs immediately after birth for 18 months, was at first also
thought to have been cured, but the virus later came back.
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