Discovery of HIV 'invisibility cloak' reveals new treatment opportunities
6-Nov-2013 - Scientists have discovered a molecular invisibility cloak that enables HIV, the virus
that causes AIDS, to hide inside cells of the body without triggering the body's
natural defence systems.
Their study shows how 'uncloaking' the virus using an experimental drug triggers an immune response that stops the virus from
replicating in cells grown in the laboratory.
The findings could lead to new treatments and help to improve existing therapies for HIV infection.
The innate immune system is the body's first line of defence against infection and incorporates an alarm system present in all cells
of the body that detects the presence of 'foreign' material from invading bacteria and viruses. When the alarm is tripped, the infected
cell begins an anti-viral programme and sends out warning signals to alert other cells that a virus is around. HIV infects vital
cells of the immune system so its ability to replicate undetected without triggering this alarm system has puzzled scientists
since the discovery of the virus.
The team identified two molecules inside host cells that are recruited by HIV after infection that stop the virus from reproducing
its genetic material too early. The effect is to shield the virus from the alarm system and stop the innate immune system from
kicking into action.
In the absence of these molecules, either by depletion from infected cells or blocking their recruitment using an experimental drug,
HIV is exposed to the alarm system and an anti-virus immune response is triggered. Targeting the cloaking molecules and not the
virus itself makes it much more difficult for the virus to mutate and become resistant to this treatment approach, a
significant problem with standard HIV therapies.
Professor Greg Towers, a Wellcome Trust Senior Research Fellow at UCL and lead author of the study, said: "HIV is extremely adept
at hiding from our body's natural defences, which is part of the reason the virus is so dangerous. Now we've identified the
virus' invisibility cloak, and how to expose it, we've uncovered a weakness that could be exploited for new HIV treatments.
"There's a great deal more research needed but the potential for this approach is huge, as a possible treatment in itself but
also as a complement to existing therapies. We're also interested to see whether blocking these cloaking molecules can help to
boost immune responses to experimental vaccines against HIV or be used to protect against HIV transmission.
"The hope is that one day we may be able develop a treatment that helps the body to clear the virus before the infection is able to
take hold."
The experimental drug used in the study is based on Cyclosporine, a drug that is widely used to prevent organ rejection in transplant
patients because of its ability to dampen the immune response. Cyclosporines have been shown to block the replication of HIV and
other viruses but are not suitable for treating infected patients because of their negative effects on the immune system. The
team used a modified version of the drug, which blocks the effects of the two cloaking molecules without suppressing immune activity.
Dr Kevin Moses, Director of Science Funding at the Wellcome Trust said: "In 2012, 2.3 million people were newly infected with HIV.
Whilst existing treatments are helping people with HIV to live longer and healthier lives, the challenge of adherence to treatment
programmes means that drug resistance remains a threat and the virus continues to burden the world's poorest communities.
Understanding how HIV interacts with the body's own defences might just be crucial for developing the best approaches to therapy."
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The study is published today in the journal Nature and was funded by the Wellcome Trust, the Medical Research Council
and the National Institute for Health Research University College London Hospitals Biomedical Research Centre.
Source: http://www.eurekalert.org/pub_releases/2013-11/wt-doh110413.php
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