Some people may transmit weaker
version of Aids
By Michael Kahn, Reuters
Published in HIV/AIDS News by LearnScapes, issue 294
21/03/2008
London - People with a genetic variation that slows down
HIV may also be causing a mutation to the Aids syndrome
that makes it less potent if transmitted to others, South
African researchers said on Friday.
The human immunodeficiency virus that causes Aids attacks
immune system cells. Like other viruses, it cannot replicate
on its own but must hijack a cell and turn it into a virus
factory. HIV must evade several genes to do this, including
an immunity gene called HLA. "Some people have versions
of the HLA gene that are known to force HIV to tolerate
mutations that damage its ability to reproduce," Carolyn
Williamson and Salim Abdool Karim at the Centre for the
Aids Programme of Research in South Africa wrote in the
Public Library of Science journal PLoS Pathogens.
The weaker virus causes slower disease progression in these
people. Now it seems this weakened virus may get passed
on and act the same way in others -- even if they do not
have the protective HLA genes, Williamson told Reuters.
"The significant difference to other studies is that
this is showing the actual benefit is due to the genetic
composition of the virus," said Williamson, an HIV/Aids
researcher at the University of Cape Town who led the study.
"This study shows you can have a survival advantage
with a virus containing specific genetic signatures associated
with lower replication."
The South African study tracked 21 women without the beneficial
form of HLA who were recently infected with the weakened
strain of HIV. The researchers found the women had much
lower levels of HIV in the body than those carrying a form
of the virus which had not mutated in this way. "It
is pretty well established if you have certain HLA genes
you are better off," Williamson said in a telephone
interview. "It is very likely that the virus in the
people who did not have the HLA genes came from individuals
who did."
The researchers followed the women from between one to
three years and found that while the levels of HIV in their
bodies fell, their number of crucial CD4 T cells that coordinate
the immune system rose. The goal of treatment is to lower
HIV levels to help the immune system renew itself and keep
people healthier longer, in part to stem the spread of the
syndrome. The researchers have not yet studied the women
to see how much slower they progressed to full-blown Aids,
but said the findings could help researchers in search of
an effective vaccine by understanding better why some survive
longer. Aids infects an estimated 33-million people globally.
It has killed about 25-million people and there is no cure
or vaccine.
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