Evolving HIV strains worry Indian
scientists By Ranjit Devraj
NEW DELHI - While India has drastically
reduced the spread of HIV over the past decade,
new strains of the virus that cause acquired
immunodeficiency syndrome (AIDS) are troubling
medical scientists in this country.The Joint
United Nations Programme on HIV and AIDS, or
UNAIDS, in its 2012 report, praises India for
doing "particularly well" in halving the number of
newly affected adults between 2000 and 2009.
But India - home to 2.4 million people
living with HIV, one million of whom are on
anti-retroviral (ARV) therapy - will need to pay
attention to the proven fact that the Human
Immunodeficiency Virus Type I (HIV-1), the most
common and pathogenic strain of the virus, has
been undergoing a process of fairly rapid viral
evolution.
Of the various genetic
families, HIV-1 subtype C is responsible for
nearly 99% of infections
in India and has a significant presence in China,
South Africa and Brazil as well.
Now,
scientists working at the Jawaharlal Nehru Centre
for Advanced Scientific Research (JNCASR) in
Bangalore have found a family of five new strains
of HIV-1 subtype C, two of which appear to be
outstripping the standard viral strain.
The study is the first of its kind to
identify that a major family of HIV-1 is
undergoing evolutionary modification, Professor
Ranga Udaya Kumar of the molecular biology and
genetics unit at JNCASR told IPS.
Kumar
said that although the studies at the center do
not show the new strains to be more pathogenic,
there are reasons to believe that they are more
infectious.
The results of the JNCASR
study were first published by the American Society
for Biochemistry and Molecular Biology in the
November 6 edition of the peer-reviewed Journal of
Biological Chemistry.
The new viral
strains appear to contain a stronger viral
promoter, said Mahesh Bachu, who led the team of
researchers at JNCASR. A promoter is a region of
DNA that codes for whichever protein the cell is
trying to produce. In other words, a virus with a
stronger promoter is expected to produce more
"daughter viruses" and spread faster in a host
population.
Importantly, in the laboratory
experiments the new HIV strains were found to be
making more daughter viruses compared to the
standard viral strains, Bachu said.
Retroviruses that cause AIDS reproduce by
transcribing their ribonucleic acid (RNA) into DNA
using an enzyme called reverse transcriptase. The
resultant DNA inserts itself into a host cell's
DNA and is reproduced along with the cell and its
daughters.
In addition to making more
daughter viruses, people infected with the new HIV
strains seem to contain more virus in their blood,
Bachu told IPS, adding that data for the study was
generated from 165 samples gleaned from hospitals
in diverse parts of the country.
Collaborators in the study included the
YRG Centre for AIDS Research and Education (YRG
CARE) in Chennai; St Johns National Academy of
Health Sciences, Bangalore; the National Institute
of Mental Health and Neurological Sciences,
Bangalore; and the All-India Institute of Medical
Sciences (AIIMS) in New Delhi.
The
clinical findings have been substantiated by
laboratory experiments using viral, immune and
molecular strategies, Bachu said. A similar
process of viral evolution has also been observed
in South Africa, China and southern Brazil -
countries that have the same family of HIV-1.
Significantly, when Bachu and his team
first observed the new strains, during earlier
studies conducted from 2000 to 2003, their
prevalence was quite low - approximately 1% to 2%
of each of the five variants.
A decade
later, the prevalence of three of the five new
HIV-1 groups had multiplied, with one group
increasing from 2% during the 2000-2003 period to
20-30% in 2010-2011.
According to Bachu,
it is important that subjects infected with the
newer 4-kappaB strains show more plasma virus in
their blood than those infected with the existing
3-kappaB HIV strain.
It is possible that a
higher viral load permits an enhanced transmission
advantage to 4-kappaB strains of HIV, contributing
to successful spread of the new viruses, Bachu
said.
The findings raise several questions
with serious implications for viral fitness,
evolution and disease management, according to
Kumar. The most important of these concerns is the
possibility of the new HIV strains altering the
landscape of HIV demographics in India.
Both Kumar and Bachu caution, however,
that the JNCASR "data should be considered only as
suggestive and not conclusive".
JNCASR and
its collaborators are now conducting observational
clinical studies to determine if the new HIV
strains are more infectious than the existing one.
It is for clinical scientists to see if
the new strains of HIV are likely to cause rapid
disease progression to AIDS, Dr Nagalingeswaran
Kumarasamy, chief medical officer at YRG Care,
told IPS.
Kumarsamy said that, as things
currently stand, there is no cause for alarm. We
need to further study the new strains and see, for
example, if there is a need to start ARV therapy
earlier than usual.
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