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- Posted Thursday July 24, 2014
TGen-led study seeks to understand why some HIV-positive men are more infectious than others
Study showed significant links between bacteria, viruses and the immune system in the semen during HIV infection
FLAGSTAFF, Ariz. - July 24, 2014 - A new study led by the Translational
Genomics Research Institute (TGen) provides insights into the
interplay among bacteria, viruses and the immune system during HIV
infection.
Currently, doctors measure HIV-positive men's infectivity - their
potential to infect others - based on their blood viral load.
However, some men produce large amounts of virus in their semen
despite having low levels in their blood. Researchers call this
"compartmentalization," where different levels of the virus can be
found in different parts of the body; in this case, in the semen,
versus the blood.
Because of the importance of semen in HIV transmission - in both
homosexual and heterosexual populations - researchers who conducted
the study published today in the journal PLOS Pathogens
sought to understand how HIV could be localized, or
compartmentalized, in the semen.
Significantly, the study revealed a link between higher levels of
HIV and higher levels of both bacteria and cytokines, biochemicals
that can be described as the immune system's alarm bells.
"Our study is trying to tackle an important problem in HIV
research," said Dr. Lance Price, Director of TGen's Center for
Microbiomics and Human Health, and one of the study's senior
authors. "We found that HIV infection affects the relationship
between semen bacteria and immune system, and both are linked to
semen HIV levels."
These findings could point to new ways to control the spread of
HIV, said Dr. Price. "Our data suggest that semen bacteria may play
a role in localized inflammation and HIV viral load in the semen,
which is an important target for reducing HIV transmission."
While HIV can be found in many body fluids (semen, vaginal
secretions, blood and breast milk), it is most commonly transmitted
via semen in both homosexual and heterosexual sex.
Homosexual men were the focus of this study because they continue
to be the population most at risk for HIV in North America. The
study included 27 homosexual men infected with HIV, and 22
homosexual men who were uninfected.
The 27 infected individuals were examined before treatment, and at
both one-month and six-month intervals following treatment with
anti-retroviral therapy (ART). Samples from the 22 uninfected
participants in the study served as controls.
"By comparing the semen bacteria in both uninfected and infected
men, we found that HIV can cause an imbalance in the semen
microbiome," said Dr. Cindy Liu, the study's lead author, a
clinical pathology resident at the Johns Hopkins School of
Medicine, and an adjunct professor at TGen at the time of the
study. "This imbalance can be corrected by HIV treatment. This
suggests that there are complex host-microbe interactions in the
semen."
"We have taken the first step to show that bacteria, HIV, and
immune response in the semen may be connected," said Dr. Rupert
Kaul, an immunologist from the University of Toronto, and another
senior author of the study. "What we need to better understand next
is the precise relationship between these three factors - whether
the bacterial imbalance is the trigger or the result of the
localized immune response."
The authors of the study,
The Semen Microbiome and Its Relationship with Local Immunology
and Viral Load in HIV Infection, are particularly excited
about what this research may mean for another important patient
population.
"Even though we have focused on men whose semen viral load can be
controlled with HIV treatment in this study," said Dr. Kaul, "we
need to study men who continue to have high HIV levels in their
semen despite being on treatment. This will be important to
improving how we treat patients and control the spread of
HIV."
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About TGen
Translational Genomics Research Institute (TGen) is a Phoenix,
Arizona-based non-profit organization dedicated to conducting
groundbreaking research with life changing results. TGen is focused
on helping patients with cancer, neurological disorders and
diabetes, through cutting edge translational research (the process
of rapidly moving research towards patient benefit). TGen
physicians and scientists work to unravel the genetic components of
both common and rare complex diseases in adults and children.
Working with collaborators in the scientific and medical
communities literally worldwide, TGen makes a substantial
contribution to help our patients through efficiency and
effectiveness of the translational process. For more information,
visit:www.tgen.org.
Press Contact:
Steve Yozwiak
TGen Senior Science Writer
602-343-8704
[email protected]