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- Posted Tuesday April 16, 2013
TGen-led study discovers dramatic changes in bacteria following male circumcision
Study examines changes in the penis microbiome
PHOENIX, Ariz. - April 16, 2013 - Male
circumcision reduces the abundance of bacteria living on the penis
and might help explain why circumcision offers men some protection
against HIV, according to a study led by the Translational Genomics
Research Institute (TGen).
Removing the foreskin caused a significant shift in the bacterial
community or microbiome of the penis, according to a study
published today by the online journal mBio.
This international collaboration focused on 156 men in Rakai,
Uganda - part of the world's largest randomized-controlled trial on
male circumcision. Researchers showed that men who were circumcised
as part of the study had 33.3 percent less bacteria on their penis
than those who remained uncircumcised one year after the study
began.
Researchers further showed that the decrease was primarily found
in 12 types of bacteria, most of which were intolerant to
oxygen.
Past studies have shown that circumcision reduces female-to-male
HIV transmission, among other benefits. This study suggests a
possible mechanism for HIV protection - the shift in the number and
type of bacteria living on the penis. Further studies will have to
be done to demonstrate that a change in the penis microbiome can
help reduce the risk of HIV transmission, according to the
authors.
At the same time, understanding the mechanisms that underlie the
benefits of male circumcision could help to identify new
intervention strategies for decreasing HIV transmission, especially
for populations with high HIV prevalence and in places where male
circumcision is culturally less acceptable, the study says.
"We know that male circumcision can prevent HIV and other diseases
in heterosexual men, but it is important to know why," said Dr.
Lance Price, the Director of TGen Center for Microbiomics and Human
Health and the study's senior author.
"We think that these dramatic changes in the penis microbiome may
explain, at least in part, why male circumcision is protective, "
said Dr. Price, who is also a Professor of Environmental and
Occupational Health in the School of Public Health and Health
Services at the George Washington University.
In heterosexual transmission of HIV, the virus on the foreskin
needs to reach its target cells, the CD4+ T-cells, which reside
primarily in blood or the lymph nodes.
Researchers hypothesize that penis bacteria may facilitate this
process in two ways: by both recruiting more HIV target cells to
the foreskin and by triggering another set of immune cells, the
Langerhans cells, to deliver the virus to susceptible T-cells.
Without this trigger, the Langerhans cells will simply destroy the
virus.
"Our findings are interesting from two perspectives. From a public
health standpoint, we were finally able to detail the bacterial
changes associated with male circumcision," said Dr. Cindy Liu,
Adjunct Professor at the Pathogen Genomics Division at TGen, and
the study's lead author.
"From an ecological perspective, our study shows how phenomena
from the macro-world actually scale to the micro level. When you
change a macro environment, such as clear cutting a forest, you
affect the animals that live there. That's intuitive. Here we show
that changing the penis environment affects the microbes that live
there as well." said Dr. Liu, who also is a member of the
Department of Pathology at the Johns Hopkins School of
Medicine.
"Even though disturbances of the microbiome are usually portrayed
as negative, such as in colitis and yeast infection after
antibiotic use," said Dr. Price, "this may be one place where
dramatic changes can be protective."
Also contributing to this study were: the Rakai Health Sciences
Program, Entebbe, Uganda, the Department of Epidemiology at the
Johns Hopkins Bloomberg School of Public Health,and the
Institute for Genome Sciences at the University of Maryland.
The study was funded by: the National Institutes of Health (NIH);
and NAU's Technology and Research Initiative Fund (TRIF) and Cowden
Endowment in Microbiology.
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About TGen
The Translational Genomics Research Institute (TGen) is a Phoenix,
Arizona-based non-profit organization dedicated to conducting
groundbreaking research with life changing results. Research at
TGen is focused on helping patients with diseases such as cancer,
neurological disorders and diabetes. TGen is on the cutting edge of
translational research where investigators are able to unravel the
genetic components of common and complex diseases. Working with
collaborators in the scientific and medical communities, TGen
believes it can make a substantial contribution to the 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]