Immune system protein in semen boosts HIV spread in female genital tissue
NIH study suggests virus uses protein to spread
February 8, 2013 - An immune system protein normally found in semen appears to enhance the spread of HIV to tissue from the
uterine cervix, according to researchers at the National Institutes of Health.
The protein interleukin 7 (IL-7) belongs to a family of proteins that regulate the immune response. IL-7 is present in
normal semen, and occurs at especially high levels in the semen of men with HIV.
The researchers developed a culture system of small pieces of tissue from the cervix and used this system to simulate
male-to-female transmission of HIV, which causes AIDS. They observed the spread of the virus in cervical tissue under controlled
laboratory conditions. In the presence of IL-7 at levels typically found in semen of men with HIV, the virus spreads to the
tissue more readily than it spreads to tissue not treated with IL-7.
According to the study authors, the finding raises the possibility that IL-7, alone or in combination with other molecules,
can foster male-to-female transmission of HIV. Similarly, they note, it's possible that the level of IL-7 in semen may determine how
infectious a particular HIV-positive male is for a female sexual partner. Also, researchers may one day be able to prevent or
delay the spread of HIV by blocking seminal IL-7.
The major targets for HIV infection are T cells, a type of immune cell that normally marshal the body's defenses against disease-causing
organisms. Generally, when these cells become infected with HIV, they quickly die before the virus can produce a large number of copies
of itself. However, the researchers found that in isolated pieces of cervical tissue, HIV-infected T cells in the presence of IL-7
live longer and so continued to produce the virus. IL-7 also stimulated uninfected T cells to divide thus increasing their
number. These new T-cells would provide additional targets for the virus, potentially increasing its spread.
Researchers have long known that biological interactions that take place in the laboratory may not always occur in the more complex
environment of a living organism. For this reason, Dr. Margolis noted that additional studies would be needed to confirm what he and
his coworkers observed in the laboratory.
"These experiments show us again how vicious HIV is," said senior author Leonid Margolis, Ph.D., head of the Section on Intercellular
Interactions at the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), where the research was
conducted. "The virus is able to commandeer an immune protein for its own benefit."
The paper was co-authored by Andrea Introini, Christophe Vanpouille, Ph.D., Andrea Lisco, M.D., Ph.D., Jean-Charles Grivel, Ph.D., and
Leonid Margolis, Ph.D., all of the NICHD. Mr. Introini also is a Ph.D student at the University of Milan, Italy.
Their findings appear in PLOS Pathogens.
Based on their results with IL-7, Dr. Margolis said, his team plans to investigate whether other immune system proteins present in
semen are involved in HIV transmission.
About the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD): The NICHD sponsors
research on development, before and after birth; maternal, child, and family health; reproductive biology and population issues; and
medical rehabilitation. For more information, visit the Institute's website
at http://www.nichd.nih.gov/.
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About the National Institutes of Health (NIH):
NIH, the nation's medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and
Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research,
and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and
its programs, visit www.nih.gov .
Contact:
Laura Sivitz Leifman
301-496-9489
Source: NIH News
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