WASHINGTON
(AFP) - A chemical found in green tea helps inhibit sexual transmission of the
virus which causes AIDS, said a study Tuesday that recommends using the compound
in vaginal creams to supplement antiretrovirals.News (Updated
May 24, 2009)
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Tue May 19, 2:41 PM
WASHINGTON
(AFP) - A chemical found in green tea helps inhibit sexual transmission of the
virus which causes AIDS, said a study Tuesday that recommends using the compound
in vaginal creams to supplement antiretrovirals.
Medical experts at
The researchers said they
determined that the green tea polyphenol, or vegetable tannin, called
epigallocatechin-3-gallate (EGCG) is capable of neutralizing a protein in sperm
which serves as a vector for viral transmission during sex.
EGCG degrades what is
known as a semen-derived enhancer of virus infection, or SEVI, described in the
study as "an important infectivity factor of HIV."
Writing in the online
edition of the Proceedings of the National Academy of Sciences, the researchers
said they "recently identified a peptide fraction in human semen that
consistently enhanced HIV-1 infection."
SEVIs capture viral
elements and attach them to the surface of target cells, enhancing cell fusion
and decreasing a cell's ability to repel viral threats.
EGCG "targets SEVI
for degradation" and "abrogates semen-mediated enhancement of HIV-1
infection in the absence of cellular toxicity," said the researchers, some
of whom work at the university's Heinrich-Pette-Institute for Experimental
Virology and Immunology.
Because of its effects on
semen-based HIV transmission threats, the study's authors said "EGCG
appears to be a promising supplement to antiretroviral microbicides to reduce
sexual transmission of HIV-1."
With the vast majority of
the world's 33 million people with HIV infected through heterosexual sex, and as
96 percent of new infections occur in poor and developing nations, researchers
said the use of green tea EGCG in topical creams would "provide a simple
and affordable prevention method" to guard against HIV transmission.
Green tea, which
originated in
By
Unsuccessful at developing
vaccines that the cause the body's natural immune system to battle the virus,
researchers are testing inserting a gene into the muscle that can cause it to
produce protective antibodies against HIV.
The new method worked in
mice and now has proved successful in monkeys, too, they reported Sunday in the
online edition of the journal Nature Medicine. The team is led by Dr. Philip R.
Johnson of the Children's
That doesn't mean an AIDS
vaccine for people is in the wings, Johnson said. Years of work may lie ahead
before a product is ready for human use.
Nevertheless, the report
was welcomed by Dr. Beatrice Hahn, an AIDS researcher the
"It shows thinking
outside the box is a good idea and can yield results, and we need perhaps more
of these nonconventional approaches," she added.
According to the
International AIDS Vaccine Initiative, AIDS is one of the most devastating
pandemics. More than 20 million people have died so far and about 33 million are
living with HIV. The Center for Disease Control and Prevention last year
estimated there are about 56,000 new HIV infections annually in the
Most efforts at blocking
AIDS have sought to stimulate the body's immune system to produce antibodies
that fight the disease. This model has worked for diseases such as measles and
smallpox. It hasn't done as well with HIV/AIDS; test vaccines have failed to
produce a protective reaction.
So Johnson decided to try
something different.
"We used a leapfrog
strategy, bypassing the natural immune system response that was the target of
all previous HIV and SIV vaccine candidates," Johnson said. HIV, or human
immunodeficiency virus, causes AIDS in people. The closely related simian virus,
or SIV, affects monkeys.
"Some years ago I
came to the conclusion that HIV was different from other viruses for which we
were trying to develop vaccines and we and might not ever be able to use
traditional approaches," Johnson said in a telephone interview.
He said the researchers
knew there were proteins that could neutralize the HIV virus, so they began
thinking about whether they could use them to fight the disease.
In a decade-long effort,
Johnson, K. Reed Clark of Nationwide Children's Hospital in
Then they needed a way to
get the immunoadhesins into the cells.
The researchers selected
the widely used adeno-associated virus as the carrier because it is an effective
way to insert DNA into the cells of monkeys or humans. That virus was injected
into muscles, where it carried the DNA of the immunoadhesins. The muscles then
began producing the protective proteins.
Scientists first tested
the idea in mice and then turned to monkeys because SIV is closely related to
HIV and would be a good test model.
A month after
administering the AAV, the nine treated monkeys were injected with SIV, as were
six not treated in advance.
None of the immunized
monkeys developed AIDS and only three showed any indication of SIV infection.
Even a year later they had high concentrations of the protective antibodies in
the blood.
All six unimmunized
monkeys became infected; four died during the experiment.
The next step is moving
toward human trials, Johnson said. He said he is working with the International
AIDS Vaccine Initiative in hopes of getting tests in humans under way in the
next few years.
The research was supported
by the National Institute of Allergy and Infectious Diseases.