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- WASHINGTON, (Reuters) - An
ingredient used to coat pills to help them last longer in the digestive
system could offer a new avenue for preventing transmission of the AIDS
virus, researchers said on Monday.
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- They said the ingredient kills not only the HIV virus
that causes AIDS, but the herpes virus and the bacteria that cause a range
of sexually transmitted diseases (STDs), including gonorrhea, trichomonas
and chlamydia.
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- Formulated into a cream, it has worked in mice to prevent
sexual transmission with no serious side-effects, said Dr. Robert Neurath,
head of the Laboratory of Biochemical Virology at the New York Blood Center.
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- The ingredient is used to coat enteric tablets, which
must dissolve in the small intestine rather than in the stomach. Known
as cellulose acetate phthalate, it holds its own in the acidic environment
of the stomach but breaks down in the more alkaline environment of the
intestine.
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- It is classified as an "inert" substance --
one that has no active effects -- and Neurath said he never dreamed such
a chemical would work.
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- "This was a step prompted by desperation,"
he said in a telephone interview.
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- Neurath's team had been looking for a microbicide --
something besides a condom that women, and men, could use that would protect
them from STDs and especially HIV. Groups that lobby for the development
of a microbicide say many men refuse to use condoms and beat sexual partners
who demand their use.
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- The result is that many women are infected each year.
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- Advocates for microbicides argue that a cream that could
be used easily and privately would save millions of lives.
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- About two years ago, Neurath said, his team modified
a milk protein that worked well against HIV and herpes viruses.
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- But they ran into a roadblock -- mad cow disease. Bovine
spongiform encephalopathy (BSE) had swept British herds and there were
some suggestions it could be passed on in milk.
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- "There was some concern expressed that milk-derived
products should not be used for medicinal purposes," Neurath said.
So his team had to look for something else.
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- "We decided to either have a quick success or get
out of the field of microbicides," he said.
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- "We looked for something inexpensive, widely available,
with possible broad activity. We also suspected that other people probably
never actually screened what are called inactive ingredients for activity,
so we thought we would be the only ones doing it."
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- They trawled through several hundred compounds listed
in a book, testing each one against HIV.
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- Finally they came upon cellulose acetate phthalate. Writing
in the British journal Biologicals, published by the International Association
of Biological Standardization, they said they formulated a cream containing
the compound.
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- Not only did it work in mice to kill viruses and bacteria,
but it did not kill the "good" bacteria such as lactobacilli,
which belong in a healthy vagina.
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- Neurath's team did not test it against sperm but assume
that it will inactivate sperm, acting as a contraceptive.
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- Other researchers are racing to get microbicides to market
and have found them in similarly unlikely places, such as a detergent widely
used in toothpaste.
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- "We were trying to avoid the use of detergents because
detergents affect cells," Neurath said.
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- Because cellulose acetate phthalate is widely used in
tablets, it must be safe, he added.
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- He feels the discovery was simply lucky.
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- "There were other compounds used for tablet coating
which are similar to the one we discovered which had absolutely no activity,"
he said. "I think it was a chance discovery."
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- The United States has the highest incidence of STDs in
the industrialized world, with 66 million people, or more than one in three
people aged 15 to 65 infected with at least one incurable STD such as HIV
or herpes.
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- An estimated 42 million people worldwide are infected
with HIV and 13 million have died of AIDS, according to the World Health
Organization. AIDS is now the fourth leading cause of death worldwide.
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- Neurath's team is working with the National Cancer Institute
and other groups to develop the cream.
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