WASHINGTON (Reuters) - A souped-up version of a naturally
occurring immune system protein can protect female monkeys from
the AIDS virus, scientists reported on
Thursday in a finding they say may lead to a new way to prevent
infection in people.
They hope to eventually use their discovery to develop a
microbicide -- a cream or gel that women and men could use to
protect themselves from sexual transmission of the deadly virus.
With 43 million people infected and more than 25 million already
dead from the incurable virus, a microbicide would be a valuable
way to help fight the epidemic.
"The vast majority of HIV infections in the
world are sexually transmitted, most commonly through
heterosexual sex," said Dr. Michael Lederman of Case Western
Reserve University in Cleveland, Ohio, who helped lead the
"But there has been substantial debate as to how the virus
actually gets into cells at these sites of transmission, called
The human immunodeficiency virus that causes AIDS uses molecular
doorways called receptors to get into CD4 T-cells, the immune
system cells that HIV infects. One of these receptors is called
"We knew that people with a mutation whose CD4 cells' surface
lack CCR5 are almost completely protected from acquiring HIV
infection," Lederman said.
It was also known that an immune system messenger chemical or
chemokine called RANTES can attach to CCR5 and keep HIV from
'A PRETTY HEFTY DOSE'
Robin Offord and Olivier Hartley of the University of Geneva in
Switzerland developed a special form of RANTES that did this
especially well. The team worked to dissolve their new chemical
in saline solution and then tested it to see if it would protect
It did, they report in this week's issue of the journal Science.
They put the solution into the vaginas of female rhesus monkeys
and 15 minutes later put in a solution containing SHIV, a hybrid
of the human HIV and the simian version of the virus that infects
The highest dose of PSC-RANTES protected all five monkeys that
got it. The second-highest concentration protected four out of
five monkeys treated, while a slightly lower concentration
protected three of five animals.
"It took a pretty hefty dose to get protection in the rhesus
monkeys," Lederman said in an interview. "In reality this is
But in laboratory tests, the chemical prevented the virus from
infecting cells for a full day. That could mean a woman could use
a gel or cream 24 hours before having sex and still be protected,
in theory at least.
The Swiss team is now working on a cheaper and easier way to make
the RANTES molecule.
Lederman said his team wants to test the compound in people. He
said it appeared to be safe and did not cause irritation in the
monkeys -- something important for a microbicide used in the
vagina or anus.
AIDS experts agree that women and some men need an alternative to
condoms to protect themselves from the AIDS virus. In many
instances women are unable to refuse sex from husbands or other
men and, even more commonly, men refuse to use condoms.
Several groups are working to develop microbicides but advocacy
groups complain the field is not funded as well as it could be.