- WASHINGTON (CNN) -- HIV can hide in the human immune system for up to 60
years, even when patients take strong drug "cocktails" that reduce
the virus to nearly undetectable levels, scientists said Monday.
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- Their findings, reported in "Nature
Medicine," are bad news for doctors who had hoped the drugs could
flush out the virus within three to five years.
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- Dr. Robert Siliciano and colleagues at
Johns Hopkins University School of Medicine discovered HIV can evade even
the most powerful anti-viral drugs available and remain hidden in what
they described as reservoirs in the immune system.
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- "What we are showing is that there
is a mechanism by which the virus can persist, essentially, for life, even
in patients who are on optimal therapy as we currently define it,"
Siliciano told Reuters in a telephone interview.
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- The research team looked at 34 patients
who were on the highly active antiretroviral therapy (HAART) drug "cocktails"
and in whom the virus was suppressed to near-zero levels.
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- Hiding in the immune system
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- Researchers already had found that the
virus hides in memory T-cells -- the immune system cells that are assigned
to recognize a new invader and then remember it in case it ever attacks
again, making it easier for the body to respond next time.
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- The latent pools of virus are hidden
in white blood cells that are "resting" and do not activate until
needed to fight an infection, such as influenza. If called upon to fight
the flu, doctors fear, these resting immune-fighter cells could flood the
patient's system with HIV.
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- AIDS experts hope a way can be found
to activate these memory T-cells and thus expose the virus hiding in them
to HAART. The drugs only work when the virus is actively replicating.
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- "We know that immunologic memory
lasts 60 years. For example, if you have a measles infection as a child,
you are protected 60 years later," Siliciano said.
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- The researchers did calculations to see
if the HIV-infected memory T-cells would last this long and found they
probably would.
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- Siliciano said the discovery of the persistence
of the reservoirs "doesn't mean a cure for HIV is impossible, but
it is an obstacle."
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- The discovery "emphasizes that patients
need to stay on their medicine possibly for the rest of their lives,"
Siliciano said.
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- Researchers aim fight at T-cells
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- Some doctors, though, including several
of those contributing to this latest research, believe it may be possible
to take some patients off the drugs, which can have some serious and potentially
dangerous side effects.
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- These doctors believe it may be possible
to speed up the elimination of the hidden reservoirs of virus by tricking
the body into fighting the resting immune-fighter cells.
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- Dr. Anthony Fauci at the National Institutes
of Health is one of those attempting to find a faster way to flush the
HIV reservoirs. He's using an old cancer drug, Interleukin-2 (IL-2), to
boost the immune systems into fighting the resting HIV-infected cells.
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- Italian researcher Dr. Franco Lori, with
labs at Georgetown University, is using another cancer drug, hydroxyurea,
to achieve a similar effect. Both report promising early results in a few
patients.
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- But Fauci stops short of using the word
"cure," saying the ultimate test will be to stop all HIV therapy
entirely and confirm the virus doesn't come back.
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- Fauci said he believes the discovery
of the longer-than-expected life span of the virus confirms he and others
are moving in the right direction.
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- "Those cells are not going to go
away spontaneously. They won't eradicate on their own, so we have to figure
out how to boost immunity and enhance the immune system to keep these pools
suppressed without the help of drugs," he said.
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- As more patients experience problems
with today's best drugs, doctors worry whether they can keep patients
on such medicines for a lifetime. Patients who'd hoped they might have
to take the two dozen or more pills each day for only a few years may face
a much longer fight to be free of the AIDS virus.
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