UPI
Science News
WASHINGTON,
April 26 (UPI) -- AIDS patients would have to take powerful drug
cocktails for at least six decades to be free of the virus that
causes the deadly disease, suggests a disturbing new study.
In
another related report, scientists also found that these AIDS
drugs, known as highly active anti-retroviral therapy (HAART),
may weaken the body's own ability to fight the AIDS virus. HAART
consists of drugs like AZT, combined with newer drugs known as
protease inhibitors or non-nucleoside reverse transcriptase inhibitors.
Taken together, the two studies suggest that patients can keep
the Human Immunodeficiency Virus (HIV) at bay, but only if they
stay on difficult and expensive drug regimens, which scientists
say is not practical because of costs, side effects and the potential
for the development of resistance.
They also say that curing AIDS, a hope kindled in researchers
after promising initial results with drug cocktails, will require
new medications or other strategies, such as anti-HIV vaccines.
Both
studies are published in the May issue of the journal Nature Medicine.
In
one study, scientists from Baltimore's Johns Hopkins University
School of Medicine monitored the immune systems of 34 HIV infected
patients for two years. All the patients were taking HAART, and
were in good health.
Scientists
had known that HIV tucks itself into resting T-cells, rare cells
that provide long term protection against diseases like measles
after exposure to the infectious agent.
In the new research, they found that infected resting T-cells,
also called memory cells, can survive for more than 60 years,
giving the AIDS virus a safe place to hide for a lifetime.
Immunologist
Robert Siliciano says, ''The results are pretty shocking. The
survival of these cells is remarkable.''
When
the three-drug cocktails first showed the potential to reduce
the amount of HIV to undetectable levels about three years ago,
doctors became excited that they had found a way to wipe out the
infection, he says.
But,
they soon discovered that undetectable does not mean that the
virus is gone. Earlier work by Siliciano and other leading research
groups found these hidden reservoirs. The virus may not have been
attacking its main target, immune system cells known as CD4, and
they weren't causing disease. Nevertheless, they are still in
the patient's system.
Siliciano
says, ''This is quite depressing news, obviously.''
He
says, ''This means you probably can't stop and expect the virus
will be gone. You can't take medicines and wait out the virus.''
Stopping
therapy would allow the infection to rebound, which is what happens
when patients stop taking drugs in a matter of weeks.
Siliciano,
lead author of the paper, says, ''It was previously shown that
the virus could persist. What was unknown is how long these cells
last.''
Dr.
Anthony Fauci, director of the National Institute of Allergy and
Infectious Diseases of the National Institutes of Health, says,
''It's a good paper, an important paper. But it tells us we really
have our work cut out for us.''
Fauci
says it is not feasible to keep patients on these difficult drug
regimens for a lifetime. Most patients taking the drugs have been
on them for two or three years, with the longest experience of
about five years in patients who participated in the clinical
trials testing the drug cocktails.
To
cure AIDS, he says, scientists will have to figure out ways to
actively flush out that latent pool of virus, or find ways to
get the immune system itself to keep the virus in check.
He
says, ''We have to figure out creative ways to deal with it.''
In
the second study, led by Louis J. Picker of the University of
Texas Southwestern Medical Center in Dallas, scientists found
that even AIDS-ravaged immune systems try to fight back, producing
cells that are primed to attack the virus.
This
response is one of the reasons why some HIV-infected people become
long-term non-progressors. Their immune systems are strong enough
to successfully ward off the disease.
But, the scientists say, the number of these anti-HIV cells diminish
over the course of long-term drug therapy.
To
measure this, Picker and his team created a method to screen immune
cells to see if they were HIV-specific, trained to attack the
virus. As expected, uninfected people had none of these cells,
while long-term non-progressors were loaded with them.
They
also found AIDS fighting T-cells, however, in patients whose disease
was progressing, says Picker.
In
the second part of the study, Picker says his team looked for
HIV- specific T-cells in patients who had been undergoing HAART
therapy. They found that the number of cells dropped or had a
significantly weakened response to the virus after drug treatment.
This
finding suggests that long-term strategies to fight AIDS will
have to include programs in which patients periodically stop taking
drugs, a sort of vacations from the therapies, or the addition
of vaccines into treatment programs.
The
Centers for Disease Control and Prevention in Atlanta estimates
that about 900,000 Americans are infected with the AIDS virus.
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