A recent imaging study by UCLA and University of Pittsburgh
researchers, which revealed the areas of the brain damaged by the
AIDS virus, may be used to determine which drugs better target the
AIDS virus in the brain.
The study, published by the Proceedings of the National Academy
of Science online on Oct. 10, used magnetic resonance images to
create 3-D scans depicting the motor and sensory regions of the
brain that are selectively attacked by the AIDS virus.
“There’s really two main findings. One of them is a
big surprise that HIV is very selective in how it damages the
brain,” said Paul Thompson, associate professor in the
department of neurology at the UCLA David Geffen School of Medicine
and a lead researcher.
“The second surprise is that the drugs don’t save
brain tissue,” he said.
The researchers found no difference in tissue loss between AIDS
patients taking antiretroviral drugs and AIDS patients who were not
taking the drugs.
Although antiretroviral drugs are effective in regulating the
AIDS virus, the virus is still able to kill neurons in the
brain.
About 15 percent of gray matter in regions related to motor,
language and sensory function were destroyed in the patients that
were studied.
This gray matter is the location of the neurons that the AIDS
virus kills. Other regions of the brain generally remained
intact.
This loss in gray matter can result in mild cognitive damage
such as difficulty concentrating and slower reaction times.
About 40 percent of AIDS patients experience such cognitive
impairment, Thompson said.
However, the imaging technique designed by the research group
can be used in drug trials to view how effective new drugs will be
in minimizing brain tissue damage.
“There is hope. Now that patients are living much longer
with HIV the focus turns to saving brain tissue from damage …
Even if you lose about 1 percent brain tissue per year we might be
able to prevent the damage with better drugs along the way,”
Thompson said.
The research group developed a new method of measuring the
thickness of gray matter. A computer is used to measure the
thickness of gray matter based on 3-D MRI scans, which use radio
frequency waves and magnetic fields to excite atoms and generate an
image. Color images of the scans are then produced to show which
areas of the brain are targeted by the virus.
“The brain is thinner in parts of the brain that control
motor skills and sensory functions,” said Oscar Lopez,
associate professor of neurology at the University of Pittsburgh
and a member of the research team.
“These imaging techniques can be used to track the
progress of AIDS and in evaluating the effects of new drugs,”
he said.
Although antiretroviral drugs are able to eliminate the majority
of the HIV/AIDS virus in the bloodstream, some of these drugs have
trouble passing the blood-brain barrier which is inhibitory to most
drugs. Certain drugs can, however, pass the barrier.
“When you put people on potent viral drug therapies, the
virus is hiding in the central nervous system of the brain … We
could get rid of 99.9 percent of the virus in people’s blood
and they still wouldn’t be cured,” said Edwin Bayrd,
executive director of the UCLA AIDS Institute.
The imaging technique developed by the research group will allow
scientists to determine which drugs are most effective at targeting
the viruses residing in the brain.
“These are really the first pictures of where the virus
does damage,” said Thompson.
The first incidence of AIDS in the United States was documented
in Los Angeles in 1981. The first patients diagnosed with AIDS were
treated at UCLA Medical Center. The virus spread throughout the
country by 1982.
About 40 million people worldwide are infected with HIV or
AIDS.