PHILADELPHIA -- Vaccines intended to protect people from
getting AIDS may also work as a treatment for those already
infected, boosting their immune system so they can temporarily
stop taking AIDS drugs.
So-called therapeutic vaccines, which harness the body's own
immune system to control HIV, have long been a goal of
research. However, data released at an AIDS vaccine conference
in Philadelphia on Friday are the first to hint this may be an
effective strategy when combined with standard AIDS drugs.
The idea is to give people a break from their AIDS medicines
that could last for weeks, months or even years. Experts
caution that much more experimentation is needed to know
whether vaccines could be used safely and effectively this way.
Nevertheless, dozens of possible new AIDS vaccines are in
development, and while most have not yet reached human testing,
drug companies are designing many of them for use both to
prevent AIDS and to treat it.
Furthest along in this kind of dual testing is Aventis
Pasteur's ALVAC-HIV, which has been given to more than 1,900
people worldwide and will enter large-scale testing to prevent
AIDS next summer. The vaccine consists of a harmless canary pox
virus that is genetically engineered to carry several genes
that make HIV proteins. The company is sponsoring 14 studies of
the vaccine as a treatment for infected people in the United
States and Europe.
Normally, when people stop taking their AIDS drugs, the virus
can reproduce again rampantly, producing billions of new
copies. By exposing the immune system in advance to HIV
proteins, experts hope it will mount a vigorous defense against
the re-emerging virus, knocking it down to acceptably low
At the meeting, called AIDS Vaccine 2001, Dr. Martin Markowitz
of the Aaron Diamond AIDS Research Center in New York City
described the first results of this strategy using ALVAC-HIV.
The study was conducted on patients who began taking AIDS drugs
within four months of catching HIV. Thirteen of them took four
doses of the vaccine before stopping their AIDS medicines,
while five others stopped treatment without being vaccinated.
The researchers were disappointed that the virus returned to
detectable levels in all the vaccinated volunteers.
Nevertheless, virus levels fell back down to low levels in six
of the vaccinated patients, compared with just one of those who
was not vaccinated.
Markowitz said this is the first study to suggest that inducing
an immune response with a vaccine influences patients' health
when used in combination with standard AIDS drugs.
"There is clearly an effect of the vaccine that justifies
continuing in this direction," he said. "It's a hint of
something good." The goal is to find a strategy that will allow
patients to stop taking AIDS drugs, at least temporarily. These
combinations of medicines have revolutionized AIDS treatment
over the past five years, changing HIV from a death sentence to
a manageable infection. Nevertheless, the treatment requires
taking several pills a day and can cause a variety of
unpleasant side effects, such as odd accumulations of body fat.
Dr. Douglas Richman of the University of California at San
Diego said priming the immune system with a vaccine is a more
sensible way to accomplish this than simply cycling people on
and off treatment, a strategy enthusiastically discussed last
year but largely abandoned because of poor results.
"It's conceivable that it could have a dramatic impact or no
impact," he said. "You can speculate until the cows come home.
We need to do the experiments."
Dr. Lawrence Corey of the University of Washington said a big
challenge is trying to invigorate an immune system that is
already weakened by HIV. "There is no proof in any system that
a vaccine has any clinical utility," he said. "The consensus in
HIV is that there is no consensus." --- Medical Editor Daniel
Q. Haney is a special correspondent for The Associated Press.