Posted on 01/16/2002 12:02:36 PM PST by Jean S
In a study that illustrates how cunning a foe AIDS is, a monkey that was given an experimental AIDS vaccine died after the virus changed just one of its genes.
HIV, which causes AIDS, already is known to mutate and grow impervious to standard AIDS drugs in at least half of all Americans being treated for the infection.
Now researchers have seen a similar outcome with an experimental vaccine that tries to stop the virus from multiplying. The mutation occurred in one of eight vaccinated rhesus monkeys in a Harvard experiment.
The findings were published in Thursday's issue of the journal Nature.
Scientists who reviewed the results described the monkey's death as "more disappointing than surprising."
It does not mean that AIDS vaccines are doomed to fail, they said, but illustrates how the virus will not be easily defeated or even contained anytime soon.
"It is sobering to find that a single-point mutation within the virus can initiate a cascade of events resulting in a clinical vaccine failure and death," said Dan H. Barouch, a clinical fellow at Harvard Medical School and lead author of the study.
More than one dozen experimental vaccines using different genetic strategies have been tested in various laboratories. Some have been successful for more than two years.
Unlike a flu shot, AIDS vaccines do not actually prevent infection by the invading virus. That is because HIV comes in many strains and changes rapidly.
Instead, the AIDS vaccines work to hold HIV infection in check. The vaccines are made with genes that carry the code for proteins in the virus. When the immune system sees these codes, it learns to stimulate production of virus-fighting cells known as killer T cells.
Details of one such vaccine program developed Merck & Co. were published in Nature along with the Harvard report. Company researchers discussed their progress at the first-ever AIDS vaccine meeting in September, and they have begun testing the vaccine in people.
In their animal study, the Merck researchers used the simian version of HIV. They said their best results were obtained by loading an SHIV gene for a protein known as gag into a genetically engineered cold virus. It stimulated the monkeys' immune systems to generate different types of killer T cells.
The Merck researchers subsequently injected lethal doses of SHIV into the animals. They said the vaccine has protected the animals, and they have not seen signs of the Harvard problem, known as "gene-escape."
"We've gone 500 days and not seen any escape," said molecular biologist Emilio Emini, director of the Merck trials. "It's something to watch for. But if the vaccine elicits a sufficiently broad genetic response, this is going to be an issue that we can deal with."
The Harvard trial took a slightly different approach. Rather than loading the gag gene onto a cold virus, the Harvard researchers injected gag DNA plus an immune cell growth factor directly into the animals.
Seven of Harvard's vaccinated animals have remained healthy for two years, even after they were injected with SHIV.
But the eighth vaccinated monkey, known as No. 798, responded differently. Six months into the trial, molecular studies showed the virus had started mutating.
Within eight months, virus levels soared within No. 798 and mutated virus was rapidly replacing the original virus. Levels of killer T cell levels plummeted. No. 798 died of AIDS-related complications one year after vaccination.
Federal scientists who reviewed both the Harvard and Merck studies said SHIV strain used in the trials is very aggressive and hard to control. It may not reflect how vaccines will perform in humans, where HIV infection is more gradual.
Developing an AIDS vaccine will be "an uphill grade for the foreseeable future," Jeffery Lifson of the National Cancer Institute and Malcolm Martin of the National Institutes of Health wrote in an accompanying editorial.
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On the Net: http://www.nature.com
AP-ES-01-16-02 1543EST
AIDS vaccine delivers Cellular attack tactic keeps virus at bay
It's big government science and it looks like it.
I think you can add breast cancer research to that.
This "vaccine" would promote participation in the same types of behavior which caused AIDS to spread in the first place. These behaviors are proven to be detrumental to the health of the participant and their partners. By this I don't mean homosexuality per se, but specific activites and behavioral patterns that can be present in straight or gay people.
FMCDH
I wonder if the mutation was caused by the chocolate or the peanut butter.
uhhmmmm...rhesus...BWAHAHAHAHAHA!!!!!...very good...spitsputter, my moniter is splattered!!!!
FMCDH
This might be a scary article if you really believed that HIV causes AIDS.
Tin-foil alert!
I just got an update on this from McAfee.
FMCDH
Hairloss In Veterinarians ?
FMCDH
FMCDH
FMCDH
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